Methods of rapid preparation of silver nanowires with high aspect ratio

Abstract

Disclosed is a method suitable for efficiently producing silver nanowires with high aspect ratio. In this method, silver nanowires with aspect ratio of more than 300 and purity of more than 80% are produced through an acid compound mediated microwave-assisted wet chemistry method. Such silver nanowires are especially suitable for the application in the flexible transparent electrodes, as they can simultaneously improve the electrical conductivity and transparency.

1 . A method of rapid preparation of silver nanowires with high aspect ratio and high purity comprising:
 forming a reaction mixture including silver nitrate, poly(vinyl pyrrolidone) (PVP), acid compound, chloride additives in polyol(s) at a first temperature, then the reaction mixture is heated to second temperature by microwave irradiation, subsequently the reaction mixture was heated to third temperature and maintained for times to form silver nanowires.   
     
     
         2 . The method of  claim 1 , wherein the concentration of the silver nitrate in the solution is in the range of 0.0˜10.15 mol/L 
     
     
         3 . The method of  claim 1 , wherein the ratio of the mass concentration of the PVP to the mass concentration of the silver nitrate in the reaction mixture is in the range of 15:1 to 0.5:1. 
     
     
         4 . The method of  claim 1 , wherein the polyol is ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, or glycerol. 
     
     
         5 . The method of  claim 1 , acid compound refers to hydrochloric acid, nitric acid, the ratio of the acid compounds in the reaction mixture is 0.0005˜0.05 mol/L. 
     
     
         6 . The method of  claim 1 , chloride additive refers to sodium chloride (NaCl), manganese chloride (MnCl 2 ), ferric chloride (FeCl 3 ). 
     
     
         7 . The method of  claim 1 , chloride additive refers to quaternary ammonium chloride by formula NR 4   + Cl − , or quaternary phosphonium chloride by formula PR 4   + Cl − . Each R in the NR 4   + Cl −  and/or PR 4   + Cl −  is the same or different and independently refers to an alkyl, alkenyl, alkynyl, aryl, or aralkyl. 
     
     
         8 . The method of  claim 1 , wherein the ratio of the molar concentration of the chloride additive to the molar concentration of the silver nitrate in the reaction mixture is in the range of 1:10000˜1:25. 
     
     
         9 . The method of  claim 1 , wherein the first temperature is in the range from 10° C. to 50° C., the second temperature is in the range from 100° C. to 170° C., the third temperature is in the range from 100° C. to 170° C. 
     
     
         10 . The method of  claim 1 , wherein the third temperature of the reaction mixture can be obtained by microwave irradiation or furnace or oven, or oil bath or heating mantle. 
     
     
         11 . The method of  claim 1 , wherein the maintenance time of third temperature is in the range from 5 minutes to 24 hours. 
     
     
         12 . The method of  claim 1 , wherein the silver nanowires obtained exhibit aspect ratio equal or greater than 300 and purity equal or greater than 80% 
     
     
         13 . A large-scale rapid preparation of silver nanowires with high aspect ratio. The detailed steps comprise:
 (a) Adding silver nitrate or silver acetate into polyol to form a reactive solution with silver ion, then adding capping agents into this solution to prepare a solution with silver ion.   (b) Adding water soluble halide into polyol and stirring it to form a transparent solution.   (c) Adding the above transparent solution prepared in step2 and acid compounds into reactive solution prepared in step 1 and stirring to form a precursor suspension.   (d) Put the suspension under microwave irradiation for minutes to get silver nanowires; then centrifugalizing and washing them by deionized water or ethanol for several times; re-dispersing in ethanol or deionized water to get the final dispersant.   
     
     
         14 . The method of  claim 13 , wherein Silver nitrate and silver acetate mentioned in step (a) is industrial-grade silver salts and the pureness is above 98%. 
     
     
         15 . The method of  claim 13 , wherein The capping agents mentioned in step (a) is polyvinyl pyrrolidone (PVP), polymerization degree of which is preferable K≧30. 
     
     
         16 . The method of  claim 13 , wherein The polyhydroxy liquid organic compounds mentioned in step (a), is ethylene glycol, glycerol or mixture of ethylene glycol and glycerol. 
     
     
         17 . The method of  claim 13 , wherein The water soluble halide mentioned in step (b), is industrial-grade sodium chloride (NaCl), manganese chloride (MnCl 2 ), ferric chloride(FeCl 3 ), potassium chloride (KCl), magnesium chloride (MgCl 2 ), zinc chloride (ZnCl 2 ), potassium bromide(KBr), sodium bromide(NaBr), cetyltriethyl ammnonium bromide(CTAB) or their mixture. 
     
     
         18 . The method of  claim 13 , wherein The acid compound mentioned in step (c) is highly concentrated HNO3, highly concentrated HCl or highly concentrated H 2 SO 4 . 
     
     
         19 . The method of  claim 13 , wherein The mol concentration of the silver nitrate or silver acetate in the reaction mixture prepared in step (1) is in the range of 0.02˜0.3 mol/L 
     
     
         20 . The method of  claim 13 , wherein The mol ratio between silver salts and the capping agent in the reaction mixture prepared in step (1) is 1:1˜1:6 
     
     
         21 . The method of  claim 13 , wherein The mol ratio between cationic control agent added in step (c) and silver salts is 1:1000˜1:25. 
     
     
         22 . The method of  claim 13 , wherein The acid compound added in step (c) in the reaction mixture is about 0.005˜0.05 mol/L and after its addition, the pH value of the reaction mixture is 1.3˜2.3.