Novel reversible metal electrodeposition device for realizing dynamic regulation and control of visible light-infrared spectrum characteristics
Technical Field
The application relates to the field of visible light and infrared dual-band compatible spectral characteristic regulation and control, in particular to a novel reversible metal electrodeposition device for realizing dynamic regulation and control of visible light-infrared spectral characteristics.
Background
In recent years, camouflage technology for a single band has been developed to a relatively mature stage and plays an important role in the battlefield. However, with the increasing diversity of detection means and the integrated combination of multi-band compatible detection systems, the use of camouflage relying on only a single band has not been satisfactory. Conventional single-band camouflage-effect-oriented target equipment faces a great threat, for example, a single visible or infrared camouflage target has been fully "exposed" to a visible-infrared compatible detector integrated into a small dual-imaging device. Thus, research into camouflage materials or structures compatible with the visible-infrared dual band has been urgent. Visible light-infrared compatible camouflage materials that have been proposed at present are mainly divided into two main categories: an infrared camouflage composite coating and metal/dielectric combination layered photonic crystal structure with the addition of a colored pigment. Wherein the typical structure comprises Al-Fe 3 O 4 Core-shell structured pigments, bi 2 O 3 ATO composite coating, al/polyurethane composite coating and Al/TiO 2 TiN layer structure, znS/Ag/ZnS sandwich structure, etc. However, the above materials or structures still have many problems brought by the design of integrated compatible camouflage, such as single visible light color, high infrared emissivity of an atmospheric window and static regulation, which is difficult to meet the camouflage requirements of weapon equipment in cross-region, multi-season and full period.
In response to these problems, embedding or integrating smart materials or micro-nano structures with tunable optical properties to develop an adaptive visible-infrared compatible camouflage device is a better solution. Based on this approach, researchers have developed a number of devices with multi-spectral dynamic modulation capabilities. Li Sairui et al designed a multilayer film structure with adjustable infrared absorption based on phase change material germanium antimony tellurium (GST) (Li S, liu K, long X, et al Numerical study of infrared broadband multilayer film absorber with tunable structural colors [ J ] Optics Communications,2020, 459:124950.). The structure had an absorption peak with an absorption intensity of about 92.06% in the vicinity of 10.9 μm, and an average absorption rate of 65.71% in the 8-13 μm band. Meanwhile, the structure can realize the change of the maximum absorptivity from 92.06% to 9.17% by utilizing different electromagnetic properties of the phase change material GST in a crystalline state and an amorphous state. In addition, the structure has specific reflection color in the visible light band, and the color can be regulated by changing the thickness of the top ZnS film. Li et al use reversible silver electrodeposition to convert infrared absorption and infrared transmission of ultra-thin nanoscale platinum films to infrared reflection, achieving reversible dynamic modulation of Δε of about 0.7 in the 3-14 μm band (Li M, liu D, cheng H, et al, modeling metals for adaptive thermal cam advance, 6 (22): eaba 3494). On this basis, they add a chromium oxide layer between the ir-high transmissive substrate and the platinum working electrode. As the thickness of the electrodeposited silver film increases, the visible light reflected by the silver film on the underside of the chromia gradually enhances the film interference effect, causing the resulting structural color to change from a relatively darker color to a brighter color. For the above devices, although their objective is to dynamically modulate the visible-infrared spectral characteristics, some limitations are faced, such as single modulation color and low emissivity modulation range. Many of the proposed devices can only have a fixed structural color (or switch between two colors) on the basis of an adjustable infrared emissivity, and cannot have an adjustable structural color in both high and low infrared emissivity states. Thus, it remains challenging to truly achieve compatible dynamic modulation of visible and infrared band spectral characteristics.
Disclosure of Invention
The application aims to provide a novel reversible metal electrodeposition device for realizing dynamic regulation and control of visible light-infrared spectrum characteristics, which is used for realizing compatible dynamic regulation and control of visible light wave band and infrared wave band spectrum characteristics, coping with different types of background environments and improving self-adaptive camouflage capability of a target.
The technical scheme for realizing the aim of the application is as follows: the novel reversible metal electrodeposition device for dynamically regulating and controlling visible light-infrared spectrum characteristics comprises an infrared conductive unit, an electrochromic unit and a visible light conductive unit, wherein the electrochromic unit is clamped between the infrared conductive unit and the visible light conductive unit; the infrared conductive unit comprises a first substrate, a dielectric layer arranged on the lower surface of the first substrate and a first transparent conductive layer formed on the lower surface of the dielectric layer; the electrochromic unit comprises a metal deposition layer with adjustable position and morphology and a gel electrolyte layer; the visible light working unit comprises a second substrate and a second transparent conductive layer which is formed on the upper surface of the second substrate and connected with the gel electrolyte layer.
Further, the metal deposition layer with adjustable position and shape is used as a medium for displaying visible light structural color, and by applying forward constant deposition voltage to the second transparent conductive layer, metal ions in the electrolyte are reduced to metal particles which are deposited on the first transparent conductive layer and are mutually connected to form a metal reflection film, so that the device presents an infrared low-emissivity state and simultaneously displays structural color related to the thickness of the medium layer; then, applying a dissolution voltage, gradually oxidizing the deposited metal particles into metal ions, dissolving the metal film, and recovering the device to an initial infrared high-emissivity state, wherein visible light shows transparent color; when negative step voltage is applied to the second transparent conductive layer, metal ions are reduced into metal particles and deposited on the second transparent conductive layer to form dispersed spherical nano particles; the diameter of the spherical nano particles can be regulated and controlled by controlling the time of voltage application, so that the device presents various changeable structural colors in an infrared high-emissivity state; then, a dissolution voltage is applied, and the deposited metal nanoparticles are gradually oxidized into metal ions and dissolved into the electrolyte, at which time the infrared state of the device remains unchanged, and the visible light effect returns from the vivid structural color to the original transparent color.
Further, the thickness of the dielectric layer is 80 nm-300 nm, and the material is selected from one of the following materials: silicon carbide, titanium dioxide, aluminum oxide, gallium arsenide.
Further, the forward constant deposition voltage V 1 =2.2 to 2.8V, time t 1 =20 to 30s; said negative step voltage V 2 =-4.4V~-2.6V,t 2 =20~80ms;V 3 =-1.6V,t 3 =0~80s。
Further, the infrared low emissivity state is that the infrared average emissivity is less than or equal to 0.25, and the infrared high emissivity state is that the infrared average emissivity is more than or equal to 0.55.
Further, the transmittance of the gel electrolyte layer in the visible light wave band is more than or equal to 0.8, the absorptivity of the gel electrolyte layer in the infrared wave band is more than or equal to 0.7, the gel electrolyte layer provides metal cations required by electrodeposition, the thickness is more than or equal to 250 mu m, and the gel electrolyte layer contains silver nitrate, wherein silver ions are used as electrodeposited/dissolved metal ions.
Further, the first transparent conductive layer is used as a counter electrode, the transmittance of the first transparent conductive layer is more than or equal to 0.7 in the visible light and infrared wave bands, and the material is selected from the following materials: platinum, gold, and combinations thereof, the first transparent conductive layer has a thickness of 1 to 5nm.
Further, the second transparent conductive layer is used as a working electrode, the transmittance of the second transparent conductive layer in the visible light wave band is more than or equal to 0.7, the selected material is indium tin oxide, and the thickness of the second transparent conductive layer is 0.2-2 mm.
Further, the transmittance of the first substrate in the visible light and infrared wave bands is more than or equal to 0.8, and the materials are respectively selected from the following groups of materials: barium fluoride, calcium fluoride, lithium fluoride, and combinations thereof, with a thickness of 0.2-1.2 mm.
Further, the transmittance of the second substrate in the visible light wave band is more than or equal to 0.8, and the materials are respectively selected from the following groups of materials: glass, barium fluoride, calcium fluoride, lithium fluoride, and combinations thereof, with a thickness of 0.2-2 mm.
Compared with the prior art, the gain effect of the application is as follows: (1) The application controls the position and the shape of the metal deposition layer by applying two different voltages to the second transparent conductive layer, successfully realizes the change of infrared emissivity in a large range, and can display various dynamic vivid structural colors no matter the device is in an infrared high-emissivity state or a low-emissivity state, thus the device really realizes the compatible dynamic regulation and control of the spectral characteristics of visible light and infrared bands; (2) According to the application, a dielectric layer is introduced into an infrared working unit, when a forward constant voltage is applied, silver is deposited on a first transparent conducting layer to form a metal high-reflection film, so that the device presents a low-emission state in an infrared band, and meanwhile, the deposited silver film and an upper dielectric layer excite an FP resonance effect to cause the device to present a specific structural color related to the thickness of the dielectric layer in a visible light band; (3) According to the application, silver particles are deposited on the second transparent conductive layer by applying negative step voltage to form dispersed spherical nano particles, and a local plasmon polariton (LSPR) effect is excited to display structural colors, and the diameter of the spherical nano particles can be regulated by controlling the time of voltage application so as to regulate and control the LSPR characteristics of the spherical nano particles, so that the device can display various variable structural colors in an infrared high-emissivity state. (4) The medium layer selected by the application is very suitable in material selection, and under the action of forward constant voltage, even in a smaller medium layer thickness variation range, the device can also present rich colors crossing the whole visible light spectrum; (5) By controlling the type and the direction of the applied voltage, the application realizes perfect combination of reversible metal electrodeposition and micro-nano structure electromagnetic effect; (6) The application adopts the ultrathin noble metal film as the first transparent conductive layer, has higher transmittance for incident light of visible light and infrared wave bands, and provides basic conditions for realizing large-range tunability of infrared emissivity.
Drawings
The above and other objects, features and advantages of the present application will become more apparent by describing embodiments of the present application in more detail with reference to the attached drawings. The accompanying drawings are included to provide a further understanding of embodiments of the application and are incorporated in and constitute a part of this specification, illustrate the application and together with the embodiments of the application, and not constitute a limitation to the application.
FIG. 1 is a schematic diagram of a device under two different deposition voltages in an embodiment of the application
FIG. 2 is a graph showing the correspondence between silicon carbide thickness variation and calculated structural color for silver deposited on a platinum counter electrode in an embodiment of the present application
FIG. 3 is a graph showing the real-time IR spectrum characteristics of a novel reversible metal electrodeposition device when a forward constant voltage is applied in an embodiment of the present application
FIG. 4 is a real-time visible color change of a novel reversible metal electrodeposition device upon application of a forward constant voltage in an embodiment of the present application
FIG. 5 is a real-time IR spectrum of a novel reversible metal electrodeposition device upon application of a negative step voltage in an embodiment of the application
FIG. 6 is a comparison of the real-time IR absorption spectra of a novel reversible metal electrodeposition device in an initial state with the application of a negative step voltage in an embodiment of the present application
FIG. 7 is a real-time visible color change of a novel reversible metal electrodeposition device upon application of a negative step voltage in an embodiment of the present application
FIG. 8 is a graph showing the tunable range of infrared emittance of a novel reversible metal electrodeposition device when two different types of voltages are applied in an embodiment of the present application
Detailed Description
The application is further illustrated by the following specific examples, which are, however, to be understood only for the purpose of more detailed description and are not to be construed as limiting the application in any way.
The application relates to a novel reversible metal electrodeposition device with dynamic regulation and control of visible light-infrared spectrum characteristics, which comprises an infrared conductive unit, an electrochromic unit and a visible light conductive unit, wherein the electrochromic unit is clamped between the infrared conductive unit and the visible light conductive unit.
The infrared conductive unit comprises a first substrate, a dielectric layer arranged on the lower surface of the first substrate and a first transparent conductive layer formed on the lower surface of the dielectric layer; the electrochromic unit comprises a metal deposition layer with adjustable position and morphology and a gel electrolyte layer; the visible light working unit comprises a second substrate and a second transparent conductive layer which is formed on the upper surface of the second substrate and connected with the gel electrolyte layer.
The first substrate is mainly used for transmitting incident light of a visible light-infrared band and serving as a support of the first transparent conductive layer, has ultrahigh transmittance in the visible light and infrared bands, and is made of the following materials: barium fluoride, calcium fluoride, lithium fluoride, and combinations thereof, with a thickness of 0.2-1.2 mm.
The dielectric layer is mainly used for forming an FP cavity with a deposited silver film to display structural color, the thickness of the dielectric layer is 80 nm-300 nm, and the material is selected from one of the following materials: silicon carbide, titanium dioxide, aluminum oxide, gallium arsenide.
The first transparent conductive layer has a thickness of 1-5 nm, is mainly used for conducting and transmitting incident light in a visible light-infrared band, has high transmittance in both the visible light and infrared bands, and is made of the following materials: platinum, gold, and combinations thereof.
The position and shape adjustable metal deposition layer is used as a medium for displaying visible light structural color, and by applying a forward constant deposition voltage to the second transparent conductive layer, metal ions in the electrolyte are reduced to metal particles which are deposited on the first transparent conductive layer and are mutually connected to form a metal reflection film, so that the device presents an infrared high reflection (low emissivity) state and simultaneously displays specific structural color related to the thickness of the medium layer. Subsequently, a dissolution voltage is applied, the deposited metal particles are gradually oxidized to metal ions, the metal film dissolves, and the device returns to the original infrared high emissivity state while visible light shows a transparent color. When a negative step voltage is applied to the second transparent conductive layer, the metal ions are reduced to metal particles and deposited on the second transparent conductive layer to form dispersed spherical nanoparticles. The diameter of the spherical nano particles can be regulated and controlled by controlling the time of voltage application, so that the device can present various changeable structural colors in an infrared high-emissivity state. Then, a dissolution voltage is applied, and the deposited metal nanoparticles are gradually oxidized into metal ions and dissolved into the electrolyte, at which time the infrared state of the device remains unchanged, and the visible light effect returns from the vivid structural color to the original transparent color.
The positive constant deposition voltage is mainly used for depositing silver films, and the voltage is V 1 =2.2 to 2.8V, the application time is t 1 =20~30s。
The negative step voltage is mainly used for depositing dispersed spherical silver nano particles, and the voltage and the application time are as follows: v (V) 2 =-4.4V~-2.6V,t 2 =20~80ms;V 3 =-1.6V,t 3 =0~80s。
The gel electrolyte layer is mainly used for providing electrodeposited silver ions, transmitting incident light in a visible light band and absorbing incident light in an infrared band. The gel electrolyte layer has high transmittance in the visible light band and high absorption property in the infrared band. When the device is in an initial state or a negative step voltage is applied, incident light in an infrared band transmitted through the first substrate, the dielectric layer and the first transparent conductive layer is absorbed by the gel electrolyte layer, and the whole device presents an infrared high-emissivity state. Silver nitrate is contained in the gel electrolyte, with silver ions as electrodeposited/dissolved metal cations.
The second transparent conductive layer is mainly used for conducting and transmitting incident light in a visible light wave band, has high transmittance in the visible light wave band, and is made of indium tin oxide with the thickness of 0.2-2 mm.
The second substrate is mainly used for transmitting incident light in a visible light band and serving as a support of the second transparent conductive layer, has ultrahigh transmittance in the visible light band, and is respectively selected from the following materials: glass, barium fluoride, calcium fluoride, lithium fluoride, and combinations thereof, with a thickness of 0.2-2 mm.
The application will now be described in detail with reference to the drawings and examples.
Examples
The material of the first substrate is barium fluoride, and the thickness is 1mm; the dielectric layer is made of silicon carbide and has the thickness of 180nm; the first transparent conductive layer is made of platinum and has a thickness of 5nm; gel electrolyte layer by adding 0.5mM silver nitrate, 2.5mM tetrabutylammonium bromide, 0.1mM copper chloride and 10wt% polyvinyl butyral to 10ml dimethyl sulfoxidePreparing a bulk polymer, wherein the thickness of the bulk polymer is 450 mu m; the second transparent conductive layer is made of indium tin oxide and has a thickness of 0.3mm; the material of the second substrate is glass, and the thickness is 1mm; the magnitude of the forward constant deposition voltage is V 1 =2.5v, time of application t 1 =20s; the magnitude of the negative step voltage and the application time are: v (V) 2 =-4V,t 2 =20ms;V 3 =-1.6V,t 3 =0 to 20s. Referring to fig. 1, when the device is in an initial state (no silver deposition), it exhibits a transparent color in the visible light band. Meanwhile, since incident light in the infrared band is absorbed by the gel electrolyte layer, the device exhibits an infrared high emissivity state.
First, the correspondence relationship between the visible light reflection characteristics of the device and the silicon carbide thickness and the presentation of structural colors when silver particles are deposited on a platinum electrode to form a metal reflection film was calculated using the finite difference time domain method (FDTD), see fig. 2. When the silicon carbide thickness is varied from 100nm to 180nm, i.e., over a thickness variation range of 80nm, the device can achieve full-color domain variation across the entire visible spectrum (from violet to red). Subsequently, device fabrication was performed and real-time visible-infrared spectral characteristics of the device under the application of a forward constant voltage were measured using an infrared spectrometer, see fig. 3 and 4. In the infrared band, silver particles have been fully electrodeposited on the platinum counter electrode and interconnected to form a metal reflective film, resulting in the infrared reflective properties of the device being maintained at a very high level, particularly in the 3-10 μm band. The average reflectivity of the device in the wave band of 3-14 μm is calculated to be as high as 0.879 (average emissivity is 0.121); in the visible light band, when the thickness of the SiC layer is 180nm, the simulation result shows that the device should be purple (figure 2), and the actual test result shows that the device is truly purple, so that the consistency of the simulation result and the experimental result is proved.
The real-time visible-infrared spectral characteristics of the device when silver particles are deposited down on the indium tin oxide working electrode to form spherical nanoparticles, i.e., when a negative step voltage is applied to the device, see fig. 5 and 7. The device has high and stable infrared absorption capacity (average emissivity is 0.702) in the whole infrared band, and average reflection of about 0.3The emissivity is due to the barium fluoride substrate on the upper side of the device being coated with a silicon carbide dielectric layer and a platinum layer, resulting in a small portion of the infrared light being reflected by the two films without entering the gel electrolyte layer. In addition, a step voltage V is applied 2 =-4V,t 2 =20ms,V 3 =-1.6V,t 3 After =20s, the infrared absorption characteristics of the device were substantially unchanged from those in the initial state, and the device remained unchanged in the infrared high-emissivity state all the time, see fig. 6. Meanwhile, in the visible light wave band, the device can apply a growth voltage V 3 Exhibits a reversible transition from clear to red to blue to deep blue within 20s.
To sum up, for the device, when a negative step voltage is applied, the device can achieve a high emissivity state in the infrared band, and according to the growth voltage V 3 The application time is long, and various dynamic structural colors based on the LSPR effect of the noble metal nano particles are presented simultaneously; while when a forward constant deposition voltage is applied, the device can achieve a low emissivity state in the infrared band and can simultaneously exhibit a specific vivid structural color based on the resonance effect of the silicon carbide dielectric layer FP (this color can be preselected based on the calculation of fig. 2). Through calculation, delta epsilon is obtained 3-14μm ≥0.583,Δε 3-5μm ≥0.643,Δε 8-14μm More than or equal to 0.562, as shown in figure 8, the proposed device not only has larger infrared emissivity tunability, but also can present vivid structural color no matter the device is in an infrared high-emissivity or low-emissivity state, and the dynamic regulation and control of the compatible spectral characteristics of visible light and infrared dual-band are successfully realized.