Au / tio2 inverse opal composite light absorption enhancement structure and device

Abstract

This invention relates to the field of photonic crystal structures and light absorption enhancement devices, and provides an Au / TiO2 inverse opal composite light absorption enhancement structure and device. The enhancement structure includes: a TiO2 inverse opal framework having a three-dimensionally ordered, periodically arranged spherical cavity structure; and Au nanoparticles distributed on the inner wall of the spherical cavities; the surface coverage of the Au nanoparticles on the inner wall of the spherical cavities is 16.7% ± 2%. By introducing the dimensionless geometric parameter of surface coverage, this invention provides a clear geometric design basis for optimizing the light absorption performance of the Au / TiO2 inverse opal composite structure, and can be widely used in optoelectronic devices such as photocatalysts, photodetectors, solar cells, and photonic sensors.

Description

Technical Field

[0001] This invention relates to the field of photonic crystal structure and light absorption enhancement device technology, and particularly to an Au / TiO2 inverse opal composite light absorption enhancement structure and device. Background Technology

[0002] TiO2 is a mainstream semiconductor material used in photocatalysis, photoelectric detection, and solar cells. However, its intrinsic band gap is as wide as 3.2 eV, which means it can only utilize ultraviolet light below 387 nm and has extremely low utilization efficiency in visible light, thus limiting its practical applications.

[0003] In existing modification schemes, three-dimensional ordered inverse opal photonic crystals can extend the light-matter interaction time through the slow photon effect, thereby enhancing light absorption in specific wavelength bands. However, this cannot solve the inherent defect of TiO2's lack of visible light response. Therefore, current technologies generally composite noble metal nanoparticles within the inverse opal framework, relying on localized surface plasmon resonance (LSPR) to generate a strong nanoscale local electric field, and using the metal optical antenna effect to broaden the visible light absorption range. In the current Au / TiO2 inverse opal system, the noble metal loading is determined solely by mass fraction calibration or experimental trial and error, failing to quantitatively reflect the spatial arrangement of gold particles within the three-dimensional confined channels. As the metal loading increases, a nonlinear competition exists between two optical effects: the near-field enhancement of LSPR by isolated gold particles can increase light absorption; however, the geometrical shielding and backscattering caused by dense particle packing induce parasitic reflection losses, weakening light-trapping capabilities. There are no quantitative evaluation indicators for the evolution of particles from independent plasmon response to coupled shielding effect. The industry lacks geometric quantitative parameters that can accurately guide the spatial arrangement of nanoparticles, making it difficult to achieve optimal control of light absorption performance. Summary of the Invention

[0004] The purpose of this invention is to address the technical problems of existing Au / TiO2 inverse opal composite structures, which lack quantitative geometric parameter design basis for the spatial distribution of metal nanoparticles and cannot effectively balance the dynamic competition between LSPR near-field enhancement and geometric shading loss. This invention provides an Au / TiO2 inverse opal composite light absorption enhancement structure and device.

[0005] This invention provides the following technical solution:

[0006] An Au / TiO2 inverse opal composite light absorption enhancement structure, comprising:

[0007] TiO2 inverse opal framework, the framework having a three-dimensional ordered periodic arrangement of spherical cavities;

[0008] Au nanoparticles are distributed on the inner wall of the spherical cavity;

[0009] The Au nanoparticles have a surface coverage of 16.7% ± 2% on the inner wall of the spherical cavity.

[0010] According to some possible implementations, the radius of the spherical cavity in the TiO2 inverse opal framework is 150 nm, and the radius of the Au nanoparticles is 25 nm.

[0011] According to some possible implementations, the TiO2 inverse opal framework is constructed based on a face-centered cubic arrangement with a lattice constant of 424.264 nm, an (111) interplanar spacing of 244.949 nm, and a periodic layer of 3 layers.

[0012] According to some possible implementations, the Au nanoparticles are distributed on the inner wall of the spherical cavity in a uniform point contact manner.

[0013] According to some possible implementations, the surface coverage Defined as the ratio of the total projected area of ​​the Au nanoparticles to the inner surface area of ​​the spherical cavity, the calculation formula is:

[0014] (1)

[0015] Where N is the number of Au nanoparticles in a single cavity, r is the radius of the Au nanoparticles, and R is the radius of the cavity.

[0016] According to some possible implementations, when the surface coverage is 16.7%, the average absorption rate of the structure in the visible light band is increased by 16.6 times compared to the pure TiO2 inverse opal structure.

[0017] On the other hand, the present invention provides an Au / TiO2 inverse opal composite light absorption enhancement device, comprising:

[0018] The substrate; and the aforementioned Au / TiO2 inverse opal composite light absorption enhancement structure disposed on the substrate.

[0019] According to some possible implementations, the device is a photocatalyst, a photodetector, a solar cell, or a photon sensor.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The Au / TiO2 inverse opal composite light absorption enhancement structure and device technology provided by this invention, on the one hand, introduces a surface coverage (C) sThe two dimensionless geometric parameters, namely () and effective shielding rate (S), transform the abstract metal loading into a quantitative index that can characterize the spatial arrangement of particles and optical response, thereby realizing the quantitative screening of the optimal metal loading of the anti-opal photocatalyst and solving the problem of blindness in traditional experimental trial and error based on mass fraction.

[0022] On the other hand, by using FDTD simulation to obtain the absorption spectra and near-field electric field distributions corresponding to different coverage rates, the dynamic competition between the near-field enhancement effect and the geometric shading effect of LSPR can be accurately elucidated, providing quantitative support for the structural design of plasmonic photocatalysts. At the same time, this invention clarifies that 16.7%±2% is the optimal surface coverage rate and 25% is the competition critical point between the two effects, defining the upper limit of coverage rate corresponding to the optimization of light absorption performance, and providing a clear and referable design boundary for the precise control of the metal loading inside the inverse opal channels. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the three-dimensional geometric model of the Au / TiO2 inverse opal composite structure provided in the embodiments of the present invention.

[0024] Figure 2 The surface coverage (C) provided in the embodiments of the present invention s The geometric definition diagram of ).

[0025] Figure 3 This is a geometric definition and schematic diagram of the effective shading rate (S) provided in the embodiments of the present invention.

[0026] Figure 4 This is a spectrum showing the absorption rate of the Au / TiO2 composite system provided in this embodiment of the invention as the Au coverage increases.

[0027] Figure 5 This is a graph showing the variation of average absorptivity, reflectivity, and transmittance in the visible light band with Au coverage, provided in an embodiment of the present invention.

[0028] Figure 6 This is a near-field electric field distribution diagram at a characteristic wavelength of 550 nm under typical Au surface coverage provided in an embodiment of the present invention.

[0029] Figure 7 These are near-infrared (0.8-3.0 μm) transmission spectra of composite structures with different Au surface coverage rates provided in the embodiments of the present invention.

[0030] Figure 8 This is a schematic diagram showing the changes in average absorptivity, reflectivity, and transmittance in the near-infrared band with Au surface coverage and three characteristic intervals provided in the embodiments of the present invention.

[0031] Figure 9This is a spatial near-field electric field distribution diagram at a wavelength of 2.0 μm with different Au surface coverage rates, provided by an embodiment of the present invention.

[0032] Figure 10 This is a graph showing the variation of absorption enhancement factor in the visible light and near-infrared bands with Au surface coverage, provided in an embodiment of the present invention.

[0033] Figure 11 Table 1, provided in this embodiment of the invention, shows the specific geometric parameters of the TiO2 inverse opal structure.

[0034] Figure 12 Table 2, provided in this embodiment of the invention, is a table of surface coverage and effective shielding rates corresponding to different numbers of Au particles. Detailed Implementation

[0035] To overcome or alleviate the obvious defects of the traditional anti-opal design method that relies on mass fraction and trial and error, this invention provides an Au / TiO2 anti-opal composite light absorption enhancement structure with quantitatively controllable geometric parameters, which solves the technical pain points of low visible light utilization and lack of quantitative basis for metal load optimization.

[0036] The present invention will now be described in detail with reference to embodiments and accompanying drawings. However, it should be understood that the embodiments and drawings are for illustrative purposes only and do not constitute any limitation on the scope of protection of the present invention. All reasonable modifications and combinations included within the inventive spirit of the present invention fall within the scope of protection of the present invention.

[0037] Example

[0038] This embodiment provides an Au / TiO2 inverse opal composite light absorption enhancement structure. The three-dimensional geometric model of the Au / TiO2 inverse opal composite structure is shown below. Figure 1 As shown, the Au / TiO2 inverse opal composite light absorption enhancement structure includes a TiO2 inverse opal framework and Au nanoparticles distributed on the inner wall of its spherical cavities. The TiO2 inverse opal framework is constructed based on a face-centered cubic arrangement, containing periodically arranged spherical cavities with a cavity radius R = 150 nm, a face-centered cubic lattice constant a = 424.264 nm, and (111) interplanar spacing d 111 =244.949 nm, the framework consists of 3 layers of periodic structures, see specific geometric parameters. Figure 11 Table 1. The Au nanoparticles have a radius of r = 25 nm and are arranged on the inner wall of the spherical cavity in a uniform point contact manner.

[0039] By adjusting the number N of Au nanoparticles within a single cavity, the surface coverage can be varied from 0% to 65.28%. This embodiment presents 10 structural schemes with different particle numbers (N=0, 6, 12, 24, 36, 48, 60, 72, 84, 94), corresponding to surface coverage ranging from 0% to 65.28% and effective shielding rates ranging from 0% to 92.65%. Specific values ​​are shown in the appendix. Figure 12 Table 2.

[0040] Surface coverage C s Defined as the ratio of the total projected area of ​​Au nanoparticles to the surface area inside the spherical cavity ( Figure 2 The calculation formula is:

[0041] (1)

[0042] Where N is the number of Au nanoparticles in a single cavity, r is the radius of the Au nanoparticles (25 nm), and R is the radius of the cavity (150 nm).

[0043] The effective shielding rate S is defined as the degree of parasitic scattering loss caused by the incident light being blocked by the Au nanoparticle layer. Figure 3 Based on the Beer-Lambert statistical decay model, the calculation formula is as follows:

[0044] (2)

[0045] The formula for calculating optical density τ is as follows:

[0046] (3)

[0047] To verify the light absorption enhancement performance of the above structure, this embodiment uses the finite-difference time-domain method (FDTD) to simulate the optical response of the Au / TiO2 inverse opal composite light absorption enhancement structure under different surface coverage. The optical constants of TiO2 are taken from the Siefke model, and the optical constants of Au are taken from the Palik model. The core region of the model is locally meshed to a precision of 3 nm; periodic boundary conditions are used in the horizontal direction to simulate an infinitely extended two-dimensional array structure; and a perfectly matched layer (PML) absorption boundary is set along the light propagation direction to eliminate non-physical reflections. Plane waves with wavelengths ranging from 0.2 μm to 3 μm are incident vertically downwards, covering the ultraviolet to near-infrared band.

[0048] The full-band reflectance spectrum R(λ) and transmission spectrum T(λ) for different Au surface coverage were collected and output using an FDTD frequency domain monitor. The absorption spectrum A(λ) of the composite structure was calculated using the formula A(λ) = 1 - R(λ) - T(λ). The average absorptivity in the visible light band was obtained by integrating the absorption spectrum from 400 nm to 800 nm.

[0049] Figure 4 The full-spectral absorption spectra of the Au / TiO2 inverse opal composite light absorption enhancement structure with different Au surface coverage are shown. Figure 4 It can be observed that as the surface coverage increases from 0% to 16.67%, the absorption rate in the visible light band increases significantly; when the surface coverage continues to increase to 25%, the absorption rate decreases.

[0050] Figure 5 The curves showing the variation of average absorptivity, reflectivity, and transmittance in the visible light band (400-800 nm) with Au surface coverage are presented. Figure 5 It is clearly evident that when the surface coverage is 16.7%, the average absorptivity significantly increases from 3.2% of the pure TiO2 inverse opal framework to 53.4%, while the reflectivity decreases from 38.8% to 25.0%. Using the pure TiO2 inverse opal framework as a benchmark, Figure 10 The absorption enhancement factor in the visible light band is shown under different surface coverage, with the enhancement factor reaching a maximum of about 16.6 times at a surface coverage of 16.7%.

[0051] Extract the spatial near-field electric field distribution at a characteristic wavelength of 0.55 μm. Figure 6 ). Figure 6 (a) shows the electric field distribution when the coverage is 8.33%, at which point the Au nanoparticles are discretely distributed, forming dispersed electric field hotspots; Figure 6 (b) shows the electric field distribution when the coverage is 16.67%. At this time, strong dipole resonance is generated on the surface of Au nanoparticles, which effectively localizes the incident light at the interface between the particles and TiO2, forming dense electric field hotspots, and the LSPR effect reaches its strongest. Figure 6 (c) shows the electric field distribution when the coverage is 25%, at which point Au nanoparticles form a quasi-continuous metal layer on the inner wall of the cavity, and the electric field strength inside the cavity decreases significantly.

[0052] The above results indicate that the near-field enhancement effect of Au nanoparticles on LSPR reaches its optimum when the surface coverage is 16.7%, resulting in the most significant improvement in visible light absorption, while effectively avoiding geometric shading and reflection loss under high coverage. Therefore, 16.7% ± 2% is determined to be the optimal surface coverage for the Au / TiO2 inverse opal composite light absorption enhancement structure.

[0053] When the surface coverage increases to 25%, the effective shading rate reaches 63.21% (Table 2), and the average visible light absorption rate decreases relative to the 16.7% coverage rate. Figure 5 This coverage rate was determined to be the critical point where the near-field enhancement effect of LSPR competes with the geometric shading effect, i.e., the upper limit critical value of the surface coverage of Au nanoparticles in the Au / TiO2 inverse opal composite light absorption enhancement structure.

[0054] also, Figure 7 , Figure 8 and Figure 9 The optical response characteristics in the near-infrared band are demonstrated. For example... Figure 8 As shown, in the near-infrared band (0.8-3.0 μm), as the surface coverage increases, the structure sequentially exhibits three characteristic regions: a transparent region (coverage 0%-33.33%, transmittance maintained above 70%), a light-trapping region (coverage approximately 50%, absorptivity rising to nearly 74%), and a metallized electromagnetic shielding region (coverage >65%, reflectivity rising to nearly 45%).

[0055] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. An Au / TiO2 inverse opal composite light absorption enhancement structure, characterized in that, include: TiO2 inverse opal framework, the framework having a three-dimensional ordered periodic arrangement of spherical cavities; Au nanoparticles are distributed on the inner wall of the spherical cavity; The surface coverage of the Au nanoparticles on the inner wall of the spherical cavity is 16.7% ± 2%.

2. The Au / TiO2 inverse opal composite light absorption enhancement structure according to claim 1, characterized in that, The radius of the spherical cavity in the TiO2 inverse opal framework is 150 nm, and the radius of the Au nanoparticles is 25 nm.

3. The Au / TiO2 inverse opal composite light absorption enhancement structure according to claim 1, characterized in that, The TiO2 inverse opal framework is constructed based on a face-centered cubic arrangement with a lattice constant of 424.264 nm, an interplanar spacing of 244.949 nm for (111) crystal planes, and a periodic layer of 3 layers.

4. The Au / TiO2 inverse opal composite light absorption enhancement structure according to claim 1, characterized in that, The Au nanoparticles are distributed on the inner wall of the spherical cavity in a uniform point contact manner.

5. The Au / TiO2 inverse opal composite light absorption enhancement structure according to claim 1, characterized in that, The surface coverage Defined as the ratio of the total projected area of ​​the Au nanoparticles to the inner surface area of ​​the spherical cavity, the calculation formula is: （1） Where N is the number of Au nanoparticles in a single cavity, r is the radius of the Au nanoparticles, and R is the radius of the cavity.

6. The Au / TiO2 inverse opal composite light absorption enhancement structure according to claim 1, characterized in that, When the surface coverage is 16.7%, the average absorption rate of the structure in the visible light band is increased by 16.6 times compared with the pure TiO2 inverse opal structure.

7. An Au / TiO2 inverse opal composite light absorption enhancement device, characterized in that, include: Base; And the Au / TiO2 inverse opal composite light absorption enhancement structure as described in any one of claims 1-6 disposed on the substrate.

8. The Au / TiO2 inverse opal composite light absorption enhancement device according to claim 7, characterized in that, The device is a photocatalyst, a photodetector, a solar cell, or a photon sensor.

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