A method for preparing Cu@Ag particles by laser
Cu@Ag particles were prepared by femtosecond and picosecond pulsed lasers, and the localized surface plasmon resonance effect was utilized to solve the problems of environmental unfriendliness and controllability of existing chemical reduction methods, thus realizing the preparation of green, environmentally friendly and controllable core-shell structures.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUANGDONG UNIV OF TECH
- Filing Date
- 2025-12-26
- Publication Date
- 2026-06-26
AI Technical Summary
Existing chemical reduction methods for preparing Cu@Ag particles are not environmentally friendly and it is difficult to precisely control the generation sequence of the core and shell.
Cu@Ag particles were prepared using femtosecond and picosecond pulsed lasers. The core and shell were generated through a stepwise process by utilizing the localized surface plasmon resonance effect, thus avoiding the use of chemical reducing agents and surfactants.
A green and environmentally friendly preparation process was achieved, the product is pure, the structure is well controllable, the size and thickness of the core-shell structure can be adjusted, and the introduction of impurities is avoided.
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Figure CN121797976B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nanomaterial preparation technology, and in particular to a method for preparing Cu@Ag particles using laser. Background Technology
[0002] The rapid upgrading and iteration of high-tech industries has placed demands on electronic devices for high-temperature, high-pressure, and high-frequency resistance, accelerating the industrialization of third-generation semiconductors. Packaging and interconnection, as a crucial link in semiconductor manufacturing, plays a vital role in providing mechanical support and electrical interconnection. However, traditional interconnect materials cannot fully meet the application requirements of third-generation semiconductor device packaging and interconnection. Nanomaterials, with their characteristics of low-temperature molding and high-temperature service, have been widely studied in recent years as materials for electronic packaging and interconnection. Currently, commonly used materials include nano-silver and nano-copper. Silver is expensive as a conductive material, while copper is inexpensive and its conductivity is close to that of silver. However, due to the nano-effect, nano-copper particles are more prone to oxidation, leading to a significant decrease in their conductivity. Therefore, using silver-coated copper nanoparticles as a conductive material can simultaneously reduce material costs and improve oxidation resistance.
[0003] Currently, most methods for preparing silver-coated copper nanoparticles employ chemical reduction. For example, Chinese patent CN114226724A uses an aqueous chemical plating method, which activates micron-sized copper powder and then reduces ammoniacal silver solution with sodium potassium tartrate to deposit a dense silver layer on the copper surface. Another example is Chinese patent CN111438373A, which uses carbon monoxide as a reducing agent in an organic phase and employs a two-step thermal decomposition method to first form copper nanonuclei at high temperatures, followed by slow deposition of a silver shell at low temperatures. This achieves controllable preparation of nanoscale spherical particles. However, the chemical reduction method for preparing Cu@Ag particles suffers from problems such as low product purity and environmental unfriendliness due to the use of toxic chemical reducing agents and surfactants. Furthermore, it presents the challenge of precisely controlling the order in which the core and shell are formed. Summary of the Invention
[0004] To address the aforementioned shortcomings, the present invention aims to propose a method for laser preparation of Cu@Ag particles, which solves the problems of existing chemical reduction methods being environmentally unfriendly and having difficulty in precisely controlling the order of core and shell formation.
[0005] To achieve this objective, the present invention adopts the following technical solution:
[0006] A method for laser preparation of Cu@Ag particles includes the following steps:
[0007] S1. Solution preparation: Dissolve the copper precursor in a solvent to obtain a copper precursor solution, and dissolve the silver precursor in a solvent to obtain a silver precursor solution;
[0008] S2. The copper precursor solution is irradiated with a femtosecond pulsed laser to reduce and generate nano-copper particle cores.
[0009] S3. Add a silver precursor solution to the liquid environment containing the nano-copper particle core, adjust the wavelength parameter of the picosecond pulse laser to achieve laser energy focusing on the surface of the nano-copper particle core, and use the picosecond pulse laser to irradiate the solution, so that silver ions are reduced and deposited on the surface of the nano-copper particle core to form a silver shell, thereby obtaining Cu@Ag particles.
[0010] Preferably, in step S3, the wavelength of the picosecond pulsed laser matches the local surface plasmon resonance peak of the copper nanoparticle core.
[0011] Preferably, in step S2, the femtosecond pulsed laser has a pulse width of 10-50 fs, a laser wavelength of 750-900 nm, and a pulse energy density of 10. 13 -10 15 W / cm 2 The repetition frequency is 1KHz-500KHz, and the irradiation time is 1-60min.
[0012] Preferably, in step S3, the picosecond pulsed laser has a pulse width of 10-50 ps, a laser wavelength of 500-650 nm, and a pulse energy density of 10. 12 -10 14 W / cm 2 The repetition frequency is 1KHz-500KHz, and the irradiation time is 1-60min.
[0013] Preferably, in step S2, the copper concentration in the reaction system is 0.5-3.0 mM;
[0014] In step S3, the silver concentration in the reaction system is 0.2-1.0 mM.
[0015] Preferably, the copper precursor is at least one of organic carboxylates, β-diketone complexes, alkoxides, hydroxides, and oxides.
[0016] Preferably, the silver precursor is at least one selected from organic carboxylates, β-diketone complexes, alkoxides, and oxides.
[0017] Preferably, in step S1, the solvent is at least one of water, ethylene glycol, methanol, and isopropanol.
[0018] Preferably, the entire preparation process is carried out under an inert or reducing atmosphere.
[0019] Furthermore, in step S2, before irradiation with a femtosecond pulsed laser, the copper precursor solution is purged with an inert gas or a reducing gas for 10-60 minutes.
[0020] The technical solution provided by this invention may include the following beneficial effects:
[0021] 1. This solution provides a method for preparing Cu@Ag particles by laser. By using femtosecond laser and picosecond laser in a stepwise manner, a core-shell preparation process can be achieved. The shell preparation process utilizes the local surface plasmon resonance effect of copper, which is beneficial to control the directional deposition of the shell and has good structural controllability. Using laser as the only energy source, no chemical reducing agents or surfactants are added during the preparation process, the product is pure, the post-processing is simple, and the process is green and environmentally friendly.
[0022] 2. By adjusting the laser parameters and the ratio of copper and silver precursors, the size and shell thickness of core-shell structured particles can be controlled, thus enabling the preparation of nanoscale spherical particles. Attached Figure Description
[0023] Figure 1 This is a flowchart of the preparation method of the present invention.
[0024] Figure 2 This is a schematic flowchart of the preparation method of the present invention. Detailed Implementation
[0025] The technical solution of the present invention will be further illustrated below through specific embodiments.
[0026] To facilitate understanding of the present invention, a more complete description is provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.
[0027] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.
[0028] A method for laser preparation of Cu@Ag particles includes the following steps:
[0029] S1. Solution preparation: Dissolve the copper precursor in a solvent to obtain a copper precursor solution, and dissolve the silver precursor in a solvent to obtain a silver precursor solution;
[0030] S2. The copper precursor solution is irradiated with a femtosecond pulsed laser to reduce and generate nano-copper particle cores.
[0031] S3. Add a silver precursor solution to the liquid environment containing the nano-copper particle core, adjust the wavelength parameter of the picosecond pulse laser to achieve laser energy focusing on the surface of the nano-copper particle core, and use the picosecond pulse laser to irradiate the solution, so that silver ions are reduced and deposited on the surface of the nano-copper particle core to form a silver shell, thereby obtaining Cu@Ag particles.
[0032] To address the problems existing in the prior art, this invention proposes a method for laser preparation of Cu@Ag particles, such as... Figure 1 and Figure 2 The process shown involves using a femtosecond pulsed laser to ionize solvent molecules, releasing free electrons. These free electrons are then surrounded by surrounding solvent molecules, forming solvated electrons. These induced solvated electrons possess extremely strong reducing properties, and they decompose Cu... 2+ When ions are completely reduced to copper atoms, the resulting copper atoms diffuse randomly in the solution. When the local concentration exceeds the supersaturation concentration, nano-copper particle nuclei are formed. The ultrashort pulse characteristics of femtosecond pulsed lasers allow the above reaction to proceed without significant thermal effects, generating a high concentration of solvated electrons only at the focal point, achieving site-specific reduction of copper ions and simultaneous nucleation to obtain nano-copper particle nuclei. Then, utilizing the localized surface plasmon resonance (LSPR) effect of copper, the wavelength parameters of the picosecond pulsed laser are adjusted to focus the laser energy onto the surface of the nano-copper particle nuclei. The free electrons on the surface of the nano-copper particle nuclei strongly absorb the laser energy due to the resonance effect, causing the laser energy to... The amount of silver ions is concentrated on the surface of the core of the copper nanoparticles. At this point, the surface of the core becomes the region with the highest energy in the entire system, providing reaction sites for the reduction of silver ions. This allows silver ions near the surface of the core to be preferentially reduced, which is beneficial for controlling the directional deposition of the shell and finally obtaining Cu@Ag particles. No chemical reducing agents or surfactants are needed throughout the process, resulting in pure products, simple post-processing, and a green and environmentally friendly process that avoids the introduction of impurities. Furthermore, the step-by-step preparation process, with the core first and then the shell, allows for precise control of the order in which the core and shell are formed. This solves the problems of existing chemical reduction methods being environmentally unfriendly and having difficulty in precisely controlling the order in which the core and shell are formed.
[0033] Furthermore, by adjusting the laser parameters of the femtosecond and picosecond pulsed lasers in steps S2 and S3, as well as the ratio of copper and silver precursors, the size and shell thickness of the core-shell structured particles can be adjusted. In step S2, the higher the pulse energy of the femtosecond pulsed laser, the more solvated electrons are generated for reduction, leading to a surge in the number of instantaneous nuclei. If the energy is too high, a large number of tiny nuclei may be generated, which can also easily lead to aggregation and widen the size distribution. Therefore, by limiting the pulse energy of the femtosecond pulsed laser, monodisperse small nuclei can be obtained, thereby obtaining the desired nano-copper particle nuclei. Moreover, the longer the irradiation time of the femtosecond pulsed laser, the more copper atoms are reduced and generated. After nucleation, new atoms will preferentially grow on the existing nano-copper particle nuclei, resulting in a gradual increase in the average size. Therefore, by adjusting the irradiation time, the average size of the nano-copper particle nuclei can be controlled to a certain extent. The higher the concentration of the copper precursor solution, the greater the total amount of metal that can be reduced under the same laser parameters, which tends to generate more nuclei or larger nuclei, and also adjusts the size of the core-shell structured particles to a certain extent. Meanwhile, in step S3, the energy of the picosecond pulsed laser affects the reduction rate of silver ions on the surface of the nano-copper particle core. Under the premise that the laser wavelength of the picosecond pulsed laser matches the LSPR, the higher the energy, the stronger the copper core is excited, the stronger the surface reduction ability, and the faster the silver shell growth rate. Adjusting the pulse energy density of the picosecond pulsed laser avoids the reduction rate of Ag being much greater than the deposition growth rate, thereby avoiding the generation of individual silver particles. The irradiation time of the picosecond pulsed laser affects the total amount of deposition. The longer the time, the thicker the silver shell formed by deposition will be. Moreover, the higher the concentration of the silver precursor solution, the greater the total amount of silver that can be deposited, and the greater the maximum shell thickness that can be achieved, thereby controlling the thickness of the shell layer.
[0034] Preferably, in step S3, the wavelength of the picosecond pulsed laser matches the local surface plasmon resonance peak of the copper nanoparticle core.
[0035] Specifically, when the core of a copper nanoparticle is irradiated by a specific light, the free electrons within the particle will collectively oscillate synchronously under the influence of the electromagnetic field of the light, which is called local surface plasmon resonance. The specific wavelength of the light wave is the corresponding local surface plasmon resonance (LSPR) peak. By tuning the wavelength of the picosecond pulsed laser used to match the LSPR peak of the obtained copper nanoparticle, the laser energy can be well focused on the surface of the copper nanoparticle core, so that silver ions near the surface of the copper nanoparticle core are preferentially reduced. This is beneficial for controlling the directional deposition of the shell and has good structural controllability.
[0036] Preferably, in step S2, the femtosecond pulsed laser has a pulse width of 10-50 fs, a laser wavelength of 750-900 nm, and a pulse energy density of 10. 13 -1015 W / cm 2 The repetition frequency is 1KHz-500KHz, and the irradiation time is 1-60min.
[0037] Specifically, the pulse width of the femtosecond laser is limited to be less than the electron-lattice relaxation time, making the thermal effect of the reaction negligible. This effectively avoids particle agglomeration, solvent decomposition, or impurity generation caused by localized overheating. Simultaneously, the laser wavelength and pulse energy density ensure efficient ionization of solvent molecules to generate a large number of solvated electrons, ensuring the Cu... 2+ This improves reduction efficiency and avoids particle agglomeration or equipment damage caused by bubble impact. Furthermore, the repetition frequency balances synthesis efficiency and system stability, ensuring the yield of copper nanoparticle cores while preventing heat accumulation.
[0038] Preferably, in step S3, the picosecond pulsed laser has a pulse width of 10-50 ps, a laser wavelength of 500-650 nm, and a pulse energy density of 10. 12 -10 14 W / cm 2 The repetition frequency is 1KHz-500KHz, and the irradiation time is 1-60min.
[0039] Specifically, by limiting the parameters of the picosecond pulsed laser to match the LSPR peak of the copper nanoparticle core, the laser energy is concentrated on the surface of the copper nanoparticle core as much as possible, so that silver ions near the surface of the copper nanoparticle core are preferentially reduced, achieving targeted deposition. At the same time, the pulse energy density is limited to ensure effective driving of silver ions to be reduced on the surface of the copper nanoparticle core while avoiding the generation of independent silver particles in other locations in the liquid environment and avoiding core-shell damage, thus balancing the uniformity and yield of silver shell deposition.
[0040] Preferably, in step S2, the copper concentration in the reaction system is 0.5-3.0 mM;
[0041] In step S3, the silver concentration in the reaction system is 0.2-1.0 mM.
[0042] Specifically, in step S2, the reaction system is a copper precursor solution with a copper concentration of 0.5-3.0 mM. This ensures the generation of a large number of copper nanoparticles while avoiding explosive nucleation caused by excessively high local concentrations. This prevents uncontrolled aggregation due to explosive nucleation, which could lead to a wide distribution and unstable morphology of the generated copper nanoparticles. At this concentration, the copper ions are evenly distributed in the solution, enabling simultaneous nucleation during femtosecond pulsed laser irradiation and resulting in uniformly sized copper nanoparticles. Meanwhile, in step S3, after adding the silver precursor solution, the silver concentration in the reaction system is 0.2-1.0 mM. This allows for selective and precise reduction deposition, ensuring that the reduction rate of the silver shell is as low as possible, less than or equal to the deposition growth rate. This ensures that the silver shell uniformly coats the copper nanoparticles, preventing the generation of free silver particles due to excessive silver ions, while also avoiding uneven coating and oxidation of the copper nanoparticles due to insufficient silver ions.
[0043] Preferably, the copper precursor is at least one of organic carboxylates, β-diketone complexes, alkoxides, hydroxides, and oxides.
[0044] Specifically, regarding copper precursors, the organic carboxylates are copper formate, copper acetate, copper propionate, copper oxalate, copper citrate, and copper tartrate; the β-diketone complexes are copper acetylacetonate and copper trifluoroacetylacetonate; the alkoxides are copper methoxide, copper ethoxide, and copper isopropoxide; and the hydroxides and oxides are copper hydroxide and copper oxide.
[0045] Preferably, the copper precursor is one or a combination of copper acetate and copper acetylacetonate.
[0046] Specifically, copper acetate exhibits good solubility in water, ethylene glycol, methanol, and isopropanol. Its decomposition products are primarily acetone, CO2, and H2O, all of which are volatile or harmless, having minimal impact on subsequent experimental systems. Copper acetylacetonate also shows good solubility in organic solvents such as ethylene glycol and isopropanol. Its decomposition products are acetone, CO, CO2, and CH4, allowing for pure reduction. Furthermore, the acetylacetonate ion is a classic face-selective adsorption ligand, which can regulate particle shape.
[0047] Preferably, the silver precursor is at least one selected from organic carboxylates, β-diketone complexes, alkoxides, and oxides.
[0048] Specifically, regarding silver precursors, the organic carboxylate salts are silver formate, silver acetate, silver propionate, silver oxalate, silver citrate, silver tartrate, and silver benzoate; the β-diketone complexes are silver acetylacetone and silver trifluoroacetylacetone; the alkoxide is silver isopropoxide; and the oxide is silver oxide.
[0049] Preferably, the silver precursor is one or a combination of silver acetate and silver acetylacetone.
[0050] Specifically, silver acetate and silver acetylacetone have good solubility in water, ethylene glycol, methanol and isopropanol and their decomposition products are clean. Among them, the acetate ion of silver acetate can act as a weak adsorption ligand, which can regulate the growth rate of different crystal faces to a certain extent and has a certain morphology control ability, which helps to form a relatively uniform, stable and high-quality silver shell coating on the surface of the core of copper nanoparticles.
[0051] Preferably, in step S1, the solvent is at least one of water, ethylene glycol, methanol, and isopropanol.
[0052] Specifically, the solvent, in conjunction with a femtosecond pulsed laser, acquires solvated electrons, thereby reducing copper and silver ions.
[0053] Preferably, the entire preparation process is carried out under an inert or reducing atmosphere.
[0054] The entire process fundamentally avoids the interference of oxygen in the preparation process, ensuring the performance and consistency of the product.
[0055] Furthermore, in step S2, before irradiation with a femtosecond pulsed laser, the copper precursor solution is purged with an inert gas or a reducing gas for 10-60 minutes.
[0056] Specifically, the copper precursor solution is purged for 10-60 minutes to remove oxygen from the solution and reduce the impact on particle preparation.
[0057] The technical solution of the present invention will be further illustrated below through specific embodiments.
[0058] Example group
[0059] Example 1
[0060] S1. Solution Preparation: Take two 100mL three-necked flasks and weigh 45mL of ethylene glycol into each flask using a graduated cylinder. Then weigh 0.908g of copper acetate and 0.835g of silver acetate into each flask. Use an ultrasonic cleaner to sonicate and heat to 63℃ for continuous stirring for 15 minutes. After stirring, pour the mixture into two prepared 50mL volumetric flasks, add ethylene glycol to the flasks to the 50mL mark, and mix thoroughly to obtain two stock solutions with a concentration of 100mM.
[0061] 99.2 mL of ethylene glycol was measured into a 100 mL quartz reaction cell. 0.8 mL of 100 mM copper acetate stock solution was measured using a quantitative pipette and added to the reaction cell. The mixture was then thoroughly mixed to obtain a copper precursor solution. The copper concentration in the reaction system was 0.8 mM.
[0062] S2. Continuously purge the solution with (95% Ar - 5% H2) hydrogen-argon gas for 15 min to remove dissolved oxygen. Then, focus the solution with a femtosecond pulsed laser with a center wavelength of 800 nm, a pulse width of 30 fs, a repetition frequency of 1 kHz, and a pulse energy of 1 mJ for 30 min. Utilize laser plasma-induced solvation electrons to reduce Cu. 2+ The reduction generates nano-copper particle cores;
[0063] S3. Under continuous hydrogen and argon gas protection, add 0.4 mL of 100 mM silver acetate stock solution to the reaction system in S2 using a quantitative pipette, mix thoroughly to make the silver concentration in the reaction system 0.4 mM. Then, switch the laser to a picosecond pulsed laser, adjust the pulse width to 10 ps and the pulse energy to 0.8 mJ; adjust the laser wavelength to 600 nm to match the LSPR peak of the copper nucleus, and continue to focus the picosecond pulsed laser on the mixed solution for 20 minutes. The laser energy is efficiently absorbed by the copper nucleus, and the energy is concentrated near the copper nucleus, which promotes the selective reduction and epitaxial growth of the silver precursor on the surface of the copper nucleus to form a silver shell.
[0064] Example 2
[0065] S1. Solution Preparation: Take two 100mL three-necked flasks. Under light-protected conditions, weigh 45mL of methanol into each flask using a graduated cylinder. Then weigh 0.654g of copper acetylacetone and 0.518g of silver acetylacetone into each flask and add them to the two flasks respectively. Use an ultrasonic cleaner to sonicate and heat to 40℃ for continuous stirring for 30min. After stirring, pour the mixture into two prepared 50mL volumetric flasks. Add methanol to the volumetric flasks to the 50mL mark and mix thoroughly to obtain two stock solutions of 50mM copper acetylacetone and silver acetylacetone.
[0066] 98.4 mL of methanol was measured into a 100 mL quartz reaction cell. 1.6 mL of 50 mM copper acetylacetonate stock solution was measured using a quantitative pipette and added to the reaction cell. The mixture was then thoroughly mixed to obtain a copper precursor solution, making the copper concentration in the reaction system 0.8 mM.
[0067] S2. Continuously introduce (95% Ar - 5% H2) hydrogen-argon gas for 20 min to remove dissolved oxygen in the solution. Then, focus the solution with a femtosecond pulsed laser with a center wavelength of 800 nm, a pulse width of 30 fs, a repetition frequency of 1 kHz, and a pulse energy of 1 mJ for 30 min, utilizing the solvation electrons induced by the laser plasma to reduce Cu. 2+ The reduction generates nano-copper particle cores;
[0068] S3. Under continuous hydrogen and argon gas protection, 0.8 mL of 50 mM copper-silver acetylacetone stock solution was added to the reaction system described in S2 using a quantitative pipette. The solution was mixed thoroughly to achieve a silver concentration of 0.4 mM. Then, the laser was switched to a picosecond pulsed laser, with the pulse width adjusted to 20 ps and the pulse energy to 0.6 mJ. The laser wavelength was adjusted to 600 nm to match the LSPR peak of the copper nucleus. The picosecond pulsed laser was used to continue focusing and irradiating the mixed solution for 20 minutes. The laser energy was efficiently absorbed by the copper nucleus, concentrating near the nucleus and causing the silver precursor to be selectively reduced and epitaxially grown on the surface of the copper nucleus, forming a silver shell.
[0069] Example 3
[0070] S1. Solution preparation: First, prepare a 1:1 volume ratio of ethylene glycol and pure water mixed solvent. Take two 100mL three-necked flasks and, under completely dark conditions, weigh 45mL of the ethylene glycol and pure water mixed solvent into each flask using a graduated cylinder. Then, weigh 0.711g of copper nitrate and 0.641g of silver nitrate into each flask and add them to the two three-necked flasks. Use an ultrasonic cleaner to sonicate and heat to 65℃ and stir continuously for 30min. After stirring, pour the mixture into two prepared 50mL volumetric flasks. Add the ethylene glycol and pure water mixed solvent to the volumetric flasks to the 50mL mark and mix well to obtain two stock solutions of copper citrate and silver citrate with a concentration of 25mM.
[0071] Measure 98.4 mL of a mixed solution of methanol and pure water into a 100 mL quartz reaction cell. Use a quantitative pipette to measure 3.2 mL of 25 mM copper citrate stock solution and add it to the reaction cell. Mix well to obtain a copper precursor solution, so that the copper concentration in the reaction system is 0.8 mM.
[0072] S2. High-purity argon gas is continuously introduced into the solution for 30 minutes to remove dissolved oxygen. Then, the solution is focused and irradiated for 30 minutes using a femtosecond pulsed laser with a center wavelength of 800 nm, a pulse width of 30 fs, a repetition frequency of 1 kHz, and a pulse energy of 1 mJ. The solvation electrons induced by the laser plasma reduce Cu. 2+ Preparation of nano-copper particle cores;
[0073] S3. Under continuous inert gas protection, 1.6 mL of 25 mM silver citrate stock solution was added to the reaction system of S2 using a quantitative pipette and mixed thoroughly to make the silver concentration in the reaction system 0.4 mM. Then, the laser was switched to a picosecond pulsed laser, the pulse width was adjusted to 10 ps, and the pulse energy was 0.6 mJ. The laser wavelength was adjusted to 600 nm to match the LSPR peak of the copper nucleus. The picosecond pulsed laser was used to continue focusing and irradiating the mixed solution for 25 minutes. The laser energy was efficiently absorbed by the copper nucleus and the energy was concentrated near the copper nucleus, which promoted the selective reduction and epitaxial growth of the silver precursor on the surface of the copper nucleus to form a silver shell.
[0074] In the example group, the desired Cu@Ag particles were obtained under the preparation method of the present invention. By monitoring with ultraviolet-visible absorption spectroscopy, the copper core plasmon resonance peak at 560-600 nm was observed to gradually weaken and eventually disappear. At the same time, a sharp silver shell plasmon resonance peak appeared and strengthened at 400-420 nm. In Example 3, the strong complexation of citrate can effectively regulate the reduction and nucleation kinetics of metal ions, which is beneficial to obtaining particles with uniform size and regular morphology. The prepared Cu@Ag core-shell structure was observed by transmission electron microscopy (TEM). Under the action of laser, the citrate ions partially decompose, which may generate gaseous products and trace amounts of amorphous carbon layers. However, the core-shell structure is expected to be protected by the amorphous carbon layers generated in the aforementioned process, thus giving it excellent antioxidant properties and long-term stability.
[0075] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.
Claims
1. A method for laser preparation of Cu@Ag particles, characterized in that, Includes the following steps: S1. Solution preparation: Dissolve the copper precursor in a solvent to obtain a copper precursor solution, and dissolve the silver precursor in a solvent to obtain a silver precursor solution; S2. The copper precursor solution is irradiated with a femtosecond pulsed laser to reduce and generate nano-copper particle cores. S3. Add a silver precursor solution to the liquid environment containing the nano-copper particle core, adjust the wavelength parameter of the picosecond pulse laser to achieve laser energy focusing on the surface of the nano-copper particle core, and use the picosecond pulse laser to irradiate the solution, so that silver ions are reduced and deposited on the surface of the nano-copper particle core to form a silver shell, thereby obtaining Cu@Ag particles.
2. The method for laser preparation of Cu@Ag particles according to claim 1, characterized in that: In step S3, the wavelength of the picosecond pulsed laser is matched with the local surface plasmon resonance peak of the copper nanoparticle core.
3. The method for laser preparation of Cu@Ag particles according to claim 1, characterized in that: In step S2, the femtosecond pulsed laser has a pulse width of 10-50 fs, a laser wavelength of 750-900 nm, and a pulse energy density of 10. 13 -10 15 W / cm 2 The repetition frequency is 1KHz-500KHz, and the irradiation time is 1-60min.
4. The method for laser preparation of Cu@Ag particles according to claim 1, characterized in that: In step S3, the picosecond pulsed laser has a pulse width of 10-50 ps, a laser wavelength of 500-650 nm, and a pulse energy density of 10. 12 -10 14 W / cm 2 The repetition frequency is 1KHz-500KHz, and the irradiation time is 1-60min.
5. The method for laser preparation of Cu@Ag particles according to claim 1, characterized in that: In step S2, the copper concentration in the reaction system is 0.5-3.0 mM; In step S3, the silver concentration in the reaction system is 0.2-1.0 mM.
6. The method for laser preparation of Cu@Ag particles according to claim 1, characterized in that: The copper precursor is at least one of organic carboxylates, β-diketone complexes, alkoxides, hydroxides, and oxides.
7. The method for laser preparation of Cu@Ag particles according to claim 1, characterized in that: The silver precursor is at least one of organic carboxylates, β-diketone complexes, alkoxides, and oxides.
8. The method for laser preparation of Cu@Ag particles according to claim 1, characterized in that: In step S1, the solvent is at least one of water, ethylene glycol, methanol, and isopropanol.
9. The method for laser preparation of Cu@Ag particles according to claim 1, characterized in that: The entire preparation process is carried out under an inert or reducing atmosphere.
10. The method for laser preparation of Cu@Ag particles according to claim 9, characterized in that: In step S2, before irradiation with a femtosecond pulsed laser, the copper precursor solution is purged with an inert gas or a reducing gas for 10-60 minutes.