Silver nanoparticles and method for preparing silver nanoparticles by using quinone compounds to regulate polyol reduction method

Abstract

The present invention provides silver nanoparticles and a method for preparing silver nanoparticles by a polyol reduction method regulated by quinone compounds, belonging to the technical field of nanomaterial preparation. The present invention mixes quinone compounds, poly N-vinyl pyrrolidone, a silver source, an additive and a polyol compound to obtain a mixed raw material liquid; the amount ratio of quinone compounds, poly N-vinyl pyrrolidone, a silver source, an additive and a polyol compound is (0.02-0.25) mol: (0.01-2) mol: (0.01-0.1) mol: (0.00001-0.0001) mol: 1L; the mixed raw material liquid is subjected to a reduction reaction under the conditions of 110-180° C. to obtain right triangular bipyramidal silver nanoparticles and / or pentagonal silver nanorods. The present invention adopts a one-pot method to prepare right triangular bipyramidal silver nanoparticles and / or pentagonal silver nanorods, which is simple to operate and has high preparation efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of nano material preparation, in particular to silver nano particles and a method for preparing the silver nano particles by adopting a quinone compound-regulated polyol reduction method. Background Art

[0002] Nanomaterials of precious metals such as gold and silver have unique catalytic and optical properties and have wide application value in optoelectronics, medicine, sensors and other fields. At the same time, since the physical and chemical properties of precious metal nanomaterials are closely related to their morphological characteristics, various morphological granular materials have been developed for different applications, especially materials with anisotropic structural characteristics, such as nanowires, nanorods, bipyramids, cubes, triangular plates, decahedron particles, etc. Among them, silver nanowires are developed as conductor materials for new flexible electronic devices, silver nanorods can be used in the biomedical field because of their good bactericidal properties, and bipyramidal silver particles have a strong plasma resonance effect and can be used in signal detection, sensing and other aspects.

[0003] At present, research on the preparation methods of silver nanorods and bipyramidal silver particles has made certain progress, and their main preparation methods can be divided into two categories. One is the plasma-mediated method, which selectively generates particles of specific morphology by inducing the plasma resonance effect of the synthesized small-sized silver seeds through light. Its advantages are good controllability of particle morphology and can be prepared at relatively low temperatures; its disadvantages are that it requires long-term irradiation and pre-preparation of silver seeds, long preparation cycle and low efficiency. The other is the polyol synthesis method, which uses polyols as solvents and silver ion reducing agents, and cooperates with the selective effect of capping agents on specific morphologies to grow particles of target morphology. Compared with the plasma-mediated method, the advantages of the polyol synthesis method are short preparation cycle and relatively simple method, so it has more application prospects. However, the polyol synthesis method usually also requires the pre-preparation of silver seed particles, and is generally carried out under high temperature conditions, with high energy consumption; in addition, due to its rapid reaction process, the control of the morphology of the synthesized particles is relatively difficult, and the yield needs to be improved.

[0004] For example, it has been reported that silver nanorods were prepared by polyol method at 185°C, but this method requires the preparation of small-sized silver seeds in advance, and the synthesized silver nanorods have a diameter of about 39 nm and a length of about 1.9 μm (Sun Y, Yin Y, Mayers BT, Herricks T, Xia Y. Uniform silver nanowires synthesis by reducing AgNO3 with ethylene glycol in the presence of seeds and poly (vinylpyrrolidone) [J]. Chemistry of Materials, 2002, 14 (11): 4736-4745.). Another study reported that single-crystalline silver nanorods were synthesized by polyol method, with a length of 8 μm and a diameter of 70 nm (Jiu J, Murai K, Kim D, Kim K, Suganuma K. Preparation of Ag nanorods with high yield by polyol process [J]. Materials Chemistry and Physics, 2009, 114 (1): 333-338.). In the prior art, there are reports on the use of gold nano seeds to prepare silver nanorods (application publication number CN107243626A), and there are studies on regulating the length of silver nanorods in the polyol method by hydrogen peroxide (application publication number CN104607653A), but this method is a two-step method and also requires the synthesis of seed particles in the first step; while reacting at high temperature, adding some materials step by step into the polyol synthesis system can also prepare silver nanorods (application publication numbers CN104551011A, CN104841946A). However, none of the above studies describe whether the prepared silver nanorods have a pentagonal structure.Generally speaking, pentagonal silver nanorods are grown from five-fold twinned seeds. Some studies have shown that pentagonal silver nanorods can be prepared by using pre-prepared decahedral particles with a five-fold twinned structure as seeds. However, the study did not use the polyol synthesis method, and the length of the obtained nanorods was only 50nm to 2μm, and the aspect ratio was within 40. To synthesize nanorods with an aspect ratio of more than 12, short nanorods must be used as seeds for further synthesis, and the overall process is relatively complicated (Pietrobon B, McEachran M, Kitaev V. Synthesis of size-controlled faceted pentagonal silver nanorods with tunable plasmonic properties and self-assembly of these nanorods [J]. ACS Nano, 2009, 3 (1): 21-26.).

[0005] There are relatively few studies on right bipyramid silver particles. Xia's team used the polyol method to synthesize right bipyramid silver particles (Wiley BJ, Xiong Y, Li ZY, YinY, XiaY. Right bipyramids of silver: A new shape derived from single twinned seeds [J]. Nano Letters, 2006, 6 (4): 765-768.; Patent No. US10981231B2). During the synthesis, a microfluidic pump was required to simultaneously add silver nitrate solution and PVP and sodium bromide solutions to the reaction system at a high temperature of 160°C. This synthesis method requires precise control, which makes it difficult to apply in practice. Mirkin's team used a plasma-mediated method to first prepare small-sized silver seeds, and then prepared them in combination with light irradiation, pH adjustment, and additives (Zhang J, Langille MR, Mirkin CA. Photomediated synthesis of silver triangular bipyramids and prisms: The effect of pH and BSPP [J]. Journal of the American Chemical Society, 2010, 132 (35): 12502-12510.; Application Publication No. US2010 / 0239675A1).There are also reports on the synthesis of right bipyramid silver particles in aqueous solution (Tavakkoli Yaraki M, Daqiqeh Rezaei S, Middha E, et al. Synthesis and Simulation Study of Right Silver Bipyramids via Seed-Mediated Growth cum Selective Oxidative Etching Approach [J]. Particle and Particle Systems Characterization, 2020, 37 (5).; McEachran M, Kitaev V. Direct structural transformation of silver platelets into right bipyramids and twinned cube nanoparticles: Morphology governed by defects [J]. Chemical Communications, 2008 (44): 5737-5739.), but it is necessary to pre-prepare 2-5 nm silver particles and thin plate-shaped silver particles as seeds respectively.

[0006] Through the above research status, it can be found that the existing synthesis technologies of silver nanorods and right bipyramidal silver nanoparticles all require the use of seed particles or step-by-step synthesis methods, which leads to complex processes and low preparation efficiency; in addition, there are few reports on the research on the preparation of pentagonal silver nanorods using the polyol method. Summary of the invention

[0007] The object of the present invention is to provide silver nanoparticles and a method for preparing silver nanoparticles by using a quinone compound to regulate a polyol reduction method. The present invention adopts a one-pot method to prepare right triangular bipyramidal silver nanoparticles and / or pentagonal silver nanorods.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] The present invention provides a method for preparing silver nanoparticles by using a quinone compound to regulate a polyol reduction method, comprising the following steps:

[0010] A quinone compound, poly N-vinyl pyrrolidone, a silver source, an additive and a polyol compound are mixed to obtain a mixed raw material solution; the amount ratio of the quinone compound, poly N-vinyl pyrrolidone, the silver source, the additive and the polyol compound is (0.02-0.25) mol: (0.01-2) mol: (0.01-0.1) mol: (0.00001-0.0001) mol: 1 L;

[0011] The mixed raw material liquid is subjected to a reduction reaction at 110-180° C. to obtain silver nanoparticles; the silver nanoparticles are right triangular bipyramidal silver nanoparticles and / or pentagonal silver nanorods.

[0012] Preferably, the quinone compound includes one or more of camphorquinone, benzoquinone, naphthoquinone, anthraquinone and phenanthrenequinone.

[0013] Preferably, the molecular weight of the poly (N-vinyl pyrrolidone) is 10,000 to 1,300,000 g / mol.

[0014] Preferably, the silver source includes one or more of silver nitrate, silver acetate, silver oxalate, silver hexafluorophosphate and silver hexafluoroantimonate.

[0015] Preferably, the additive includes one or more of sodium chloride, potassium chloride, ferric chloride, cupric chloride, hexadecyltrimethylammonium chloride, sodium bromide, potassium bromide and hexadecyltrimethylammonium bromide.

[0016] Preferably, the polyol compound includes one or more of ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, neopentyl glycol, diethylene glycol and glycerol.

[0017] Preferably, the reduction reaction time is 2 to 7 hours.

[0018] Preferably, the reduction reaction is carried out under stirring conditions, and the stirring rate is 100-600 rpm.

[0019] Preferably, after the reduction reaction, the method further comprises: performing solid-liquid separation on the product system obtained after the reduction reaction, washing the obtained solid material to obtain silver nanoparticles; the reagent used for the washing comprises methanol, ethanol or acetone.

[0020] The present invention provides silver nanoparticles prepared by the preparation method described in the above technical solution, wherein the silver nanoparticles are right triangular bipyramidal silver nanoparticles and / or pentagonal silver nanorods;

[0021] The long side length of the right triangular bipyramidal silver nanoparticles is 100 to 400 nm;

[0022] The two end faces of the pentagonal silver nanorod are planes, the diameter is 40-110nm, and the length is 0.2-3μm.

[0023] The present invention provides a method for preparing silver nanoparticles by using a quinone compound to regulate a polyol reduction method, comprising the following steps: mixing a quinone compound, poly N-vinyl pyrrolidone, a silver source, an additive and a polyol compound to obtain a mixed raw material liquid; the amount ratio of the quinone compound, poly N-vinyl pyrrolidone, the silver source, the additive and the polyol compound is (0.02-0.25) mol: (0.01-2) mol: (0.01-0.1) mol: (0.00001-0.0001) mol: 1L; performing a reduction reaction on the mixed raw material liquid at 110-180°C to obtain silver nanoparticles; the silver nanoparticles are right triangular bipyramidal silver nanoparticles and / or pentagonal silver nanorods. Based on the polyol reduction method, the present invention can regulate the morphology of silver nanoparticles by using quinone compounds, and finally can prepare right triangular bipyramidal silver nanoparticles and / or pentagonal silver nanorods by a one-pot method, without the need to prepare seed particles in advance, with simple operation and high preparation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The SEM image and size distribution diagram of the right triangular bipyramidal silver nanoparticles prepared in Example 1;

[0025] Figure 2 TEM image of the right triangular bipyramidal silver nanoparticles prepared in Example 1, as well as the lattice fringe image and the crystal plane spacing annotation image;

[0026] Figure 3 The SEM image and size distribution diagram of the pentagonal silver nanorods prepared in Example 2;

[0027] Figure 4 TEM image, SEM image, lattice fringe image and interplanar spacing annotation image of the pentagonal silver nanorods prepared in Example 2;

[0028] Figure 5 The SEM images and yield graphs of silver nanoparticles prepared under different camphorquinone concentration conditions in Example 3;

[0029] Figure 6 The SEM images and yield graphs of silver nanoparticles prepared under different poly (N-vinyl pyrrolidone) concentration conditions in Example 4;

[0030] Figure 7 The SEM images and yield graphs of silver nanoparticles prepared under different reaction temperature conditions in Example 5;

[0031] Figure 8XRD patterns of silver nanoparticles prepared under two different conditions;

[0032] Fig. 9 is the C1s XPS spectrum and fitting curve;

[0033] Fig.10 FTIR spectra of silver nanoparticles prepared for camphorquinone and pure poly N -vinyl pyrrolidone;

[0034] Fig.11 Schematic diagram of the synthesis mechanism of right-trigonal bipyramidal silver nanoparticles and pentagonal silver nanorods regulated by camphorquinone. DETAILED DESCRIPTION

[0035] The present invention provides a method for preparing silver nanoparticles by using a quinone compound to regulate a polyol reduction method, comprising the following steps:

[0036] A quinone compound, poly N-vinyl pyrrolidone, a silver source, an additive and a polyol compound are mixed to obtain a mixed raw material solution; the amount ratio of the quinone compound, poly N-vinyl pyrrolidone, the silver source, the additive and the polyol compound is (0.02-0.25) mol: (0.01-2 mol): (0.01-0.1) mol: (0.00001-0.0001) mol: 1 L;

[0037] The mixed raw material liquid is subjected to a reduction reaction at 110-180° C. to obtain silver nanoparticles; the silver nanoparticles are right triangular bipyramidal silver nanoparticles and / or pentagonal silver nanorods.

[0038] The present invention mixes quinone compounds, poly N-vinyl pyrrolidone, silver source, additives and polyol compounds to obtain a mixed raw material liquid. In the present invention, the quinone compounds preferably include one or more of camphorquinone, benzoquinone, naphthoquinone, anthraquinone and phenanthrenequinone, and more preferably camphorquinone; the quinone compounds can regulate the synthesis of right triangular bipyramidal silver nanoparticles and / or pentagonal silver nanorods. In the present invention, the molecular weight of the poly N-vinyl pyrrolidone is preferably 10000 to 1300000 g / mol, and specifically can be one or more of 10000 g / mol, 40000 g / mol, 55000 g / mol, 360000 g / mol and 1300000 g / mol, and more preferably 360000 g / mol; the poly N-vinyl pyrrolidone is specifically used as a selective end-capping agent. In the present invention, the silver source preferably includes one or more of silver nitrate, silver acetate, silver oxalate, silver hexafluorophosphate and silver hexafluoroantimonate, and more preferably silver nitrate. In the present invention, the additive preferably includes one or more of sodium chloride, potassium chloride, ferric chloride, cupric chloride, hexadecyltrimethylammonium chloride, sodium bromide, potassium bromide and hexadecyltrimethylammonium bromide, and more preferably ferric chloride; the function of the additive is to prevent particle agglomeration. In the present invention, the polyol compound preferably includes one or more of ethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, diethylene glycol and glycerol, and more preferably ethylene glycol; the polyol compound specifically serves as a solvent and a reducing agent.

[0039] In the present invention, the usage ratio of the quinone compound, poly N-vinyl pyrrolidone, silver source, additive and polyol compound is preferably (0.02-0.25) mol: (0.01-2) mol: (0.01-0.1) mol: (0.00001-0.0001) mol: 1L. The present invention preferably further selects a suitable raw material ratio according to the specific morphology of the desired silver nanoparticles. Specifically, when it is necessary to prepare right triangular bipyramidal silver nanoparticles, the amount ratio of the quinone compound, poly N-vinyl pyrrolidone, silver source, additive and polyol compound is preferably (0.02-0.25) mol: (0.08-2) mol: (0.01-0.1) mol: (0.00001-0.0001) mol: 1 L, more preferably (0.1-0.15) mol: (0.08-0.1) mol: (0.05-0.06) mol: (0.00005-0.0001) mol: 1 L, and further preferably 0.116 mol: 0.093 mol: 0.0 58mol:0.000084:1L; when it is necessary to prepare pentagonal silver nanorods, the dosage ratio of the quinone compound, poly N-vinyl pyrrolidone, silver source, additive and polyol compound is preferably (0.02-0.25)mol:(0.01-0.08)mol:(0.01-0.1)mol:(0.00001-0.0001)mol:1L, more preferably (0.1-0.15)mol:(0.06-0.08)mol:(0.05-0.06)mol:(0.00005-0.0001)mol:1L, and further preferably 0.116mol:0.069mol:0.058mol:0.000084:1L.

[0040] In the present invention, the method of mixing the quinone compound, poly (N-vinyl pyrrolidone), silver source, additive and polyol compound is preferably as follows: firstly dissolve the quinone compound and poly (N-vinyl pyrrolidone) in the polyol compound, then add the silver source to dissolve, and finally add the additive, and continue stirring to mix evenly.

[0041] After obtaining the mixed raw material liquid, the present invention performs a reduction reaction on the mixed raw material liquid at 110-180°C to obtain silver nanoparticles; the silver nanoparticles are right triangular bipyramidal silver nanoparticles and / or pentagonal silver nanorods. In the present invention, if the reduction reaction temperature is too low, the product is irregular small particles; if the reduction reaction temperature is too high, the product is mainly silver nanowires. The present invention preferably further selects a suitable reduction reaction temperature according to the specific morphology of the required silver nanoparticles. Specifically, when it is necessary to prepare right triangular bipyramidal silver nanoparticles, the reduction reaction temperature is preferably 110-170°C, more preferably 120°C; when it is necessary to prepare pentagonal silver nanorods, the reduction reaction temperature is preferably 120-180°C, more preferably 150°C. In the present invention, the reduction reaction time is preferably 2-7h, more preferably 5h. In the present invention, the reduction reaction is preferably carried out under stirring conditions, and the stirring rate is preferably 100-600rpm, more preferably 300rpm.

[0042] In the present invention, after the reduction reaction, the method preferably further comprises: centrifuging and washing the product system obtained after the reduction reaction to obtain silver nanoparticles. In the present invention, the number of centrifugal washing is preferably 3 to 5 times, the speed of each centrifugal washing is preferably 500 to 8000 rpm, more preferably 4000 rpm, and the time of each centrifugal washing is preferably 5 minutes. In the present invention, the reagent used for the centrifugal washing preferably includes methanol, ethanol or acetone; the present invention preferably removes the reaction solvent and unreacted reagents by centrifugal washing.

[0043] The invention adopts a one-pot method to prepare silver nanoparticles, wherein the silver nanoparticles are right triangular bipyramidal silver nanoparticles and / or pentagonal silver nanorods, wherein the yield of the right triangular bipyramidal silver nanoparticles is preferably 80-100%, and the yield of the pentagonal silver nanorods is preferably 80-100%. The silver nanoparticles prepared by the invention can be dispersed in ethanol for storage.

[0044] The invention can realize the preparation of a main product of a single morphology of right triangular bipyramidal silver nanoparticles or pentagonal silver nanorods by adjusting the raw material ratio and the temperature of the reduction reaction, and has simple operation and high preparation efficiency.

[0045] Specifically, with regard to the preparation of right trigonal bipyramidal silver nanoparticles, the preparation of right trigonal bipyramidal silver nanoparticles in the prior art requires the preparation of seed particles first, and the preparation process needs to be precisely controlled, with high overall process difficulty and low preparation efficiency. The method provided by the present invention does not require the dropwise addition of raw materials, nor does it require the prefabrication of seed particles; the preparation temperature is as low as 110°C, which is 50°C lower than the ordinary polyol synthesis method; and the preparation yield is relatively high. Among them, the present invention uses an appropriate amount of poly N-vinyl pyrrolidone and a lower reduction reaction temperature to facilitate the generation of single twin structure seeds; the use of quinone compounds can significantly enhance the stability of single twin structure seeds in the synthesis system through surface coating; a large number of single twin seeds eventually grow into right trigonal bipyramidal silver nanoparticles with a high yield.

[0046] As far as the preparation of pentagonal silver nanorods is concerned, the prior art uses a polyol synthesis method to synthesize silver nanorods, and no description is given from the product level as to whether the prepared silver nanorods have a pentagonal structure; other methods also require pre-synthesized decahedral particles or short nanorods as seed particles, and then continue to synthesize pentagonal nanorods. The present invention uses quinone compounds to regulate the polyol reduction method, and synthesizes high-yield pentagonal silver nanorods in one pot, without the need to add reaction reagents in steps or prefabricated seed particles. Among them, the appropriate reduction reaction temperature in the present invention first promotes the generation of five-fold twin structure seeds that can grow into pentagonal silver nanorods; quinone compounds are used to stabilize small particle seeds through surface coating, so that a large number of five-fold twin seeds exist in the synthesis system; limited silver sources allow many five-fold twin seeds to grow into short pentagonal silver nanorods with a high yield.

[0047] The present invention provides silver nanoparticles prepared by the preparation method described in the above technical solution, wherein the silver nanoparticles are right triangular bipyramidal silver nanoparticles and / or pentagonal silver nanorods. In the present invention, the long side length of the right triangular bipyramidal silver nanoparticles is 100 to 400 nm, preferably 200 to 380 nm, more preferably 250 to 370 nm, and further preferably 310 to 360 nm. In the present invention, the two end faces of the pentagonal silver nanorods are planes, and the diameter is preferably 40 to 110 nm, more preferably 50 to 100 nm, and further preferably 65 to 80 nm; the length of the pentagonal silver nanorods is 0.2 to 3 μm, preferably 0.4 to 2 μm, and further preferably 0.6 to 1.5 μm.

[0048] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] Example 1

[0050] The steps for preparing right trigonal bipyramidal silver nanoparticles are as follows:

[0051] 0.289g camphorquinone (CQ) and 0.155g poly (N-vinyl pyrrolidone) (PVP) were added to 15mL ethylene glycol, stirred until completely dissolved, 0.150g AgNO3 was added to the resulting solution, and after dissolution, 2.1mL of ethylene glycol solution with a concentration of 600μM FeCl3 was added, stirred evenly, and a mixed raw material liquid was obtained; the mixed raw material liquid was placed in an oil bath preheated to 120°C, and reacted for 5h at a magnetic stirring rate of 300rpm; the obtained product system was mixed with ethanol, and then centrifuged and washed, the precipitate was collected, the precipitate was mixed with ethanol and centrifuged and washed again, and the centrifugal washing was repeated 3 times, the centrifuge speed used for centrifugal washing was set to 4000rpm, and the time for each centrifugal washing was 5min, and the final precipitate was right triangular bipyramidal silver nanoparticles.

[0052] Figure 1 The SEM image and size distribution diagram of the right triangular bipyramidal silver nanoparticles prepared in Example 1 are shown in FIG. Figure 1 A and B in the figure are SEM images of the right triangular bipyramid silver nanoparticles at different magnifications, and C is a side length size distribution diagram of the right triangular bipyramid silver nanoparticles. Figure 1 It can be seen that the product prepared in Example 1 is mainly right triangular bipyramidal silver nanoparticles, and its yield is 88% according to statistics, mixed with a small amount of silver nanorods; the side length of the right triangular bipyramidal silver nanoparticles is mainly distributed in the range of 310 to 360 nm.

[0053] Figure 2 TEM image of the right triangular bipyramidal silver nanoparticles prepared in Example 1, as well as the lattice fringe image and the crystal plane spacing annotation image, Figure 2 A in the figure is a TEM image of the right triangular bipyramid silver nanoparticle, B is a local high-resolution TEM image of the right triangular bipyramid silver nanoparticle, and the inset is a lattice fringe image and a crystal plane spacing annotation image. Figure 1 and Figure 2 It can be seen that the right triangular bipyramidal silver nanoparticles prepared in Example 1 are composed of two symmetrically connected right tetrahedrons, and the edges of the right triangular bipyramidal silver nanoparticles are clear and sharp; Figure 2 From B in FIG. 1 , it can be seen that the surface of the right trigonal bipyramid silver nanoparticle has a lattice spacing of 0.21 nm, thus confirming that the right trigonal bipyramid surface is a (100) crystal plane.

[0054] Example 2

[0055] The steps for preparing pentagonal silver nanorods are as follows:

[0056] 0.289 g camphorquinone (CQ) and 0.115 g poly (N-vinyl pyrrolidone) (PVP) were added to 15 mL ethylene glycol, stirred until completely dissolved, 0.150 g AgNO3 was added to the resulting solution, and after dissolution, 2.1 mL of 600 μM FeCl3 ethylene glycol solution was added, stirred and dissolved to obtain a mixed raw material solution; the mixed raw material solution was placed in an oil bath preheated to 150° C., and reacted for 5 hours at a magnetic stirring rate of 300 rpm; the resulting product system was mixed with ethanol, and then centrifuged and washed, the precipitate was collected, the precipitate was mixed with ethanol and centrifuged and washed again, and the centrifugal washing was repeated 3 times, the centrifuge speed used for centrifugal washing was set to 4000 rpm, and the time for each centrifugal washing was 5 minutes, and the final precipitate was pentagonal silver nanorods.

[0057] Figure 3 The SEM image and size distribution diagram of the pentagonal silver nanorods prepared in Example 2 are shown in FIG. Figure 3 A and B are SEM images of the pentagonal silver nanorods at different magnifications, and C and D are diameter and length size distribution diagrams of the pentagonal silver nanorods, respectively. Figure 3 It can be seen that the product prepared in Example 3 is mainly nanorods, and the yield is 87% according to statistics; and the diameter of the nanorods is mainly distributed in the range of 65 to 80 nm, and the length is mainly distributed in the range of 0.8 to 1.5 μm.

[0058] Figure 4 TEM image, SEM image, lattice fringe image and interplanar spacing annotation image of the pentagonal silver nanorods prepared in Example 2; Figure 4 A in the figure is a TEM image of the pentagonal silver nanorod, and the inset is a SEM image of the end face of the pentagonal silver nanorod; B is a local high-resolution TEM image of the pentagonal silver nanorod, and the inset is a lattice fringe image and a crystal plane spacing annotation image. Figure 4 As can be seen from A in Example 2, the end faces of the pentagonal silver nanorods prepared in Example 2 are flat and have been confirmed to have a pentagonal structure. Figure 4 From B in FIG. 1 , it can be seen that the surface of the pentagonal silver nanorod has a 0.22 nm interplanar spacing, and the side surface is a (100) crystal plane.

[0059] Example 3

[0060] The method of Example 1 was followed, wherein the AgNO3 concentration in the mixed raw material solution was 0.058 M, the molar ratio of PVP to AgNO3 was maintained at 1.2:1, the molar ratios of CQ to AgNO3 were 0 (i.e., no CQ was added), 0.2, 0.6, 1, 2 and 4, respectively, and the reaction temperature was 120°C (parameters not specifically stated were operated according to Example 1).

[0061] Figure 5 The SEM images and yield graphs of silver nanoparticles prepared under different CQ concentration conditions in Example 3 are shown in FIG. Figure 5 A is the SEM image of silver nanoparticles prepared without adding CQ, B to E are the SEM images of silver nanoparticles prepared when the molar ratio of CQ to AgNO3 is 0.2, 0.6, 1, 2 and 4, respectively, and F is the yield of nanowires, nanorods and bipyramids under different conditions.

[0062] Depend on Figure 5 It can be seen from A in that when CQ is not added, the product is mainly silver nanowires (AgNWs) and a small amount of short rods, and the ends of the short rods are irregular. When a small amount of CQ is added, Figure 5 As shown in B, the product is silver nanowires, which have a more uniform morphology and a larger diameter than the nanowires in A. When the amount of CQ is increased to a molar ratio of 0.6 to AgNO3, as shown in Figure 5 As shown in C, it can be clearly seen that the product contains bipyramidal particles with a yield of about 15%. At this time, 85% of the main product is still nanowires. When the molar ratio of CQ to AgNO3 continues to increase, the number of bipyramidal particles continues to increase, accompanied by a decrease in the number of nanowires. When the molar ratio of CQ to AgNO3 is 2, Figure 5 As shown in D, there are a large number of bipyramidal particles (60%) and nanorods (35%) in the product, and there are no nanowires in the product. Figure 5 From E in the figure, it can be found that both the bipyramidal particles and nanorods in the product are obviously etched, and a large number of nearly spherical small particles are produced, indicating that too much CQ is not conducive to the preparation of bipyramidal particles and nanorods.

[0063] Example 4

[0064] The method of Example 1 was followed, wherein the AgNO3 concentration in the mixed raw material solution was 0.058 M, the molar ratio of CQ to AgNO3 was maintained at 2:1, the molar ratios of PVP to AgNO3 were 0.4, 0.8, 1.6 and 3.2, respectively, and the reaction temperature was 120°C (parameters not specifically stated were followed in Example 1).

[0065] Figure 6 The SEM images and yield graphs of silver nanoparticles prepared under different PVP concentration conditions in Example 4 are shown in FIG. Figure 6 A to C in the figure are SEM images of silver nanoparticles prepared when the molar ratio of CQ to AgNO3 is 0.4, 0.8 and 1.6, respectively, and D is the yield of bipyramids under different conditions. Figure 6It can be seen that with the increase of PVP concentration, the number of bipyramidal particles gradually increased, and the yield reached a maximum of 88% when the molar ratio of PVP to AgNO3 was 1.6, but too much PVP led to a decrease in the yield of bipyramidal particles.

[0066] Example 5

[0067] The method of Example 1 was followed, wherein the amounts of AgNO3 and FeCl3 were the same as in Example 1, in a molar ratio of PVP:CQ:AgNO3=1.2:2:1, and the reaction temperatures were 100°C, 110°C, 120°C and 150°C, respectively (parameters not specifically stated were followed in Example 1).

[0068] Figure 7 The SEM images and yield graphs of silver nanoparticles prepared under different reaction temperature conditions in Example 5 are shown in FIG. Figure 7 A to D in the figure are SEM images of silver nanoparticles prepared at reaction temperatures of 100°C, 110°C, 120°C and 150°C, respectively, and E is a graph showing the yield of silver nanorods under different reaction temperature conditions. Figure 7 It can be seen that when the reaction temperature is 100℃, only irregular small particles are synthesized; when the reaction temperature is increased to 110℃, although a small amount of bipyramidal particles and nanorods are synthesized, there are still a large number of irregular particles. When the reaction temperature is increased to 120℃, short nanorods are synthesized, and the size of the bipyramidal particles is significantly larger. When the reaction temperature is increased to 150℃, the diameter of the nanorods and the number of bipyramidal particles are significantly reduced, and the yield of nanorods under this reaction temperature condition reaches 87%. The results show that the yield of nanorods increases with the increase of reaction temperature, and the higher temperature of 150℃ is more suitable for synthesizing nanorods in the CQ-regulated process. This can be attributed to the relatively faster growth of silver nanoparticles caused by higher temperatures, making the five-fold twins more stable than the single twins in the synthesis system, thereby obtaining high-yield pentagonal silver nanorods.

[0069] Example 6

[0070] X-ray diffraction (XRD) was used to characterize the silver particles prepared under two different conditions. Specifically, the method of Example 1 was followed, wherein one preparation condition was that the molar ratio of PVP, CQ and AgNO3 was 1.2:2:1, and the other preparation condition was that CQ was omitted. Figure 8The XRD patterns of silver nanoparticles prepared under two different conditions, where the red line is the XRD pattern of silver nanoparticles prepared using CQ, the black line is the XRD pattern of silver nanoparticles prepared without CQ, and the green line is the standard XRD peak of bulk silver in reference PDF card No. 65-2871. The results show that according to the standard XRD peak of silver, the theoretical value of the intensity ratio between the (111) and (100) peaks of bulk silver is 2.5. In this embodiment, the corresponding peak intensity ratio of the silver nanoparticles prepared without CQ is 4.6. This higher intensity indicates that the prepared silver nanoparticles are mainly silver nanowires rich in (111) crystal planes. However, for the silver particles prepared using CQ, the intensity ratio between the (111) and (100) peaks is 1.9, which is lower than the ratio of bulk silver, indicating that the product contains a large number of right trigonal bipyramidal silver nanoparticles rich in (100) crystal planes. This result shows that the addition of CQ promotes the growth of right trigonal bipyramidal silver nanoparticles.

[0071] In order to further explore the regulatory mechanism of CQ on the synthesis of silver nanoparticles, X-ray photoelectron spectroscopy (XPS) test was carried out on the prepared silver nanoparticles. Fig. 9 is the C1s XPS spectrum and fitting curve, Fig. 9 A in the figure corresponds to silver nanoparticles prepared under the condition that the molar ratio of PVP, CQ and AgNO3 is 1.6:2:1, wherein the amounts of AgNO3 and FeCl3 are the same as those in Example 1; B corresponds to pure CQ, and C corresponds to pure PVP. Fig. 9 As shown in A, by fitting and splitting the C1s peak, four obvious peaks can be found at 288.78eV, 287.43eV, 285.63eV and 284.49eV respectively; the corresponding peaks of pure CQ are at 284.73eV, 285.61eV, 286.50eV and 288.80eV, and the corresponding peaks of pure PVP are at 284.49eV, 285.42eV and 287.14eV. The corresponding chemical groups and their positions are shown in Table 1. Fig. 9 The peak of the silver nanoparticle product corresponding to A at 287.43eV corresponds to the 287.14eV peak of C=O in the pure PVP molecule, indicating that PVP is coated on the surface of the silver nanoparticle product, which is consistent with the PVP coating mechanism confirmed in the classical polyol method for synthesizing silver nanowires. Among them, 288.80eV is the peak of C=O in CQ, and Fig. 9 The silver nanoparticle product corresponding to A in FIG. 1 also has a characteristic peak at a very close position of 288.78 eV, which can indicate that CQ molecules are adsorbed on the surface of the silver nanoparticles. Therefore, it is preliminarily determined that CQ plays a coating role in the synthesis of silver nanoparticles.

[0072] Table 1 C1s binding energy in pure PVP and CQ molecules

[0073]

[0074]

[0075] The prepared silver nanoparticles (the molar ratio of PVP, CQ and AgNO3 was 1.6:2:1) and pure PVP and pure CQ were tested by infrared spectroscopy (FTIR). Fig.10 The FTIR spectra of CQ (camphorquinone), prepared silver nanoparticles and pure PVP (polyvinylpyrrolidone) show that the peak positions corresponding to C=O of pure CQ and PVP are 1745 cm -1 and 1652cm -1 In terms of the coating mechanism of PVP on silver nanoparticles, studies have confirmed that the interaction between C=O and silver causes the corresponding characteristic peak to blue-shift to 1643 cm -1 position, and this embodiment Fig.10 As shown in the spectrum of silver nanoparticles, the -1 There is an obvious characteristic peak at 1723cm -1 The characteristic peak at 1745cm is particularly significant, which should be caused by the interaction between C=O in CQ and silver. -1 The result of the blue shift here indicates that CQ is coated with silver through the reaction of C=O with silver during the synthesis of silver nanoparticles, which is similar to PVP.

[0076] Combined with the above research results, it can be inferred that CQ has a regulatory mechanism for the synthesis of right triangular bipyramidal silver nanoparticles and pentagonal silver nanorods. Fig.11 The schematic diagram of the synthesis mechanism of right triangular bipyramidal silver nanoparticles and pentagonal silver nanorods regulated by CQ is shown in Path I. With the addition of CQ, seeds with quintuple twins and single twins were obtained, while seeds generated by the traditional polyol method without CQ were mainly quintuple twins. This is because the traditional polyol method only uses PVP as a selective coating agent. PVP, as a macromolecular long-chain structure, needs to overcome steric hindrance when coating small-sized seed particles, while CQ, as a small molecule, has more advantages in coating seeds. Therefore, it can be coated on the surface of single twins to make them more stable, thereby inducing single twins and quintuple twins to exist in the synthesis system as dominant seeds at the same time, and then they grow into right triangular bipyramidal silver nanoparticles and pentagonal silver nanorods, respectively. Fig.11Paths II and III are the regulatory mechanisms for synthesizing right triangular bipyramidal silver nanoparticles and pentagonal silver nanorods as single morphologies respectively by adjusting the PVP concentration and temperature. As shown in Path II, at a relatively low temperature of 120°C, with the increase in the amount of PVP, the product is mainly right triangular bipyramidal silver nanoparticles. The increase in PVP concentration increases the viscosity of the synthetic solution. Both the higher viscosity and the relatively lower temperature lead to a slower growth rate of silver nanoparticles, which is more conducive to the stability of single twins and then grows into right triangular bipyramidal silver nanoparticles. In contrast, the relatively high temperature of 150°C enables silver nanoparticles to have a faster growth rate, which is more conducive to the stability of pentagonal twin seeds. At the same time, more seeds are generated at high temperature, and a large number of short pentagonal silver nanorods are generated while the total amount of silver source in the synthetic system remains unchanged.

[0077] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing silver nanoparticles by using a quinone compound to regulate the polyol reduction method, comprising the following steps: A quinone compound, poly N-vinyl pyrrolidone, a silver source, an additive and a polyol compound are mixed to obtain a mixed raw material liquid; the amount ratio of the quinone compound, poly N-vinyl pyrrolidone, the silver source, the additive and the polyol compound is (0.02-0.25) mol: (0.01-2) mol: (0.01-0.1) mol: (0.00001-0.0001) mol: 1L; the quinone compound is one or more of camphorquinone, naphthoquinone and phenanthrenequinone; The mixed raw material liquid is subjected to a reduction reaction at 110-180° C. to obtain silver nanoparticles; the silver nanoparticles are right triangular bipyramidal silver nanoparticles and / or pentagonal silver nanorods; By adjusting the ratio of the quinone compound and the silver source, the silver nanoparticles can be adjusted to be single right triangular bipyramidal silver nanoparticles, or single pentagonal silver nanorods, or a mixture of right triangular bipyramidal silver nanoparticles and pentagonal silver nanorods.

2. The method according to claim 1, characterized in that The molecular weight of the poly N-vinyl pyrrolidone is 10000-1300000 g / mol.

3. The method according to claim 1, characterized in that The silver source includes one or more of silver nitrate, silver acetate, silver oxalate, silver hexafluorophosphate and silver hexafluoroantimonate.

4. The method according to claim 1, characterized in that: The additive includes one or more of sodium chloride, potassium chloride, ferric chloride, copper chloride, hexadecyltrimethylammonium chloride, sodium bromide, potassium bromide and hexadecyltrimethylammonium bromide.

5. The method according to claim 1, characterized in that The polyol compound includes one or more of ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, neopentyl glycol, diethylene glycol and glycerol.

6. The method according to claim 1, characterized in that The reduction reaction time is 2 to 7 hours.

7. The method according to claim 1 or 6, characterized in that: The reduction reaction is carried out under stirring conditions, and the stirring rate is 100-600 rpm.

8. The method according to claim 1, characterized in that After the reduction reaction, the method further comprises: centrifuging and washing the product system obtained after the reduction reaction to obtain silver nanoparticles; the reagent used for the centrifugal washing includes methanol, ethanol or acetone.

9. The method according to claim 1, characterized in that: The two end faces of the pentagonal silver nanorod are flat, with a diameter of 40-110 nm and a length of 0.2-3 μm.

10. The method according to claim 1, characterized in that The long side length of the right triangular bipyramidal silver nanoparticles is 100-400 nm.

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