Silver nanoparticles with broad-spectrum absorption characteristics and a synthesis method thereof

Abstract

The present invention discloses a silver nanoparticle with wide spectrum absorption characteristics and its preparation method and use. The silver nanoparticle has a tooth-shaped branch structure, including a silver nanocore and a tooth-shaped branch that radiates outward from the center of the silver nanocore and grows epitaxially along the circumference, and the gap size between adjacent tooth-shaped branches is 5-20 nm. Its preparation method includes: step S1, seed presynthesis: adding sodium citrate solution to a silver salt solution under magnetic stirring conditions for seed presynthesis, the time is 45min-90min; step S2, branched growth: adding a reducing agent ascorbic acid solution and / or glucose dropwise to the solution of step S1, branched growth, the time is 30min-120min; step S3, centrifuging the product obtained in step S2 with a centrifugal solvent. The silver nanoparticles provided by the present invention show more excellent light absorption characteristics, and can achieve full-band broadband absorption within the spectral range of 400-1000 nm, which greatly improves the utilization efficiency of the material to sunlight.

Description

Technical Field

[0001] The invention belongs to the technical field of metal nano material preparation, and particularly relates to a synthesis technology of silver nano particles with wide spectrum absorption characteristics. Background Art

[0002] As environmental pollution and energy crisis become increasingly serious, renewable energy has received widespread attention. Solar energy conversion is an important scientific frontier in the field of new energy, but it faces many challenges in achieving efficient utilization. In order to concentrate as much solar energy as possible to meet the huge energy demand, it is crucial to improve the efficiency of solar energy absorption.

[0003] Plasmonic metal nanomaterials have large scattering and absorption cross sections. The localized surface plasmon resonance characteristics formed after light excitation can significantly enhance the absorption of light by metal nanoparticles and greatly enhance the interaction between light and matter. At the same time, the hot carriers generated by plasmon relaxation can effectively convert solar energy into chemical energy and drive the chemical reaction of materials. Therefore, plasmonic metal nanomaterials provide a feasible path to improve the efficiency of solar energy conversion and solve energy problems.

[0004] Surface plasmon resonance, as a structure-driven light absorption mode, is strongly affected by factors such as material properties, size, configuration, and surrounding media. Although most plasmon nanoparticles with different morphologies have been successfully synthesized (spherical, polyhedral, coral-shaped, rod-shaped, etc.), most plasmon metal nanoparticles still exhibit strong plasmon resonance characteristics mainly in the visible light region, making their utilization efficiency of sunlight still low. Considering the broadband characteristics of the solar spectrum, achieving visible light and near-infrared light absorption covering the entire solar spectrum is of great significance for improving solar energy utilization efficiency and meeting practical application requirements. Therefore, it is necessary to develop a plasmon metal nanomaterial to further improve light energy utilization and achieve efficient and large-scale solar energy collection. Summary of the invention

[0005] In order to overcome the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a silver nanoparticle with wide spectrum absorption characteristics, the silver nanoparticle morphology is a toothed branch structure, the toothed branch structure includes a silver nanocore and a toothed branch that radiates outward from the center of the silver nanocore along the circumference. The gap size between adjacent toothed branches is 5-20nm. Different gap sizes between toothed branches, and toothed branches of different lengths, widths, and curvatures lead to different plasmon resonance modes, which are finally superimposed to form a broadband plasmon resonance.

[0006] At the same time, another object of the present invention is to provide a synthesis method for preparing the above-mentioned silver nanoparticles with wide spectrum absorption characteristics. The method only changes the seed presynthesis time, the branching growth time, and the synergistic relationship between the two, and by regulating the synergistic effect between the reactants and sodium citrate and the reactants and the reducing agent, silver nanoparticles with wide spectrum absorption characteristics can be obtained, and their morphology presents a tooth-like branched structure.

[0007] Another object of the present invention is to provide an application of the above-mentioned silver nanoparticles with wide spectrum absorption characteristics in the field of solar energy conversion technology. By using the above-mentioned silver nanoparticles with wide spectrum absorption characteristics, the local electromagnetic field intensity around the silver nanoparticles is greatly improved through the strong coupling effect between the tooth-like branch structures of the silver nanoparticles, and then the full-band broadband absorption can be achieved in the spectral range of 400-1000 nm, which significantly improves the utilization efficiency of sunlight.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A silver nanoparticle with wide spectrum absorption characteristics. The silver nanoparticle has a tooth-shaped branch structure. The tooth-shaped branch structure includes a silver nanocore and tooth-shaped branches that radiate outward from the center of the silver nanocore and grow epitaxially along the circumference.

[0010] Preferably, the gap size between adjacent tooth-like branches is 5-20 nm.

[0011] A method for synthesizing silver nanoparticles having broad spectrum absorption characteristics comprises the following steps:

[0012] Step S1, seed presynthesis: adding sodium citrate solution to the silver salt solution under magnetic stirring conditions to perform seed presynthesis, the seed presynthesis time is 45 min - 90 min;

[0013] Step S2, branching growth: adding a reducing agent ascorbic acid solution and / or glucose dropwise to the solution of step S1 to perform branching growth, the branching growth time being 30 min - 120 min;

[0014] Step S3, centrifugally separating the product obtained in step S2 using a centrifugal solvent to obtain silver nanoparticles with broad spectrum absorption characteristics dispersed in the centrifugal solvent.

[0015] Preferably, in step S1, the concentration ratio of the silver salt solution to the sodium citrate solution is 1:10-1:20.

[0016] Preferably, the concentration of the reducing agent ascorbic acid solution in step S2 is 0.02-0.1 M.

[0017] Preferably, the centrifugation solvent in step S3 is anhydrous ethanol.

[0018] The invention also discloses application of silver nanoparticles with wide spectrum absorption characteristics in the field of solar energy conversion technology.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] 1. The present invention provides a silver nanoparticle with wide spectrum absorption characteristics, wherein the morphology is a tooth-shaped branch structure, the tooth-shaped branch structure includes a silver nanocore and tooth-shaped branches that radiate outward from the center of the silver nanocore and grow epitaxially along the circumference. The gap size between adjacent tooth-shaped branches is 5-20 nm, and the nanoparticle size is uniform.

[0021] The silver nanoparticles with the dentate branch structure have the characteristics of a broad peak in the extinction spectrum, which corresponds to a higher level of resonant absorption than the dipole resonance. Multiple plasmon resonance bands overlap, and at the same time, the strong coupling between the dentate branch structures greatly enhances the local electromagnetic field intensity around them, so that the silver nanoparticles with the dentate branch structure can achieve full-band broadband absorption in the spectral range of 400-1000 nm, significantly improving the utilization efficiency of sunlight.

[0022] 2. The present invention also provides a method for synthesizing silver nanoparticles with wide-spectrum absorption characteristics. The method only changes the seed presynthesis time, the branching growth time, and the synergistic relationship between the two. By regulating the synergistic effect between the reactants and sodium citrate and the reactants and the reducing agent, silver nanoparticles with wide-spectrum absorption characteristics can be obtained, and their morphology presents a toothed branched structure.

[0023] The present invention controls the branching growth of silver nanoparticles according to the reaction kinetics between reactants and reducing agents, and obtains silver nanoparticles with a dentate branching structure without introducing a surface protective agent as a structure directing agent. The reaction conditions are simple and the process is simple. In the traditional method of preparing the surface morphology of nanoparticles with anisotropic shapes, surfactants or structure directing agents with different functional groups with different binding strengths are mostly used. In order to remove the hindrance of stubborn surfactants, more cumbersome and energy-consuming post-processing steps will be added, such as annealing, ultraviolet treatment or acetic acid treatment, which will seriously affect its large-scale use. The preparation method of the dentate branching silver nanoparticles synthesized by the present method is simple, reliable, and easy to operate and implement. It can be completed by mixing the silver salt solution, sodium citrate solution and ascorbic acid solution in steps at room temperature.

[0024] 3. The present invention also provides the application of silver nanoparticles with broad-spectrum absorption characteristics in the field of solar energy conversion technology. Compared with the plasmonic metal nanomaterials with narrow-band absorption characteristics obtained by existing synthesis methods, the silver nanoparticles provided by the present invention exhibit more excellent light absorption characteristics. In the spectral range of 400-1000 nm, broadband absorption across the entire band can be achieved, greatly improving the utilization efficiency of the material for sunlight. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the embodiments of the present invention.

[0026] Figure 1 It is a synthesis method of silver nanoparticles with broad-spectrum absorption characteristics in the present invention;

[0027] Figure 2 It is a typical scanning electron microscope image of the silver nanoparticles obtained in Example 1;

[0028] Figure 3 It is a typical transmission electron microscope image of the silver nanoparticles obtained in Example 1;

[0029] Figure 4 It is the normalized extinction spectrum of the silver nanoparticles obtained in Example 1;

[0030] Figure 5 It is a typical scanning electron microscope image of the silver nanoparticles obtained in Comparative Example 1;

[0031] Figure 6 It is the normalized extinction spectrum of the silver nanoparticles obtained in Comparative Example 1;

[0032] Figure 7 It is a typical scanning electron microscope image of the silver nanoparticles obtained in Example 2;

[0033] Figure 8 It is the normalized extinction spectrum of the silver nanoparticles obtained in Example 2;

[0034] Figure 9 It is a typical scanning electron microscope image of the silver nanoparticles obtained in Comparative Example 2;

[0035] Figure 10 It is the normalized extinction spectrum of the silver nanoparticles obtained in Comparative Example 2;

[0036] Figure 11 It is a typical scanning electron microscope image of the silver nanoparticles obtained in Example 3;

[0037] Figure 12is the normalized extinction spectrum of the silver nanoparticles obtained in Example 3;

[0038] Figure 13 is a typical scanning electron microscope image of the silver nanoparticles obtained in Example 4;

[0039] Figure 14 is the normalized extinction spectrum of the silver nanoparticles obtained in Example 4;

[0040] Figure 15 is a typical scanning electron microscope image of the silver nanoparticles obtained in Example 5;

[0041] Figure 16 is the normalized extinction spectrum of the silver nanoparticles obtained in Example 5. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below through the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0043] The present invention provides a silver nanoparticle with wide spectrum absorption characteristics. The silver nanoparticle has a tooth-shaped branch structure. The tooth-shaped branch structure includes a silver nanocore and tooth-shaped branches that radiate outward from the center of the silver nanocore and grow epitaxially along the circumference. The tooth-shaped branch structure can be a uniformly distributed tooth-shaped branch structure or a non-uniformly distributed tooth-shaped branch structure. The gap size between adjacent tooth-shaped branches is 5-20 nm. The silver nanoparticle with a tooth-shaped branch structure can achieve full-band light broadband absorption in the 400-1000nm spectrum range.

[0044] Specifically, the present invention provides a silver nanoparticle having a wide spectrum absorption characteristic, wherein the silver nanoparticle has a uniformly distributed tooth-like branch structure. Figure 2 and Figure 3 The corresponding typical scanning electron microscope images and transmission electron microscope images are shown respectively. From the images, it can be clearly observed that the silver nanoparticles have a uniformly distributed serrated branch structure. Figure 4 is the normalized extinction spectrum of the silver nanoparticles. From the spectrum, it can be found that the silver nanoparticles show wide-spectrum absorption characteristics in the wavelength range of 400 ~ 1000 nm, indicating that the silver nanoparticles with this structure can achieve full-band broadband absorption of light in the 400-1000nm spectral range.

[0045] The following is a more clear explanation of the principle that the silver nanoparticles with broad spectrum absorption characteristics provided by the present invention show broad spectrum absorption characteristics within a wavelength range of 400 to 1000 nm.

[0046] Multiple plasmon resonance modes excited within metal nanostructures endow them with unique optical properties. For metal nanostructures of different shapes, the excited plasmon resonance modes are different, which directly affects the spectral position and shape of local surface plasmon resonance.

[0047] Silver nanoparticles with dentate branch structures have different gap sizes, lengths, widths, and curvatures between the dentate structure branches. This structure will result in different plasmon resonance modes, which finally superimpose to form broadband plasmon resonance. In addition, the strong coupling effect between the dentate structures greatly enhances the intensity of the local electromagnetic field around them, enabling the silver nanoparticles to have nearly full-band light absorption ability and achieving full-band broadband absorption in the spectral range of 400 - 1000 nm.

[0048] The broad peak obtained in this invention corresponds to resonance absorption at a higher level than dipole resonance. Multiple plasmon resonance frequency bands overlap, resulting in good absorption ability in the visible to infrared light range. Compared with the plasmonic metal nanomaterials with narrow-band absorption characteristics obtained in existing synthesis methods, it shows more excellent light absorption characteristics, greatly improving the utilization efficiency of the material for sunlight.

[0049] This invention also provides a kind of silver nanoparticles with broadband spectral absorption characteristics. The silver nanoparticles have an unevenly distributed dentate branch structure. Figure 7 and Figure 8 are the corresponding typical scanning electron microscope pictures and normalized extinction spectra respectively. It can be clearly observed from Figure 7 that the silver nanoparticles have an unevenly distributed dentate branch structure. At the same time, it can be seen from Figure 8 the spectrum that these silver nanoparticles with an uneven dentate branch structure show broadband spectral absorption characteristics in the wavelength range of 400 - 1000 nm, indicating that the silver nanoparticles of this structure have the ability to achieve full-band light broadband absorption in the 400 - 1000 nm spectral range.

[0050] This invention provides another kind of silver nanoparticles with broadband spectral absorption characteristics. The silver nanoparticles have an unevenly distributed dentate branch structure. Figure 11 and Figure 12 are the corresponding typical scanning electron microscope pictures and normalized extinction spectra respectively. It can be clearly observed from Figure 11 that the silver nanoparticles have an unevenly distributed dentate branch structure. At the same time, it can be seen from Figure 12 the spectrum that these uneven dentate branch structure silver nanoparticles show broadband spectral absorption characteristics in the wavelength range of 400 - 1000 nm, indicating that the silver nanoparticles of this structure have the ability to achieve full-band light broadband absorption in the 400 - 1000 nm spectral range.

[0051] The invention provides another kind of silver nanoparticles with broadband absorption characteristics. The silver nanoparticles have a non-uniformly distributed dentate branch structure. Figure 13 And Figure 14 Figure (a) and Figure (b) are respectively the corresponding typical scanning electron microscope images and normalized extinction spectra. It can be clearly observed from Figure 13 Figure (a) that the silver nanoparticles have a non-uniformly distributed dentate branch structure. At the same time, it can be seen from Figure 14 Figure (b) that these silver nanoparticles show broadband absorption characteristics in the wavelength range of 400 - 1000 nm, indicating that the silver nanoparticles with this structure have the ability to achieve full-band broadband light absorption in the 400 - 1000 nm spectral range.

[0052] The invention also provides a method for synthesizing silver nanoparticles with broadband absorption characteristics, including the following steps:

[0053] Step S1, seed pre-synthesis: Add a sodium citrate solution to a silver salt solution under magnetic stirring for seed pre-synthesis. The time for seed pre-synthesis is 45 min - 90 min;

[0054] Step S2, branched growth: Add a reducing agent ascorbic acid solution and / or glucose dropwise to the solution in Step S1 for branched growth. The time for branched growth is 30 min - 120 min.

[0055] Step S3, centrifuge and separate the product obtained in Step S2 with a centrifugation solvent, and silver nanoparticles with broadband absorption characteristics dispersed in the centrifugation solvent are obtained.

[0056] Among them,

[0057] In Step S1, the concentration ratio of the silver salt solution to the sodium citrate solution is 1:10 - 1:20.

[0058] In Step S2, the concentration of the reducing agent ascorbic acid solution is 0.02 - 0.1 M.

[0059] In Step S3, the centrifugation solvent is absolute ethanol.

[0060] Next, multiple embodiments of the method for synthesizing silver nanoparticles with broadband absorption characteristics will be used to further illustrate this preparation method. Example 1

[0061] In this example, silver nanoparticles with broadband absorption characteristics are prepared by the following method.

[0062] Step S1, seed pre-synthesis: Prepare 0.01 M silver nitrate precursor solution and 0.1 M sodium citrate precursor solution respectively. Then add 0.2 mL of 0.01 M silver nitrate solution to 2 mL of deionized water, with a stirring speed of 800 rpm. Use a syringe to drop 0.1 mL of 0.1 M sodium citrate precursor solution into the above solution for seed pre-synthesis. The stirring speed of the solution is 500 - 600 rpm, and the reaction time is 1 h;

[0063] Step S2, branched growth: Use a syringe to drop 0.3 ml of 0.04 M ascorbic acid reducing agent solution into the above solution for branched growth. Under the condition of a 25 °C water bath and a magnetic stirring speed of 500 - 600 rpm for 30 min. The color of the solution changes from colorless to light gray and finally to dark gray.

[0064] Step S3, centrifuge and wash the final product obtained above with absolute ethanol at 8000 rpm, and finally obtain silver nanoparticles with broadband absorption characteristics dispersed in ethanol.

[0065] Figure 1 It is a synthesis method of silver nanoparticles with broadband absorption characteristics provided by the present invention.

[0066] Figure 2 and Figure 3 are respectively the typical scanning electron microscope image and transmission electron microscope image of the silver nanoparticles with broadband absorption characteristics prepared in Example 1. It can be observed from Figure 2 and Figure 3 that the silver nanoparticles show a uniformly distributed tooth-like branched structure. Figure 4 is the normalized extinction spectrum of the tooth-like branched structure silver nanoparticles prepared in Example 1. It can be observed from the figure that the prepared silver nanoparticles show broadband absorption characteristics in the wavelength range of 400 - 1000 nm. The above evidence strongly shows that the above technical solution successfully prepares silver nanoparticles with broadband absorption characteristics and a tooth-like branched structure.

[0067] From a mechanistic perspective, it can be explained that sodium citrate acts as a shape-directing agent in this reaction. In a manner similar to a functional surfactant, it controls the shape of the nanocrystals through carboxyl groups. First, use sodium citrate to reduce the Ag precursor, and the silver ions are reduced to atoms and aggregated to form Ag seeds. The carboxyl groups of sodium citrate are adsorbed on specific crystal planes of the Ag particles, resulting in different growth rates of different crystal planes of the Ag seeds and selectively growing into nanocrystals. Subsequently, use ascorbic acid as a reducing agent and capping agent. The Ag seeds continue to branch and grow through the oriented attachment growth mechanism and Ostwald ripening mechanism, further promoting the branched growth of the Ag seeds, and finally obtaining silver nanoparticles with a tooth-like branched structure.

[0068] This method changes the seed pre-synthesis time, the branched growth time, and their synergistic relationship. Without introducing a surface protecting agent as a structure-directing agent, by only regulating the synergy between the reaction of the reactant with sodium citrate and the reaction of the reactant with the reducing agent, silver nanoparticles with broadband absorption characteristics can be obtained, and their morphology presents a toothed branched structure. The reaction conditions are simple, the preparation method is simple and easy to operate and implement, and it can be completed at room temperature, which is especially beneficial to large-scale production applications.

[0069] To further clearly illustrate the regulation effect of the seed pre-synthesis time on the morphology of silver nanoparticles, Comparative Example 1, Comparative Example 2 and Example 1 are designed for further comparative illustration below. Comparative Example 1

[0070] Step S1, seed pre-synthesis: Prepare 0.01 M silver nitrate precursor solution and 0.1 M sodium citrate precursor solution respectively. Then add 0.2 mL of 0.01 M silver nitrate solution to 2 mL of deionized water, and the stirring speed is 800 rpm. Use a syringe to drop 0.1 mL of 0.1 M sodium citrate precursor solution into the above solution for seed pre-synthesis. The stirring speed of the solution is 500 - 600 rpm, and the reaction time is 30 min;

[0071] Step S2, use a syringe to drop 0.3 ml of 0.04 M ascorbic acid reducing agent solution into the above solution for branched growth. In a 25 °C water bath, stir magnetically for 30 min under the condition of a rotation speed of 500 - 600 rpm. The color of the solution changes from colorless to light gray and finally to dark gray.

[0072] Step S3, centrifuge and wash the above-obtained final product with absolute ethanol at 8000 rpm, and finally obtain silver nanoparticles dispersed in ethanol.

[0073] In summary, the difference between the above Comparative Example 1 and Example 1 is only that the reaction time in Step 1 is 30 min.

[0074] Figure 5 and Figure 6 are the typical scanning electron microscope pictures and their normalized extinction spectra of the silver nanoparticles obtained in Comparative Example 1 respectively. It can be seen from Figure 5 that the silver nanoparticles prepared in Comparative Example 1 present a structure mixed with uneven disc-shaped and toothed structures. At the same time, it is observed Figure 6 that, compared with the broadband characteristics in Example 1, Figure 6The extinction spectrum shows relatively narrow peak characteristics, indicating that the silver nanoparticles with an uneven disc-shaped and tooth-shaped mixed structure prepared in Comparative Example 1 do not have broad-spectrum absorption characteristics in the wavelength range of 400 - 1000 nm. Comparative Example 2

[0075] Step S1, seed pre-synthesis: Prepare 0.01 M silver nitrate precursor solution and 0.1 M sodium citrate precursor solution respectively. Then add 0.2 mL of 0.01 M silver nitrate solution to 2 mL of deionized water, and the stirring speed is 800 rpm. Use a syringe to drop 0.1 mL of 0.1 M sodium citrate precursor solution into the above solution for seed pre-synthesis. The stirring speed of the solution is 500 - 600 rpm, and the reaction time is 2 h;

[0076] Step S2, branched growth: Use a syringe to drop 0.3 ml of 0.04 M ascorbic acid reducing agent solution into the above solution for branched growth. In a 25 °C water bath, stir magnetically for 30 min under the condition of a rotation speed of 500 - 600 rpm. The color of the solution changes from colorless to light gray and finally to dark gray.

[0077] Step S3, centrifuge and wash the final product obtained above with absolute ethanol at 8000 rpm to finally obtain uneven disc-shaped silver nanoparticles dispersed in ethanol.

[0078] In summary, the difference between Comparative Example 2 and Example 1 is only that the reaction time in Step 1 is 2 h.

[0079] Figure 9 and Figure 10 are respectively the typical scanning electron microscope pictures and the normalized extinction spectra of the uneven disc-shaped silver nanoparticles obtained in Comparative Example 2. As can be seen from Figure 9 it, the silver nanoparticles prepared in Comparative Example 2 show an uneven disc shape. At the same time, it is observed Figure 10 that the extinction spectrum shows relatively narrow peak characteristics, indicating that the silver nanoparticles with an uneven disc shape prepared in Comparative Example 2 do not have broad-spectrum absorption characteristics in the wavelength range of 400 - 1000 nm.

[0080] By comparing Example 1, Comparative Example 1 and Comparative Example 2, it can be found that the seed pre-synthesis time is the main influencing factor affecting the formation of the tooth-shaped branched structure. When the seed pre-synthesis time is too short, the synthesized nanostructure tends to be a mixed mode of uneven disc shape and tooth shape. This indicates that the reaction is not complete and the seed pre-synthesis time needs to be further extended. When the seed pre-synthesis time is too long, the synthesized nanostructure tends to be an uneven disc shape. This is attributed to the fact that the nanostructure will eventually evolve into a stable shape through Ostwald ripening as the reaction time prolongs. Example 2

[0081] In this example, silver nanoparticles with broad-spectrum absorption characteristics were prepared by the following method.

[0082] Step S1, seed pre-synthesis: Prepare 0.01 M silver acetate precursor solution and 0.1 M sodium citrate precursor solution respectively. Then add 0.2 mL of 0.01 M silver acetate solution to 2 mL of deionized water, and the stirring speed is 800 rpm. Use a syringe to drop 0.1 mL of 0.1 M sodium citrate precursor solution into the above solution for seed pre-synthesis. The stirring speed of the solution is 500 - 600 rpm, and the reaction time is 90 min;

[0083] Step S2, branched growth: Use a syringe to drop 0.3 ml of 0.04 M glucose reducing agent solution into the above solution for branched growth. Under the condition of a 25 °C water bath and a rotational speed of 500 - 600 rpm, magnetically stir for 30 min. The color of the solution changes from colorless to light gray and finally to dark gray.

[0084] Step S3, centrifuge and wash the final product obtained above with absolute ethanol at 8000 rpm to finally obtain silver nanoparticles dispersed in ethanol.

[0085] Figure 7 and Figure 8 are the typical scanning electron microscope pictures and normalized extinction spectra of a kind of silver nanoparticles with broad-spectrum absorption characteristics prepared in Example 2. From Figure 7 it can be observed that the structure of the silver nanoparticles is an uneven tooth-like branched structure. At the same time, from Figure 8 the spectrum, it can be seen that such silver nanoparticles show broad-spectrum absorption characteristics in the wavelength range of 400 - 1000 nm, and can achieve broadband absorption of light in the whole band. Example 3

[0086] In this example, silver nanoparticles with broad-spectrum absorption characteristics were prepared by the following method.

[0087] Step S1, seed pre-synthesis: Prepare 0.01 M silver nitrate precursor solution and 0.1 M sodium citrate precursor solution respectively. Then add 0.2 mL of 0.01 M silver salt silver nitrate solution to 2 mL of deionized water, and the stirring speed is 800 rpm. Use a syringe to drop 0.1 mL of 0.1 M sodium citrate precursor solution into the above solution for seed pre-synthesis. The stirring speed of the solution is 500 - 600 rpm, and the reaction time is 1 h;

[0088] Step S2, branched growth: 0.3 ml of 0.04 M ascorbic acid reducing agent solution was added dropwise to the above solution using a syringe for branched growth. Under the conditions of a 25 °C water bath and a magnetic stirring speed of 500 - 600 rpm for 1 h. The color of the solution changed from colorless to light gray and finally to dark gray.

[0089] Step S3, the final product obtained above was centrifugally washed with absolute ethanol at 8000 rpm, and finally silver nanoparticles dispersed in ethanol were obtained.

[0090] Figure 11 and Figure 12 are respectively the typical scanning electron microscope images and normalized extinction spectra of a kind of silver nanoparticles with broad-spectrum absorption characteristics prepared in this embodiment. From Figure 11 it can be observed that the silver nanoparticles are an uneven tooth-like branched structure. At the same time, from Figure 12 the spectrum, it can be seen that such uneven tooth-like branched structure silver nanoparticles show broad-spectrum absorption characteristics in the wavelength range of 400 - 1000 nm, and can achieve broadband absorption of light in the whole band. Example 4

[0091] In this example, silver nanoparticles with broad-spectrum absorption characteristics were prepared by the following method.

[0092] Step S1, seed pre-synthesis: 0.01 M silver nitrate precursor solution and 0.1 M sodium citrate precursor solution were respectively prepared, and then 0.2 mL of 0.01 M silver nitrate solution was added to 2 mL of deionized water, and the stirring speed was 800 rpm. 0.1 mL of 0.1 M sodium citrate precursor solution was added dropwise to the above solution using a syringe for seed pre-synthesis, the stirring speed of the solution was 500 - 600 rpm, and the reaction time was 1 h;

[0093] Step S2, branched growth: 0.3 ml of 0.04 M ascorbic acid reducing agent solution was added dropwise to the above solution using a syringe for branched growth. Under the conditions of a 25 °C water bath and a magnetic stirring speed of 500 - 600 rpm for 2 h. The color of the solution changed from colorless to light gray and finally to dark gray.

[0094] Step S3, the final product obtained above was centrifugally washed with absolute ethanol at 8000 rpm, and finally silver nanoparticles dispersed in ethanol were obtained.

[0095] Figure 13 and Figure 14 are respectively the typical scanning electron microscope images and normalized extinction spectra of a kind of silver nanoparticles with broad-spectrum absorption characteristics prepared in this embodiment. From Figure 13It can be observed that it is an uneven tooth-like branched structure. At the same time, from Figure 14 the spectrogram, it can be seen that such uneven tooth-like branched structure silver nanoparticles show broadband spectral absorption characteristics in the wavelength range of 400 - 1000 nm, and can achieve broadband light absorption in the full wavelength band.

[0096] By comparing Examples 1, 3, and 4, it can be found that when the seed pre-synthesis time is the same and only the branching reaction time is changed, the finally prepared silver nanoparticles all show a tooth-like branched structure, and the structural differences are small. In Example 1, when the branching time is 30 min, the finally prepared silver nanoparticles show a uniformly distributed tooth-like branched structure, as Figure 2 shown; in Examples 3 and 4, the branching times are 1 h and 2 h respectively, and the finally prepared silver nanoparticles are uneven tooth-like branched structures as Figure 11 , Figure 13 shown. At the same time, it can be found through the normalized extinction spectrum that the silver nanoparticles prepared in the three examples show broadband spectral absorption characteristics in the wavelength range of 400 - 1000 nm, and can achieve the ability of broadband light absorption in the full wavelength band. Example 5

[0097] In this example, silver nanoparticles with broadband spectral absorption characteristics are prepared by the following method.

[0098] Step S1, seed pre-synthesis: Prepare 0.01 M silver nitrate precursor solution and 0.1 M sodium citrate precursor solution respectively. Then add 0.2 mL of 0.01 M silver nitrate solution to 2 mL of deionized water, and the stirring speed is 800 rpm. Use a syringe to drop 0.1 mL of 0.1 M sodium citrate precursor solution into the above solution for seed pre-synthesis. The stirring speed of the solution is 500 - 600 rpm, and the reaction time is 45 min;

[0099] Step S2, branching growth: Use a syringe to drop 0.3 ml of 0.04 M ascorbic acid reducing agent solution into the above solution for branching growth. In a 25 °C water bath, stir magnetically for 30 min under the condition of a rotation speed of 500 - 600 rpm. The color of the solution changes from colorless to light gray and finally to dark gray.

[0100] Step S3, centrifuge and wash the finally obtained product with absolute ethanol at 8000 rpm, and finally obtain silver nanoparticles dispersed in ethanol.

[0101] Figure 15 and Figure 16 are respectively the typical scanning electron microscope pictures and normalized extinction spectra of a kind of silver nanoparticles with broadband spectral absorption characteristics prepared in this example. From Figure 15It can be observed that it is an uneven tooth-like branched structure. At the same time, from Figure 16 the spectrogram, it can be seen that such uneven tooth-like branched structure silver nanoparticles show broad-spectrum absorption characteristics in the wavelength range of 400-1000 nm, and can achieve broadband absorption of light in the whole band.

[0102] Comparing Examples 1, 2, and 5, it can be found that when the branching reaction time is 30 min, only changing the seed pre-synthesis time, the finally prepared silver nanoparticles all show a tooth-like branched structure, and the structural differences are small. In Example 1, when the seed pre-synthesis time is 1 h, the finally prepared silver nanoparticles show a uniformly distributed tooth-like branched structure, as Figure 2 shown; in Examples 2 and 5, the seed pre-synthesis times are 90 min and 45 min respectively, and the finally prepared silver nanoparticles are uneven tooth-like branched structures as Figure 7 , Figure 15 shown. At the same time, it can be found through the normalized extinction spectrum that the silver nanoparticles prepared in the three examples show broad-spectrum absorption characteristics in the wavelength range of 400-1000 nm, and can achieve the broadband absorption ability of light in the whole band.

[0103] The present invention also provides an application of silver nanoparticles with broad-spectrum absorption characteristics in the field of solar energy conversion technology. Compared with the plasmonic metal nanomaterials with narrow-band absorption characteristics obtained in the existing synthesis methods, such as Comparative Examples 1 and 2, the silver nanoparticles with tooth-like branched structure prepared by the present invention show more excellent light absorption characteristics. For example, in Examples 1-5, broadband absorption in the whole band is achieved in the spectral range of 400-1000 nm, greatly improving the utilization efficiency of the material for sunlight.

Claims

1. A silver nanoparticle with broad-spectrum absorption characteristics, characterized in that, The silver nanoparticles have a tooth-like branch structure, which includes a silver nanocore and tooth-like branches that radiate outward from the center of the silver nanocore and grow epitaxially along the circumference; The synthesis method of the silver nanoparticles comprises the following steps: Step S1, seed presynthesis: adding sodium citrate solution to the silver salt solution under magnetic stirring conditions to perform seed presynthesis, the seed presynthesis time is 45 min - 90 min; The concentration ratio of the silver salt solution to the sodium citrate solution is 1:10 - 1:20; Step S2, branching growth: adding a reducing agent ascorbic acid solution and / or glucose dropwise to the solution of step S1 to perform branching growth, the branching growth time being 30 min - 120 min; The molar ratio of the silver salt solution to the reducing agent is 1:6; Step S3, centrifugally separating the product obtained in step S2 using a centrifugal solvent to obtain silver nanoparticles with broad spectrum absorption characteristics dispersed in the centrifugal solvent; The silver nanoparticles are used in the field of solar energy conversion technology; The silver nanoparticles have a wide spectrum absorption characteristic within the wavelength range of 400-1000 nm, and achieve full-band broadband absorption within the spectrum range of 400-1000 nm.

2. The silver nanoparticles with broadband absorption characteristics according to claim 1, characterized in that, The gap size between adjacent tooth-like branches is 5-20nm.

3. The silver nanoparticles with broadband absorption characteristics according to claim 1, wherein: The concentration of the ascorbic acid solution in step S2 of the synthesis method of silver nanoparticles is 0.02-0.1M.

4. A silver nanoparticle having a wide-spectrum absorption characteristic according to claim 1, characterized in that: The centrifugation solvent in step S3 of the synthesis method of silver nanoparticles is anhydrous ethanol.

5. Application of the silver nanoparticles with broad spectrum absorption characteristics according to claim 1 in the field of solar energy conversion technology.

Images