Process For Producing Silver Nanowires

Abstract

Described are processes for the production of silver nanowires comprising forming a reaction mixture including a polyol, an organic chemical adsorbed to a silver surface, a chemical to form a halide and/or pseudohalide and a chemical which forms a redox pair. A silver salt is added to the reaction mixture and temperature is maintained to form the silver nanowires.

1 . A process for the production of silver nanowires, the process comprising:
 a) providing of a reaction mixture comprising
 a polyol, 
 an organic chemical adsorbed on to a silver surface, 
 a chemical which forms one or more of a halide and a pseudohalide, wherein the chemical which forms a halide is a salt of one or more of the halides Cl − , Br −  and I −  and wherein the chemical which forms a pseudohalide is a salt of one or more of the pseudohalides SCN − , CN − , OCN −  and CNO − , 
 a chemical which forms a redox pair, the chemical selected from the group consisting of bromine, iodine, vanadium and mixtures thereof, 
   b) adding a silver salt in an amount such that the concentration of silver in the reaction mixture is at least 0.5 wt. %, based on the total weight of the reaction mixture, the silver salt being added at a temperature of the reaction mixture of at least 100° C., and   c) maintaining the temperature of the reaction mixture of at least 100° C. for the duration of the reaction.   
     
     
         2 . The process according to  claim 1 , wherein the silver salt is added in an amount such that the concentration of silver in the reaction mixture is at least 1.0 wt. %, based on the total weight of the reaction mixture. 
     
     
         3 . The process of  claim 1 , wherein the reaction mixture comprises one or more of the chemical which forms the halide and the chemical which forms the pseudohalide in an amount such that the concentration of the halide and/or of the pseudohalide in the reaction mixture is in a range of from 5 ppm to 2,000 ppm. 
     
     
         4 . The process of  claim 1 , wherein the chemical which forms the halide comprises one or more of NaCl, NaBr, NaI, KCl, KBr and KI. 
     
     
         5 . The process of  claim 1 , wherein the chemical which forms the pseudohalide comprises one or more of NaSCN and KSCN. 
     
     
         6 . The process of  claim 1 , wherein the reaction mixture provided in step a) additionally comprises an iron salt, the iron salt forming an Fe(II)/Fe(III) redox pair. 
     
     
         7 . The process of  claim 1 , wherein the reaction mixture provided in step a) additionally comprises a copper salt, the copper salt forming a redox pair. 
     
     
         8 . The process of  claim 1 , wherein the chemical which forms a redox pair comprises one or more of elemental vanadium, a vanadium oxide, a vanadium hydroxide, a vanadium sulphate, a vanadium nitrate, a vanadium chloride and mixtures of these compounds. 
     
     
         9 . The process of  claim 8 , wherein the redox pair comprises one or more of Br − /Br 2 /BrO 3   − , I − /I 2 /IO 3   −  and/or V(0)/V(II)/V(III)/V(IV)/V(V). 
     
     
         10 . The process of  claim 1 , wherein the concentration in the reaction mixture of the chemical which forms a redox pair is in a range of from 5 ppm to 2,000 ppm. 
     
     
         11 . The process of  claim 1 , wherein the reaction mixture provided in step a) additionally comprises at least one inorganic or organic acid. 
     
     
         12 . The process of  claim 11 , wherein the acid comprises one or more of HCl, HBr, HI and HNO 3 . 
     
     
         13 . The process of  claim 11 , wherein the addition of the acid takes place in an amount such that the concentration of acid in the reaction mixture is in a range of from 0.01 wt. % to 2.0 wt. %, based on the total weight of the reaction mixture. 
     
     
         14 . The process of  claim 1 , wherein the silver salt is added at a temperature of the reaction mixture of at least 145° C. 
     
     
         15 . The process of  claim 1 , wherein in step c) the temperature of the reaction mixture of at least 145° C. is maintained for the duration of the reaction. 
     
     
         16 . The process of  claim 1 , wherein after step c) step
 d) isolating silver nanowires from the reaction mixture,   wherein a suitable solvent is added for isolation of the silver nanowires from the reaction mixture and the supernatant is then decanted off.   
     
     
         17 . The process of  claim 16 , wherein after step c) and before step d) step
 c 1 ) cooling the reaction mixture
 to room temperature. 
   
     
     
         18 . A process for the production of silver nanowires, the process comprising:
 preparing a reaction mixture comprising a polyol, an organic chemical adsorbed on to a silver surface, a chemical which forms one or more of a halide and a pseudohalide, a chemical which forms a redox pair and at least one of an inorganic acid and an organic acid, wherein the chemical which forms a halide is a salt of one or more of the halides Cl − , Br −  and I −  and the chemical which forms a pseudohalide is a salt of one or more of the pseudohalides SCN − , CN − , OCN −  and CNO −  and is present in the range of about 5 ppm to about 2000 ppm and wherein the chemical which forms a redox pair is selected from the group consisting of bromine, iodine, vanadium and mixtures thereof;   adding a silver salt to the reaction mixture at a temperature of at least 100° C., the silver salt present in a concentration of at least 0.5 wt. % based on the total weight of the reaction mixture;   maintaining the reaction mixture at a temperature of at least 100° C. for the duration of the reaction to form silver nanowires;   cooling the reaction mixture to about room temperature; and   isolating the silver nanowires from the cool reaction mixture, wherein isolating the silver nanowires comprises adding a suitable solvent to the cool reaction mixture and decanting off a supernatant.