Plasmon resonance enhanced polishing method for online synthesis of heterogeneous photocatalyst

Abstract

The invention discloses a plasmon resonance enhanced polishing method for on-line synthesis of a heterogeneous photocatalyst, and belongs to the field of ultra-precision machining.The method comprises the following steps that nano-particles with photocatalytic properties are selected as the photocatalyst; selecting a metal salt as a precursor, preparing a metal salt solution, and mixing a photocatalyst into the metal salt solution to prepare a polishing solution; visible catalytic light is irradiated to the contact area of the polishing solution and a workpiece, the precursor is induced by a light source to improve the interface photocatalytic reaction rate, meanwhile, metal nanoparticles are separated out on line, and the interface photocatalytic reaction is enhanced so as to remarkably improve the material removal rate; the narrow-band-gap visible light catalyst conduction band electrons are consumed through the reduction reaction of the precursor, recombination of photon-generated carriers is avoided so as to improve the photocatalytic reaction rate, and meanwhile the photocatalytic reaction rate is synergistically improved through surface plasmon enhanced light scattering and injection of metal nanoparticle hot electrons into the photocatalyst conduction band. And the material removal rate is obviously improved.

Description

Technical Field

[0001] The present invention belongs to the field of ultra-precision machining, and particularly relates to a method for plasmon resonance enhanced polishing of an online synthesized multiphase photocatalyst. Background Art

[0002] The major national demands such as semiconductor manufacturing, aerospace, biomedicine, and ultra-precision instruments drive the innovative development of manufacturing technologies, and put forward higher requirements for the surface machining quality and material removal rate of hard and brittle semiconductor materials. For example, the surface accuracy requirement of synchrotron radiation light source X-ray mirrors obtained by grinding and polishing single crystal silicon reaches the atomic level; the atomic-scale efficient manufacturing of new semiconductor substrates such as diamond, silicon carbide, and gallium nitride is an inevitable choice for the development of high-power devices and even quantum devices.

[0003] For the ultra-precision machining of hard and brittle materials, traditional machining methods include chemical mechanical polishing. An oxide layer is formed on the surface of the workpiece by acid-base oxidants in the polishing fluid, and then removed by using hard abrasive grains, which will cause a certain degree of scratching on the surface; in order to achieve manufacturing at a smaller scale, a series of machining methods have been proposed later. For example, the colloidal jet polishing technology is used to adapt to various hardness materials, but in practical applications, problems such as particle dispersion and particle size control need to be solved; magnetorheological finishing uses a strong magnetic field to control the magnetorheological fluid in contact with the workpiece to polish the workpiece, but it is difficult to guarantee the control accuracy and the equipment price is high during the actual machining process.

[0004] Some scholars have proposed photocatalytic assisted polishing. This method mainly relies on abrasive grains with photocatalytic properties in the ultraviolet band, such as TiO 2 , ZnO, SnO 2 etc. Under the catalytic action of ultraviolet light, an oxide layer is formed on the surface of the workpiece to be machined in cooperation with strong oxidants such as hydrogen peroxide or potassium permanganate, and then the oxide layer is removed by mechanical action. The existing PACMP technology still faces many challenges: First, the mainstream photocatalysts (such as TiO 2 , ZnO) only respond to ultraviolet light (wavelength < 400 nm, only accounting for 4% of the solar spectrum), and high-energy ultraviolet light sources need to be configured, which greatly limits the energy utilization efficiency, and ultraviolet irradiation will accelerate the aging of the polishing pad; Second, the catalyst is mostly added to the polishing fluid after offline synthesis, and its agglomeration sedimentation and poor interfacial contact result in low utilization rate of photo-generated charges, and the catalyst synthesis process is complex, and the synthesis cost is relatively high compared with the entire polishing process; Third, the electron-hole recombination rate is fast (nanosecond level) during the photocatalytic process, which seriously restricts the effective progress of the surface redox reaction. Therefore, developing a photocatalytic system with visible light response, high stability and capable of online synthesis during the polishing process has become the key to breaking through the bottleneck of photocatalytic assisted polishing technology. Summary of the Invention

[0005] The purpose of the present invention is to provide a plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts, so as to solve the problems in the existing photocatalytic polishing method, such as complicated synthesis process, single catalytic light source band, high recombination rate of photogenerated carriers of narrow bandgap catalysts resulting in low material removal rate.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is: The present invention relates to a plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts, which comprises the following steps: S1. Selecting narrow band gap nanoparticles with photocatalytic properties as photocatalytic media; S2. Selecting a metal salt as a precursor for the interfacial photocatalytic reaction and configuring a metal salt solution, and mixing the photocatalyst into the metal salt solution to form a polishing solution, and placing the workpiece in the polishing solution; S3. Select a broad-spectrum light source as a visible catalytic light to irradiate the area where the polishing liquid contacts the workpiece. During the polishing process, the metal ions in the precursor are reduced to metal elements under the irradiation of the visible catalytic light, and then aggregated into metal nanoparticles and attached to the surface of the photocatalyst. The metal nanoparticles induce surface plasmon effects under the irradiation of the visible catalytic light, promote the photochemical reaction at the interface between the photocatalyst and the workpiece, and induce the formation of interface bridge bonds. S4. Promote the flow of polishing liquid and drive the flow of catalytic medium, thereby achieving atomic-level removal of the workpiece surface.

[0007] Preferably, in S1, the photocatalyst is hydrothermally treated by a hydrothermal method to terminate the surface of the photocatalyst with hydroxyl groups, specifically by mixing the photocatalyst powder and deionized water and transferring them to a high-pressure reactor, and heating them in an electric oven at 80-300°C for 2-20h, then washing with deionized water, and finally drying them at 80°C for 12h.

[0008] Preferably, in S1, the photocatalyst is gC responsive to visible catalytic light. 3 N 4 、SrTiO 3 , WO 3 , CuO, and the particle size of the photocatalyst is 10~1000nm.

[0009] Preferably, in S2, the precursor is any one of silver nitrate, chloroplatinic acid, gold chloride and aluminum sulfate.

[0010] Preferably, in the polishing liquid configured in S2, the concentration of the photocatalyst is 0.1-10 g / L, and the concentration of the precursor is 0.01-1 g / L.

[0011] Preferably, the wavelength range of the visible catalytic light in S3 covers 400 - 800 nm, and the power range is 0.5 - 500 W.

[0012] Preferably, the metal salt solution in S2 is an aqueous solution. In S3, the precursor also participates in the photocatalytic reduction reaction under the irradiation of the catalytic light source, consuming the photo-generated electrons in the conduction band of the photocatalyst, enabling the photo-generated holes in the valence band to migrate to the surface of the catalyst, participating in the oxidation reaction of water, and generating hydroxyl radicals adsorbed on the surface of the catalyst.

[0013] Preferably, the particle size of the metal nanoparticles formed by aggregation in S3 is 5 - 300 nm.

[0014] Preferably, in S3, when the photon frequency of the incident visible catalytic light is consistent with the internal electron vibration frequency of the metal nanoparticles, it causes the coupled oscillation of electrons, thereby inducing the surface plasmon resonance effect, enhancing the scattering of the visible catalytic light to improve the effective light absorption intensity of the photocatalyst. At the same time, it promotes the injection of free electrons in the metal nanoparticles into the conduction band of the photocatalyst, synergistically improving the photocatalytic reaction rate, and further promoting the bonding at the interface between the photocatalyst and the workpiece.

[0015] Preferably, in S3, by regulating the concentration of the precursor, the intensity of the catalytic light source, and the wavelength of the visible catalytic light, the quantitative control of the photoreduction reaction of the precursor is realized, thereby controlling the reduction rate of the metal element and the aggregation particle size of the metal nanoparticles, regulating the intensity of the plasmon resonance effect, and finally realizing the controllable material removal with single-atom layer precision for the workpiece.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1. The plasmon resonance enhanced polishing method for online synthesis of heterogeneous photocatalysts involved in the present invention uses nanoparticles with photocatalytic properties as the photocatalyst, uses metal salts as the precursor for the interfacial photocatalytic reaction and mixes them with the photocatalyst to prepare the polishing liquid. Under the irradiation of visible catalytic light, after the metal ions in the precursor participate in the reduction reaction, metal nanoparticles with plasmon resonance effect in the visible catalytic light range are formed online on the surface of the photocatalyst. The metal nanoparticles enhance the scattering of the visible catalytic light to improve the effective light absorption intensity of the photocatalyst. At the same time, the free electrons in the metal nanoparticles are excited and injected into the conduction band of the photocatalyst, synergistically improving the photocatalytic reaction rate and significantly increasing the material removal rate.

[0017] 2. The plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts involved in the present invention selects metal salts as precursors for interfacial photocatalytic reactions and prepares metal salt solutions, and mixes them with nanoparticles having photocatalytic properties in a certain proportion to prepare polishing liquid, irradiates visible catalytic light to the area in contact with the polishing liquid and the workpiece, and the precursors participate in the photocatalytic reduction reaction to consume the photogenerated electrons in the conduction band of the photocatalyst, and the photogenerated holes in the valence band are able to migrate to the surface of the catalytic medium and participate in the oxidation reaction of water, thereby generating more hydroxyl free radicals that are adsorbed on the surface of the catalytic medium, avoiding the recombination of photogenerated carriers to increase the photocatalytic reaction rate.

[0018] 3. The plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts involved in the present invention selects nanoparticles with visible light catalytic activity as photocatalysts, and hydrothermally treats the photocatalysts to graft hydroxyl groups on their surfaces, thereby improving the photocatalytic activity of the photocatalyst body, thereby achieving a significant increase in the material removal rate during the processing process.

[0019] 4. The plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts involved in the present invention can achieve quantitative control of the photoreduction reaction of the precursor by regulating the concentration of the precursor, the intensity of the visible catalytic light, and the wavelength of the visible catalytic light, while controlling the rate and particle size of the metal element precipitation to regulate the intensity of the surface plasmon effect, thereby achieving controllable material removal with a single atomic layer accuracy of the workpiece to be processed. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the process of the plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts; Figure 2 Schematic diagram of the plasmon resonance enhanced polishing method for in-line synthesis of heterogeneous photocatalysts. DETAILED DESCRIPTION

[0021] The technical scheme of the present invention is further specifically described below through specific embodiments. The embodiments are for the purpose of explaining the present invention, not for limiting the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0022] The present invention relates to a plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts, which comprises the following steps: S1. Select nanoparticles with photocatalytic properties as photocatalysts and perform hydrothermal treatment on the photocatalysts to terminate the hydroxyl groups on their surfaces. The specific method of hydrothermal treatment is: transfer the photocatalyst powder and deionized water to a high-pressure reactor, heat it in an electric oven at 80-300°C for 2-20 hours, then wash the photocatalyst with deionized water, and finally dry it at 80°C for 12 hours. The above-mentioned photocatalyst uses a photocatalyst that responds to visible light, such as: gC 3 N 4 、SrTiO 3 , WO 3 , CuO, with a particle size of 10~1000nm; S2. Select a metal salt as a precursor of the interfacial photocatalytic reaction and prepare a metal salt solution, and mix the photocatalyst into the metal salt solution to form a polishing liquid, and place the workpiece in the polishing liquid; the precursor is a metal salt that is easily reduced, such as silver nitrate, chloroplatinic acid, gold chloride, aluminum sulfate, etc., and the metal salt solution is an aqueous solution; the concentration of the photocatalyst in the prepared polishing liquid is 0.1~10g / L, and the concentration of the precursor is 0.01~1g / L.

[0023] S3. Select a broad spectrum light source as the visible catalytic light, the wavelength range of the visible catalytic light is 400~800nm, and the power range is 0.5~500W. Figure 1 As shown, the visible catalytic light is irradiated to the area where the polishing liquid contacts the workpiece, and the precursor participates in the photocatalytic reduction reaction to consume the photogenerated electrons e in the conduction band of the photocatalyst. - , so that the valence band photogenerated holes h + Gain Energy E g After that, they migrate to the surface of the photocatalyst and participate in the oxidation reaction of water, thereby generating more hydroxyl free radicals to be adsorbed on the surface of the catalytic medium, increasing the photocatalytic reaction rate on the surface of the workpiece to be processed, thereby increasing the material removal rate; at the same time, under the irradiation of visible catalytic light, the metal ions in the precursor are reduced to metal elements, agglomerated into metal nanoparticles of 5~300nm, and then precipitated metal nanoparticles and attached to the surface of the photocatalyst, inducing the surface plasmon effect under the irradiation of visible catalytic light, significantly improving the material removal rate. At the same time, by regulating the concentration of the precursor, the intensity of the visible catalytic light, and the wavelength of the visible catalytic light, quantitative control of the photoreduction reaction of the precursor is achieved, and the precipitation rate and particle size of the metal element are controlled to regulate the intensity of the plasmon effect, so as to achieve controllable material removal of the single atomic layer precision of the workpiece to be processed.

[0024] The specific principle of step 3 is as follows Figure 2As shown, when the photon frequency of the incident visible catalytic light is consistent with the internal electron vibration frequency of the metal nanoparticles, it will cause the coupled oscillation of electrons, thereby inducing the surface plasmon effect, and radiating an electromagnetic wave with a frequency close to the resonance frequency along the surface of the metal nanoparticles, enhancing the scattering of the visible catalytic light to improve the effective light absorption intensity of the photocatalyst. At the same time, when the free electrons e in the metal nanoparticles - absorb photon energy greater than its work function, they will be excited and jump to the surface of the metal particles to form hot electrons, which are then injected into the conduction band of the photocatalyst and react with water molecules to form superoxide radicals O 2 - Furthermore, a large number of hydroxyl radicals -OH are formed and adsorbed on the surface of the photocatalyst, improving the interfacial photocatalytic reaction rate, and then inducing and promoting the bonding between the catalyst and the workpiece interface, achieving a significant increase in the material removal rate.

[0025] In this article, specific examples are used to elaborate on the principles and implementation methods of the present invention. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts, characterized in that: It includes the following steps: S1. Selecting nanoparticles with photocatalytic properties as photocatalysts; S2. Selecting a metal salt as a precursor for the interfacial photocatalytic reaction and configuring a metal salt solution, and mixing the photocatalyst into the metal salt solution to form a polishing solution, and placing the workpiece in the polishing solution; S3. Select a broad-spectrum light source as a visible catalytic light to irradiate the area where the polishing liquid contacts the workpiece. The metal ions in the precursor are reduced to metal elements under the irradiation of the visible catalytic light and aggregated into metal nanoparticles, which are attached to the surface of the photocatalyst. The metal nanoparticles induce a surface plasmon effect under the irradiation of the visible catalytic light, which promotes the bonding between the photocatalyst and the workpiece interface. S4. Promote the flow of polishing liquid and drive the flow of catalytic medium, thereby achieving atomic-level removal of the workpiece surface.

2. The plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts according to claim 1, characterized in that: In S1, the photocatalyst is hydrothermally treated by a hydrothermal method to terminate the surface of the photocatalyst with hydroxyl groups. The specific method is: the photocatalyst powder and deionized water are mixed and transferred to a high-pressure reactor, and heated in an electric oven at 80-300°C for 2-20h, then washed with deionized water, and finally dried at 80°C for 12h.

3. The plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts according to claim 2, characterized in that: In S1, the photocatalyst uses any one of nanoparticles of g-C3N4, SrTiO3, WO3, and CuO that responds to visible catalytic light, and the particle size of the photocatalyst is 10~1000nm.

4. The plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts according to claim 1, characterized in that: In S2, the precursor is any one of silver nitrate, chloroplatinic acid, gold chloride, and aluminum sulfate.

5. The plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts according to claim 4, characterized in that: In the polishing liquid configured in S2, the concentration of the photocatalyst is 0.1-10 g / L, and the concentration of the precursor is 0.01-1 g / L.

6. The plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts according to claim 1, characterized in that: The wavelength range of the visible catalytic light in S3 is 400-800nm, and the power range is 0.5-500W.

7. The plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts according to claim 1, characterized in that: The metal salt solution in S2 is an aqueous solution. In S3, the precursor also participates in the photocatalytic reduction reaction under the irradiation of the catalytic light source, consumes the photogenerated electrons in the conduction band of the photocatalyst, and makes the photogenerated holes in the valence band migrate to the catalyst surface, participate in the oxidation reaction of water, and generate hydroxyl free radicals that are adsorbed on the catalyst surface.

8. The plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts according to claim 1, characterized in that: The particle size of the metal nanoparticles agglomerated in the S3 is 5-300 nm.

9. The plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts according to claim 1, characterized in that: In S3, when the photon frequency of the incident visible catalytic light is consistent with the internal electron vibration frequency of the metal nanoparticles, it causes coupled oscillation of the electrons, thereby inducing a surface plasmon effect, enhancing the scattering of the visible catalytic light to increase the effective light absorption intensity of the photocatalyst, and at the same time promoting the injection of free electrons in the metal nanoparticles into the conduction band of the photocatalyst, synergistically improving the photocatalytic reaction rate, and further promoting the bonding between the photocatalyst and the workpiece interface.

10. The plasmon resonance enhanced polishing method for online synthesis of multiphase photocatalysts according to claim 1, characterized in that: In S3, quantitative control of the photoreduction reaction of the precursor is achieved by regulating the concentration of the precursor, the intensity of the catalytic light source, and the wavelength of the visible catalytic light, thereby controlling the reduction rate of the metal element and the agglomeration particle size of the metal nanoparticles to regulate the intensity of the plasmon effect, and ultimately achieving controllable material removal of the workpiece with a single atomic layer precision.

Images