Methods for the production of silver nanowires

Abstract

Embodiments of the present invention are directed to novel methods for the solution-based production of silver nanowires by adaptation of the polyol process. Some embodiments of the present invention can be practiced at lower temperature and/or at higher concentration than previously described methods. In some embodiments reactants are added in solid form rather than in solution. In some embodiments, an acid compound is added to the reaction.

1 : A method for the production of silver nanowires comprising reacting:
 i) at least one polyol;   ii) at least one silver compound capable of producing silver metal when reduced;   iii) at least one organic protective agent (OPA); and   iv) at least one bromide;   as reactants in a reaction at a reaction temperature and under conditions that produce silver nanowire.   
     
     
         2 : The method according to  claim 1 , further comprising at least one chloride as a reactant. 
     
     
         3 : The method of  claim 1 , wherein the polyol is ethylene glycol, glycerol, glucose, diethylene glycol, tri-ethylene glycol, a propylene glycol, a butanediol, a dipropylene glycol or a polyethylene glycol. 
     
     
         4 : The method of  claim 1 , wherein the silver compound is at least one selected from the group consisting of silver nitrate, silver nitrite, silver oxide, silver fluoride, silver hydrogen fluoride, silver carbonate, silver oxalate, silver azide, silver tetrafluoroborate, silver acetate, silver propionate, silver butanoate, silver ethylbutanoate and silver pivalate. 
     
     
         5 : The method of  claim 1 , wherein the organic protective agent (OPA) is at least one selected from the group consisting of poly(vinyl pyrrolidone) (PVP), poly(vinyl alcohol) (PVA), sodium dodecyl sulfate (SDS), laurylamine and hydroxypropyl cellulose. 
     
     
         6 : The method of  claim 1 , wherein the product solution comprises at least 20 weight percent (20 wgt %) silver nanowires. 
     
     
         7 : The method of  claim 1 , wherein the silver nanowires have an aspect ratio of at least 200. 
     
     
         8 : The method of  claim 1 , wherein the organic protective agent (OPA) is added to the reaction in solid form. 
     
     
         9 : The method of  claim 1 , wherein the silver compound is reacted as a silver solution comprising the silver compound in a first portion of the polyol and the organic protective agent is reacted as an OPA solution comprising the organic protective agent in a second portion of the polyol. 
     
     
         10 : The method of  claim 8 , wherein the silver solution and the OPA solution are mixed for reaction with a third portion of the polyol in a reaction vessel. 
     
     
         11 : The method of  claim 1 , further comprising reacting at least one acid compound. 
     
     
         12 : The method of  claim 1 , wherein the reaction produces bulk silver nanowire product having a length weighted average of at least 10 μm. 
     
     
         13 . The method of  claim 1 , wherein the reaction produces bulk silver nanowire product having an aspect ratio weighted average that is at least 125. 
     
     
         14 : The method of  claim 1 , wherein the silver nanowires have an aspect ratio of at least 500. 
     
     
         15 : The method of  claim 1 , wherein the silver nanowires have an aspect ratio of at least 750. 
     
     
         16 : The method of  claim 1 , wherein a weighted average length of the silver nanowires is from 25-30 μm. 
     
     
         17 : The method of  claim 1 , further comprising:
 reacting aa least one compound selected from the group consisting of a compound comprising Fe(II) and/or Fe(III) and an acid compound.   
     
     
         18 : The method of  claim 17  wherein an acid compound is reacted and the acid compound is nitric acid. 
     
     
         19 : The method of  claim 1 , wherein the reaction temperature is within a range from about 130° C. and about 170° C. 
     
     
         20 : A method for the production of silver nanowires, comprising:
 i) mixing as reactants for a reaction:
 a) at least one silver solution comprising at least one silver compound capable of producing silver metal when reduced; 
 b) at least one polyol; 
 c) at least one organic protective agent; and 
 d) at least one bromide; 
   to produce a mixture; and   ii) reacting the mixture at a reaction temperature and under conditions that produce a product solution comprising silver nanowires.   
     
     
         21 : The method according to  claim 20 , further comprising mixing at least one chloride. 
     
     
         22 : The method of  claim 20 , wherein the polyol is selected from the group consisting of ethylene glycol, glycerol, glucose, diethylene glycol, tri-ethylene glycol, a propylene glycol, a butanediol, a dipropylene glycol and a polyethylene glycol. 
     
     
         23 : The method of  claim 20 , wherein the silver compound is selected from the group consisting of silver nitrate, silver nitrite, silver oxide, silver fluoride, silver hydrogen fluoride, silver carbonate, silver oxalate, silver azide, silver tetrafluoroborate, silver acetate, silver propionate, silver butanoate, silver ethylbutanoate and silver pivalate. 
     
     
         24 : The method of  claim 20 , wherein the organic protective agent (OPA) is selected from the group consisting of poly(vinyl pyrrolidone) (PVP), poly(vinyl alcohol) (PVA), sodium dodecyl sulfate (SDS), laurylamine and hydroxypropyl cellulose. 
     
     
         25 : The method of  claim 1 , wherein the method further comprises reacting a compound or compounds selected from the group consisting of:
 ii) at least one compound comprising Fe(II) and/or Fe(III); and   iii) at least one acid compound.   
     
     
         26 : The method of  claim 25 , wherein an acid compound is reacted and the acid compound is nitric acid. 
     
     
         27 : The method of  claim 20  wherein the reaction temperature is in the range from about 130° C. to about 170° C. 
     
     
         28 : A composition for the production of silver nanowires comprising:
 i) at least one polyol;   ii) at least one silver compound capable of producing silver metal when reduced;   iii) at least one organic protective agent (OPA); and   iv) at least one bromide.   
     
     
         29 : The composition according to  claim 28 , further comprising a compound selected from the group consisting of
 i) at least one compound comprising Fe(II) and/or Fe(III); and   ii) at least one acid compound.   
     
     
         30 : The composition according to  claim 29 , wherein the acid compound is present and is nitric acid.