Method for preparation of metal nanowires

专利摘要:
The present invention refers toamethod for the preparation of zero-valent-transition metalnanowiressuch as crystalline silver nanowires,andto areactor ovenfor the preparation of zero- valent-transition metalnanowires.
公开号:ES2809623A2
申请号:ES202090063
申请日:2019-06-12
公开日:2021-03-04
发明作者:Mamalek Mojtaba Meshkat；Mohammad-Reza Azani；Azin Hassanpour；Nicoló Plaia
申请人:INTERCOMET S L；
IPC主号:

专利说明:

[0004] FIELD OF THE TECHNIQUE OF THE INVENTION
[0006] The present invention relates to the area of metallic nanowires. More specifically, the present invention relates to methods for preparing zero valence transition metal nanowires and to a furnace for said method.
[0008] BACKGROUND
[0010] Metallic nanowire networks have received great attention for the manufacture of transparent conductive films (PCT) in optoelectronic applications such as touch screens, liquid crystal displays and solar cells. By using high conductivity metallic nanowires, transparent conductive films with low laminar resistance and high transmittance can be obtained. Among the different metals, silver (Ag) has great electrical and thermal conductivities, and is capable of improving the electrical and optical properties of PCTs. Thus, PCTs based on silver nanowires have been used successfully in organic solar cells and light-emitting diodes (LEDs); Here, silver nanowires stand out as promising optoelectric materials with similar performance to indium tin oxide, as well as flex and stretch stability.
[0012] Abbasi et al. (Abbasi NM et al, Mater. Chem. Phys, 2015, 166, 1-15) has reported on various manufacturing processes to prepare silver nanowires, such as polyol processes, solvothermic methods, techniques with ultraviolet radiation, photoreduction techniques , electrodeposition processes and DNA template methods, among others. Among the different approaches described, the solvothermal method is the most suitable for producing nanowires on a large scale. However, an obstacle to the large-scale production of nanowires by solvothermal methods is the limitation of the size of the reactors for larger-scale processes. Furthermore, when several reactors are used at the same time, the nanowires obtained in the different batches are not homogeneous. On the other hand, the methods described above have difficulties in refining the final characteristics of the products.
[0014] Solvothermic methods often result in products that comprise a mixture of nanowires and nanoparticles. The presence of nanoparticles has an adverse effect on the optical and / or electrical properties of the final product. Furthermore, despite the fact that in the nanowires with a ratio of
[0015] tall aspect (length / diameter), the thinner the nanowires obtained by
[0016] solvothermic methods, the higher the ratio of nanoparticles / nanowires that are
[0017] get on the products. Subsequently, these methods usually require a step of
[0018] additional purification to reduce the amount of nanoparticles present in the products
[0019] end. Currently, dead-end filtration, centrifugation, gel electrophoresis,
[0020] Selective precipitation and cross-flow filtration are the most commonly used techniques for
[0021] purify the products. However, these methods have several limitations. By
[0022] For example, simple dead-end filtration can damage the nanowires and add impurities to the
[0023] filter cake. Nanowires can also undergo aggregation and deformation by
[0024] centrifugation. In addition, despite being a very effective purification method, the
[0025] Gel electrophoresis is difficult to scale up to accommodate large-scale production methods.
[0026] scale.
[0028] United States Patent Application No. US20110045272A1 describes the use of
[0029] selective precipitation agents for the purification of metallic nanostructures. In
[0030] In particular, the use of a solvent such as acetone to add and precipitate the nanowires
[0031] metals and separate them from nanoparticles and other impurities. However, the use of
[0032] large amounts of solvents make this method environmentally unfriendly
[0033] environment and difficult to apply to large-scale purification.
[0035] In United States Patent Application No. US2013 / 0039806A1 a
[0036] Tangential flow (cross flow) filtration method for use in large-scale purification
[0037] scale the nanowire slurries to remove nanoparticles and other impurities. Without
[0038] However, the filters available for cross-flow filtration have sizes of
[0039] small pores, expensive, difficult to clean, and only last a few uses. In addition, the
[0040] The reduced internal diameter of these filters favors the aggregation of the nanowires.
[0042] Therefore, there is a clear need in particular for a large-scale method that is
[0043] efficient and low cost for the synthesis of valence transition metal nanowires
[0044] zero with high purity and high aspect ratio.
[0046] BRIEF DESCRIPTION OF THE INVENTION
[0048] The present inventors have developed a high-performance, low-cost method for the preparation of zero valence transition metal nanowires.
[0049] In particular, it has been observed that when using a solvothermic method for the preparation of zero valence transition metal nanowires that comprise a translational and / or rotational movement of the reactors during a heating step, transition metal nanowires of zero valence are obtained. High performance crystalline and pure zero valence with uniform mean diameters and lengths. Furthermore, since the method of the present invention is a simple process, it can be applied to the large-scale production of zero valence transition metal nanowires. Furthermore, by means of simple modifications in some parameters of the method of the present invention, the characteristics of the zero valence transition metallic nanowires, such as the mean diameter or the range of lengths, can be modulated.
[0051] Therefore, a first aspect of the invention is directed to a method for the preparation of transition metal nanowires of zero valence comprising the steps of:
[0052] i) providing a reaction mixture comprising: at least one coating agent, at least one transition metal salt, and at least one polar solvent;
[0053] ii) adding the reaction mixture obtained in step (i) to at least one reactor; iii) heating the at least one reactor of step (ii) at a temperature between 30 and 300 ° C for a period between 10 min and 7 days, at a pressure of at least 100 KPa, in a reactor furnace to obtain a suspension comprising zero valence transition metal nanowires;
[0054] wherein said at least one reactor comprises a longitudinal axis X-X 'and performs at least one of the following movements:
[0055] - a translation movement along a path, and - a rotational movement around the longitudinal axis X-X 'or around a W-W axis parallel to said longitudinal axis X-X'; and iv) optionally carrying out a purification process of the suspension obtained in step (iii) to achieve a purified suspension comprising zero valence transition metal nanowires.
[0057] In one disclosure, the present invention describes the zero valence transition metal nanowires that can be obtained by the zero valence transition metal nanowires preparation method defined above.
[0058] In one disclosure, the present invention describes a conductive ink composition comprising the zero valence transition metal nanowires defined above and at least one solvent.
[0060] In one disclosure, the present invention describes the use of the zero valence transition metal nanowires defined above in optoelectronics, biochemical detection, biomedical imaging, surface enhanced Raman scattering field, catalysis, electromagnetic interference shielding, and antimicrobial applications.
[0062] In a further aspect, the present invention is directed to a reactor furnace for the preparation of transition metal nanowires of zero valence, comprising:
[0063] - a thermally insulated chamber, comprising at least one inlet and a temperature control means;
[0064] - a conveyor adapted to carry out a translation movement along a path;
[0065] - at least one turntable located on the conveyor; Y
[0066] - at least one reactor located on the rotating platform;
[0067] wherein said at least one reactor comprises a longitudinal axis X-X '; Y
[0068] wherein said rotating platform is adapted to effect a rotational movement around the longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X '.
[0070] In a later disclosure, the present invention describes a filtration unit for the preparation of zero valence transition metal nanowires comprising:
[0071] to. a filter receptacle comprising an inlet, a first outlet, and a second outlet; Y
[0072] b. at least one cylindrical filter housed within the receptacle between the inlet and the first and second outlets;
[0073] where the input and the two outputs communicate fluidly.
[0075] DRAWINGS
[0077] Figure 1: (a) Perspective view of a reactor furnace of a particular embodiment of the present invention, (b) top view and front sectional view of a conveyor of a particular embodiment of the present invention and (c) exploded view of a turntable with three reactors of a particular embodiment of the present invention.
[0078] Figure 2: (a) Perspective view of a filtering unit of a particular embodiment of the present invention and (b) top view and front sectional view of a filtering unit of a particular embodiment of the present invention.
[0080] Figure 3: High resolution scanning electron microscope (SEM) micrographs showing silver nanowires synthesized in Example 2 in (a) Reaction 4, (b) Reaction 3, (c) reaction 2 and (d) reaction 1.
[0082] Figure 4: (a) Transmission electron microscope (TEM) micrograph of a single silver nanowire from reaction 2 of Example 2; (b) High resolution TEM photomicrograph of PVP (about 1.5 nm thick) on the surface of a silver nanowire; (d) Electron diffraction pattern of a randomly selected silver nanowire; and (c) X-ray energy dispersion spectroscopy (EDX) spectrum of the silver nanowire.
[0084] Figure 5: SEM micrograph of the silver nanowires from reaction 3 of example 2 (a) before and (b) after a purification process.
[0086] DETAILED DESCRIPTION OF THE INVENTION
[0088] Unless otherwise defined, all technical and scientific terms used herein have the same meaning commonly understood by one of ordinary skill in the art to which this disclosure belongs. As used herein, the singular forms "a", "an", "the" and "she" include reference to the plural, unless the context clearly indicates otherwise.
[0090] Method for the preparation of zero valence transition metal nanowires
[0092] As already mentioned, in a first aspect, the present invention refers to a method for the preparation of zero valence transition metal nanowires comprising the steps of:
[0093] i) obtaining a reaction mixture comprising: at least one coating agent, at least one transition metal salt and at least one polar solvent;
[0094] ii) adding the reaction mixture obtained in step (i) to at least one reactor; iii) heating the at least one reactor of step (ii) at a temperature between 30 and 300 ° C for a period between 10 min and 7 days, at a pressure of at least 100 KPa, in a reactor furnace to obtain a suspension comprising zero valence transition metal nanowires;
[0095] wherein said at least one reactor comprises a longitudinal axis X-X 'and performs at least one of the following movements:
[0096] - a translational motion along a path, and
[0097] - a rotational movement around the longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X '; Y
[0098] iv) optionally carry out a purification process of the suspension obtained in step (iii) to achieve a purified suspension comprising zero valence transition metal nanowires.
[0100] In the context of the present invention, the term "nanowires" refers to nanostructures with nanoscale thicknesses or diameters. Examples of nanowires include, but are not limited to, nanrods, nanofibers, nanofibrils, and nanotubes. present invention, the expression "zero valence transition metal nanowires" refers to nanowires that comprise a zero valence transition metal in their composition, preferably a zero valence transition metal selected from Ag, Cu, Au, Pt, Pd, Co, Zn, Cd, Pb and their combinations; preferably selected from Ag, Au, Cu, Pd and Pt; more preferably selected from Ag, Cu and Pt, even more preferably Ag.
[0102] In the context of the present invention, the term "method for the preparation of zero valence transition metal nanowires" comprises the preparation of a suspension comprising zero valence transition metal nanowires, a suspension purified with valence transition metal nanowires zero, milled with zero valence transition metal nanowires and / or solids comprising dry zero valence transition metal nanowires.
[0104] In the context of the present invention, the terms "nanowire thickness" and "nanowire diameter" are synonymous. In the context of the present invention, the term "nanowire diameter" or "nanowire diameters" refers to the shortest dimension of a nanowire. In the context of the present invention, the term "nanowire length" or "nanowire lengths" refers to the longest dimension of a nanowire.
[0105] In the context of the present invention, the term "aspect ratio" refers to the relationship between the sizes of the nanowires in the different dimensions. As a non-limiting example, the aspect ratio of a zero valence transition metal nanowire is the quotient between its longest side or its length and its shortest side or its diameter or thickness; that is, if a zero valence transition metal nanowire has a length of 40,000 nm and a diameter of 20 nm, its aspect ratio will be 2000.
[0107] In a particular embodiment, the method of the present invention is a method for the preparation of zero valence transition metal nanowires, as defined above, where the zero valence transition metal is selected from Ag, Cu, Au, Pt , Pd, Co, Zn, Cd, Pb and their combinations; preferably where the zero valence transition metal is selected from Ag, Au, Cu, Pd and Pt; more preferably where the zero valence transition metal is selected from Ag, Cu and Pt; even more preferably where the zero valence transition metal is Ag.
[0109] In a particular embodiment, the method defined above is a method for the preparation of silver metallic nanowires, preferably crystalline silver metallic nanowires.
[0111] In a preferred embodiment, the zero valence transition metal nanowires of the method for the preparation of zero valence transition metal nanowires defined above are the Ag, Cu, Au, Pt, Pd, Co, Zn, Cd, Pb and their combinations; preferably the nanowires of Ag, Au, Cu, Pd and Pt; and more preferably the Ag nanowires.
[0113] In a particular embodiment, the zero valence transition metal nanowires of the method for the preparation of zero valence transition metal nanowires defined above have a diameter of less than 500 nm, preferably less than 100 nm, more preferably less than 50 nm, and even more preferably less than 20 nm.
[0115] In a particular embodiment, the zero valence transition metal nanowires of the method for the preparation of zero valence transition metal nanowires defined above have a length greater than 5 microns, preferably between 5 and
[0116] 300 microns, and more preferably between 10 and 200 microns.
[0118] In a particular embodiment, the zero valence transition metal nanowires of the method For the preparation of zero valence transition metal nanowires defined above they have an aspect ratio between 100 and 5000, preferably between 300 and 2000.
[0120] In a particular embodiment, the zero valence transition metal nanowires of the method for the preparation of zero valence transition metal nanowires defined above are zero valence transition crystalline metal nanowires, preferably zero valence transition crystalline metal nanowires in individual twinning. , and more preferably single twinned crystalline silver nanowires.
[0122] In the context of the present invention, the term "single twinned" refers to crystalline zero valence transition metal nanowires in which two different crystals share some of the same crystal lattice points symmetrically.
[0124] In a particular embodiment, the zero valence transition metal nanowires of the method for the preparation of zero valence transition metal nanowires defined above have a polygonal structure.
[0126] In a particular embodiment, the zero valence transition metal nanowires of the method for the preparation of zero valence transition metal nanowires defined above comprise a layer of coating agent on their surface, preferably a layer of PVP coating agent on their surface. surface.
[0128] The method of the present invention for the preparation of zero valence transition metal nanowires comprises a step of (i) providing a reaction mixture comprising: at least one coating agent, at least one transition metal salt and at least one polar solvent.
[0130] The term "coating agent" refers to an organic molecule capable of forming a monolayer that is strongly absorbed on the surface of nanostructures to facilitate their anisotropic growth and prevent aggregation of nanostructures.
[0132] Some examples of suitable protective agents for the method of the present invention are, among others, polymers and their copolymers of polyvinylpyrrolidone (PVP), polyacrylamide (PAA), polyvinyl butyral (PVB) or polyacrylic (PA), cetyltrimethylammonium bromide (CTAB ), vitamin C, vitamin B, dodecylbenzenesulfonic acid (DBS), tetrabutylammonium bromide (TBAB), sodium dodecyl sulfonate (SDS) and their combinations.
[0134] In a preferred embodiment, the at least one coating agent from step (i) is polyvinylpyrrolidone (PVP).
[0136] Polyvinylpyrrolidone (PVP) is a polymer with different average molecular weights. Some examples of average molecular weights of PVP suitable for the method of the present invention are, among others, 55,000, 360,000, 1,300,000 and the like.
[0138] In a preferred embodiment, the at least one coating agent is PVP with an average molecular weight greater than 300,000 (PVP-K300).
[0140] The term "transition metal salt" refers to a neutral compound that has a positively charged metal ion and a negatively charged counterion. The counterion can be organic or inorganic. Examples of transition metal salts include, but are not limited to, transition metal nitrates, transition metal chlorides, transition metal perchlorates, transition metal acetates and the like.
[0142] In a preferred embodiment, the transition metal salt is selected from a zero valence transition metal among a salt of Ag, Cu, Au, Pt, Pd, Co, Zn, Cd, Pb and their combinations, preferably selected from a salt of Ag, Au, Cu, Pd and Pt; preferably selected from a salt of Ag, Cu and Pt.
[0144] In a preferred embodiment, the at least one transition metal salt is a silver salt. Some examples of silver salts include silver nitrate (AgNO ³ ), silver chloride (AgCl), silver perchlorate (AgClO4), silver acetate CH ³ CO ² Ag (or AgC2H3O2) and Similar.
[0146] In a preferred embodiment, the at least one transition metal salt from step (i) is silver nitrate (AgNO ³ ).
[0148] In a preferred embodiment, the reaction mixture obtained in step (i) has a molar fraction of coating agent: transition metal salt between 0.1 and 10, preferably between 1 and 7, more preferably between 1.5 and 4 ,5.
[0150] Normally, the silver salt is soluble in the at least one polar solvent and dissociates in the silver ion and counter ion of opposite charges. Reduction of the silver salt in the solvent produces elemental silver. Elemental silver crystallizes or grows to become a one-dimensional nanostructure, that is, nanowires. The at least one coating agent, such as PVP, or the at least one polar solvent can also have reducing properties and act as reducing agents, that is, reducing silver ions to elemental silver.
[0152] In a particular embodiment, the reaction mixture of step (i) also comprises at least one reducing agent.
[0154] In a more particular embodiment, the at least one reducing agent and the at least one polar solvent of the reaction mixture of step (i) are ethylene glycol (EG).
[0156] The term "polar solvent" refers to a solvent capable of dissolving the at least one transition metal salt and the at least one coating agent. Normally, the polar solvent is a chemical reagent because it has at least two hydroxyl groups, such as diols, polyols, glycols, or mixtures of these. Some examples of suitable polar solvents for the method of the present invention are, among others, ethylene glycol, glycerol, glucose, glycerin, 1,2-propylene glycol, 1,3-propylene glycol, and mixtures thereof.
[0158] In a preferred embodiment, the at least one polar solvent from step (i) is ethylene glycol (EG).
[0160] In a particular embodiment, the reaction mixture of step (i) also comprises at least one additive salt.
[0162] In a more particular embodiment, the reaction mixture of step (i) further comprises at least two additive salts.
[0164] The term "additive salt" or "ionic additive" refers to a salt containing cationic and anionic species associated through ionic interactions that can easily dissociate in polar solvents such as water, alcohol, diols, and polyols (including ethylene glycol , glycerol, glucose, glycerin, 1,2-propylene glycol and 1,3-propylene glycol). The cation can be organic, including the ammonium cation (NH ⁴ +) or a proton (H +), or it can be inorganic. Anions are usually inorganic. Some examples of anions are, among others: halides (Cl-, Br-, I-, F "), hydrogen sulfate (HSO ⁴ "), sulfate (SO ^{4 "2} ), phosphate (PO ^{4- 3} ), sulfonates (RSO ³ -), aryl, alkyl and the like.
[0165] The term "ammonium salt" refers to a salt formed by a quaternary ammonium cation (NH ⁴ +), where each of the four hydrogens can be replaced by organic groups. Therefore, the substituted quaternary ammonium cation is It is usually shown by the formula (NR ⁴ +), where each R is the same or different and independently an alkyl, an alkenyl, an alkynyl, an aryl, etc. The quaternary ammonium cation can create quaternary ammonium salt by means of different anions.
[0167] Some examples of anions are, among others, halides (Cl-, Br-, I-, F-), hydrogen sulfate (HSO ⁴ -), sulfate (SO ^4-2 ), phosphate (PO ^{4- 3} ), sulfonates (RSO ³ -), aryl, alkyl and the like.
[0169] Examples of quaternary ammonium salts include tetrapropylammonium chloride (TPA-C), tetrapropylammonium bromide (TPA-B), 1-butyl-3-methylimidazolium chloride (BMIM-Cl), bromide of 1-butyl-3-methylimidazolium (BMIM-Br) and their combinations.
[0171] In a particular embodiment, the reaction mixture from step (i) further comprises at least one additive salt as, where the at least one additive salt from step (i) is selected from KCl, KBr, NaCl, NaBr and their combinations.
[0173] In a preferred embodiment, the reaction mixture from step (i) further comprises at least one additive salt as, where the at least one additive salt from step (i) is selected from KCl, KBr, NaCl, KBr and an ammonium salt selected from the group of TPA-B, TPA-C, BMIM-Cl and their combinations.
[0175] In a more preferred embodiment, the reaction mixture from step (i) further comprises one at least one additive salt as, where the at least one additive salt from step (i) is selected from KBr, TPA-C and their combinations.
[0177] In a more preferred embodiment, the reaction mixture from step (i) further comprises a combination of TPA-C and KBr.
[0179] In a more preferred embodiment, the reaction mixture from step (i) further comprises NaCl.
[0181] In a more preferred embodiment, the reaction mixture of step (i) further comprises BMIN-Cl.
[0183] Without wishing to be bound by any particular theory, the present inventors believe that by changing the additive salts used in step (i) of the method of the present invention, characteristics such as the mean diameter or the range of lengths of the present invention can be modified. the zero valence transition metal nanowires obtained.
[0185] In a preferred embodiment, the reaction mixture obtained in step (i) also comprises two additive salts, as long as at least one of said additive salts is an ammonium salt, and where the ratio of molar concentrations between the ammonium salt and the other additive salt is between 0.5 and 5, and preferably between 1 and 3.
[0187] In an even more preferred embodiment, the reaction mixture obtained in step (i) comprises KBr and TPA-C, where the KBr / TPA-C mole fraction is between 0.5 and 5, preferably between 1 and 3, and more preferably between 1.5 and 2.5.
[0189] In the context of the present invention, the expression "reaction mixture" refers to a combination of different substances in which a reaction can occur under certain conditions (for example, at a certain pressure or temperature), particularly to obtain a suspension comprising zero valence transition metal nanowires.
[0191] In a particular embodiment, the method for the preparation of zero valence transition metal nanowires further comprises:
[0192] - provide
[0193] a solution of at least one coating agent in at least one polar solvent; Y
[0194] a solution of at least one transition metal salt in at least one polar solvent; Y
[0195] - mixing the solution of at least one coating agent in at least one polar solvent and the solution of at least one transition metal salt in at least one polar solvent to form a reaction mixture comprising at least one coating agent, at least least one transition metal salt and at least one polar solvent.
[0196] In a more particular embodiment, the method for the preparation of zero valence transition metal nanowires further comprises:
[0197] - provide
[0198] a solution of at least one coating agent in at least one polar solvent;
[0199] a solution of at least one transition metal salt in at least one polar solvent; Y
[0200] a solution of at least one additive salt optionally in at least one polar solvent; Y
[0201] - adding to the solution of at least one coating agent in at least one polar solvent, the solution of at least one additive salt in at least one polar solvent and then the solution of at least one transition metal salt in at least one solvent polar to form a reaction mixture comprising at least one coating agent, at least one transition metal salt, at least one additive salt, and at least one polar solvent.
[0203] In a still more particular embodiment, the solution of at least one coating agent in at least one polar solvent is prepared by heating the at least one coating agent in the at least one polar solvent and then cooling it.
[0205] As a non-limiting example, PVP as a coating agent can be completely dissolved in ethylene glycol as a polar solvent by heating it at 80-120 ° C for 2 hours.
[0207] In an even more particular embodiment, the solution of at least one transition metal salt in at least one polar solvent is prepared at room temperature by stirring.
[0209] In a still more particular embodiment, the solution of at least one additive salt in at least one polar solvent is prepared at room temperature by stirring.
[0211] The method of the present invention for the preparation of zero valence transition metal nanowires comprises a step (ii) of adding the reaction mixture obtained in step (i) to at least one reactor.
[0213] In the context of the present invention, the term "reactor" refers to a reactor with high resistance to temperature and pressure for synthesis processes. reaction, the pressure within the reactor can be increased by applying a pressure outside the reactor or by gas or steam generated by the reaction in the reactor. Some non-limiting examples of suitable reactors for the method of the present invention are solvothermal or hydrothermal reactors, such as sealed autoclaves. In a particular embodiment, the at least one reactor of step (ii) is capable of maintaining the pressure between 1 and 500 kPa, preferably between 100 and 400 kPa, and more preferably between 100 and 200 kPa.
[0215] In a particular embodiment, the at least one reactor of step (ii) is a solvothermal reactor.
[0217] In a more particular embodiment, the at least one reactor of step (ii) comprises at least one chemically inert material and at least one heat-conducting material.
[0219] In a more particular embodiment, the at least one reactor of step (ii) comprises
[0220] to. at least one chemically inert material selected from polytetrafluoroethylene (PTFE), ceramic, silica and their combinations; Y
[0221] b. at least one heat conducting material selected from stainless steel, aluminum, copper, bronze, chrome, brass, beryllium and their combinations.
[0223] Some examples of suitable solvothermic reactors for the method of the present invention are, among others, PTFE lined stainless steel reactors, PTFE lined aluminum reactors and the like.
[0225] In a preferred embodiment, the at least one reactor in step (ii) is selected from a PTFE lined stainless steel reactor and a PTFE lined aluminum reactor, preferably it is a PTFE lined aluminum reactor.
[0227] In a particular embodiment, the at least one reactor of step (ii) is a PTFE-lined aluminum reactor comprising an internal PTFE lining layer between 50 and 500 microns.
[0229] In a particular embodiment, the at least one reactor of step (ii) is a PTFE-lined aluminum reactor with an outer layer of aluminum between 0.1 and 5 mm.
[0231] In a particular embodiment, the at least one reactor of step (ii) has a capacity between 25 ml and 10,000 ml, preferably between 500 ml and 5000 ml; more preferably between 1000 and 3000 ml.
[0233] Without wishing to be bound by any particular theory, the present inventors believe that the use of at least one PTFE-lined aluminum reactor in the method of the present invention enables high performance zero valence transition metal nanowires to be obtained with a smooth and controlled aspect ratio.
[0235] Furthermore, the present inventors believe that the method of the present invention is capable of utilizing several larger capacity solvothermic reactors and therefore can be scaled up.
[0237] The method of the present invention for the preparation of zero valence transition metal nanowires comprises a step (iii) of heating the at least one reactor of step (ii) to a temperature between 30 and 300 ° C for a period between 10 min. and 7 days at a pressure of at least 100 kPa in a reactor furnace to obtain a suspension comprising zero valence transition metal nanowires;
[0238] wherein said at least one reactor comprises a longitudinal axis X-X 'and performs at least one of the following movements:
[0239] - a translational motion along a path, and
[0240] - a rotational movement around the longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X '.
[0242] In a particular embodiment, step (iii) of the method for the preparation of zero valence transition metal nanowires defined above further comprises heating the at least one reactor of step (ii) to a temperature between 30 and 300 ° C, preferably between 100 and 200 ° C, and more preferably between 120 and 180 ° C.
[0244] In a particular embodiment, step (iii) of the method for the preparation of zero valence transition metal nanowires defined above further comprises heating the at least one reactor of step (ii) for a period between 10 min and 7 days, preferably between 1 hour and 50 hours, and more preferably between 2 hours and 40 hours.
[0246] In a particular embodiment, step (iii) of the method for the preparation of zero valence transition metal nanowires defined above further comprises heating the at least one reactor of step (ii) to a pressure of at least 100 KPa, preferably of at least 120 KPa, and more preferably at least 140 KPa. In a particular embodiment, step (iii) of the method for the preparation of zero valence transition metal nanowires defined above further comprises a pressure between 1 and 1000 kPa, preferably between 1 and 500 kPa, more preferably between 100 and 400 kPa, and still more preferably between 100 and 200 kPa. The term "kPa" or "KPa" is understood as the unit of kilopascal pressure, as known in the art (that is, 1 Pa in base units of the international system [SI] is equal to Kg * m-1 * s -two).
[0248] In a more particular embodiment, step (iii) of the method for the preparation of zero valence transition metal nanowires defined above further comprises heating the at least one reactor of step (ii) at a temperature between 100 and 200 ° C for a period between 1 hour and 50 hours at a pressure of at least 120 kPa in a reactor furnace to obtain a suspension comprising transition metal nanowires of zero valence;
[0249] wherein said at least one reactor comprises a longitudinal axis X-X 'and at least one of the following movements:
[0250] - a translational motion along a path, and
[0251] - a rotational movement around the longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X '.
[0253] In an even more particular embodiment, step (iii) of the method for the preparation of zero valence transition metal nanowires defined above further comprises heating the at least one reactor of step (ii) to a temperature between 120 and 190 ° C during a period between 2 hours and 40 hours at a pressure of at least 140 KPa in a reactor furnace to obtain a suspension comprising zero valence transition metal nanowires; wherein said at least one reactor comprises a longitudinal axis X-X 'and performs at least one of the following movements:
[0254] - a translational motion along a path, and
[0255] - a rotational movement around the longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X.
[0257] In a particular embodiment, step (iii) of the method for the preparation of zero valence transition metal nanowires defined above further comprises heating the at least one reactor of step (ii) to a temperature between 120 and 190 ° C; wherein said heating of the at least one reactor of step (ii) comprises the following steps:
[0258] to. heating the at least one reactor from an initial temperature to a final temperature between 120 and 190 ° C;
[0259] b. maintain a temperature between 120 and 190 ° C for a certain time;
[0260] c. optionally performing a combination of steps a) and b); I
[0261] d. bring the temperature down to room temperature.
[0263] In the context of the present invention, the term "room temperature" refers to a temperature between 15 degrees centigrade (° C) and 25 ° C.
[0265] In a particular embodiment, step (iii) of the method for the preparation of zero valence transition metal nanowires defined above further comprises heating the at least one reactor of step (ii) to a temperature between 120 and 190 ° C; wherein said heating of the at least one reactor of step (ii) comprises the following steps:
[0266] to. heating the at least one reactor from an initial temperature to a final temperature between 120 and 190 ° C;
[0267] b. maintain a temperature value between 120 and 190 ° C for a period between 5 and 50 hours;
[0268] c. optionally performing a combination of steps a) and b); I
[0269] d. bring the temperature down to room temperature.
[0271] The method of the present invention for the preparation of zero valence transition metal nanowires comprises a step (iii) of heating the at least one reactor of step (ii); wherein said at least one reactor comprises a longitudinal axis X-X 'and performs at least one of the following movements:
[0272] - a translational motion along a path, and
[0273] - a rotational movement around the longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X '.
[0275] In a particular embodiment, the at least one reactor of step (iii) of the method for the preparation of zero valence transition metal nanowires performs at least one rotational movement around the longitudinal axis X-X 'or around an axis W- W 'parallel to said longitudinal axis X-X'.
[0277] In a particular embodiment, the at least one reactor of step (iii) of the method for the preparation of zero valence transition metal nanowires simultaneously performs a rotational movement around the longitudinal axis XX 'or around an axis WW' parallel to said longitudinal axis X-X ', as well as a translational movement along a trajectory.
[0279] In the context of the present invention, the term "translational motion" refers to displacement from one point in space to another. Some examples of translational motion are, among others, the displacement of the at least one reactor of the present invention from one point in space to another following a linear, looped, orbital, elliptical or circular path and / or combinations thereof.
[0281] In the context of the present invention, the term "trajectory" refers to the path or path that the at least one reactor of the present invention follows while performing a translational movement. Some examples of suitable trajectory for the method of the present invention are, among others, a linear, looped, orbital, elliptical or circular trajectory and / or combinations thereof.
[0283] In the context of the present invention, the term "closed path" refers to the path or path that the at least one reactor of the present invention follows while performing a translational movement that begins and ends at the same point in space. Some examples of a closed path suitable for the method of the present invention are, among others, a linear, looped, orbital, elliptical or circular path and / or combinations thereof.
[0285] In the context of the present invention, the expression "rotational movement" refers to the movement produced around an axis or center (or point) of rotation, that is, the number of rotations carried out around an axis of rotation. Some examples of rotational axes suitable for the method of the present invention are, among others, a longitudinal axis X-X 'of the at least one reactor of the present invention and an axis W-W' parallel to said longitudinal axis X-X '. Some examples of rotational movements are, among others, concentric or eccentric movements around an axis of rotation.
[0287] In the context of the present invention, the expression "a longitudinal axis X-X '" refers to a longitudinal axis of rotation of a reactor parallel to its length that passes through its center and constitutes an axis of symmetry. As a non-limiting example, for a cylindrical reactor its longitudinal axis X-X 'is parallel to its length and passes through its center.
[0289] In a particular embodiment, the translation movement of step (iii) of the method of the present invention is a uniform translation movement.
[0290] In a particular embodiment, the rotational movement of step (iii) of the method of the present invention is a uniform rotational movement.
[0292] In the context of the present invention, the expression "uniform movement" refers to a movement at a constant speed (in which the speed remains constant), that is, without acceleration, and in particular to a movement at a constant speed of the at least one reactor of the present invention.
[0294] In the context of the present invention, the term "rpm" is a measure of frequency; where i) with respect to the translational movement following a closed path, "rpm" refers to the number of complete closed paths performed in a period (one minute); and ii) with respect to the rotational movement, "rpm" refers to the number of complete rotations carried out in a period around the longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X ' . As a non-limiting example, "rpm" is a measure of frequency that refers to the number of times that the at least one reactor of the present invention completes a closed path in one minute while performing a translation movement following a closed path or ii) with the number of times that the at least one reactor rotates around its longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X 'while performing a rotational movement.
[0296] In a particular embodiment, the at least one reactor of step (iii) performs the translation movement following a linear path.
[0298] In a particular embodiment, the at least one reactor of step (iii) performs the translation movement following a linear path at a constant speed between 0.1 and 10 m / min.
[0300] In a particular embodiment, the at least one reactor of step (iii) performs the translation movement following a closed path.
[0302] Some examples of a closed path suitable for the method of the present invention are, among others, a closed loop, orbital, elliptical or circular path and / or combinations thereof.
[0304] In a particular embodiment, the translation movement following a closed path or the rotational movement of step (iii) is carried out at a constant frequency between 1 and 100 rpm; more preferably at a constant frequency between 1 and 50 rpm.
[0305] In a more particular embodiment, the at least one reactor of step (Ni) performs the translation movement following a closed path at a constant frequency between 1 and 100 rpm, preferably at a constant frequency between 1 and 50 rpm, and more preferably at a constant frequency between 1 and 10 rpm.
[0307] In a particular embodiment, the at least one reactor of step (iii) performs the translation movement following a closed circular path around an axis Y-Y 'parallel to said longitudinal axis X-X'.
[0309] In a more particular embodiment, the at least one reactor of step (iii) performs the translation movement following a closed circular path around an axis Y-Y 'parallel to said longitudinal axis X-X' at a constant frequency between 1 and 100 rpm, preferably at a constant frequency between 1 and 50 rpm, and more preferably at a constant frequency between 1 and 10 rpm.
[0311] In a particular embodiment, the at least one reactor of step (iii) performs the translation movement following a closed elliptical path around a Y-Y 'axis parallel or perpendicular to said longitudinal axis X-X'.
[0313] In a more particular embodiment, the at least one reactor of step (iii) performs the translation movement following a closed elliptical path around an axis Y-Y 'parallel to said longitudinal axis X-X'.
[0315] In a more particular embodiment, the at least one reactor of step (iii) performs the translation movement following a closed elliptical path around a Y-Y 'axis perpendicular to said X-X' longitudinal axis.
[0317] In a more particular embodiment, the at least one reactor of step (iii) performs the translation movement following a closed elliptical path around an axis Y-Y 'parallel to said longitudinal axis X-X' at a constant frequency between 1 and 100 rpm, preferably at a constant frequency between 1 and 50 rpm, and more preferably at a constant frequency between 1 and 10 rpm.
[0319] In a particular embodiment, the at least one reactor performs the rotational movement around the longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X 'at a constant frequency between 1 and 100 rpm, preferably at a constant frequency between 1 and 50 rpm.
[0321] Without wishing to be bound by any particular theory, the present inventors have surprisingly discovered that when the at least one reactor performs the translation movement following a trajectory in step (iii) of the method of the present invention, the metallic nanowires zero valence transition of the suspension obtained are homogeneous and have a uniform aspect ratio to each other. Furthermore, when said at least one reactor is at least two reactors, the zero valence transition metal nanowires that are achieved in the suspension obtained in each of the at least two reactors are homogeneous and have a uniform aspect ratio to each other.
[0323] Without wishing to be bound by any particular theory, the authors of the present invention have surprisingly discovered that when the at least one reactor with a longitudinal axis X-X 'performs the rotational movement around an axis W-W' parallel to said longitudinal axis X X ', in step (iii) of the method of the present invention, the zero valence transition metal nanowires of the suspension obtained have a higher aspect ratio than when the at least one reactor does not perform a movement of rotation. In particular, when the at least one reactor performs the rotational movement at about 50 rpm, the zero valence transition metal nanowires of the suspension obtained have a greater length. Therefore, the present inventors have surprisingly discovered that the aspect ratio of the zero valence transition metal nanowires can be modulated by changing the conditions of the rotational motion.
[0325] Without wishing to be bound by any particular theory, the present inventors have surprisingly discovered that when the at least one reactor with a longitudinal axis X-X 'performs the rotational movement around said longitudinal axis X-X', the The length range of the zero valence transition metal nanowires is narrowed, that is, the zero valence transition metal nanowires are more uniform.
[0327] In a particular embodiment, the at least one reactor of the method of the present invention is at least two reactors.
[0329] In a particular embodiment, the at least one reactor of the method of the present invention is at least two reactors, where said two reactors carry out the translational movement following a trajectory and the rotational movement around an axis W-W 'parallel to the mentioned longitudinal axis X-X '.
[0331] In a particular embodiment, the at least one reactor of the method of the present invention is at least two reactors, where said two reactors simultaneously perform the translational movement following a trajectory and the rotational movement around an axis W-W 'parallel to the mentioned longitudinal axis X-X '.
[0333] In a more particular embodiment, the at least one reactor of the method of the present invention is at least three reactors.
[0335] In a particular embodiment, the at least one reactor of the method of the present invention is at least three reactors, where said three reactors carry out the translational movement following a trajectory and the rotational movement around an axis W-W 'parallel to the aforementioned longitudinal axis X-X '.
[0337] In a particular embodiment, the at least one reactor of the method of the present invention is at least three reactors, where said three reactors simultaneously perform the translational movement following a trajectory and the rotational movement around an axis W-W 'parallel to the mentioned longitudinal axis X-X '.
[0339] In a particular embodiment, the at least one reactor is heated by means of a reactor furnace.
[0341] In a particular embodiment, step (iii) of the method for the preparation of zero valence transition metal nanowires defined above further comprises a reactor furnace; said reactor furnace comprises:
[0342] - a thermally insulated chamber, comprising at least one inlet and a temperature control means;
[0343] - a conveyor adapted to carry out the translation movement along a path; Y
[0344] - at least one rotating platform located on the conveyor, where said rotating platform is adapted to effect the rotational movement around the longitudinal axis X-X 'or around the axis W-W' parallel to said longitudinal axis X-X '; Y
[0345] - where the at least one reactor is located on the turntable.
[0347] In a more particular embodiment, step (iii) of the method for the preparation of nanowires Zero valence transition metals defined above further comprises a reactor furnace (1); said reactor furnace (1) comprises:
[0348] - a thermally insulated chamber (1.1), comprising at least one inlet (1.2) and a temperature control means;
[0349] - a conveyor (2) adapted to carry out a translation movement along a path;
[0350] - at least one rotating platform (3) located on the conveyor (2); Y
[0351] - at least one reactor (4) located on the rotating platform (3), wherein said at least one reactor (4) comprises a longitudinal axis X-X '; Y
[0352] - where said rotating platform (3) is adapted to effect a rotational movement around the longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X '; Y
[0353] - where the at least one reactor (4) is located on the rotating platform;
[0354] preferably as shown in Figure 1.
[0356] In the context of the present invention, the expression "thermally insulated chamber" refers to a chamber that maintains a constant relative temperature inside. Said thermally insulated chamber optionally comprises means for transferring thermal energy by convection and radiation. Furthermore, said The chamber may be capable of maintaining the pressure or be suitable to maintain it, preferably a pressure between 1 and 500 kPa, more preferably between 100 and 200 kPa.
[0358] In the context of the present invention, the expression "temperature control means" refers to means capable of maintaining a constant temperature within the thermally insulated chamber for a certain period and / or modifying the temperature from an initial value until reaching a final value for a certain period within the thermally insulated chamber, and optionally include temperature sensors.
[0360] In the context of the present invention, the term "conveyor" refers to a common piece of mechanical handling equipment that moves materials from one place to another following a path and that is adapted to carry out a certain number of paths for a certain time. .
[0362] In a more particular embodiment, the conveyor comprises at least one load transport surface.
[0363] In a more particular embodiment, the conveyor comprises a double traction element specially adapted to describe a curved path, such as a circular path.
[0365] In the context of the present invention, the expression "turntable" refers to a platform adapted to rotate around a fixed axis, where said platform is adapted to describe a determined number of rotations during a certain time.
[0367] In a particular embodiment, the rotating platform of the present invention comprises a reactor support, preferably a suitable reactor support to maintain pressures between 1 and 500 kPa, more preferably between 100 and 200 kPa.
[0369] In a particular embodiment, the reactor furnace of step (iii) of the method for the preparation of zero valence transition metallic nanowires defined above further comprises a natural convection reactor furnace, a forced air reactor furnace or combinations thereof.
[0371] In a particular embodiment, the reactor furnace of step (iii) of the method for the preparation of zero valence transition metal nanowires defined above also comprises air circulation means.
[0373] In the context of the present invention, the air circulation means is, for example, a fan that accelerates heat transfer (convection) and air exchange within the thermally insulated chamber of the reactor furnace of the present invention and that distribute the temperature evenly within the thermally insulated chamber.
[0375] In a particular embodiment, the reactor furnace of step (iii) of the method for the preparation of zero valence transition metal nanowires defined above further comprises the at least one rotating platform adapted to perform the rotational movement around the longitudinal axis X-X 'or around the axis W-W' parallel to said longitudinal axis XX 'at the same time as the translational movement along a path of the conveyor.
[0377] In a particular embodiment, the reactor furnace of step (iii) of the method for the preparation of transition metal nanowires of zero valence defined above also comprises the conveyor adapted to perform a translation movement following a linear path at a constant speed between 0, 1 and 1 m / min, preferably between 0.2 and 0.80 m / min, more preferably between 0.3 and 0.6 m / min.
[0379] In a particular embodiment, the reactor furnace of step (iii) of the method for the preparation of zero valence transition metal nanowires defined above also comprises the conveyor adapted to perform a translational movement following a closed path at a constant frequency between 1 and 100 rpm, preferably at a constant frequency between 1 and 50 rpm, more preferably at a constant frequency between 1 and 10 rpm.
[0381] In a particular embodiment, the reactor furnace of step (iii) of the method for the preparation of zero valence transition metallic nanowires defined above further comprises the at least one rotating platform of the reactor furnace adapted to perform a rotational movement around the longitudinal axis. X-X 'or around an axis W-W' parallel to said longitudinal axis X-X 'at a constant frequency between 1 and 100 rpm, preferably at a constant frequency between 1 and 60 rpm, and more preferably at 50 rpm.
[0383] In a particular embodiment, the reactor furnace of step (iii) of the method for the preparation of zero valence transition metal nanowires defined above further comprises either the at least one rotating platform of the reactor furnace adapted to perform a rotational movement around the longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X 'or the conveyor adapted to perform a translation movement following a closed path at a constant frequency between 1 and 100 rpm, more preferably at a constant frequency between 1 and 50 rpm.
[0385] In a particular embodiment, the reactor furnace of step (iii) of the method for the preparation of zero valence transition metal nanowires defined above further comprises the at least one reactor located on the rotating platform.
[0387] In a particular embodiment, the reactor furnace of step (iii) of the method for the preparation of zero valence transition metal nanowires defined above further comprises the at least one reactor located in the center of the rotating platform.
[0389] In a particular embodiment, the reactor furnace of step (iii) of the method for the preparation of zero valence transition metal nanowires defined above further comprises at least two reactors located on the at least one rotating platform.
[0391] In a particular embodiment, the reactor furnace of step (iii) of the method for the preparation of Zero valence transition metal nanowires defined above further comprises at least two reactors located on the at least one rotating platform at a similar distance from the center of the platform.
[0393] In a particular embodiment, the reactor furnace of step (iii) of the method for the preparation of transition metal nanowires of zero valence defined above also comprises at least two reactors located on the at least one rotating platform at a similar distance from the center of the platform, where said distance is less than twice the outer diameter of the reactor, preferably between 1 and 1000 cm from the center of the reactor to the center of the platform, more preferably between 2 and 35 cm from the center of the reactor to the center of the turntable.
[0395] In the context of the present invention, the expression "located on" in relation to the at least one reactor or to the two reactors located on the at least one turntable relates to the fact that said reactors are positioned and fixed at a point determined on said at least one turntable. By way of non-limiting examples:
[0396] - when a reactor comprising a longitudinal axis X-X 'is located in the center of the rotating platform, said reactor is capable of rotating around the longitudinal axis X-X';
[0397] - when a reactor comprising a longitudinal axis X-X 'is located at a distance from the center of the rotating platform, so that said distance is less than twice the outer diameter of the reactor, said reactor is capable of rotating movement about an axis W-W 'parallel to said longitudinal axis X-X'; Y
[0398] - when at least two reactors comprising a longitudinal axis X-X 'are located at a similar distance from the center of the turntable, so that said distance is less than twice the outer diameter of the at least two reactors, the at least two reactors are capable of rotating around an axis W-W 'parallel to said longitudinal axis X-X'.
[0400] In a more particular embodiment, the reactor furnace of step (iii) of the method for the preparation of zero valence transition metal nanowires defined above located on the at least one turntable at a distance from the center of the turntable, said at least a reactor is capable of performing an eccentric rotation around the axis W-W 'parallel to said longitudinal axis X-X'.
[0402] In a more particular embodiment, the reactor furnace of step (iii) of the method for the preparation transition metal nanowires of zero valence defined above further comprises at least two reactors located on the at least one turntable at a similar distance from the center of the turntable; both reactors are capable of performing an eccentric rotation around the axis W-W 'parallel to said longitudinal axis X-X'.
[0404] In a more particular embodiment, the reactor furnace of step (iii) of the method for the preparation of zero valence transition metal nanowires defined above is suitable to maintain a pressure between 100 and 200 kPa; preferably it is a solvothermal or hydrothermal reactor as is known in the art, more preferably it comprises a sealed autoclave.
[0406] During the heating period of step (iii), the reaction mixture becomes more viscous and cloudy, until the presence of a gray or green color indicates that the suspension comprises silver nanowires.
[0408] The method of the present invention for the preparation of zero valence transition metal nanowires comprises a step (iv) of optional performance of a purification process of the suspension obtained in step (iii) to obtain a purified suspension comprising metallic nanowires zero valence transition.
[0410] In a particular embodiment, the purification process of step (iv) of the method for the preparation of zero valence transition metal nanowires defined above comprises a filtration process.
[0412] In a particular embodiment, the purification process of step (iv) of the method for the preparation of zero valence transition metal nanowires defined above comprises:
[0413] to. performing an angular filtration of the suspension from step (iv) to obtain a retentate comprising zero valence transition metal nanowires; b. dispersing the retentate obtained in step (a) in a solvent to form an inflow comprising zero valence transition metal nanowires; and c. performing a tangential flow filtration of the inflow obtained in step (b) to obtain a purified suspension comprising zero valence transition metal nanowires; Y
[0414] d. optionally, repeat steps (a) to (c).
[0415] In a particular embodiment, the purification process of step (iv) of the method for the preparation of zero valence transition metal nanowires defined above further comprises repeating one or more of steps (a) to (c).
[0417] In the context of the present invention, the term "purification" refers to the reduction of unwanted materials in the purified suspension. In the context of the present invention, the purified suspension comprises zero valence transition metal nanowires. Examples of unwanted materials include, but are not limited to, solvents, nanoparticles such as zero valence transition metal nanoparticles, salts, coating agents, and the like. Some examples of zero valence transition metal nanoparticles are, among others, Ag, Cu, Au, Pt, Pd, Co, Zn, Cd, Pb nanoparticles and their combinations, preferably Ag, Au, Cu, Pd nanoparticles and Pt, more preferably Ag nanoparticles.
[0419] In the context of the present invention, the term "retained" refers to the material that is retained by the filter during a purification step. A non-limiting example of a retentive is a retentive solid or sludge comprising zero valence transition metal nanowires.
[0421] In the context of the present invention, the expression "inlet flow" refers to the flow that feeds the filtration unit and optionally enters through the inlet of the latter.
[0423] In a particular embodiment, the "inflow" of step (iv) is a suspension comprising zero valence transition metal nanowires.
[0425] In the context of the present invention, the term "filtration flow" refers to the flow that exits the filtration unit after exiting the filter as permeate or filtrate and optionally exits the filter unit outlet. Non-limiting examples of materials that the filtration stream may comprise are solvents, ions, and nanoparticles.
[0427] In the context of the present invention, the term "angular filtration" refers to a filtration process where the inflow and the direction of the filtration flow are at an angle between 90 and 180 degrees, preferably between 100 and 170 degrees.
[0429] In the context of the present invention, the terms "tangential flow filtration" or "cross flow filtration" refer to a filtration in which the inflow and the filtration flow direction form an angle of about 90 degrees.
[0431] In a particular embodiment, the purification process of step (iv) of the method for the preparation of zero valence transition metal nanowires defined above further comprises a purified suspension comprising zero valence transition metal nanowires, preferably silver nanowires.
[0433] In a particular embodiment, the purification process of step (iv) of the method for the preparation of zero valence transition metal nanowires defined above further comprises a purified suspension comprising zero valence transition metal nanowires and valence transition metal nanoparticles. zero, where the weight percent of the zero valence transition metal nanoparticles is less than 20%, preferably less than 10%, more preferably less than 5%, still more preferably less than 1%.
[0435] Without wishing to be bound by any particular theory, the present inventors believe that the purification process of the present invention makes it possible to obtain a suspension of zero valence transition metal nanowires with a lower percentage by weight of nanoparticles. In particular, the present inventors have surprisingly discovered that the purification step of the method for the preparation of zero valence transition metal nanowires of the present invention gives rise to highly purified zero valence transition metal nanowires without causing aggregations or damage to the structure of zero valence transition metal nanowires. Furthermore, the purification process of the present invention is environmentally friendly and suitable for large-scale purification processes. Furthermore, the purification process of the present invention allows the use of durable and long-lasting filters.
[0437] In a particular embodiment, the method for the preparation of zero valence transition metal nanowires defined above further comprises diluting the suspension comprising the zero valence transition metal nanowires resulting from step (iii) to form a dilute suspension comprising zero valence transition metal nanowires, preferably diluting the suspension resulting from step (iii) 20 times to form a dilute suspension comprising zero valence transition metal nanowires, more preferably diluting the suspension resulting from step (iii) 40 times to form a dilute suspension comprising zero valence transition metal nanowires.
[0438] In a particular embodiment, the method for the preparation of zero valence transition metal nanowires defined above further comprises drying the purified suspension of zero valence transition metal nanowires from step (iv) to obtain zero valence transition metal nanowires.
[0440] Furthermore, the purified and dried zero valence transition metal nanowires obtained by the method defined above can be easily redispersed, for example, by gentle mechanical stirring, in water and / or in organic solvents. The resulting redispersions of the purified zero valence transition metal nanowires show great stability, so it is not necessary to add surfactants or stabilizers that produce unwanted residues. Some non-limiting examples of redispersing solvents are, among others, water and alcohols such as methanol, ethanol, isopropanol, and the like.
[0442] The resulting redispersions in suitable solvents are stable for characterizations and storage, but also for the preparation of conductive ink compositions.
[0444] In a particular embodiment, the tangential flow filtration of step (c) of the purification process of step (iv) of the method for the preparation of zero valence transition metal nanowires defined above further comprises the recirculation of the inflow comprising nanowires zero valence transition metals.
[0446] In the context of the present invention, the term "recirculating" refers to continuously circulating the inflow comprising zero valence transition metal nanowires during tangential flow filtration.
[0448] In a particular embodiment, the tangential flow filtration of step (c) of the purification process of step (iv) of the method for the preparation of zero valence transition metal nanowires defined above further comprises the recirculation of the inflow comprising nanowires zero valence transition metals at a flow rate range between 10 and 2500 ml / min per filter, preferably between 25 and 1500 ml / min per filter, more preferably between 50 and 750 ml / min per filter.
[0449] In a particular embodiment, the tangential flow filtration of step (c) of the purification process of step (iv) of the method for the preparation of zero valence transition metal nanowires defined above further comprises the recirculation of the inflow comprising nanowires zero valence transition metals for a period between 1 and 200 hours, preferably between 5 and 150 hours, still more preferably between 6 and 100 hours.
[0451] In a particular embodiment, the purification process of step (iv) of the method for the preparation of zero valence transition metal nanowires defined above further comprises a filtration unit (F) comprising:
[0452] to. a filter receptacle comprising an inlet, a first outlet, and a second outlet;
[0453] b. at least one cylindrical filter housed within the receptacle between the inlet and the first and second outlets; Y
[0454] where the input and the two outputs communicate fluidly.
[0456] In a more particular embodiment, the purification process of step (iv) of the method for the preparation of zero valence transition metal nanowires defined above further comprises a filtration unit (F) comprising:
[0457] to. a filter receptacle comprising an inlet (10), a first outlet (20), and a second outlet (30);
[0458] b. at least one cylindrical filter housed within the receptacle between the inlet (10) and the first (20) and the second outlets (30); Y
[0459] where the inlet (10) and the two outlets (20) and (30) communicate fluidly, preferably as shown in Figure 2.
[0461] In a particular embodiment, the cylindrical filter is at least 2 filters in parallel housed within the receptacle of the filtration unit, preferably at least 5 filters, more preferably at least 10 filters.
[0463] In a particular embodiment, the cylindrical filter of the method for the preparation of zero valence transition metallic nanowires defined above comprises at least one material selected from ceramics, metals and alloys such as stainless steel, preferably alloys such as stainless steel, plus preferably steel stainless.
[0465] In a particular embodiment, the at least one cylindrical filter of the method for the preparation of transition metal nanowires of zero valence defined above is a stainless steel filter.
[0467] In a particular embodiment, the at least one cylindrical filter of the method for the preparation of zero valence transition metal nanowires defined above comprises a metal mesh, preferably a stainless steel metal mesh.
[0469] In a particular embodiment, the at least one cylindrical filter of the method for the preparation of zero valence transition metal nanowires defined above has a pore diameter between 0.01 and 10 microns, preferably between 0.1 and 5 microns, more preferably between 0.5 and 3 microns.
[0471] The filter device for the preparation of zero valence transition metal nanowires defined above is easy to clean, withstands various uses and prevents aggregation of the zero valence transition metal nanowires.
[0473] Zero valence transition metal nanowires.
[0475] According to a disclosure, the invention describes the zero valence transition metal nanowires that can be obtained by the method for the preparation of zero valence transition metal nanowires defined above in any of its embodiments.
[0477] In a particular embodiment, the zero valence transition metal nanowires defined above are crystalline silver nanowires.
[0479] In a particular embodiment, the zero valence transition metal nanowires defined above have a diameter less than 70 nm and an aspect ratio greater than 500; preferably the zero valence transition metal nanowires defined above have a diameter less than 50 nm and an aspect ratio greater than 700, more preferably the zero valence transition metal nanowires defined above have a diameter less than 30 nm and an aspect ratio greater than 1000.
[0481] Conductive ink composition.
[0483] According to a disclosure, the invention describes a conductive ink composition comprising zero valence transition metal nanowires obtained by the method for the preparation of zero valence transition metal nanowires defined above in any of its embodiments.
[0485] Furthermore, the good wetting or drying of the purified suspension comprising the zero valence transition metal nanowires defined above allows them to be used to coat different substrates.
[0487] In a particular embodiment, the conductive ink composition with zero valence transition metallic nanowires is capable of coating a surface.
[0489] In a particular embodiment, the conductive ink composition defined above further comprises a solvent.
[0491] Applications.
[0493] According to one disclosure, the invention describes the use of the above defined zero valence transition metal nanowires in optoelectronics, biochemical detection, biomedical imaging, surface enhanced Raman scattering field, catalysis, electromagnetic interference shielding and antimicrobial applications.
[0495] Reactor furnace.
[0496] According to a further aspect, the invention is directed to a reactor furnace for the preparation of transition metal nanowires of zero valence, comprising:
[0497] - a thermally insulated chamber, comprising at least one inlet and a temperature control means;
[0498] - a conveyor adapted to carry out a translation movement along a path;
[0499] - at least one turntable located on the conveyor; Y
[0500] - at least one reactor located on the rotating platform, wherein said at least one reactor comprises a longitudinal axis X-X '; Y
[0501] wherein said rotating platform is adapted to effect a rotational movement around the longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X '.
[0503] A particular embodiment of the present invention is directed to a reactor furnace (1) for the preparation of zero valence transition metal nanowires, comprising:
[0504] - a thermally insulated chamber (1.1), comprising at least one inlet (1.2) and a temperature control means;
[0505] - a conveyor (2) adapted to carry out a translation movement along a path;
[0506] - at least one rotating platform (3) located on the conveyor (2); Y
[0507] - at least one reactor (4) located on the rotating platform (3), wherein said at least one reactor (4) comprises a longitudinal axis X-X '; Y
[0508] wherein said rotating platform (3) is adapted to effect a rotational movement around the longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X ', preferably as shown in Figure 1 .
[0510] In a particular embodiment, the reactor furnace of the present invention is for the preparation of the zero valence transition metal nanowires of the present invention described above.
[0512] Filtration unit.
[0514] According to a disclosure, the invention describes a filtration unit (F) comprising:
[0515] to. a filter receptacle comprising an inlet, a first outlet, and a second outlet;
[0516] b. at least one cylindrical filter housed within the receptacle between the inlet and the first and second outlets; Y
[0517] where the input and the two outputs communicate fluidly.
[0519] A particular embodiment of the present invention is directed to a filtration unit (F) comprising:
[0520] c. a filter receptacle comprising an inlet (10), a first outlet (20), and a second outlet (30);
[0521] d. at least one cylindrical filter housed within the receptacle between the inlet (10) and the first (20) and the second outlets (30); Y
[0522] where the inlet (10) and the two outlets (20) and (30) communicate fluidly, preferably as shown in Figure 2.
[0524] In a particular embodiment, the at least one cylindrical filter further comprises a stainless steel wire mesh, wherein said wire mesh has a pore diameter range between 0.01 and 10 microns.
[0526] In a particular embodiment, the filtration unit of the present invention is for the preparation of the zero valence transition metal nanowires of the present invention described above.
[0528] The reactor furnace for the preparation of zero valence transition metal nanowires has all the advantages and characteristics defined above for the method of preparation of the zero valence transition metal nanowires of the present invention in any of its embodiments.
[0530] EXAMPLES
[0532] The invention is illustrated by the following examples, which in no way limit the scope of the invention.
[0534] Example 1: Preparation of silver nanowires using three different ovens.
[0536] The following solutions were prepared independently:
[0537] - Solution of 1.27 mg / ml of KBr in ethylene glycol (EG) (KBr stock solution);
[0538] - Solution of 2.06 mg / ml of tetrapropylammonium chloride (TPA-C) in EG (TPA-C stock solution);
[0539] - 8.83 mg / ml solution of polyvinylpyrrolidone (PVP) in EG (PVP solution); ^{and - AgNO 3} solution of 10.71 mg / ml in EG (AgNO ³ solution).
[0541] Procedure: The PVP solution described above was heated to 110 ° C with vigorous stirring using a 500 ml round bottom flask in an oil bath with a temperature probe. Once the temperature had stabilized at 110 ° C, the solution was kept at that temperature for 2 hours and then it was allowed to cool down to room temperature. Subsequently, a mixture of TPA-C and KBr stock solutions with a 1.65 mole fraction of TPA-C / KBr was added, and then the AgNO3 solution was added (in that order) to the PVP solution, stirring it at temperature. environment to form a reaction mixture. The reaction mixture was stirred for a further 5 min at room temperature and divided equally among 15 solvothermal reactors (PTFE-lined stainless steel reactors) of 50 ml capacity each.
[0543] Next, three different ovens were used to heat the reactors containing the same reaction mixture. These ovens were as follows:
[0545] to. a convection oven, where thermal energy was transferred by convection and radiation to the chamber load; the convection oven used was a Nahita ™ 631 PLUS series;
[0547] b. an air circulation furnace, where thermal energy was transferred by convection and radiation to the chamber load; and a fan accelerated heat transfer (convection) and air exchange, and distributed the temperature evenly within the chamber; the air circulation oven used was a POL-EKO ™, model SLW 400; Y
[0549] c. a reactor furnace (Figure 1) composed of a conveyor that followed an elliptical curved path of 9 m and 15 circular rotating platforms of 37 cm in diameter each, located on the conveyor. The platforms could carry from 1 to 5 reactors, depending on the dimensions of the reactors and the platform. These reactors were cylindrical solvothermic reactors and comprised a longitudinal axis of rotation defined as X-X 'that passed through the center of the cylinder. The reactors could be placed and fixed in the center of said turntable or at some distance from the center of the platform (Figures 1b and 1c). Therefore, each of the platforms could rotate around said axis of rotation X X 'or around an axis of rotation W-W' parallel to said axis of rotation X-X '(Figure 1c). When several reactors were placed at a certain distance from the center, this distance was the same in all of them. This oven also comprises a thermally insulated chamber with temperature control means. Thermal energy is transferred by convection and radiation to the thermally insulated chamber, and a fan accelerates heat transfer (convection) and air exchange and distributes the temperature evenly within the chamber.
[0551] The 15 reactors containing the same amount of reaction mixture were heated as follows:
[0552] - 5 reactors were placed in different positions inside the convection oven preheated to 145 ° C, and the temperature was maintained for 7 hours;
[0553] - 5 reactors were placed in different positions inside the air circulation furnace and heated from room temperature to 180 ° C in 30 min, kept at 180 ° C for 60 min, heated from 160 ° C to 180 ° C in 30 min and kept at 160 ° C for 5 hours; Y
[0554] - 5 reactors were placed in the reactor furnace; each reactor was placed in the center of a different platform of the reactor furnace; the reactors were then warmed up from room temperature to 180 ° C in 30 min, held at 180 ° C for 60 min, heated from 160 ° C to 180 ° C in 30 min, and held at 160 ° C for 5 hours; Y
[0555] During the heating steps, the conveyor moved following an elliptical path at a constant frequency of 1 rpm and, therefore, the reactors described a translational movement following an elliptical path at a constant frequency of 1 rpm.
[0557] After cooling to room temperature, the obtained suspensions (comprising nanowires, nanoparticles, unreacted salts, ions and unreacted polymer) were purified using the filtration unit of Figure 2 as follows. A volume of 1 ml of the suspension was diluted and filtered by angle filtration as described in Example 5, thus obtaining a retentate. The retentate was then dispersed in a solvent to form an inflow with nanowires. Subsequently, a tangential filtration step was carried out as described in Example 5, where said flow of Inlet was recirculated through the filtration unit (F) of Figure 2 at a flow rate of 65 ml / min for 4 h. During recirculation, the inflow composed of nanowires and nanoparticles traveled tangentially along the surface of the stainless steel filter of the filtration unit. The nanoparticles present in said inflow were selectively separated and removed from the product comprising the nanowires by means of said filter. Finally, the excess solvent was removed from the dispersion that comprised the nanowires, and the product obtained that comprised the silver nanowires was dispersed and kept in deionized water, alcohol or a mixture of both for storage or later characterization.
[0559] Table 1 shows the characteristics of the silver nanowires obtained in the products.
[0564] The nanowires obtained with the reactor furnace had uniform diameters, lengths and yields in all the samples obtained from the five reactors. However, the products obtained from a convection oven and an air oven differed among the 5 reactors placed in different positions in said ovens. Therefore, the ranges of the diameters and lengths of these products were wider than those of the products obtained in the reactor furnace (see Table 1).
[0566] Example 2: Synthesis of uniform silver nanowires with different diameters.
[0568] Uniform silver nanowires with different mean diameters were synthesized through four different reactions called reaction 1 to 4 as follows:
[0570] Reaction 1 (silver nanowires with a mean diameter of 17 ± 3 nm):
[0571] The following solutions were prepared independently:
[0572] - Solution of 1.20 mg / ml of KBr in EG (KBr stock solution);
[0573] - Solution of 5.00 mg / ml of TPA-C in EG (TPA-C stock solution);
[0574] - 8.83 mg / ml solution of PVP powder in EG (PVP solution); Y
[0575] - Solution of 10.71 mg / ml of AgNO ³ in EG (AgNO ³ solution).
[0577] Procedure: The PVP solution was heated to 110 ° C with vigorous stirring in a 50 ml round bottom flask equipped with a silicone oil bath and a temperature probe, and was kept at that temperature for 2 hours. The oil bath was subsequently removed and the reaction was allowed to cool to room temperature. The PVP solution was then transferred to a 50 ml solvothermal reactor.
[0579] A mixture of TPA-C and KBr stock solutions with a 1.61 mole fraction of TPA-C / KBr was quickly added to the PVP solution with stirring. ^{The AgNO 3} solution was then added to the mixture and stirred for 5 min to form a reaction mixture.
[0581] The reactor furnace was used to heat the solvothermal reactor. The reactor with the reaction mixture was placed in the center of a platform of the reactor furnace; they were heated to 135 ° C and kept at that temperature for 7 h; during heating, the reactors described a translational movement following an elliptical path at 1 rpm.
[0583] After allowing the reaction mixture to cool to room temperature, the product obtained was purified as described in Example 1, and the solids obtained with silver nanowires were dispersed and kept in deionized water, in alcohol or in a mixture of both, for its conservation or later characterization.
[0585] Reaction 2 (silver nanowires with a mean diameter of 30 ± 7 nm):
[0586] This example followed the same procedure explained in reaction 1. The only differences introduced in the process were the following:
[0587] The following solutions were prepared independently:
[0588] - Solution of 1.96 mg / ml of KBr in EG (the KBr stock solution); Y
[0589] - Solution of 4.20 mg / ml of TPA-C in EG (the stock solution of TPA-C).
[0590] A mixture with a 2.33 mole fraction of TPA-C / KBr obtained from the solutions described above was quickly added to the PVP solution. Likewise, the reactors that containing the reaction mixture were heated to 160 ° C and kept at that temperature for 7 h.
[0592] Reaction 3 (silver nanowires with a mean diameter of 70 ± 12 nm):
[0593] This example followed the same procedure explained in reaction 1.
[0594] The only differences introduced in the process were the following:
[0595] Only NaCl was used. A solution of 1.51 mg / ml of NaCl in EG (the NaCl stock solution) was prepared and 97 µl of said solution was added to the reactor containing the reaction mixture. The reactors containing the reaction mixture were heated to 160 ° C and kept at that temperature for 7 h.
[0597] Reaction 4 (silver nanowires with a mean diameter of 100 ± 20 nm):
[0599] This example followed the same procedure explained in reaction 1.
[0600] The only differences introduced in the process were the following:
[0602] Only BMIM-Cl was used. A 4.73 mg / ml solution of BMIM-Cl in EG (the BMIM-Cl stock solution) was prepared and 108 µl of said solution was added to the reactor containing the reaction mixture. The reactors containing the reaction mixture were heated to 160 ° C and kept at that temperature for 7 h.
[0604] Table 2 shows the characteristics of the silver nanowires obtained by reactions 1 to 4 in a reactor furnace. The results showed that by simple modifications of the method for obtaining silver nanowires in a reactor furnace, such as the salts used and the temperature and heating time, the characteristics of the nanowires, such as the mean diameter or the interval, can be modified. of lengths. In particular, the products obtained with reactions 1 to 4 show that by changing the salts used, nanowires with mean diameters or ranges of different lengths can be obtained.
[0609] Example 3: Extension of the synthesis of silver nanowires in different reactors
[0611] The synthesis of uniform silver nanowires has been expanded using different types of reactors: a 50 ml PTFE lined stainless steel solvothermic reactor, a 1 L PTFE lined stainless steel solvothermal reactor and a 1 L lined aluminum reactor made of PTFE.
[0613] The following solutions were prepared independently:
[0614] - Solution of 3.72 mg / ml of NaCl in EG (NaCl stock solution);
[0615] - 8.83 mg / ml solution of PVP in EG (PVP solution); Y
[0616] - Solution of 10.71 mg / ml of AgNO ³ in EG (AgNO ³ solution).
[0618] Reaction 5:
[0619] The above-described PVP solution was heated to 110 ° C with vigorous stirring using a 2L round bottom flask, and once the temperature reached 110 ° C, it was kept at that temperature for 2 hours. Subsequently, the reaction was allowed to cool to room temperature. Next, 13.76 ml of NaCl stock solution was added rapidly to the PVP solution with stirring, and then the AgNO ³ solution was also rapidly added with vigorous stirring at room temperature to form a reaction mixture. Subsequently, 35 ml of the reaction mixture was poured into a 50 ml stainless steel solvothermal reactor lined with PTFE. Furthermore, 700 ml batches of the same reaction mixture were added to a 1 L PTFE lined stainless steel solvothermal reactor and a 1 L PTFE lined aluminum reactor, respectively. Said reactors were heated to 160 ° C and kept at that temperature for 7 hours in the reactor furnace; during heating, the conveyor moved following an elliptical path at a constant frequency of 1 rpm and, therefore, the reactors described a translational motion following an elliptical path at a constant frequency of 1 rpm.
[0621] After allowing it to cool to room temperature, the reaction mixture was purified as described in Example 1, and the solids obtained with silver nanowires were dispersed and kept in deionized water, in alcohol or in a mixture of both, for their conservation or later characterization.
[0622] Table 3 shows the yields and characteristics of the products obtained using different reactors.
[0624] When using a 1L stainless steel reactor lined with PTFE, no nanowires are produced. However, using the designed 1L aluminum reactor lined with PTFE under the same conditions (temperature and time), new nanowires of different diameter, length and performance can be obtained. In addition, using the PTFE-coated aluminum reactor, 20 times more silver nanowires have been obtained with similar ranges of lengths and diameters and with a similar performance adjusting the temperature program used in the reactor furnace as follows: heating it from room temperature to 180 ° C in 30 min, keeping it at 180 ° C for 60 min, heating it from 180 ° C to 160 ° C in 30 min and keeping it at 160 ° C for 5 hours.
[0626] Table 3 shows the characteristics of the silver nanowires (yield, mean ranges of diameters and lengths) that were obtained in the different reactors (size and materials). The results showed that the method is susceptible to expansion.
[0628]
[0629]
[0632] Example 4: Effect of translational and rotational movements performed at different frequencies on silver nanowires
[0634] The following solutions were prepared separately:
[0635] - mg / ml NaCl in EG (NaCl stock solution);
[0636] - 8.83 mg / ml solution of PVP in EG (PVP solution); Y
[0637] - Solution of 10.71 mg / ml of AgNO ³ in EG (AgNO ³ solution).
[0639] Reaction 6:
[0640] The above-described PVP solution was heated to 110 ° C with vigorous stirring in a 100 ml round bottom flask (equipped with a silicone oil bath and a temperature probe), and kept at that temperature for 2 hours. The oil bath was subsequently removed and the reaction was allowed to cool to room temperature. Then 0.294 ml of NaCl stock solution was quickly added with stirring. Next, the AgNO ³ solution, prepared by dissolving AgNO ³ salt in EG in a 50 ml round bottom flask for 30 min with high speed stirring, was rapidly added to the mixture and kept stirring vigorously for 5 minutes at room temperature .
[0642] Two 50 ml solvothermic reactors were then filled with the reaction mixture. Said reactors containing the reaction mixture were placed in the reactor furnace described above, heated to 160 ° C and kept at that temperature for 7 h.
[0644] During the 7 hours of heating at 160 ° C, the first reactor was kept in the same place. The second reactor was placed on the platform 20 cm from the center of the platform. Therefore, during heating, said second reactor carried out the following simultaneous movements: a translation movement following an elliptical path at a frequency constant of 1 rpm and a rotational movement about an axis of rotation WW parallel to the longitudinal axis of the reactor X-X 'at a constant frequency of 10 rpm. Said axis of rotation W-W 'passed through the center of the platform, so that the platform was rotating around said axis of rotation WW during heating.
[0646] After allowing it to cool to room temperature, the reaction mixture was purified as described in Example 1, and the products obtained with silver nanowires were dispersed and kept in deionized water, in alcohol or in a mixture of both, for their conservation or later characterization.
[0648] Reaction 7:
[0649] This example followed the same procedure explained in reaction 6, but with a rotational movement around the axis of rotation W-W 'parallel to the longitudinal axis of the reactor X-X' at a constant frequency of 50 rpm.
[0651] Reaction 8:
[0652] This example followed the same procedure explained in reaction 6, but with a rotational movement around the axis of rotation W-W 'parallel to the longitudinal axis of the reactor X-X' at a constant frequency of 100 rpm.
[0654] Reaction 9:
[0655] This example followed the same procedure as explained in reaction 6. However, in this example, the second reactor was placed in the center of the platform. Therefore, during heating, said second reactor carried out the following simultaneous movements: a translation movement following an elliptical path at a constant frequency of 1 rpm and a rotational movement around the longitudinal axis of the reactor X X 'at a constant frequency 10 rpm. Therefore, said axis of rotation X-X 'passed through the center of the platform; the platform was rotating around said axis of rotation X-X 'during heating at a constant frequency of 10 rpm.
[0657] Reaction 10:
[0658] This example followed the same procedure explained in reaction 9, but with a rotational movement around the longitudinal axis of the reactor (X-X ') at a constant frequency of 50 rpm.
[0660] Reaction 11:
[0661] This example followed the same procedure explained in reaction 9, but with a rotational movement around the longitudinal axis of the reactor (X-X ') at a constant frequency of 100 rpm.
[0663] Table 4 shows the effect of the changes introduced in the rpm of the rotational movement on the characteristics of the silver nanowires (diameter, length and yield).
[0665] The results showed that the changes introduced in the frequency of the rotational movement carried out around the longitudinal axis of the reactor X-X 'at a constant frequency (that is, the reactor is placed in the center of the platform and the axis of rotation X- X 'passes through the center of said platform) can considerably reduce the length ranges of the silver nanowires. In this way, more uniform nanowires are produced.
[0667] In addition, the changes introduced in the frequency of the rotational movement performed around an axis of rotation W-W 'parallel to the longitudinal axis of the reactor X-X' at a constant frequency (that is, the reactor is placed on the platform at a a certain distance from the center of said platform and the axis of rotation W-W 'passes through the center of said platform) can significantly affect the length, diameter and performance of silver nanowire products. In particular, when the frequency of the rotary movement carried out around an axis of rotation W-W 'parallel to the longitudinal axis of the reactor X-X' at a constant frequency was around 50 rpm, the maximum performance values were obtained and lengths in the nanowires.
[0669]
[0670]
[0673] Example 5: Purification
[0675] The products of reactions 1-3 were purified and their characteristics were studied, in particular the amount of nanoparticles present in the products.
[0677] Figure 2 shows a diagram of the filtration unit. The filtration unit used in the examples comprised a filter receptacle (220mm long and 20mm outer diameter) with an inlet, a first outlet, and a second outlet. Inside the filtration unit was a cylindrical stainless steel wire mesh filter with a pore diameter of 2 microns. Said filter was housed within the receptacle between the inlet and the first and second outlets. In addition, the filtration unit allowed fluid communication between the inlet and the two outlets.
[0679] The purification process was as follows. 1 ml of the reaction mixture obtained from reaction 1 (a mixture comprising nanowires, nanoparticles, unreacted salts, ions and unreacted polymer) was purified.
[0681] Said 1 ml was diluted twice with deionized water to form a suspension. Then, angular filtration of the suspension was performed using the filtration unit described above to obtain a retentate comprising nanowires. The outlet of the filtration unit was closed during the angular filtration step. Therefore, the fluid circulated from the inlet to the outlet passing through the steel filter. stainless. Most of the nanowires, a few large particles, some of the unreacted ethylene glycol and excess salts, among other things, were retained forming a filter cake (or retained). To remove excess ethylene glycol and salts, a few milliliters of deionized water were used to wash said filter cake (or retentate).
[0682] The retentate was then dispersed in deionized water to form an inflow comprising the nanowires, and a tangential filtration step was performed.
[0684] During said tangential filtration step, the inlet and the two outlets of the filtration unit were open. The inflow was diluted using 100 ml of deionized water (ie, with a dilution factor of 100) and recirculated through the filter socket at a flow rate of 65 ml / min for 180 min. Consequently, the inflow comprising nanowires and nanoparticles traveled tangentially across the filter surface during recirculation. Most of the nanoparticles present in said inflow were selectively separated from the nanowires as they passed through the filter and left the filtration unit through the outlet as a filtration stream.
[0686] Subsequently, the outlet was closed again and all the excess deionized water was removed through the filter and the outlet. The filter cake or purified retentate within the filter comprising the nanowires was then dried by passing N ² gas through it, and then dispersed in different solvents for further characterization and storage.
[0687] The same purification procedure explained above was used for the suspensions obtained from reactions 2 and 3, but using different flow rates and dilution factors: 130 ml / min and 40, and 260 ml / min and 20, respectively.
[0689] Table 5 shows the weight percentage of silver nanoparticles (NPAg) present in the solids obtained by modifying different parameters in the described purification process. It should be noted that these results can be improved by increasing the time or / and the dilution factor of the purification process.
[0691]
[0692]
[0695] Example 6: Characterization of nanowires by SEM and TEM spectroscopy
[0697] The quality and dimensions (mean diameter, length ranges and yield) of the silver nanowires in some of the previous examples were evaluated using scanning electron microscopy (SEM) (Figure 3), transmission electron microscopy (TEM) and through electron diffraction measurements (Figure 4).
[0699] The SEM photomicrographs were taken using a Hitachi model TM3030 benchtop microscope with a magnification range between 15 and 30,000 X. The microscope has a pre-centered cartridge filament as the electron gun and a 4 segment high sensitivity semiconductor BSE detector as the system. single detection. This system operates at room temperature and in ambient air conditions. The photomicrographs were developed using the TM3030 application. Samples for SEM observation were prepared by drop casting on a glass substrate. Figure 3 shows the SEM photomicrographs: Figure 3d, example 2, reaction 1; Figure 3c, example 2, reaction 2; Figure 3b, example 2, reaction 3; and Figure 3a, example 2, reaction 4. In each of the photomicrographs shown in Figure 3, uniform silver nanowires with a diameter similar to each other can be observed.
[0701] Each mean diameter value was calculated from an average of the values obtained by measuring the diameters of more than 100 nanowires using high resolution SEM photomicrographs. Diameter and length ranges were also calculated from the lengths of more than 100 nanowires measured with high resolution SEM photomicrographs. Furthermore, the mass percentage of NPAg in the samples was calculated by measuring the surface of the NPAg and that of the silver nanowires in SEM photomicrographs.
[0703] Silver nanowire dispersions are obtained in water or in a suitable mixture of water and / or organic solvents, such as ethanol, 1-propanol, 2-propanol and methanol, stirring for 10 min. Optical absorption spectroscopy (OAS) was obtained on silver nanowire dispersions using a Perkin Elmer LAMBDA 750 UV / Vis / NIR diode array in a range of 300-800 nm with air as a reference and a resolution of 1 nm. OAS measurements were used to estimate nanowire concentration silver using the Beer-Lambert law, according to the relationship A = £ bc, where A is the absorbance, b [cm] is the length of the light path, c [gL-1] is the scattering concentration of dispersion silver nanowires and £ [Lg ^ .cm'1] is the absorption coefficient. The absorption coefficient £ (Lg ^ .cm'1) was experimentally situated at the maximum peak for each nanowire of mean diameter. The yield (%) of each reaction was calculated by comparing the amount of silver obtained in the final samples of the nanowires with the amount of silver present at the beginning of the reaction.
[0705] TEM photomicrographs were obtained on a JEOL model JEM 2100 transmission electron microscope with an acceleration voltage of 200 KV. The microscope has TEM and STEM modes of operation with a bright field detector, a multi-scan CCD camera, and a XEDS composition analysis mode. EELS analysis was carried out in electron energy loss spectroscopy (EELS), with a point resolution of 2.5A and a goniometer with a ± 30 ° inclination. All TEM samples were prepared by dripping the dispersions onto carbon-coated copper grids.
[0707] Figure 4 shows one of the characterizations of the nanowires obtained in example 2 (reaction 2). Figure 4a shows a TEM photomicrograph of a silver nanowire with a uniform diameter along its length. In a larger magnification, shown in Figure 4b, a PVP layer approximately 1.5 nm thick can be seen covering the surface of the nanowires and two panels of a polygonal nanowire structure. Electron diffraction patterns of an area of silver nanowires attributed to planes (111) and (110) are shown in Figure 4c. In a single crystal this angle is 35 °. The angle between these two areas was less than 30 °, which indicates that the silver nanowires are single twinned crystals. Figure 3d shows the EDX spectrum of silver nanowires, according to which they are made up of pure silver with no salts remaining in their composition.

权利要求:
Claims (15)
[1]
1. A method for the preparation of zero valence transition metal nanowires comprising the following steps:
i) providing a reaction mixture comprising: at least one coating agent, at least one transition metal salt, and at least one polar solvent;
ii) adding the reaction mixture obtained in step (i) to at least one reactor; iii) heating the at least one reactor of step (ii) at a temperature between 30 and 300 ° C for a period between 10 min and 7 days, at a pressure of at least 100 KPa, in a reactor furnace to obtain a suspension comprising zero valence transition metal nanowires;
wherein said at least one reactor comprises a longitudinal axis X-X 'and performs at least one of the following movements:
- a translational motion along a path, and
- a rotational movement around the longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X '; Y
iv) optionally carry out a purification process of the suspension obtained in step (iii) to achieve a purified suspension comprising zero valence transition metal nanowires.
[2]
2. The method for the preparation of zero valence transition metal nanowires according to claim 1, wherein the reaction mixture obtained in step (i) comprises a molar fraction coating agent: transition metal salt between 0.1 and 10 .
[3]
3. The method for the preparation of zero valence transition metal nanowires according to any of the preceding claims, wherein said at least one reactor of step (iii) performs at least one rotational movement around the longitudinal axis X-X 'or around of an axis W-W 'parallel to said longitudinal axis X-X'.
[4]
4. The method for the preparation of zero valence transition metal nanowires according to any of the preceding claims, wherein said reactor of step (iii) simultaneously performs a rotational movement around the longitudinal axis X-X 'or around an axis W -W 'parallel to said longitudinal axis X-X', and a translation movement that follows a path.
[5]
5. The method for the preparation of zero valence transition metal nanowires according to any of the preceding claims, where either the translational movement following a closed path or the rotational movement of step (iii) are carried out at a constant frequency of between 1 and 100 rpm.
[6]
6. The method for the preparation of zero valence transition metal nanowires according to any of the preceding claims, wherein the reactor furnace comprises:
- a thermally insulated chamber, comprising at least one inlet and a temperature control means;
- a conveyor adapted to carry out the translation movement along a path; Y
- at least one rotating platform located on the conveyor, where said rotating platform is adapted to effect the rotational movement around the longitudinal axis X-X 'or around the axis W-W' parallel to said longitudinal axis X-X '; Y
where the at least one reactor is located on the turntable.
[7]
7. The method for the preparation of zero valence transition metal nanowires according to any of the preceding claims, wherein the at least one reactor is at least two reactors, and wherein said at least two reactors perform the translation movement following a path and the rotational movement around an axis W-W 'parallel to the aforementioned longitudinal axis X-X'.
[8]
8. The method for the preparation of zero valence transition metal nanowires according to any of the preceding claims, wherein the purification process of step (iv) comprises:
to. performing an angular filtration of the suspension from step (iv) to obtain a retentate comprising zero valence transition metal nanowires;
b. dispersing the retentate obtained in step (a) in a solvent to form an inflow comprising zero valence transition metal nanowires; and c. performing a tangential flow filtration of the inflow obtained in step (b) to obtain a purified suspension comprising zero valence transition metal nanowires; Y
d. optionally, repeat steps (a) to (c).
[9]
9. The method for the preparation of zero valence transition metal nanowires according to claim 8, wherein the tangential flow filtration of step (c) further comprises the recirculation of the inflow comprising zero valence transition metal nanowires.
[10]
The method for the preparation of zero valence transition metal nanowires according to any of the preceding claims, wherein the purification process of step (iv) comprises a filtration unit (F) comprising:
to. a filter receptacle comprising an inlet, a first outlet, and a second outlet;
b. at least one cylindrical filter housed within the receptacle between the inlet and the first and second outlets; Y
where the input and the two outputs communicate fluidly.
[11]
The method for the preparation of zero valence transition metal nanowires according to any of the preceding claims, wherein the zero valence transition metal nanowires are crystalline silver nanowires.
[12]
12. A reactor furnace for the method of preparing zero valence transition metal nanowires according to claims 1-11, comprising:
- a thermally insulated chamber, comprising at least one inlet and a temperature control means;
- a conveyor adapted to carry out a translation movement along a path;
- at least one turntable located on the conveyor; Y
- at least one reactor located on the rotating platform, wherein said at least one reactor comprises a longitudinal axis X-X '; Y
wherein said rotating platform is adapted to effect a rotational movement around the longitudinal axis X-X 'or around an axis W-W' parallel to said longitudinal axis X-X '.
[13]
The reactor furnace of claim 12 or the method according to any of claims 1-11; where the at least one reactor is suitable to maintain the pressure between 1 and 500 kPa; preferably at least one solvothermal or hydrothermal reactor.
[14]
14. The reactor furnace of any of claims 12 or 13, wherein the turntable located on the conveyor comprises at least one reactor support.
[15]
15. The reactor furnace of any of claims 12-14, wherein the turntable on the conveyor comprises a suitable reactor support to maintain a pressure between 1 and 500 kPa.

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引用文献:

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公开号 | 申请日 | 公开日 | 申请人 | 专利标题

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法律状态:
2021-03-04| BA2A| Patent application published|Ref document number: 2809623 Country of ref document: ES Kind code of ref document: A2 Effective date: 20210304 |

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优先权:

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申请号 | 申请日 | 专利标题

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EP18382414.3A|EP3581296A1|2018-06-12|2018-06-12|Method for preparation of metal nanowires|

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PCT/EP2019/065394|WO2019238781A1|2018-06-12|2019-06-12|Method for preparation of metal nanowires|

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