Preparation method and application of core-shell type monodisperse spherical gold nanoparticle / cerium dioxide composite material
By preparing core-shell monodispersed spherical gold nanoparticles/cerium dioxide composite materials, the problems of complex preparation process of traditional composite nanostructures and difficulty in controlling shell thickness are solved, and efficient catalytic performance and stability are achieved, which is suitable for the fields of heterogeneous catalysis and photocatalysis.
Patent Information
- Application Number
- CN202511025977.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-24
- Publication Date
- 2025-10-10
AI Technical Summary
The preparation process of existing noble metal-cerium dioxide composite nanostructures is complex, and the shell thickness is difficult to control, making it difficult to achieve controllable composite of plasma metal nanocrystals and ceria, which limits the synergistic effects of the material in light absorption, carrier excitation and separation, and surface chemical reactions.
A method for preparing a core-shell monodisperse spherical gold nanoparticle/cerium dioxide composite material is adopted. By precisely controlling the thickness of the CeO2 shell, a composite material with adjustable localized surface plasmon resonance properties is formed. The method includes the following steps: diluting an aqueous solution of chloroauric acid, adding sodium citrate, forming a gold nanoseed colloidal solution, dispersing CTAB, and performing a high-temperature hydrothermal reaction.
A clear core-shell structure combination of gold nanoparticles and cerium dioxide was achieved, which improved the catalytic efficiency, possessed heterogeneous catalytic and photocatalytic properties, and demonstrated high catalytic activity and stability.
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Figure CN120754847A_ABST
Abstract
Description
Technical Field
[0001] The invention discloses a preparation method and application of a core-shell type monodispersed spherical gold nanoparticle / cerium dioxide composite material, belonging to the technical field of catalysis. Background Art
[0002] Catalytic technology is a core driver of modern industry and sustainable development, playing an irreplaceable role in energy conversion, environmental protection, and chemical production. By efficiently accelerating reactions, reducing energy consumption, and improving selectivity, catalysts provide key solutions to global challenges such as energy and the environment. However, as requirements for catalytic performance continue to increase, traditional single-component catalysts are increasingly facing challenges such as insufficient activity, poor stability, or excessive cost, prompting a continuous search for new, more efficient catalysts.
[0003] Noble metal-semiconductor oxide core-shell nanomaterials have attracted considerable attention due to their unique physicochemical properties. These materials utilize a noble metal (e.g., Pt, Pd, Au) as the core or shell and a semiconductor oxide (e.g., TiO2, CeO2) as the other component. Their performance can be significantly optimized by precisely manipulating their composition, size, and interfacial interactions. The noble metal provides highly active sites, while the oxide modulates the electronic structure and enhances stability.
[0004] CeO2, a highly active rare earth oxide with a wide bandgap (3.19 eV) and a high dielectric constant (24.5), can form a Schottky barrier with plasmonic metals (such as AuNPs) to promote carrier separation, making it an ideal candidate for plasmonic photocatalysis. AuNPs, due to their plasmonic properties, have important applications in catalytic degradation of pollutants and environmental sensing.
[0005] In related technologies, there have been studies on improving the catalytic activity of precious metal and ceria composite nanostructures. However, the following challenges remain: (1) the preparation process is complex, requiring additional modification steps to enhance activity; (2) it is difficult to precisely control the thickness of the ceria shell; and (3) it is difficult to achieve a controlled composite of plasmonic metal nanocrystals and ceria in a specific geometric configuration, thus limiting the synergistic effects of the materials in terms of light absorption, carrier excitation and separation, and surface chemical reactions.
[0006] Based on this, the present invention innovatively developed a controllable preparation method for a core-shell monodisperse spherical gold nanoparticle / cerium dioxide (AuNPs@CeO2) composite. By precisely controlling the thickness of the CeO2 shell, the localized surface plasmon resonance (LSPR) properties of the gold nanoparticles were effectively manipulated. This composite material can be used as a multifunctional catalyst. Summary of the Invention
[0007] One of the purposes of the present invention is to provide a method for preparing a core-shell monodisperse spherical gold nanoparticle / cerium dioxide composite material, which specifically comprises the following steps: (1) The chloroauric acid aqueous solution is diluted with water and heated to obtain a diluted solution of the chloroauric acid aqueous solution, and then the sodium citrate aqueous solution is added to the diluted solution of the chloroauric acid aqueous solution, and heated to react to obtain a gold nanoseed colloidal solution.
[0008] (2) The tris(hydroxymethylaminomethane) aqueous solution is diluted with water and heated to obtain a dilution of the tris(hydroxymethylaminomethane) aqueous solution. The gold nanoseed colloid solution and the chloroauric acid aqueous solution are then added to the dilution successively, heated to react to form a mixed solution. The mixed solution is then condensed and refluxed. Spherical gold nanoparticles (AuNPs) of different particle sizes are prepared by adjusting the amount of water used to dilute the tris(hydroxymethylaminomethane) aqueous solution and the amount of gold nanocolloid seed solution.
[0009] (3) The prepared AuNPs are washed by centrifugation to form a concentrated solution, and a CTAB aqueous solution is added to the concentrated solution to disperse the AuNPs to form a dispersion.
[0010] (4) EDTA-NH3 and Ce(NO3)3 aqueous solutions are sequentially added to the dispersion and stirred thoroughly to form a mixed solution, and the mixed solution is placed in a reaction vessel (preferably a tetrafluoroethylene reactor) to react to obtain a core-shell type monodispersed spherical gold nanoparticle / cerium dioxide (AuNPs@CeO2) composite material.
[0011] Preferably, the concentration of the chloroauric acid aqueous solution in step (1) is 25 mmol / L; the molar concentration of the dilution of the chloroauric acid aqueous solution is 0.2577 mmol / L and is in a boiling state; the sodium citrate aqueous solution is added to the dilution of the chloroauric acid aqueous solution in a volume ratio of 1:1-10 of the chloroauric acid aqueous solution to the sodium citrate aqueous solution; the mass percentage concentration of the sodium citrate aqueous solution is 1%; and the conditions for the heating reaction are: the reaction is continued at above 90°C for 30 minutes.
[0012] Preferably, the concentration of the tris(hydroxymethylaminomethane) aqueous solution in step (2) is 0.1 mol / L; the molar concentration of the diluent of the tris(hydroxymethylaminomethane) aqueous solution is 4.082 mmol / L and the temperature is 90°C; the gold nanoseed colloid solution and the chloroauric acid aqueous solution are sequentially added to the diluent in a volume ratio of 2-5:1:1 of the tris(hydroxymethylaminomethane) aqueous solution, the gold nanoseed colloid solution and the chloroauric acid aqueous solution; the mass percentage concentration of the chloroauric acid aqueous solution is 1%; and the heating reaction is carried out at a temperature above 90°C.
[0013] Preferably, the condensation reflux time in step (2) is 30 min; and the specific method for preparing the spherical gold nanoparticles by adjusting the water amount of the diluted aqueous solution of tris-hydroxymethyl aminomethane and the amount of the gold nanocolloid seed solution is as follows: the total volume of the reaction solution is always 50 mL by adjusting the water amount of the diluted aqueous solution of tris-hydroxymethyl aminomethane and the amount of the gold nanocolloid seed solution.
[0014] Preferably, the centrifugal washing condition in step (3) is as follows: centrifugal washing is performed twice at a rotation speed of 5000 rpm.
[0015] Preferably, the aqueous solution of CTBA in step (3) is added into the concentrated solution at a volume ratio of 1-4:1; the concentration of the aqueous solution of CTBA is 0.2 mmol / L, and the dispersion condition in the concentrated solution is as follows: stirring and dispersion are performed at a temperature of 30 DEG C and a rotation speed of 200 rpm for 30 min.
[0016] Preferably, the aqueous solution of EDTA and the aqueous solution of Ce(NO3)3 in step (4) are added into the dispersion liquid at a volume ratio of 5-20:1; the aqueous solution of Ce(NO3)3 is added into the dispersion liquid at a volume ratio of 1:300; the concentration of the aqueous solution of EDTA-NH3 is 0.01 mol / L, and the concentration of the aqueous solution of Ce(NO3)3 is 0.1 mol / L.
[0017] Preferably, the aqueous solution of EDTA and the aqueous solution of Ce(NO3)3 in step (4) are dispersed at a rotation speed of 300 rpm and subjected to high-temperature hydrothermal reaction at 90 DEG C for 5 h.
[0018] Another object of the present application is to provide an application of the core-shell type monodisperse spherical gold nanoparticle / cerium dioxide composite material in the field of heterogeneous catalysis and photocatalysis.
[0019] The mechanism of the present application is as follows: The composite material formed by coating a cerium dioxide layer on the surface of the spherical gold nanoparticles can produce a synergistic effect in a catalytic reaction, so that the AuNPs@CeO2 has both heterogeneous catalytic and photocatalytic properties; and the unique preparation process makes the composite material exhibit extremely high catalytic efficiency.
[0020] The present application has the following beneficial effects: (1) The composite nanostructure prepared by the present invention realizes the combination of monodisperse gold nanoparticles and ceria in a clear core-shell structure. The core-shell structure makes full use of the LSPR-induced light focusing of gold nanoparticles to enhance light absorption, the charge transfer on the surface of gold nanocrystals, and the ceria shell layer to protect the gold nanocore from chemical corrosion, remodeling and aggregation to improve the synergistic catalytic performance.
[0021] (2) The present invention adopts a shell-controllable preparation method to achieve the adjustable characteristics of localized surface plasmon resonance (LSPR) of gold nanoparticles; and obtains a composite material with a cerium dioxide coating layer thickness of 16.43±1.17nm.
[0022] (3) The composite nanostructure has the functions of heterogeneous catalytic degradation of 4-nitrophenol and photocatalytic degradation of methylene blue, indicating that the nanocatalyst has excellent catalytic activity and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 Schematic diagram of the process of synthesizing AuNPs@CeO2 in the present invention.
[0024] Figure 2 The AuNPs prepared in Example 1 of the present invention ( Figure 2 (a)), AuNPs@CeO2 ( Figure 2 (b) Transmission electron microscopy (TEM) image and ultraviolet-visible (UV-vis) spectrum ( Figure 2 (c)).
[0025] Figure 3 This is a transmission electron microscopy (TEM) image of the AuNPs@CeO2 with adjustable shell thickness prepared in Example 2 of the present invention, wherein Figure 3 a is the TEM image of AuNPs@CeO2 after adding a fixed ratio of EDTA-NH3 and Ce(NO3)3 aqueous solution once (where the amount of Ce(NO3)3 aqueous solution added is 10µL), Figure 3 b is the TEM image of AuNPs@CeO2 with the addition of EDTA-NH3 and Ce(NO3)3 aqueous solution in a fixed ratio for 3 times (where the amount of Ce(NO3)3 aqueous solution added is 30µL), Figure 3 c is the TEM image of AuNPs@CeO2 with the addition of EDTA-NH3 and Ce(NO3)3 aqueous solution in a fixed ratio for 5 times (where the amount of Ce(NO3)3 aqueous solution added is 50µL), Figure 3 d is the TEM image of AuNPs@CeO2 with the addition of EDTA-NH3 and Ce(NO3)3 aqueous solution in a fixed ratio for 7 times (the amount of Ce(NO3)3 aqueous solution added was 70µL).
[0026] Figure 4 The morphology, elemental analysis (Mapping) and line profile of AuNPs@CeO2 prepared in Example 3 of the present invention are shown in FIG. Figure 4 (ab) are morphology images of AuNPs@CeO2.
[0027] Figure 5 The photocatalytic degradation effect of gold nanoparticles (AuNPs), cerium dioxide nanoparticles (CeO2), and core-shell monodisperse spherical gold nanoparticles / cerium dioxide (AuNPs@CeO2) composites with different shell thicknesses prepared in Comparative Example 1, Comparative Example 2, and Example 2 of the present invention on 4-nitrophenol is shown.
[0028] Figure 6 The photocatalytic degradation effect diagram of gold nanoparticles (AuNPs), cerium dioxide nanoparticles (CeO2), and core-shell monodisperse spherical gold nanoparticles / cerium dioxide (AuNPs@CeO2) composite materials with a CeO2 shell thickness of 16.43±1.17 nm prepared in Comparative Example 1, Comparative Example 2, and Example 2 of the present invention on organic pollutants (methylene blue). DETAILED DESCRIPTION
[0029] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the contents described above.
[0030] Example 1 Preparation method of core-shell monodispersed spherical gold nanoparticles / cerium dioxide composite material: (1) A 25 mmol / L chloroauric acid aqueous solution was diluted with boiling ultrapure water and heated continuously to keep boiling to obtain a 0.2577 mmol / L chloroauric acid aqueous solution dilution. Subsequently, a 1% by mass sodium citrate aqueous solution was quickly added to the mixture at a volume ratio of 1:5 between the chloroauric acid aqueous solution and the sodium citrate aqueous solution. The reaction was continued at above 90°C for 30 min to obtain a stable gold nanoseed colloidal solution.
[0031] (2) A 0.1 mol / L tris(hydroxymethyl)aminomethane aqueous solution was diluted with ultrapure water at 90°C to form a dilution solution with a molar concentration of 4.082 mmol / L and a temperature of 90°C. Then, the gold nanocolloidal seed solution and a 1% chloroauric acid aqueous solution were added to the dilution solution at a volume ratio of 5:1:1 of tris(hydroxymethyl)aminomethane (TB) aqueous solution, gold nanoseed colloid solution and chloroauric acid aqueous solution. The mixture was reacted at above 90°C to form a mixed solution. The mixed solution was then condensed and refluxed for 30 minutes to grow AuNPs. The amount of ultrapure water used to dilute the tris(hydroxymethyl)aminomethane aqueous solution and the amount of gold nanoseeds used were adjusted to ensure that the total volume of the reaction solution was always maintained at 50 mL during the experiment to prepare AuNPs. Figure 2 a is a typical morphology of AuNPs prepared in Example 1.
[0032] (3) The prepared AuNPs were centrifuged and washed twice at 5000 rpm to remove excess TB solution in the supernatant to form an AuNPs concentrate. 0.2 mol / L CTAB aqueous solution was added to the concentrate at a volume ratio of 1:1 between the concentrate and the CTAB aqueous solution. The mixture was stirred and dispersed at 200 rpm for 30 min at 30°C to allow the CTAB molecules to adsorb on the surface of the AuNPs.
[0033] (4) 0.01 mol / L EDTA-NH3 and 0.1 mol / L Ce(NO3)3 aqueous solution were added to the dispersion in a ratio of 10:1, wherein the volume ratio of Ce(NO3)3 aqueous solution to dispersion was 1:300. The solutions were fully mixed under stirring at 300 rpm to form a mixed solution. The mixed solution was placed in a reactor and subjected to high-temperature hydrothermal reaction at 90 °C for 5 h to obtain core-shell monodispersed spherical gold nanoparticles / cerium dioxide composite materials; Figure 2 b is a typical morphology of the AuNPs@CeO2 composite material prepared in Example 1, Figure 2 The maximum absorption peak in c is located at 562nm, which is a typical UV-visible spectrum of the AuNPs@CeO2 composite material prepared in Example 1. It can be seen from the figure that after the surface of the nano-gold is coated with a cerium dioxide shell layer, the maximum spectral peak position will undergo an obvious red shift in the spectrum.
[0034] Example 2 Preparation method of core-shell monodisperse spherical gold nanoparticles / cerium dioxide composite materials with different shell thicknesses: (1) A 25 mmol / L chloroauric acid aqueous solution was diluted with boiling ultrapure water and heated continuously to keep boiling to obtain a 0.2577 mmol / L chloroauric acid aqueous solution dilution. Subsequently, a 1% by mass concentration of sodium citrate aqueous solution was quickly added to the mixture at a volume ratio of 1:10 between the chloroauric acid aqueous solution and the sodium citrate aqueous solution. The reaction was continued at above 90°C for 30 min to obtain a stable gold nanoseed colloidal solution.
[0035] (2) A 0.1 mol / L tris(hydroxymethyl)aminomethane aqueous solution was diluted with ultrapure water at 90°C to form a dilution solution with a molar concentration of 4.082 mmol / L and a temperature of 90°C. Then, the gold nanocolloidal seed solution and a 1% by mass concentration of chloroauric acid aqueous solution were added to the dilution solution at a volume ratio of 4:1:1 of tris(hydroxymethyl)aminomethane aqueous solution, gold nanoseed colloid solution and chloroauric acid aqueous solution. The mixture was reacted at above 90°C to form a mixed solution. The mixed solution was then condensed and refluxed for 30 minutes to grow AuNPs. The amount of ultrapure water used to dilute the tris(hydroxymethyl)aminomethane aqueous solution and the amount of gold nanoseeds used were adjusted to ensure that the total volume of the reaction solution was always maintained at 50 mL during the experiment to prepare AuNPs.
[0036] (3) The prepared AuNPs were centrifuged and washed twice at 5000 rpm to remove excess TB solution in the supernatant to form an AuNPs concentrate. 0.2 mol / L CTAB aqueous solution was added to the concentrate at a volume ratio of 2:1 between the concentrate and the CTAB aqueous solution. The mixture was stirred and dispersed at 200 rpm for 30 min at 30°C to allow the CTAB molecules to adsorb on the surface of the AuNPs.
[0037] (4) 0.01 mol / L EDTA-NH3 and 0.1 mol / L Ce(NO3)3 aqueous solution were added to the dispersion in a volume ratio of 5:1, wherein the volume ratio of Ce(NO3)3 aqueous solution to dispersion was 1:300. The fixed ratio of EDTA-NH3 and Ce(NO3)3 aqueous solution was repeatedly added 1, 3, 5, and 7 times (each time the amount of Ce(NO3)3 aqueous solution added was 10 μL), and then the solution was fully mixed under stirring at 300 rpm to form a mixed solution. The mixed solution was placed in a reactor and subjected to high-temperature hydrothermal reaction at 90 °C for 5 h to obtain core-shell monodispersed spherical gold nanoparticles / cerium dioxide composite materials with different morphologies and thicknesses.
[0038] Figure 3 The gold nanoparticle seeds prepared in Example 2 were grown by repeatedly adding a fixed ratio of EDTA-NH3 and Ce(NO3)3 aqueous solution once ( Figure 3 a), 3 times ( Figure 3 b), 5 times ( Figure 3 c) and 7 times ( Figure 3 d) Typical TEM electron microscope morphology of the obtained AuNPs@CeO2 composite materials with different morphologies and thicknesses. It can be seen from the figure that with the addition of different amounts of EDTA-NH3 and Ce(NO3)3 aqueous solutions, the thickness and morphology of cerium dioxide on the surface of the spherical gold nanoparticles / cerium dioxide composite materials will change significantly.
[0039] Example 3 Preparation method of core-shell monodispersed spherical gold nanoparticles / cerium dioxide composite material: (1) A 25 mmol / L chloroauric acid aqueous solution was diluted with boiling ultrapure water and heated continuously to keep boiling to obtain a 0.2577 mmol / L chloroauric acid aqueous solution dilution. Subsequently, a 1% by mass concentration of sodium citrate aqueous solution was quickly added to the mixture in a ratio of 1:1 between the volume of the chloroauric acid aqueous solution and the sodium citrate aqueous solution. The reaction was continued at above 90°C for 30 min to obtain a stable gold nanoseed colloidal solution.
[0040] (2) A 0.1 mol / L tris(hydroxymethyl)aminomethane aqueous solution was diluted with ultrapure water at 90°C to form a dilution solution with a molar concentration of 4.082 mmol / L and a temperature of 90°C. Then, the gold nanocolloidal seed solution and a 1% chloroauric acid aqueous solution were added to the dilution solution in a volume ratio of 2:1:1 of tris(hydroxymethyl)aminomethane aqueous solution, gold nanoseed colloid solution and chloroauric acid aqueous solution. The mixture was reacted at above 90°C to form a mixed solution. The mixed solution was then condensed and refluxed for 30 minutes to allow AuNPs to grow. The amount of ultrapure water used to dilute the tris(hydroxymethyl)aminomethane aqueous solution and the amount of gold nanoseeds used were adjusted to ensure that the total volume of the reaction solution was always maintained at 50 mL during the experiment to prepare AuNPs.
[0041] (3) The prepared AuNPs were centrifuged and washed twice at 5000 rpm to remove excess TB solution in the supernatant to form an AuNPs concentrate. 0.2 mol / L CTAB aqueous solution was added to the concentrate at a volume ratio of 4:1 between the concentrate and the CTAB aqueous solution. The mixture was stirred and dispersed at 200 rpm for 30 min at 30°C to allow the CTAB molecules to adsorb on the surface of the AuNPs.
[0042] (4) 0.01 mol / L EDTA-NH3 and 0.1 mol / L Ce(NO3)3 aqueous solution were added to the dispersion in a ratio of 20:1, wherein the volume ratio of Ce(NO3)3 aqueous solution to dispersion was 1:300. The solutions were fully mixed under stirring at 300 rpm to form a mixed solution. The mixed solution was placed in a reactor and subjected to high-temperature hydrothermal reaction at 90 °C for 5 h to obtain core-shell monodispersed spherical gold nanoparticles / cerium dioxide composite materials.
[0043] Figure 4 The following are the morphology and element distribution diagrams of the AuNPs@CeO2 composite material prepared in Example 3. The morphology diagram shows that the AuNPs@CeO2 composite material has a rounded spherical morphology, while the element distribution diagram indicates that the composite material does contain gold (Au), cerium (Ce), and oxygen (O). In particular, the Ce and O contents are significantly lower than that of Au, indicating that the ceria content in the AuNPs@CeO2 only forms a thin shell on the outer surface of the gold. This also demonstrates that ceria is successfully coated on the surface of the gold nanoparticles.
[0044] Comparative Example 1 Preparation of AuNPs: (1) A 25 mmol / L chloroauric acid aqueous solution was diluted with boiling ultrapure water and heated continuously to keep boiling to obtain a 0.2577 mmol / L chloroauric acid aqueous solution dilution. Subsequently, a 1% by mass concentration of sodium citrate aqueous solution was quickly added to the mixture at a volume ratio of 1:10 between the chloroauric acid aqueous solution and the sodium citrate aqueous solution. The reaction was continued at above 90°C for 30 min to obtain a stable gold nanoseed colloidal solution.
[0045] (2) A 0.1 mol / L tris(hydroxymethyl)aminomethane aqueous solution was diluted with ultrapure water at 90°C to form a dilution solution with a molar concentration of 4.082 mmol / L and a temperature of 90°C. Then, the gold nanocolloidal seed solution and a 1% chloroauric acid aqueous solution were added to the dilution solution in a volume ratio of 4:1:1 of tris(hydroxymethyl)aminomethane aqueous solution, gold nanoseed colloid solution and chloroauric acid aqueous solution. The mixture was reacted at above 90°C to form a mixed solution. The mixed solution was then condensed and refluxed for 30 minutes to allow AuNPs to grow. The amount of ultrapure water used to dilute the tris(hydroxymethyl)aminomethane aqueous solution and the amount of gold seeds used were adjusted to ensure that the total volume of the reaction solution was always maintained at 50 mL during the experiment to prepare AuNPs.
[0046] Comparative Example 2 Preparation of CeO2: In an environment of 30°C, add 1mL of 0.2mol / L CTAB to 2mL of ultrapure water. After the CTAB is evenly dispersed, add 1mL of 0.01mol / L EDTA-NH3 and stir at 300rpm for 3min. Then add 100µL of 0.1mol / L Ce(NO3)3 aqueous solution and stir at 300rpm for 3min. Then, place it in a drying oven at 90°C and dry it for 4h to obtain pure CeO2 catalytic material.
[0047] Process and effect evaluation of heterogeneous catalytic reduction of 4-nitrophenol (4-NP) by core-shell monodispersed spherical gold nanoparticles / ceria composites: 4-NP and sodium borohydride (NaBH4) were mixed in water at a molar ratio of 1:200, and the spherical gold nanoparticles / cerium dioxide composite material was added thereto at a molar ratio of 4469.3:22.35:1 of sodium borohydride, 4-NP, and the spherical gold nanoparticles / cerium dioxide composite material prepared in Example 2. The reaction progress was monitored by an ultraviolet-visible spectrophotometer (UV-vis) in the wavelength range of 250-500 nm at a scanning rate of 0.5 nm / s. The characteristic absorption peak (λ max ) intensity change kinetic analysis to evaluate the catalytic efficiency of the catalyst. In order to evaluate the heterogeneous catalytic cycle stability of the spherical gold nanoparticles / cerium dioxide composite material, five consecutive catalytic experiments were carried out under the same reaction conditions. The specific operation is as follows: after the completion of the first catalytic reaction, 0.04mL0.01mol / L 4-NP aqueous solution and 0.16mL0.5mol / L NaBH4 aqueous solution were added to the reaction system to maintain the reactant molar ratio (C 4-NP :C NaBH4 =1:200) to restart the catalytic reaction. The reaction progress was monitored by UV-visible spectrophotometry (UV-vis) in each cycle, and the changes in the intensity of the characteristic absorption peaks at different times were recorded. The apparent rate constant (K app By comparing the K app The photocatalytic degradation effects of gold nanoparticles (AuNPs), cerium dioxide nanoparticles (CeO2), and spherical gold nanoparticles / cerium dioxide (AuNPs@CeO2) composite materials on 4-nitrophenol were analyzed. Figure 5 .from Figure 5 As can be seen from the figure, when AuNPs are used alone for catalysis, K app Only 0.00642 minutes -1 The catalytic effect of CeO2 is not ideal. app Only 0.0642 minutes -1In contrast, when AuNPs@CeO2 with different shell thicknesses were introduced into the system, the characteristic absorption peak of 4-NP changed significantly within the same reaction time, indicating that the thickness of the gold nanoparticles and CeO2 shells made different AuNPs@CeO2 composite materials have a significant effect on the catalytic activity.
[0048] Process and effect evaluation of photocatalytic degradation of organic pollutants (methylene blue, MB) by core-shell monodispersed spherical gold nanoparticles / cerium dioxide composites: MB and NaOH were mixed in water at a molar ratio of MB to NaOH of 1:100-1:500, and the spherical gold nanoparticles / cerium dioxide composite material prepared in Example 2 was added thereto at a molar ratio of MB to catalyst of 20.12:1. 2 Under the irradiation of a xenon lamp cold light source with high irradiance, the photocatalytic reaction was carried out at a constant temperature of (25±0.5)℃ and a magnetic stirring of 300rpm. During the experiment, 150μL of reaction solution was taken every 3 minutes, and a UV-visible spectrophotometer (scanning range 300-900nm, rate 0.5nm / s) was used to detect the change in the intensity of the MB characteristic absorption peak at 665nm, and the photocatalytic performance of the catalyst was evaluated by kinetic analysis. Five consecutive catalytic experiments were carried out under the same reaction conditions to evaluate the photocatalytic cycle stability of the spherical gold nanoparticles / cerium dioxide composite material. That is, after the first catalytic reaction was completed, 240μL of 1.5mol / L MB aqueous solution and 60μL of 3% w / v NaOH aqueous solution were added to the reaction system to restart the catalytic reaction. By comparing the K app The reusability and stability of spherical gold nanoparticles / cerium dioxide composite materials were obtained. The photocatalytic degradation effects of gold nanospheres (AuNPs), cerium dioxide nanoparticles (CeO2), and spherical gold nanoparticles / cerium dioxide (AuNPs@CeO2) composite materials (CeO2 shell thickness is 16.43±1.17nm) on methylene blue were shown. Figure 6 As can be seen from the figure, at 250μW / cm 2 Under the irradiation of white light source, the photocatalytic effect of noble metal gold nanoparticles on MB is poor. After a reaction time of 3 hours, the characteristic absorption peak intensity of MB only decreased by about 59.3%. app 0.00381min -1 Pure cerium dioxide nanoparticles have a certain photocatalytic effect on MB. The entire catalytic process takes 30 minutes, and its conversion efficiency is about 83.8%. app 0.032285min -1In contrast, the AuNPs@CeO2 composite material essentially completed the catalytic process within 21 minutes, with a conversion efficiency of 93.5%. This indicates that gold nanoparticles significantly enhance the photocatalytic degradation of MB by ceria.
[0049] The complete experimental process is as follows Figure 1 The flowchart is shown in Figure 4, which not only explains the process of preparing AuNPs@CeO2 but also illustrates the process of applying AuNPs@CeO2 for heterogeneous catalysis and photocatalytic performance. Figure 5 and Figure 6 The heterogeneous catalytic effect of the AuNPs@CeO2 composite material prepared in Example 2 on 4-p-nitrophenol is shown respectively ( Figure 5 ) and photocatalytic degradation effect on methylene blue ( Figure 6 ). It can be seen that compared with pure gold nanoparticles without ceria coating or pure ceria particles, the composite material exhibits a significant catalytic rate advantage, indicating that the composite nanomaterial has broad application prospects in the field of catalysis.
[0050] The catalytic performance test and analysis revealed that the spherical gold nanoparticle / cerium dioxide composite materials prepared in Example 1, Example 2, and Example 3 had similar morphology, element distribution, and heterogeneous catalytic and photocatalytic properties.
[0051] While various embodiments of the present invention have been described above, the foregoing description is intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or improvements to existing technologies, or to enable others skilled in the art to understand the embodiments disclosed herein.
Claims
1. A method for preparing a core-shell monodisperse spherical gold nanoparticle / cerium dioxide composite material, characterized in that: The specific steps include: (1) diluting the chloroauric acid aqueous solution with water and heating it to obtain a dilute solution of the chloroauric acid aqueous solution, then adding the sodium citrate aqueous solution to the dilute solution of the chloroauric acid aqueous solution, and heating the solution to obtain a gold nanoseed colloidal solution; (2) diluting the tris(hydroxymethylaminomethane) aqueous solution with water and heating it to obtain a dilute solution of the tris(hydroxymethylaminomethane) aqueous solution, then successively adding the gold nanoseed colloid solution and the chloroauric acid aqueous solution to the dilute solution, heating them to react to form a mixed solution, then condensing and refluxing the mixed solution, and preparing spherical gold nanoparticles by adjusting the amount of water used to dilute the tris(hydroxymethylaminomethane) aqueous solution and the amount of the gold nanocolloid seed solution; (3) washing the prepared spherical gold nanoparticles by centrifugation to form a concentrated solution, and adding an aqueous solution of hexadecyltrimethylammonium bromide to the concentrated solution to disperse the particles and form a dispersion; (4) Adding EDTA ammonia solution and Ce(NO3)3 aqueous solution to the dispersion in sequence and stirring thoroughly to form a mixed solution, the mixed solution was placed in a reaction vessel to react and obtain a core-shell type monodispersed spherical gold nanoparticle / cerium dioxide composite material.
2. The method for preparing the core-shell monodispersed spherical gold nanoparticle / cerium dioxide composite material according to claim 1, characterized in that: The molar concentration of the chloroauric acid aqueous solution in step (1) is 25 mmol / L; the molar concentration of the dilution of the chloroauric acid aqueous solution is 0.2577 mmol / L and is in a boiling state; the sodium citrate aqueous solution is added to the dilution of the chloroauric acid aqueous solution in a volume ratio of 1:1-10 of the chloroauric acid aqueous solution to the sodium citrate aqueous solution; the mass percentage concentration of the sodium citrate aqueous solution is 1%; and the conditions for the heating reaction are: the reaction is continued at above 90°C for 30 minutes.
3. The method for preparing the core-shell monodispersed spherical gold nanoparticle / cerium dioxide composite material according to claim 1, characterized in that: The molar concentration of the tris(hydroxymethylaminomethane) aqueous solution in step (2) is 0.1 mol / L; the molar concentration of the dilution of the tris(hydroxymethylaminomethane) aqueous solution is 4.082 mmol / L and the temperature is 90°C; the gold nanoseed colloid solution and the chloroauric acid aqueous solution are sequentially added to the dilution in a ratio of 2-5:1:1 of the tris(hydroxymethylaminomethane) aqueous solution, the gold nanoseed colloid solution and the chloroauric acid aqueous solution; the mass percentage concentration of the chloroauric acid aqueous solution is 1%; and the heating reaction is carried out at a temperature above 90°C.
4. The method for preparing the core-shell monodispersed spherical gold nanoparticle / cerium dioxide composite material according to claim 1, characterized in that: The condensation reflux time in step (2) is 30 min; the specific method for preparing spherical gold nanoparticles by adjusting the amount of water used to dilute the tris(hydroxymethyl)aminomethane aqueous solution and the amount of gold nanocolloidal seed solution is as follows: the total volume of the reaction solution is always 50 mL by adjusting the amount of water used to dilute the tris(hydroxymethyl)aminomethane aqueous solution and the amount of gold nanocolloidal seed solution.
5. The method for preparing the core-shell monodispersed spherical gold nanoparticle / cerium dioxide composite material according to claim 1, characterized in that: The centrifugal washing conditions in step (3) are: centrifugal washing twice at a speed of 5000 rpm.
6. The method for preparing the core-shell monodispersed spherical gold nanoparticle / cerium dioxide composite material according to claim 1, characterized in that: The cetyltrimethylammonium bromide aqueous solution in step (3) is added to the concentrated solution at a volume ratio of 1-4:1 between the concentrated solution and the cetyltrimethylammonium bromide aqueous solution; the molar concentration of the cetyltrimethylammonium bromide aqueous solution is 0.2 mmol / L, and the conditions for dispersion in the concentrated solution are: stirring and dispersing at 200 rpm for 30 minutes at a temperature of 30°C.
7. The method for preparing the core-shell monodispersed spherical gold nanoparticle / cerium dioxide composite material according to claim 1, characterized in that: In step (4), the EDTA ammonia solution and the Ce(NO3)3 aqueous solution are added to the dispersion at a volume ratio of 5-20:1; the Ce(NO3)3 aqueous solution is added to the dispersion at a volume ratio of 1:300; the molar concentration of the EDTA ammonia solution is 0.01 mol / L, and the molar concentration of the Ce(NO3)3 aqueous solution is 0.1 mol / L; the EDTA ammonia solution and the Ce(NO3)3 aqueous solution are dispersed at 300 rpm and hydrothermally reacted at 90°C for 5 h.
8. Use of the core-shell monodispersed spherical gold nanoparticle / cerium dioxide composite material prepared by the method according to any one of claims 1 to 7 in the fields of heterogeneous catalysis and photocatalysis.