# US 2019/0168309 A1 · Large-scale mutl-step synthesis method for ultralong silver nanowire with contrallable diameter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0168309 A1 - Document ID: US20190168309A1 - Status: Published application - Kind: A1 - Application number: 15/735,129 - Filed: 2017-03-03 - Published: 2019-06-06 - Earliest claimed: 2016-10-26 - Assignees: Southeast University - Applicants: Southeast University - Inventors: Xiaoyang ZHANG; Tong ZHANG; Xiaomei XUE - Web page: https://patentgrep.com/patent/US20190168309A1 ## CPC - B22F 9/24: starting from liquid metal compounds, e.g. solutions - C30B 7/14: the crystallising materials being formed by chemical reactions in the solution - C30B 29/02: Elements - C30B 29/60: characterised by shape - C30B 33/08: Etching - B22F 1/0547: {Nanofibres or nanotubes} - B22F 2009/245: {Reduction reaction in an Ionic Liquid [IL]} - B82Y 40/00: Manufacture or treatment of nanostructures - C22C 5/06: Alloys based on silver - B22F: WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER (making alloys by powder metallurgy C22C); APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER - C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR - B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES - C22C: ALLOYS (treatment of alloys C21D, C22F) ## Abstract A large-scale multi-step synthesis method for ultralong silver nanowire with controllable diameter, comprises: an ethylene glycol solution containing polyvinylpyrrolidone and sodium chloride is fully heated to obtain a solution with strong reducibility, and then silver nitrate in glycol solution is added for a generation of a large number of crystal seeds; hydrogen peroxide is used to achieve the selection of the crystal seeds for a small amount of crystal seeds with particular sizes; the temperature is immediately raised to increase the reaction rate until the threshold of the etching crystal seeds of nitric acid is broke through; the temperature is lowered for long-timed reaction to slow down the reaction rate, reduce the probability of the isotropic seeds by self-nucleation and promote the absorption of small nucleus in the radial direction of large nucleus or nanowire, thus obtaining the ultralong silver nanowire. ## Claims ### Claim 1 A method of large-scale multi-step synthesis for an ultralong silver nanowire with a controllable diameter comprising the following steps: step 1, phase of screening of crystal seeds: heating ethylene glycol solution containing a surfactant at a temperature of 140 to 160° C. to obtain a solution I with strong reducibility; adding alkali metal halide dissolved in ethylene glycol into the solution I to yield a solution II; dissolving silver nitrate in ethylene glycol for preparing a precursor solution, the concentration of silver nitrate is between 0.001 to 5 mol/L; adding the precursor solution into the solution II that reduces silver nitrate rapidly into a large number of multiple twinned crystal seeds with different sizes and part of isotropic seeds; adding etching agent into the above solution with a large number of crystal seeds results in preferentially etching the isotropic seeds which are not resistant to etching and the multiple various sizes of the twinned crystals, thus screening limited amount of particular sizes of the multiple twinned crystal seeds; step 2, phase of breaking through the threshold of etching multiple twinned crystal seeds: after the addition of etching agent in Step 1, increasing the reaction temperature immediately to 160-200° C. for a continuous reaction in the temperature until turbidities appearing; increasing the temperature significantly boosts the reaction rate until the threshold of etching multiple twinned crystal seeds by few by-products, namely nitric acid, is broken through; step 3, phase of longitudinal growth: decreasing the reaction temperature to 60-140° C. for a completed reaction under such condition once the appearance of turbidities; the decrease of temperature, which effectively reduces the reaction rate and depletes the isotropic seeds generated by self-nucleation, allows more free silver ions to be reduced longitudinally along nanowires for obtaining ultralong silver nanowires. ### Claim 2 (depends on 1) The method according to claim 1, wherein the surfactant is polyvinylpyrrolidone (PVP) or the surfactant is capable of being absorbed on <100> crystal surface, mainly including sodium polystyrene sulphonate (PSS), polyacrylic acid (PAA); the concentration of PVP in the reaction system is 0.001-10 mol/L. ### Claim 3 (depends on 1) The method according to claim 1, wherein the alkali metal halide used is sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide or potassium iodide, the concentration of the alkali metal halide is 0.001-10 mmol/L. ### Claim 4 (depends on 1) The method according to claim 1, wherein the etching agent is hydrogen peroxide, which is added in a manner of single-time addition. ### Claim 5 (depends on 1) The method according to claim 1, wherein the concentration of the etching agent is 0.001-0.5 mol/L, and the diameter of the silver nanowire is controlled by adjusting the amount of the etching agent. ### Claim 6 (depends on 2) The method according to claim 2, wherein the molar ratio of the silver nitrate to PVP is 1:0.1-100. ### Claim 7 (depends on 1) The method according to claim 1, wherein the method can be utilized for a large-scale synthesis and the amount of the silver nitrate in the reaction system can be expanded to over 100 g.