WO2020019384A1 - 一种银纳米环的制备方法 - Google Patents

一种银纳米环的制备方法 Download PDF

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WO2020019384A1
WO2020019384A1 PCT/CN2018/101212 CN2018101212W WO2020019384A1 WO 2020019384 A1 WO2020019384 A1 WO 2020019384A1 CN 2018101212 W CN2018101212 W CN 2018101212W WO 2020019384 A1 WO2020019384 A1 WO 2020019384A1
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polyvinylpyrrolidone
silver
molecular weight
ethylene glycol
glycol solution
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PCT/CN2018/101212
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English (en)
French (fr)
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王海波
曾西平
靳世东
吴俊青
李晓明
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深圳市华科创智技术有限公司
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Priority to US17/252,739 priority Critical patent/US11511345B2/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/054—Nanosized particles
    • B22F1/0549—Hollow particles, including tubes and shells
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/07—Metallic powder characterised by particles having a nanoscale microstructure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • B22F2009/245—Reduction reaction in an Ionic Liquid [IL]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2301/00—Metallic composition of the powder or its coating
    • B22F2301/25—Noble metals, i.e. Ag Au, Ir, Os, Pd, Pt, Rh, Ru
    • B22F2301/255—Silver or gold
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2304/00—Physical aspects of the powder
    • B22F2304/05—Submicron size particles
    • B22F2304/054—Particle size between 1 and 100 nm

Definitions

  • the invention relates to the technical field of metal nanomaterials preparation, in particular to a method for preparing silver nanorings.
  • Metal nanomaterials refer to metal materials in which at least one dimension in the three-dimensional space is at the nanoscale or is composed of them as basic units. At present, various metal nanomaterials such as gold, silver, nickel, iron, and copper have been studied. At the same time, these metal nanomaterials have various morphologies such as spherical, stripe, rectangular, and polyhedron. These metal nanoparticles with different morphologies can produce unique physical and chemical properties and show excellent properties not found in many bulk metals. These properties play an important role in the fields of electricity, optics, and magnetism.
  • nano-scale metal silver As a kind of precious metal, silver is widely favored because of its stable properties, soft texture and high thermal conductivity. Compared with the corresponding macroscopic silver metal, nano-scale metal silver has special chemical, optical, and electrical properties, and has a strong inhibitory and killing effect on a variety of pathogenic microorganisms. These special properties are concentratedly applied In the construction of nanoelectronic devices, optical devices and biological antibacterial agents.
  • Patent No. CN102658373A discloses a method for preparing silver nanorings, but the silver nanorings produced by this method have a low yield.
  • the invention aims at the above technical problems, and provides a method for preparing a silver nanoring with high yield.
  • a method for preparing a silver nanoring includes the following steps:
  • Polyvinylpyrrolidone includes small molecular weight polyvinylpyrrolidone with a molecular weight of 55000-58000 and large molecular weight polyvinylpyrrolidone with a molecular weight of 360000-1300000. ;
  • the mass ratio of the small molecular weight polyvinylpyrrolidone and the large molecular weight polyvinylpyrrolidone is 0.8-1.2: 1.
  • step (3) silver nitrate is dissolved in a small molecular weight polyvinylpyrrolidone-ethylene glycol solution at 0-5 ° C to prepare a silver nitrate-polyvinylpyrrolidone-ethylene glycol solution.
  • step (4) the large molecular weight polyvinylpyrrolidone-ethylene glycol solution in step (4) is heated to 130-175 ° C.
  • the dropping time of the silver nitrate-polyvinylpyrrolidone-ethylene glycol solution in step (4) is 30 minutes, and 50% of the total silver nitrate-polyvinylpyrrolidone-ethylene glycol solution is added dropwise within 1-10 minutes, The remaining 50% silver nitrate-polyvinylpyrrolidone-ethylene glycol solution was added dropwise over the remaining time.
  • reaction solution also includes a mixed solution of 40-120 mmol / L potassium bromide and potassium chloride.
  • the mass ratio of potassium bromide and potassium chloride is 1-3: 1.
  • a mixed solution of potassium bromide and potassium chloride is dissolved in a polyvinylpyrrolidone-ethylene glycol solution of large molecular weight after heating.
  • the mixed solution of potassium bromide and potassium chloride is dissolved in a large molecular weight polyvinylpyrrolidone-ethylene glycol solution before heating.
  • polyvinylpyrrolidone of different molecular weight is used as a surface protection agent.
  • Polyvinylpyrrolidone interacts with crystal faces of different silver atom clusters, so that the growth rate of each crystal face of the silver nanocrystals is different, which is beneficial to Gradient silver wires are grown, and silver nanorings are formed under sufficient reaction time.
  • polyvinylpyrrolidone of different molecular weights has different selective adsorption properties for silver and different The stability of ZnO also affects the growth rate of silver atoms along different crystal planes to different degrees, which is more conducive to the production of silver nanorings and has a higher yield.
  • the method for preparing silver nanorings of the present invention dissolves silver nitrate in a small molecular weight polyvinylpyrrolidone-ethylene glycol solution in a frozen environment.
  • the frozen state can slow down or inhibit the reduction of anions to zero-valent silver, which is beneficial to the formation of small silver.
  • the molecular weight polyvinylpyrrolidone-coated nano-silver complex is added dropwise to a large molecular weight polyvinylpyrrolidone-ethylene glycol solution to form nano-silver nanoparticles that are coated and complexed with polyvinylpyrrolidone of large and small molecular weight.
  • Particles, further affected by the effect of polyvinylpyrrolidone of different sizes and molecular weights on the growth rate of different crystal planes of silver, are conducive to the growth of radian silver wires, which in turn generate silver nanorings.
  • the silver nanoring prepared by the invention has a perfect round, smooth surface and oval cross section, the ring diameter is between 15-40 ⁇ m, the line thickness of the ring cross section is between 20-50nm, and the nanowire diameter is about 25nm.
  • the entire silver nanoring is a secondary twin structure.
  • the preparation method is simple in process and low in cost.
  • the prepared silver nanoring has excellent crystal structure and can be used as a transparent flexible conductive material.
  • FIG. 1 is a scanning electron microscope image (1) of a silver nanoring prepared by the present invention
  • FIG. 3 is a scanning electron microscope image (3) of a silver nanoring prepared by the present invention.
  • a method for preparing a silver nanoring according to the present invention includes the following steps:
  • Polyvinylpyrrolidone includes small molecular weight polyvinylpyrrolidone with a molecular weight of 55000-58000 and large molecular weight polyvinylpyrrolidone with a molecular weight of 360000-1300000. ,;
  • polyvinylpyrrolidone interacts with crystal faces of different silver atom clusters, the growth rate of each crystal face of silver nanocrystals is different, and nanomaterials with special morphology are obtained.
  • polyvinylpyrrolidone-ethylene glycol solutions of different molecular weights are prepared.
  • silver ligands are combined into different growth motifs.
  • Silver nitrate is dissolved in a small molecular weight polyvinylpyrrolidone-ethylene glycol solution to form a low molecular weight complex of silver.
  • the silver surface is coated with a small molecular weight polyvinylpyrrolidone.
  • the silver ions are reduced to zero-valent silver, and a part of the small molecular weight polyvinylpyrrolidone on the silver surface is replaced with a large molecular weight polyvinylpyrrolidone.
  • polyvinylpyrrolidone of different molecular weights Under the action of polyvinylpyrrolidone of different molecular weights, the growth rate of silver on both sides is different, which is conducive to the growth of silver wires with radians and the formation of silver nanorings with sufficient reaction time. It can be seen that the application of polyvinylpyrrolidone with different molecular weights is conducive to obtaining silver nanocrystals with different crystal plane growth rates, which is conducive to the formation of cyclic silver nanomaterials and improve the yield of silver nanorings.
  • the mass ratio of the small molecular weight polyvinylpyrrolidone and the large molecular weight polyvinylpyrrolidone is 0.8-1.2: 1.
  • polyvinylpyrrolidone has a selective adsorption effect on the crystal surface of nano-silver crystals.
  • the selective adsorption of polyvinylpyrrolidone of different molecular weights has a certain difference. It plays a role in regulating the shape of nanocrystals and is conducive to the production of silver nanorings. .
  • step (3) silver nitrate is dissolved in a small molecular weight polyvinylpyrrolidone-ethylene glycol solution at 0-5 ° C to prepare a silver nitrate-polyvinylpyrrolidone-ethylene glycol solution. More specifically, the silver nitrate solution is placed in a freezer and stirred to keep the temperature of the silver nitrate solution at about 0-5 ° C., and the silver nitrate is added dropwise to the small molecular weight polyvinylpyrrolidone-ethylene glycol solution.
  • Adding silver nitrate in a frozen state can slow or inhibit the reduction of silver ions to zero-valent silver, and form a nano-silver complex with a small molecular weight coating, and then dropwise add it to a large molecular weight polyvinylpyrrolidone-ethylene glycol solution. It is conducive to the formation and complexing of silver nanoparticles with polyvinylpyrrolidone of large and small molecular weight, and it is helpful to adjust the growth rate of each crystal plane to form silver nanorings and improve the yield of silver nanorings.
  • the temperature of the large molecular weight polyvinylpyrrolidone-ethylene glycol solution in step (4) is 130-175 ° C after the temperature is raised.
  • a silver nitrate-polyvinylpyrrolidone-ethylene glycol solution was added dropwise, ethylene glycol was used as a solvent and a reducing agent, and polyvinylpyrrolidone was used as a surface protective agent.
  • a silver nanoring was prepared by an alcohol thermal reduction method.
  • the dropping time of the silver nitrate-polyvinylpyrrolidone-ethylene glycol solution in step (4) is 30 minutes, and 50% of the total silver nitrate-polyvinylpyrrolidone-ethylene glycol solution is added dropwise within 1-10 minutes, The remaining 50% silver nitrate-polyvinylpyrrolidone-ethylene glycol solution was added dropwise over the remaining time.
  • stepwise dropwise addition the rapid dropwise addition in the front stage is beneficial to the formation of a large number of nanocrystalline nuclei; the relatively slow dropwise addition in the rear is to control the growth kinetics of the silver nanorings, slow down the growth rate, and facilitate the final stage of the silver nanorings Docking in a loop.
  • the reaction solution also includes a mixed solution of 40-120 mmol / L potassium bromide and potassium chloride; the mass ratio of potassium bromide and potassium chloride is 1-3: 1.
  • the mixed solution of potassium bromide and potassium chloride is dissolved in a high molecular weight polyvinylpyrrolidone-ethylene glycol solution after heating.
  • the mixed solution of potassium bromide and potassium chloride is dissolved in a large molecular weight polyvinylpyrrolidone-ethylene glycol solution before heating.
  • the silver nitrate-polyvinylpyrrolidone-ethylene glycol solution is added dropwise to the large molecular weight polyvinylpyrrolidone-ethylene glycol solution through an automatic liquid adding device capable of controlling the speed.
  • the automatic liquid adding device is beneficial for controlling the stepwise dropping process and improving the reaction effect.
  • a method for preparing a silver nanoring includes the following steps:
  • Polyvinylpyrrolidone includes a small molecular weight polyvinylpyrrolidone with a molecular weight of 55,000 and a large molecular weight polyvinylpyrrolidone with a molecular weight of 360,000, and a small molecular weight polyvinylpyrrolidone.
  • the mass ratio to the large molecular weight polyvinylpyrrolidone is 1: 1;
  • a method for preparing a silver nanoring includes the following steps:
  • Polyvinylpyrrolidone includes a small molecular weight polyvinylpyrrolidone with a molecular weight of 58000 and a large molecular weight polyvinylpyrrolidone with a molecular weight of 1.300000, and a small molecular weight polyvinylpyrrolidone.
  • the mass ratio to the large molecular weight polyvinylpyrrolidone is 0.8: 1;
  • a method for preparing a silver nanoring includes the following steps:
  • Polyvinylpyrrolidone includes a small molecular weight polyvinylpyrrolidone with a molecular weight of 55,000 and a large molecular weight polyvinylpyrrolidone with a molecular weight of 1.300000, and a small molecular weight polyvinylpyrrolidone.
  • the mass ratio with the large molecular weight polyvinylpyrrolidone is 1.2: 1;
  • a method for preparing a silver nanoring includes the following steps:
  • Polyvinylpyrrolidone includes a small molecular weight polyvinylpyrrolidone with a molecular weight of 56000 and a large molecular weight polyvinylpyrrolidone with a molecular weight of 1.300000, and a small molecular weight polyvinylpyrrolidone.
  • the mass ratio to the large molecular weight polyvinylpyrrolidone is 1: 1;
  • the silver nanorings prepared by the above examples have perfect round, smooth surfaces and oval cross sections.
  • the ring diameter is between 15-40 ⁇ m
  • the line thickness of the ring cross section is between 20-50nm
  • the nanowire diameter is about 25nm.
  • the preparation method of the silver nanoring adopts an alcohol thermal reduction method, which is simple in process and low in cost; at the same time, the growth rate of different crystal planes of silver crystals is controlled by polyvinylpyrrolidone of different molecular weight, and the yield of the prepared silver nanoring is It is higher, and the surface of the prepared silver nanoring is smooth and has excellent crystal structure, which can be used for transparent flexible conductive materials.

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Abstract

一种银纳米环的制备方法，选用不同分子量的聚乙烯吡咯烷酮作表面保护剂，并将硝酸银在冷冻环境下溶于小分子量的聚乙烯吡咯烷酮-乙二醇溶液中，可减缓或者抑制阴离子被还原成零价银，最终有利于形成大小分子量的聚乙烯吡咯烷酮共同包覆、络合的纳米银粒子，而不同分子量的聚乙烯吡咯烷酮对银的选择吸附性不同，且不同的稳定性使其对银原子沿着不同晶面的生长速率的影响程度也不同，更有利于银纳米环的产生，同时产率更高。银纳米环的制备方法制得的银纳米环具有完美的圆形、光滑的表面和椭圆形的截面，且具有优异的晶体结构，可用作透明柔性导电材料。

Description

一种银纳米环的制备方法
本公开基于申请号为201810842307.4，申请日为2018年7月27日的中国专利申请提出，并要求该中国专利申请的优先权，该中国专利申请的全部内容在此引入本申请作为参考。
技术领域
本发明涉及金属纳米材料制备技术领域，尤其涉及一种银纳米环的制备方法。
背景技术
金属纳米材料是指三维空间中至少有一维处于纳米尺度或由它们作为基本单元构成的金属材料。目前已经对金、银、镍、铁、铜等多种金属纳米材料进行了研究，同时这些金属纳米材料具有球形、条形、长方形、多面体等各异的形貌。这些不同形貌的金属纳米粒子能够产生独特的物理化学性质从而表现出很多体相金属所没有的优异性能，这些性能在电学、光学、磁学等领域具有重要的作用。
银作为贵金属的一种，因其性质稳定、质地柔软，具有较高的导热导电率，广泛受到人们的青睐。而纳米级的金属银单质与相应宏观的银金属相比，具有特殊的化学、光学和电学性质，且对多种致病微生物都有强烈的抑制和杀灭作用，这些特殊的性质被集中应用在构建纳米电子器件、光学器件以及生物抗菌剂等方面。
目前多种形貌的银纳米材料主要通过化学方法制备，这些形貌包括纳米线、纳米棒、纳米球、纳米片等，但环状结构的银纳米材料相关研究较少。公开号为CN102658373A的专利公开了一种银纳米环的制备方法，但该方法制得的银纳米环的产率较低。
发明内容
本发明针对上述技术问题，提供一种产率较高的银纳米环的制备方法。
本发明采用以下技术方案：
一种银纳米环的制备方法，包括以下步骤：
(1)按照摩尔比为1-10:1的比例称取聚乙烯吡咯烷酮和硝酸银，聚乙烯吡咯烷酮包括分子量为55000-58000的小分子量聚乙烯吡咯烷酮和分子量为360000-1300000的大分子量聚乙烯吡咯烷酮；
(2)分别将小分子量聚乙烯吡咯烷酮和大分子量聚乙烯吡咯烷酮溶于乙二醇中，制成小分子量的聚乙烯吡咯烷酮-乙二醇溶液和大分子量的聚乙烯吡咯烷酮-乙二醇溶液备用；
(3)将硝酸银在冷冻环境下溶于小分子量的聚乙烯吡咯烷酮-乙二醇溶液中制成硝酸银-聚乙烯吡咯烷酮-乙二醇溶液备用；
(4)将大分子量的聚乙烯吡咯烷酮-乙二醇溶液升温，再将硝酸银-聚乙烯吡咯烷酮-乙二醇溶液以分段滴加的方式滴加至升温后的大分子量的聚乙烯吡咯烷酮-乙二醇溶液中，制得反应液；
(5)将反应液以30-80r/min的速度搅拌，待反应液颜色由无色变为亮黄色时停止搅拌，最终变为土黄色时，将反应液离心，用酒精或丙酮清洗离心后的沉淀物，收集清洗液，得到含有银纳米环的溶液。
进一步的，小分子量聚乙烯吡咯烷酮和大分子量聚乙烯吡咯烷酮的质量比为0.8-1.2:1。
进一步的，步骤(3)中将硝酸银在0-5℃下溶于小分子量聚乙烯吡咯烷酮-乙二醇溶液中制成硝酸银-聚乙烯吡咯烷酮-乙二醇溶液。
进一步的，步骤(4)中大分子量的聚乙烯吡咯烷酮-乙二醇溶液升温至130-175℃。
进一步的，步骤(4)中硝酸银-聚乙烯吡咯烷酮-乙二醇溶液的滴加时间为30min，在1-10min内滴加硝酸银-聚乙烯吡咯烷酮-乙二醇溶液总量的50％，再在剩余时间滴加余下50％的硝酸银-聚乙烯吡咯烷酮-乙二醇溶液。
进一步的，反应液中还包括40-120mmol/L的溴化钾和氯化钾的混合溶液。
进一步的，溴化钾和氯化钾的质量比为1-3:1。
进一步的，溴化钾和氯化钾的混合溶液溶于升温后的大分子量的聚乙烯吡 咯烷酮-乙二醇溶液中。
进一步的，溴化钾和氯化钾的混合溶液溶于升温前的大分子量的聚乙烯吡咯烷酮-乙二醇溶液中。
本发明的银纳米环的制备方法，选用不同分子量的聚乙烯吡咯烷酮作表面保护剂，聚乙烯吡咯烷酮与不同银原子团簇体晶面相互作用，使得银纳米晶体各个晶面的生长速度不同，有利于生长出有弧度的银线，并在足够的反应时间下生成银纳米环；相较于近似分子量的聚乙烯吡咯烷酮与银相互作用，不同分子量的聚乙烯吡咯烷酮对银的选择吸附性不同，且不同的稳定性使其对银原子沿着不同晶面的生长速率的影响程度也不同，更有利于银纳米环的产生，且产率更高。
本发明的银纳米环的制备方法，将硝酸银在冷冻环境下溶于小分子量的聚乙烯吡咯烷酮-乙二醇溶液中，冷冻状态可减缓或者抑制阴离子被还原成零价银，有利于形成小分子量聚乙烯吡咯烷酮包覆的纳米银络合物，再将其滴加至大分子量的聚乙烯吡咯烷酮-乙二醇溶液中后，可形成大小分子量的聚乙烯吡咯烷酮共同包覆、络合的纳米银粒子，进一步的在大小不同分子量的聚乙烯吡咯烷酮对银的不同晶面的生长速度的影响效果不同的作用下，有利于生长出有弧度的银线，进而生成银纳米环。
本发明制得的银纳米环具有完美的圆形、光滑的表面和椭圆形的截面，环直径在15-40μm之间，环截面的线粗细在20-50nm之间，纳米线直径25nm左右，整个银纳米环都是二次孪晶结构。同时该制备方法工艺简单、成本低，制备的银纳米环具有优异的晶体结构，可用作透明柔性导电材料。
附图说明
为了更清楚的说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单的介绍，显而易见的，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其它附图。
图1为本发明制得的银纳米环的扫描电子显微镜图(1)；
图2为本发明制得的银纳米环的扫描电子显微镜图(2)；
图3为本发明制得的银纳米环的扫描电子显微镜图(3)。
具体实施方式
下面将结合本发明中的附图，对本发明实施例中的技术方案进行清楚、完整的描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通的技术人员在没有做出创造性劳动的前提下所获得的所有其它实施例，都属于本发明的保护范围。
本发明的一种银纳米环的制备方法，包括以下步骤：
(1)按照摩尔比为1-10:1的比例称取聚乙烯吡咯烷酮和硝酸银，聚乙烯吡咯烷酮包括分子量为55000-58000的小分子量聚乙烯吡咯烷酮和分子量为360000-1300000的大分子量聚乙烯吡咯烷酮，；
(2)分别将小分子量聚乙烯吡咯烷酮和大分子量聚乙烯吡咯烷酮溶于乙二醇中，制成小分子量的聚乙烯吡咯烷酮-乙二醇溶液和大分子量的聚乙烯吡咯烷酮-乙二醇溶液备用；
(3)将硝酸银在冷冻环境下溶于小分子量的聚乙烯吡咯烷酮-乙二醇溶液中制成硝酸银-聚乙烯吡咯烷酮-乙二醇溶液备用；
(4)将大分子量的聚乙烯吡咯烷酮-乙二醇溶液升温，再将硝酸银-聚乙烯吡咯烷酮-乙二醇溶液以分段滴加的方式滴加至升温后的大分子量的聚乙烯吡咯烷酮-乙二醇溶液中，制得反应液；
(5)将反应液以30-80r/min的速度搅拌，待反应液颜色由无色变为亮黄色时停止搅拌，最终变为土黄色时，将反应液离心，用酒精或丙酮清洗离心后的沉淀物，收集清洗液，得到含有银纳米环的溶液。
由于聚乙烯吡咯烷酮与不同银原子团簇体晶面相互作用，使得银纳米晶体各个晶面的生长速度不同，进而得到特殊形貌的纳米材料。本发明实施例中银纳米环的制备方法，分别制备大小不同分子量的聚乙烯吡咯烷酮-乙二醇溶液，在不同分子量的聚乙烯吡咯烷酮作用下，银的配位体组合成不同的生长基元，这些生长元素吸附到不同晶面的稳定性不同，进而直接影响银原子沿着不同晶面的生长速率。将硝酸银溶于小分子量的聚乙烯吡咯烷酮-乙二醇溶液中，形成银的低分子量络合物，银表面包覆小分子量的聚乙烯吡咯烷酮，当将其滴加到 大分子量的聚乙烯吡咯烷酮-乙二醇溶液中后，银离子被还原成零价银，且银表面的部分小分子量聚乙烯吡咯烷酮被大分子量聚乙烯吡咯烷酮替代。在大小不同分子量的聚乙烯吡咯烷酮的作用下，银两侧的生长速度不同，有利于生长出有弧度的银线，并在足够的反应时间下生成银纳米环。可见，通过大小不同分子量的聚乙烯吡咯烷酮的应用，有利于得到晶面生长速度不同的银纳米晶体，进而有利于环状银纳米材料的形成，提高银纳米环的产率。
具体的，小分子量聚乙烯吡咯烷酮和大分子量聚乙烯吡咯烷酮的质量比为0.8-1.2:1。聚乙烯吡咯烷酮作为盖帽剂，对纳米银晶体的晶面有选择性吸附作用，不同分子量的聚乙烯吡咯烷酮的选择吸附性有一定差异，起到调控纳米晶体形状的作用，有利于银纳米环的产生。
具体的，步骤(3)中将硝酸银在0-5℃下溶于小分子量聚乙烯吡咯烷酮-乙二醇溶液中制成硝酸银-聚乙烯吡咯烷酮-乙二醇溶液。更具体的，将硝酸银溶液置于冷冻室搅拌，使硝酸银溶液的温度保持在0-5℃左右，再将硝酸银滴加到小分子量聚乙烯吡咯烷酮-乙二醇溶液中。硝酸银在冷冻状态下加入，可减缓或者抑制银离子被还原成零价银，并形成小分子量包覆的纳米银络合物，再滴加至大分子量聚乙烯吡咯烷酮-乙二醇溶液中后有利于形成大小分子量聚乙烯吡咯烷酮共同包覆、络合的纳米银粒子，有助于调节各个晶面的生长速度来形成银纳米环，提高银纳米环的产率。
具体的，步骤(4)中大分子量的聚乙烯吡咯烷酮-乙二醇溶液升温后的温度为130-175℃。溶液升温后滴加硝酸银-聚乙烯吡咯烷酮-乙二醇溶液，乙二醇作为溶剂和还原剂、聚乙烯吡咯烷酮作为表面保护剂，利用醇热还原法来制备银纳米环。
具体的，步骤(4)中硝酸银-聚乙烯吡咯烷酮-乙二醇溶液的滴加时间为30min，在1-10min内滴加硝酸银-聚乙烯吡咯烷酮-乙二醇溶液总量的50％，再在剩余时间滴加余下50％的硝酸银-聚乙烯吡咯烷酮-乙二醇溶液。采用分段滴加的方式，前段快速滴加有利于大量的纳米晶核的形成；后面相对缓慢滴加，是为了控制银纳米环生长动力学，减缓生长速度，有利于银纳米环最终阶段的对接成环。
具体的，反应液中还包括40-120mmol/L的溴化钾和氯化钾的混合溶液； 溴化钾和氯化钾的质量比为1-3:1。
具体的，溴化钾和氯化钾的混合溶液溶于升温后的大分子量的聚乙烯吡咯烷酮-乙二醇溶液中。
具体的，溴化钾和氯化钾的混合溶液溶于升温前的大分子量的聚乙烯吡咯烷酮-乙二醇溶液中。
具体的，硝酸银-聚乙烯吡咯烷酮-乙二醇溶液通过可控制速度的自动加液装置滴加至大分子量的聚乙烯吡咯烷酮-乙二醇溶液中。自动加液装置有利于对分段滴加过程进行控制，提高反应效果。
下面结合具体实施例对本发明的银纳米环的制备方法作进一步的描述。
实施例1
一种银纳米环的制备方法，包括以下步骤：
(1)按照摩尔比为2:1的比例称取聚乙烯吡咯烷酮和硝酸银，聚乙烯吡咯烷酮包括分子量为55000的小分子量聚乙烯吡咯烷酮和分子量为360000的大分子量聚乙烯吡咯烷酮，小分子量聚乙烯吡咯烷酮和大分子量聚乙烯吡咯烷酮的质量比为1:1；
(2)分别将小分子量聚乙烯吡咯烷酮和大分子量聚乙烯吡咯烷酮溶于乙二醇中，制成小分子量的聚乙烯吡咯烷酮-乙二醇溶液和大分子量的聚乙烯吡咯烷酮-乙二醇溶液备用；
(3)将硝酸银在0℃下溶于小分子量的聚乙烯吡咯烷酮-乙二醇溶液中制成硝酸银-聚乙烯吡咯烷酮-乙二醇溶液备用；
(4)将大分子量的聚乙烯吡咯烷酮-乙二醇溶液升温至150℃，再将硝酸银-聚乙烯吡咯烷酮-乙二醇溶液以分段滴加的方式滴加至升温后的大分子量的聚乙烯吡咯烷酮-乙二醇溶液中，并滴加80mmol/L的溴化钾和氯化钾的混合溶液，制得反应液；
(5)将反应液以50r/min的速度搅拌，待反应液颜色由无色变为亮黄色时停止搅拌，最终变为土黄色时，将反应液离心，用酒精或丙酮清洗离心后的沉淀物，收集清洗液，得到含有银纳米环的溶液。
实施例2
一种银纳米环的制备方法，包括以下步骤：
(1)按照摩尔比为8:1的比例称取聚乙烯吡咯烷酮和硝酸银，聚乙烯吡咯烷酮包括分子量为58000的小分子量聚乙烯吡咯烷酮和分子量为1300000的大分子量聚乙烯吡咯烷酮，小分子量聚乙烯吡咯烷酮和大分子量聚乙烯吡咯烷酮的质量比为0.8:1；
(2)分别将小分子量聚乙烯吡咯烷酮和大分子量聚乙烯吡咯烷酮溶于乙二醇中，制成小分子量的聚乙烯吡咯烷酮-乙二醇溶液和大分子量的聚乙烯吡咯烷酮-乙二醇溶液备用；
(3)将硝酸银在5℃下溶于小分子量的聚乙烯吡咯烷酮-乙二醇溶液中制成硝酸银-聚乙烯吡咯烷酮-乙二醇溶液备用；
(4)将大分子量的聚乙烯吡咯烷酮-乙二醇溶液升温至175℃，再将硝酸银-聚乙烯吡咯烷酮-乙二醇溶液以分段滴加的方式滴加至升温后的大分子量的聚乙烯吡咯烷酮-乙二醇溶液中，并滴加40mmol/L的溴化钾和氯化钾的混合溶液，制得反应液；
(5)将反应液以30r/min的速度搅拌，待反应液颜色由无色变为亮黄色时停止搅拌，最终变为土黄色时，将反应液离心，用酒精或丙酮清洗离心后的沉淀物，收集清洗液，得到含有银纳米环的溶液。
实施例3
一种银纳米环的制备方法，包括以下步骤：
(1)按照摩尔比为10:1的比例称取聚乙烯吡咯烷酮和硝酸银，聚乙烯吡咯烷酮包括分子量为55000的小分子量聚乙烯吡咯烷酮和分子量为1300000的大分子量聚乙烯吡咯烷酮，小分子量聚乙烯吡咯烷酮和大分子量聚乙烯吡咯烷酮的质量比为1.2:1；
(2)分别将小分子量聚乙烯吡咯烷酮和大分子量聚乙烯吡咯烷酮溶于乙二醇中，制成小分子量的聚乙烯吡咯烷酮-乙二醇溶液和大分子量的聚乙烯吡咯烷酮-乙二醇溶液备用；
(3)将硝酸银在3℃下溶于小分子量的聚乙烯吡咯烷酮-乙二醇溶液中制成硝酸银-聚乙烯吡咯烷酮-乙二醇溶液备用；
(4)将大分子量的聚乙烯吡咯烷酮-乙二醇溶液升温至130℃，再将硝酸银-聚乙烯吡咯烷酮-乙二醇溶液以分段滴加的方式滴加至升温后的大分子量的聚 乙烯吡咯烷酮-乙二醇溶液中，并滴加120mmol/L的溴化钾和氯化钾的混合溶液，制得反应液；
(5)将反应液以80r/min的速度搅拌，待反应液颜色由无色变为亮黄色时停止搅拌，最终变为土黄色时，将反应液离心，用酒精或丙酮清洗离心后的沉淀物，收集清洗液，得到含有银纳米环的溶液。
实施例4
一种银纳米环的制备方法，包括以下步骤：
(1)按照摩尔比为1:1的比例称取聚乙烯吡咯烷酮和硝酸银，聚乙烯吡咯烷酮包括分子量为56000的小分子量聚乙烯吡咯烷酮和分子量为1300000的大分子量聚乙烯吡咯烷酮，小分子量聚乙烯吡咯烷酮和大分子量聚乙烯吡咯烷酮的质量比为1:1；
(2)分别将小分子量聚乙烯吡咯烷酮和大分子量聚乙烯吡咯烷酮溶于乙二醇中，制成小分子量的聚乙烯吡咯烷酮-乙二醇溶液和大分子量的聚乙烯吡咯烷酮-乙二醇溶液备用；
(3)将硝酸银在0℃下溶于小分子量的聚乙烯吡咯烷酮-乙二醇溶液中制成硝酸银-聚乙烯吡咯烷酮-乙二醇溶液备用；
(4)向大分子量的聚乙烯吡咯烷酮-乙二醇溶液中滴加100mmol/L的溴化钾和氯化钾的混合溶液，再升温至140℃，再将硝酸银-聚乙烯吡咯烷酮-乙二醇溶液以分段滴加的方式滴加至升温后的大分子量的聚乙烯吡咯烷酮-乙二醇溶液中，制得反应液；
(5)将反应液以50r/min的速度搅拌，待反应液颜色由无色变为亮黄色时停止搅拌，最终变为土黄色时，将反应液离心，用酒精或丙酮清洗离心后的沉淀物，收集清洗液，得到含有银纳米环的溶液。
将上述实施例制得的银纳米环用扫描电子显微镜观察，如图1-3所示，可见本发明实施例制得的银纳米环具有完美的圆形、光滑的表面和椭圆形的截面，环直径在15-40μm之间，环截面的线粗细在20-50nm之间，纳米线直径在25nm左右。
本发明的银纳米环的制备方法，采用醇热还原法，工艺简单、成本低；同时通过大小不同分子量的聚乙烯吡咯烷酮控制银晶体不同晶面的生长速度，制 得的银纳米环的产率更高，且所制备的银纳米环表面光滑，具备优异的晶体结构，可用于透明柔性导电材料。
以上借助具体实施例对本发明做了进一步描述，但是应该理解的是，这里具体的描述，不应理解为对本发明的实质和范围的限定，本领域内的普通技术人员在阅读本说明书后对上述实施例做出的各种修改，都属于本发明所保护的范围。

Claims (10)

  1. 一种银纳米环的制备方法，其特征在于，包括以下步骤：
    (1)按照摩尔比为1-10:1的比例称取聚乙烯吡咯烷酮和硝酸银，所述聚乙烯吡咯烷酮包括分子量为55000-58000的小分子量聚乙烯吡咯烷酮和分子量为360000-1300000的大分子量聚乙烯吡咯烷酮；
    (2)分别将小分子量聚乙烯吡咯烷酮和大分子量聚乙烯吡咯烷酮溶于乙二醇中，制成小分子量的聚乙烯吡咯烷酮-乙二醇溶液和大分子量的聚乙烯吡咯烷酮-乙二醇溶液备用；
    (3)将硝酸银在冷冻环境下溶于小分子量的聚乙烯吡咯烷酮-乙二醇溶液中制成硝酸银-聚乙烯吡咯烷酮-乙二醇溶液备用；
    (4)将大分子量的聚乙烯吡咯烷酮-乙二醇溶液升温，再将硝酸银-聚乙烯吡咯烷酮-乙二醇溶液以分段滴加的方式滴加至升温后的大分子量的聚乙烯吡咯烷酮-乙二醇溶液中，制得反应液；
    (5)将反应液以30-80r/min的速度搅拌，待反应液颜色由无色变为亮黄色时停止搅拌，最终变为土黄色时，将反应液离心，用酒精或丙酮清洗离心后的沉淀物，收集清洗液，得到含有银纳米环的溶液。
  2. 根据权利要求1所述的银纳米环的制备方法，其特征在于，所述小分子量聚乙烯吡咯烷酮和大分子量聚乙烯吡咯烷酮的质量比为0.8-1.2:1。
  3. 根据权利要求1或2所述的银纳米环的制备方法，其特征在于，步骤(3)中将硝酸银在0-5℃下溶于小分子量聚乙烯吡咯烷酮-乙二醇溶液中制成硝酸银-聚乙烯吡咯烷酮-乙二醇溶液。
  4. 根据权利要求1-3中任一项所述的银纳米环的制备方法，其特征在于，步骤(4)中大分子量的聚乙烯吡咯烷酮-乙二醇溶液升温后的温度为130-175℃。
  5. 根据权利要求1-4中任一项所述的银纳米环的制备方法，其特征在于，步骤(4)中硝酸银-聚乙烯吡咯烷酮-乙二醇溶液的滴加时间为30min，在1-10min内滴加硝酸银-聚乙烯吡咯烷酮-乙二醇溶液总量的50％，再在剩余时间滴加余下50％的硝酸银-聚乙烯吡咯烷酮-乙二醇溶液。
  6. 根据权利要求1-5中任一项所述的银纳米环的制备方法，其特征在于，所述反应液中还包括40-120mmol/L的溴化钾和氯化钾的混合溶液。
  7. 根据权利要求6所述的银纳米环的制备方法，其特征在于，所述溴化钾和氯化钾的质量比为1-3:1。
  8. 根据权利要求6或7所述的银纳米环的制备方法，其特征在于，所述溴化钾和氯化钾的混合溶液溶于升温后的大分子量的聚乙烯吡咯烷酮-乙二醇溶液中。
  9. 根据权利要求6或7所述的银纳米环的制备方法，其特征在于，所述溴化钾和氯化钾的混合溶液溶于升温前的大分子量的聚乙烯吡咯烷酮-乙二醇溶液中。
  10. 根据权利要求1-9中任一项所述的银纳米环的制备方法，其特征在于，所述硝酸银-聚乙烯吡咯烷酮-乙二醇溶液通过自动加液装置滴加至大分子量的聚乙烯吡咯烷酮-乙二醇溶液中。
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