Light absorbing device, method of manufacture and use

Abstract

The present application relates to a kind of light absorption device, preparation method and use, light absorption device includes porous template and metal material, the porous template is provided with several through holes, the inner wall of the through hole is deposited with the metal material, the metal material is in the form of metal particles distribution in the inner wall of the through hole, the deposition range of the metal material is only limited on the inner wall of the through hole.This device forms localized plasmon effect by depositing metal particles on porous template, realizes the wide spectrum absorption of sunlight and photo-thermal conversion.

Description

Technical Field

[0001] This invention relates to a light-absorbing device, its preparation method, and its application, belonging to the field of optics. Background Technology

[0002] Plasma absorbers have wide applications in nanophotonics, photochemistry, and biophotonics. Plasma-enhanced solar vaporization, with its unique capabilities of spectral manipulation and subwavelength light concentration, is beneficial for various applications ranging from solar evaporation and sterilization to solar water treatment. Multifunctional metal absorbers, such as gold nanoparticle nanofluids, gold nanowires, and metal particles supported on paper or wood, are dedicated to generating interfacial vapor, thereby improving solar thermal conversion efficiency. Three-dimensional (3D) plasma absorbers composed of self-assembled nanoparticles induced by nanoporous templates (NPT) have attracted considerable attention due to their interesting basic mechanism of broadband light absorption and their potential applications in scalable and cost-effective manufacturing processes for physical vapor deposition (PVD) or multiple photonic functions. However, due to the lack of effective insulation and significant heat loss from metals with relatively high thermal conductivity, such self-floating plasma solar evaporators (with a large-area metal film in direct contact with a large amount of water) can only achieve about 60% solar thermal efficiency under a single solar irradiation, far lower than that of conventional carbon-based materials equipped with external thermal insulators / floats (about 80%). Therefore, the ability of self-floating plasma solar evaporators to simultaneously achieve broadband light absorption and effective heat insulation is crucial for solar thermal conversion under natural solar irradiance conditions. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a light-absorbing device that achieves broadband absorption of sunlight by depositing metal particles on a porous template. The through-hole structure arranged in the porous template, combined with the metal particles on the inner wall of the through-holes, forms a localized plasmon effect, thereby enabling efficient heating of water.

[0004] The present invention provides a method for fabricating a light-absorbing device, comprising the following steps to obtain a porous template: the porous template is provided with a plurality of through holes, the through holes penetrating the first side and the second side of the porous template;

[0005] Depositing metal material on the porous template: taking the first side as the deposition side, depositing metal material on the porous template, wherein the metal material is deposited on the first side and the inner wall of the through hole;

[0006] Metal film removal: Remove the metal material deposited on the first side, retaining the metal material on the inner wall of the through hole.

[0007] As a preferred embodiment, the porous template in this invention is a sheet material with a thickness of 40-60 μm. The first side and the second side are opposite sides. When depositing metal material, the first side is the coating side. A portion of the metal material is deposited on the first side to form a metal film, while another portion of the metal enters the through hole and is deposited on the inner wall of the through hole to form metal particles.

[0008] As a preferred option, the contact angle of the porous template is less than 90 degrees. Under this setting, the porous template is hydrophilic and transports water upward through capillary action, achieving heating and evaporation at the top of the porous template. The porous template can withstand high temperatures of up to 150 degrees Celsius during the deposition process without failure, and can withstand etching with an ion beam of 75mA for 2-4 minutes without dissociation during the etching process.

[0009] As a preferred embodiment, the deposition method for the metallic material in this invention is electron beam evaporation deposition, which satisfies one or more of the following conditions:

[0010] - The vacuum degree is (0.5~1)×10 -3 Pa;

[0011] - Electron gun voltage is 5-7 keV;

[0012] - Current is 200~400uA;

[0013] -Deposition rate is

[0014] As a preferred embodiment, the metal particles in this invention are distributed within a depth range of 0 to 2 μm near the opening of the channel on the first side.

[0015] As a preferred embodiment, the porous template of the present invention has periodically distributed through holes with a pore diameter of 250-400 nm and a pore spacing of 300-400 nm.

[0016] As a preferred embodiment, in this invention, electron beam evaporation stops when the thickness of the metal film on the first side reaches 60-80 nm, and the coating process is completed.

[0017] As a preferred embodiment, the metallic material used in this invention is selected from gold, silver, and aluminum, with gold being the preferred choice. Firstly, gold possesses stable chemical properties, maintaining its good shape and properties even after prolonged contact with water, and is not oxidized. Secondly, gold exhibits excellent plasmon resonance properties. The plasmon resonance peaks of gold nanoparticles are located in the visible light range (500–600 nm). By adjusting the particle shape and size, the position of the resonance absorption peak can be adjusted, thereby achieving broad-spectrum absorption.

[0018] On the other hand, a light-absorbing device is provided, including a porous template and a metal material. The porous template is provided with a plurality of through holes, and the metal material is deposited on the inner wall of the through holes. The metal material is distributed in the form of metal particles on the inner wall of the through holes to form a plasmonic structure. The plasmonic structure localizes the light within the light-absorbing device. In the final light-absorbing device, the distribution range of the metal material is limited to the inner wall of the through holes, and no metal particles are distributed on the outer surface of the porous template.

[0019] As a preferred option, the through-hole can be divided into a deposition zone and a non-deposition zone based on whether metal particles are deposited. The deposition zone is close to the first side of the porous template, and the non-deposition zone is close to the second side of the porous template.

[0020] On another aspect, the application of the aforementioned light-absorbing device is provided. The light-absorbing device floats on the water surface and heats the water by absorbing sunlight, causing the water to evaporate. When the light-absorbing device is placed on the water surface, the non-deposition area is placed in the water and in contact with the water body, while the deposition area is preferably placed above the water surface. The water in the water body is transported to the deposition area through the capillary force of the through hole and heated and evaporated in the deposition area. In use, the deposition area serves as a light-receiving surface.

[0021] As a preferred method, the second side faces down and the first side faces up, so that light enters from the first side of the deposited metal particles and heats and evaporates the water in the pore.

[0022] The beneficial effects of this invention are as follows: By depositing metal particles on a porous substrate template, and through the localized plasmon effect of the metal particles and the periodic through-hole structure of the template, light is localized within the light absorption device to heat and evaporate water, thereby achieving a solar thermal conversion efficiency of 80%.

[0023] The present invention removes the gold film on the first side in several ways. First, it solves the problem of poor water wettability of the gold film, which is a metal, allowing it to fully contact and heat the water droplet. Second, removing the gold film changes the heating site from the overall heating of the gold film to the heating of the water by the nanoparticles, that is, from bulk heating to interfacial heating. This interfacial heating allows the evaporated water to overflow fully, avoiding the energy waste problem of bulk heating. Third, it retains the gold particles that play an important role in spectral absorption. The remaining metal particles can still achieve broad-spectrum light absorption, while achieving light localization and high photothermal conversion.

[0024] In use, the non-deposition area of ​​this invention is placed in the water body in contact with the water, while the deposition area is placed above the water surface. This arrangement utilizes a nanoporous membrane to provide a channel for water transport, and the evaporation position of the light-absorbing device is located at the top of the water transport channel, shortening the distance of water vapor transport and ultimately increasing the evaporation rate of water vapor. Furthermore, the evaporation structure, which removes the gold film on the first side, places the hydrophobic gold particles in the deposition area at the top. This allows heating only of the water transported to the deposition area via capillary action, avoiding heat loss caused by the gold film directly heating the entire water body. Additionally, the deposition area, positioned above the light-absorbing device, serves as the light-receiving surface, increasing the mid-infrared reflectivity of the light-absorbing device and reducing its radiation loss. Attached Figure Description

[0025] Figure 1(a) Longitudinal cross-sectional view of the device structure in this invention;

[0026] Figure 1(b) Cross-sectional view of the device structure in this invention;

[0027] Figure 2 Example 1: Optical photograph of the device before etching;

[0028] Figure 3 Example 1: Optical photograph of the device after etching;

[0029] Figure 4 Example 1: SEM top view of the device before etching;

[0030] Figure 5 Example 1: SEM top view of the device after etching;

[0031] Figure 6 , Figure 7 The images shown are SEM cross-sectional views of the device before and after etching in Example 1.

[0032] Figures 8-11 The absorption spectra of samples with etching times of 2 min, 4 min, 6 min and 8 min when light is incident from different sides are shown.

[0033] Figure 12 Water evaporation rate graphs of the samples obtained in Example 1 and Comparative Example 1;

[0034] Figure 13 AAO spectral testing without gold plating;

[0035] Figure 14 Example 1: Comparison of the conversion efficiency of the light absorption device with other samples. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0037] The method for fabricating a light-absorbing device in this invention includes obtaining a porous template, depositing a metal material, and removing the metal film. The porous template has a plurality of through holes, which are cylindrical holes with a cross-section that can be circular, square, or irregular. The through holes are preferably periodically distributed, and evenly distributed. The template is a sheet, including a first side and a second side. The axial direction of the through holes is consistent with the thickness direction of the template. The through holes penetrate the first side and the second side. Preferably, the axial directions of the through holes are parallel. This arrangement facilitates control of the deposition amount, and a uniform and stable plasmon structure is formed in each region.

[0038] Furthermore, the porous template in this invention can be any template with nanopores, preferably an AAO template. This template has a regular pore size distribution, good compatibility with metal particles, and facilitates the deposition of metal particles. The method for obtaining it adopts a two-step anodic oxidation method, including: (1) placing the aluminum foil in 0.3M phosphoric acid at 5°C for anodic oxidation, starting from 50V, increasing by 10V every 2 minutes until reaching 150V, and then maintaining it for 24 hours to complete the first oxidation. (2) dissolving the alumina film formed in the first oxidation, and performing the second oxidation under the same conditions as the first oxidation. (3) after the second oxidation, placing the aluminum foil with the porous alumina film into a mixture containing 1M CuCl2 and 0.1M HCl to dissolve and remove the aluminum substrate. (4) finally transferring the porous alumina film into 5wt% H3PO4 and expanding the pores at 30°C for about 1 hour to obtain a porous alumina template with a pore size of 250-400nm. Absorption spectroscopy tests were conducted on porous alumina templates (AAO) with different pore sizes and thicknesses to verify the influence of pore size and thickness on the light absorption capacity of the AAO templates. The light absorption capacity was mainly examined in the visible light and near-infrared bands (0.2-4 μm). Figure 13As shown, the pore size is 200 nm, and the thicknesses are 20 μm, 35 μm, and 60 μm, respectively. With increasing thickness, the spectral absorption increases. When the thickness is 35 μm and the pore size is 200 nm and 300 nm, respectively, the porous alumina template with a pore size of 300 nm exhibits better absorption performance than the porous alumina template with a pore size of 200 nm. In this invention, a pore size of 250–350 nm is preferred, and an average pore size of 300 nm is even more preferred, with a through-hole spacing of 300 nm. Under this setting, the light absorption rate of the AAO template in the near-infrared (2–4 μm) range can exceed 50%, which is beneficial for improving the photothermal conversion efficiency of the light absorption device. With a pore size setting of 250–350 nm, the deposition range of metal particles within the pores is large, which is conducive to forming particle sizes of 20–100 nm. The optical absorption device generates local plasmon resonance with a spacing of 0-30 nm, resulting in different resonance absorption peaks and thus achieving high absorption over a wide spectral range with an absorption rate of over 80%.

[0039] In this invention, the template thickness is preferably 40-60 μm. The template with this thickness not only provides sufficient channel length for deposited metal particles, but also ensures the toughness and strength of the template. Furthermore, when the device is used as a water evaporation treatment material, it can ensure that the water is heated after it leaves the water body.

[0040] Deposited metallic materials: In this invention, the preferred method for depositing metallic particles is electron beam evaporation deposition. This deposition method allows the metallic material to be deposited on a porous template at the atomic scale, facilitating control of the deposition size to form a stable plasmonic structure. The deposited metallic material exhibits a plasmonic effect, preferably gold, silver, or aluminum, with gold being the most preferred material due to its excellent localized plasmonic effect.

[0041] In electron beam evaporation deposition, an electron beam of a certain energy is focused and bombards a gold target. The high-energy electron beam generates a large amount of heat, causing gold atoms to evaporate. The evaporated gold atoms disperse throughout the chamber and gradually deposit on the surface of the AAO template and inside the channels. A gold film of a certain thickness is formed on the template surface (first side). Inside the channels, gold atoms collide and aggregate, eventually adhering to the sidewalls of the channels to form gold nanoparticles. Since gold atoms are deposited from the end closer to the first side to the end closer to the second side within the channels, the particles formed near the opening of the first side are larger, and the particles gradually become smaller towards the bottom of the channel. The deposition conditions are: vacuum degree (0.5~1)×10 -3 Pa; electron gun voltage 5–7 keV; current 200–400 uA; under these settings, the deposition rate is The deposition rate affects the size and distribution of metal particles. At this rate, the resulting metal particles are of suitable size and uniformly distributed, achieving an absorption rate of over 80% across a broad spectrum. Below this rate, the metal particles are small and concentrated in the smaller particles, with light absorption primarily concentrated in the lower wavelength range (400-500 nm). Above this rate, the metal particles are too large and concentrated in the larger particles, failing to achieve good absorption of lower wavelengths. Under this setting, the uniform size distribution of the metal particles is beneficial for forming a broadband absorber. Deposition is stopped when the metal film thickness on the first side reaches 60-80 nm. The metal particles within the vias are distributed along the inner wall of the channels at a depth of 0-2 μm from the surface, with particle sizes of 10-70 nm and interparticle spacing of 0-10 nm. This distribution ensures that the intensity of visible and near-infrared light, the main energy distribution regions of sunlight, is localized around the metal particles, resulting in strong absorption. Sunlight is localized within the light-absorbing device by the gold particles within the channels, achieving light absorption and thus photothermal conversion.

[0042] Metal film removal: Any method for removing the metal film on the first side can be used, but the metal particle structure inside the through hole should not be damaged. Ion beam etching is preferred. Ion beam etching uses the principle of glow discharge to ionize argon gas to form argon ions, which are then accelerated by an electric field to bombard the sample surface. Under the action of bombardment, the atoms on the surface will be blasted away from the surface. The etching time is 5 to 8 minutes.

[0043] The light-absorbing device prepared by the above method is shown in Figure 1. Metal particles 4, specifically gold particles, are deposited at the end of the through hole near the first side 1 of the porous template 5. No metal particles are deposited on the inner wall of the through hole 3 near the second side 2.

[0044] The light-absorbing device of this invention can be used to obtain freshwater resources through seawater evaporation. Specifically, the device floats on the water surface with the first side facing upwards and the second side facing downwards. The end with deposited metal particles is on the water surface, while the end without deposited metal particles is in contact with the water. Water is transported upwards to the metal particle end through the nanocapillaries of the AAO template for evaporation. This arrangement prevents the light-absorbing area (the area with deposited metal particles) from directly contacting the water source, thus blocking heat conduction from the light-absorbing device to the water and avoiding heat loss. Furthermore, the metal surface being on the light-receiving surface increases the mid-infrared reflectivity to a certain extent and reduces radiation loss. Additionally, water vapor escapes directly from the evaporation area (the area with deposited metal particles) at the pore opening, resulting in high mass transport efficiency.

[0045] Example 1

[0046] A method for fabricating a light-absorbing device includes the following steps:

[0047] Step 1: Selecting the substrate material. In this embodiment, porous alumina template (AAO) is used as the nanoparticle channel (hereinafter referred to as NPT). AAO is prepared by a two-step anodizing method. The preparation method includes: (1) placing aluminum foil in 0.3M phosphoric acid at 5°C for anodizing. The oxidation voltage starts from 50V and increases by 10V every 2 minutes until it reaches 150V. Then it is maintained for 24 hours to complete the first oxidation. (2) Dissolve the alumina film formed in the first oxidation and perform the second oxidation under the same conditions as the first oxidation. (3) After the second oxidation, place the aluminum foil with the porous alumina film into a mixture containing 1M CuCl2 and 0.1M HCl to dissolve the aluminum substrate. (4) Transfer the porous alumina film into 5wt% H3PO4 and expand the pores at 30°C for about 1 hour to obtain the NPT of Example 1. The thickness of the NPT is measured to be about 50 micrometers and its pore size is 250-400nm.

[0048] Step 2: Deposit metal particles by evaporation. Gold (Au) is deposited onto the surface of the NPT and into the pores of the surface using electron beam evaporation. Specifically, electron beam evaporation deposition is performed using a Gatan, model 682 PVD physical vapor deposition system, and the deposition conditions are: vacuum degree 1×10⁻⁶. -3 Pa, deposition rate is The deposition thickness was 70 nm. The resulting product was the light-absorbing device of Example 1, hereinafter referred to as Au / NPT.

[0049] Au / NPT comprises NPT and gold particles attached to the inner walls of the NPT vias. The gold particles are distributed at a depth of 0–2 μm from the ordered surface of the NPT inwards. Au / NPT may also include a gold layer covering the ordered surface of the NPT, which may only cover the areas on the surface without vias. The thickness of the gold layer is 70 nm. After depositing gold onto the surface of the NPT, the Au / NPT surface is obtained.

[0050] Step 3: Remove the gold layer of Au / NPT obtained by ion beam etching for 6 minutes to obtain the etched light absorption device.

[0051] Visible light images of the device before and after etching, such as Figure 2 and Figure 3 As shown, the light absorption device before etching is as follows: Figure 2 As shown, the surface has a gold film. After etching the gold layer, as... Figure 3 As shown, after the gold film is removed, the light-absorbing device appears black. The scanning electron microscope image is as follows. Figure 4 and Figure 5 As shown, Figure 4This is a scanning electron microscope (SEM) image of Au / NPT before etching. As shown in the image, the Au / NPT surface contains multiple pores of varying sizes, ranging from 250 to 400 nm. The average pore size is approximately 300 nm. The pore sizes and shapes are relatively similar. The SEM images before and after gold etching are shown below. Figure 6 and Figure 7 As shown, the morphology and distribution of metal particles in the through hole did not change significantly before and after etching, and etching does not affect the distribution of metal particles in the through hole.

[0052] Examples 2-4

[0053] The difference from Example 1 is that the etching times in step 3 are 2 min, 4 min, and 8 min, respectively.

[0054] Comparative Example 1

[0055] The only difference from Example 1 is that step 3 was not performed, i.e., the gold layer was not etched.

[0056] Obtain spectral measurement data of the optical absorption devices in Examples 1-4, such as Figures 8-11As shown, the absorbance of light-absorbing devices with different etching times in Examples 1-4 was measured in the spectral range of 250 nm to 16 μm. In the figure, 2 min-AAO and 2 min-Au represent devices obtained with an etching time of 2 min. 2 min-AAO represents the spectral data of light incident from the second side (unetched side), and 2 min-Au represents the spectral data of light incident from the first side (the side where the metal layer was etched away). 4 min-AAO and 4 min-Au represent devices obtained with an etching time of 4 min. 4 min-AAO represents the spectral data of light incident from the second side (unetched side), and 4 min-Au represents the spectral data of light incident from the first side (the side where the metal layer was etched away). 6 min-AAO and 6 min... -Au is the device obtained by etching for 6 min, 6min-AAO is the spectral data of light incident from the second side (unetched side), 6min-Au is the spectral data of light incident from the first side (the side where the metal layer is removed by etching), 8min-AAO and 8min-Au are the devices obtained by etching for 8 min, 8min-AAO is the spectral data of light incident from the second side (unetched side), and 8min-Au is the spectral data of light incident from the first side (the side where the metal layer is removed by etching). As can be seen from the curves in the figure: (1) In the visible light part, the absorption rate of each group of devices measured from the first side is higher than that measured from the second side, indicating that light incident from the first side is beneficial to improve the spectral absorption rate of the device. (2) As the etching time increases, the spectral measurement data of the etched surface show that the absorbance in the visible light region does not change much, but there is a huge decrease in the 4-8 μm band, which means that its radiation loss will also decrease. The spectral curves of the samples with 6 min etching time and the samples with 8 min etching time have little change, which can be interpreted as the etching being completed. The gold on the surface is completely etched away, leaving only the gold particles in the channel, which retains its high absorbance in the visible light range and reduces its emissivity in the mid-infrared range (i.e., its thermal radiation loss).

[0057] Solar water vapor generation experiments were conducted on the light-absorbing device (i-Au / NPT) of Example 1 and the light-absorbing device (Au / NPT) of Comparative Example 1.

[0058] The steam generating device includes:

[0059] (1) Light source: Sunlight simulator (Newport94043A, ClassAAA), dual-lens focusing system (Beijing Beiguang Century Instrument Co., Ltd.; convex lens #1 with a focal length of 200mm and a diameter of 100mm; convex lens #2 with a focal length of 50mm and a diameter of 30mm);

[0060] (2) Container: Dewar flask (Shanghai Glass Factory), 28mm inner diameter, 38mm outer diameter, 96mm height;

[0061] (3) Measuring devices: power meter (Coherent#1097901, 10W, 19mm diameter probe), analytical balance (FA2004, 0.1mg accuracy), thermocouple (the thermocouple probe is coated with a layer of highly reflective titanium oxide by atomic layer deposition, which suppresses the heat generated by direct light shining on the probe), serial communication component (RS232), computer.

[0062] Experimental environment parameters include:

[0063] i-Au / NPT and pure water control group: ambient temperature 24℃, humidity 42%;

[0064] Au / NPT and pure water control group: ambient temperature 24℃, humidity 48%.

[0065] The experimental steps include:

[0066] (1) Set up 4 Dewar bottles filled with water. In the first Dewar bottle, place the light-absorbing device (Au / NPT) of Comparative Example 1 parallel to the water surface, with the side with the gold layer deposited facing down and close to the water surface. Part of the light-absorbing device is submerged in the water.

[0067] The light-absorbing device of Comparative Example 1 was placed in the second Dewar flask with the side with the gold layer deposited facing upwards and away from the water surface, and the side without the gold layer deposited facing downwards. Part of the light-absorbing device was immersed in the water, i.e. (Au / NPT-reversed).

[0068] The light-absorbing device (i-Au / NPT) of Example 1 was placed in the third Dewar flask. The device was placed parallel to the water surface, with the side containing deposited metal particles facing upwards and away from the water surface, while the side without deposited metal particles faced downwards. The area where metal particles were deposited was not in direct contact with the water surface. The porous structure with through-holes provides a convenient channel for the dissipation of the continuously generated water vapor flow, while avoiding direct contact between the hydrophobic metal layer and the water, greatly increasing the contact area with the water.

[0069] The fourth Dewar flask is a pure water control group, meaning the Dewar flask contains only water and no light-absorbing device is placed inside.

[0070] (2) The light generated by the solar simulator (Newport94043A) is filtered by a filter to obtain solar radiation that conforms to the AM1.5G spectral standard. The solar radiation is then focused by a dual-lens system and incident on the composite material device in the Dewar flask (for the pure water control group experiment, the light is focused and incident on the water surface).

[0071] (3) Before the experiment, the incident light power density CoptP0 was measured and set in advance using a power meter, with the unit being kW·cm. -2Meanwhile, during the steam generation process, the analytical balance can measure the decrease in water mass, and then calculate the water mass loss rate, which is the water steam generation rate in terms of mass, expressed in kg / cm².

[0072] To obtain a stable steam generation rate, the water vapor generation rate (m) was the average water vapor generation rate measured from 0 to 4000 seconds after the start of illumination. A serial communication system and a computer were used to record data during the experiment.

[0073] Experimental results are as follows Figure 12 As shown in the figure, the three curves represent the water vapor evaporation rates obtained by the samples of Example 1 and Comparative Example 1 under different measurement methods. Au / NPT and Au / NPT-reversed are both unetched samples of Comparative Example 1. Au / NPT has its first side (the side with the deposited gold film) facing downwards and in contact with the water. Au / NPT-reversed has its second side (the side without the deposited gold film) facing downwards and in contact with the water, while the gold film side faces upwards. i-Au / NPT is the etched sample of Example 1, with its first side (the side with the etched gold film removed) facing upwards and its second side facing upwards in contact with the water during the experiment. As can be seen from the three curves in the figure, in Comparative Example 1, the side without gold film is facing downwards, while the side with gold film is facing downwards, indicating that the gold film is in direct contact with the water, which would heat the entire water body and cause heat loss. The evaporation rate of Example 1 is significantly higher than that of the two settings in Comparative Example 1, indicating that the light absorption rate of the device is greatly improved after removing the gold film. In addition, the evaporation efficiency of the device obtained in Example 1 is compared with existing photothermal evaporation devices (black cellulose fabric, reduced graphene oxide-multi-walled carbon nanotubes), Au / alumina (Comparative Example 1), and Al / alumina (Al particles are deposited on a porous alumina template, and the surface aluminum layer is not etched away). Figure 14 As shown, etching to remove the metal layer produces a very significant effect, and the evaporation efficiency of the photothermal device in this invention is significantly higher than that of traditional photothermal devices. The conversion efficiency of this invention, which is greater than 80%, has very good utilization value and prospects.

[0074] The foregoing has shown and described the basic principles and main features of the present invention, as well as the advantages of this patent. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for fabricating a light-absorbing device, characterized in that: Includes the following steps Obtaining a porous template: The porous template is provided with a plurality of through holes, the through holes penetrating the first side and the second side of the porous template; Depositing metal material on the porous template: taking the first side as the deposition side, depositing metal material on the porous template, wherein the metal material is deposited on the first side and the inner wall of the through hole; Metal film removal: Remove the metal material deposited on the first side, while retaining the metal material on the inner wall of the through hole; When the light-absorbing device is placed on the water surface, its second side faces downward and is in contact with the water. The porous template is a sheet material with a thickness of 40~60μm. The contact angle between the porous template and water is less than 90°. The through-holes of the porous template are periodically distributed with a pore size of 250~400nm and a pore spacing of 300~400nm.

2. The method for fabricating the light-absorbing device according to claim 1, characterized in that: The first side and the second side are opposite sides. When depositing metal material, the first side is the coating side. A part of the metal material is deposited on the first side to form a metal film, and another part of the metal enters the through hole and is deposited on the inner wall of the through hole to form metal particles.

3. The method for fabricating the light-absorbing device according to claim 1 or 2, characterized in that: Electron beam evaporation deposition is a method for depositing metallic materials, and it satisfies one or more of the following conditions: —The vacuum degree is (0.5~1)×10 -3 Pa; —The electron gun voltage is 5~7keV; —Current current is 200~400 uA; —The deposition rate is 2~4 Å / s.

4. The method for fabricating the light-absorbing device according to claim 2, characterized in that: The metal particles are distributed within a depth range of 0~2μm from the orifice opening.

5. The method for fabricating the light-absorbing device according to claim 2, characterized in that: Electron beam evaporation stops when the thickness of the metal film on the first side reaches 60~80nm, and the coating process is complete.

6. The method for fabricating the light-absorbing device according to claim 1, characterized in that: The metallic material is selected from one of gold, silver, and aluminum.

7. A light-absorbing device, characterized in that: The device includes a porous template and a metal material. The porous template has several through holes, and the metal material is deposited on the inner wall of the through holes. The metal material is distributed in the form of metal particles on the inner wall of the through holes to form a plasmonic structure. The deposition range of the metal material is limited to the inner wall of the through holes. When the light-absorbing device is placed on the water surface, its second side faces downward and is in contact with the water. The porous template is a sheet material with a thickness of 40~60μm. The contact angle between the porous template and water is less than 90°. The through-holes of the porous template are periodically distributed with a pore size of 250~400nm and a pore spacing of 300~400nm.

8. The light-absorbing device according to claim 7, characterized in that: The metal particles satisfy one or a combination of the following: The particle size of the metal particles is 20-100 nm; The spacing between metal particles is 0-30 nm.

9. The light-absorbing device according to claim 7, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 6.

10. The use of the light-absorbing device according to claim 7, characterized in that: When the light-absorbing device is placed on the water surface, it absorbs light and generates heat, which heats the water and causes it to evaporate.

11. The use of the light-absorbing device according to claim 10, characterized in that: The light-absorbing device is prepared by the method described in claim 1. When the light-absorbing device is placed on the water surface, the second side faces downward and is in contact with the water. Light is incident from the first side, and the water is transported upward along the through hole of the light-absorbing device to the metal particles where it is heated and evaporated.

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