阅读说明：本技术 电致变色复合薄膜及其制备方法 (Electrochromic composite film and preparation method thereof ) 是由 刘晨 晋丁亥 张霞 李琴琴 蔡秀霞 于 2021-07-02 设计创作，主要内容包括：本发明涉及一种电致变色材料,尤其涉及一种电致变色复合薄膜及其制备方法。解决现有WO-3无机电致变色材料着色效率低、变色速度慢的问题,通过溶剂热法制备具有弱还原性的多孔WO-(3-x)薄膜,并利用其还原性原位生长金纳米颗粒,金纳米颗粒能够有效的将近红外光能转化成热能,使复合薄膜具有较高的光-热转换效率,并拓展材料的光响应范围至可见光区。进一步引入在近红外光区具有光吸收的金纳米棒,使复合薄膜的光-热转换效率进一步提高,并使复合材料的光响应能够覆盖近红外光谱,实现电压调控复合材料在宽光谱范围内的变色。(The invention relates to an electrochromic material, in particular to an electrochromic composite film and a preparation method thereof. Solves the existing WO 3 The inorganic electrochromic material has the problems of low coloring efficiency and low color changing speed, and porous WO with weak reducibility is prepared by a solvothermal method 3‑x The film grows the gold nanoparticles in situ by utilizing the reducibility of the film, and the gold nanoparticles can effectively convert near-infrared light energy into heat energy, so that the composite film has higher light-heat conversion efficiency, and the photoresponse range of the material is expanded to a visible light region. The gold nanorods with light absorption in the near infrared region are further introduced, so that the light-heat conversion efficiency of the composite film is further improved, and the light response of the composite material can be coatedAnd covering the near infrared spectrum to realize the color change of the voltage regulation composite material in a wide spectrum range.)

1. The preparation method of the electrochromic composite film is characterized by comprising the following steps of:

step 1, growing WO₃A two-dimensional nano-film;

step 1.1, sequentially ultrasonically cleaning FTO glass in a cleaning solution, and then drying for later use;

step 1.2, mixing Na₂WO₄·2H₂Dispersing O in deionized water, and after the O is completely dissolved, dropwise adding HCl solution until flocculent precipitate is generated;

step 1.3, spin-coating the suspension solution obtained in the step 1.2 on the surface of the FTO glass treated in the step 1.1, then transferring the FTO glass to a tube furnace, oxidizing at high temperature, cooling and taking out;

step 1.4, spin-coating the suspension solution obtained in the step 1.2 on the surface of the FTO glass treated in the previous step, then transferring the FTO glass into a tube furnace, oxidizing at high temperature, cooling and taking out;

step 1.5, repeating the operation of step 1.4 for a plurality of times to form uniform WO₃A seed-covered substrate;

step 1.6, WCl₆Dissolving in absolute ethanol, and immersing the substrate obtained in step 1.5 in WCl₆Reacting in the solution at high temperature; under high pressure and temperature, WCl₆Alcoholysis and formation of WO_3-x(ii) a Wherein x is 0 or 1, and represents W element with different valence states;

step 2, preparing gold nanoparticle composite WO₃Film AuP/WO₃；

Step 2.1, washing the surface of the FTO glass obtained in the step 1.6 with secondary water, drying, immediately immersing into a chloroauric acid-ethanol solution, and standing for a set time; taking out, washing with ethanol and secondary water respectively, and removing unreacted chloroauric acid on the surface;

step 2.2, placing the sample in an oven to be dried to prepare AuP/WO₃A film.

2. The method for preparing an electrochromic composite film according to claim 1, further comprising the following steps after step 2:

step 3, preparing gold nanoparticle/rod composite WO₃Film AuPR/WO₃；

Step 3.1, AuP/WO prepared₃Immersing the film in ethanedithiol solution, taking out the film after setting time, and washing the film for multiple times by using ethanol;

step 3.2 preparation of AuP/WO binding thiol₃Immersing the film in the gold nanorod solution, standing for a set time, taking out, washing with ethanol for multiple times, and drying.

3. The method for preparing the electrochromic composite film according to claim 2, wherein the gold nanorod solution in step 3.2 is prepared by the following steps:

s1, preparing a seed crystal solution;

preparation of HAuCl₄And aqueous CTAB; adding fresh NaBH into the solution quickly₄The solution is stirred vigorously and then kept away from light;

s2, preparing a growth solution;

weighing CTAB and sodium oleate into deionized water, adding AgNO after complete dissolution₃Stirring the solution, and adding HAuCl₄Continuing stirring the solution;

s3, directionally growing Au nanorods;

adjusting the pH value of the growth solution to 2.0, and adding an ascorbic acid solution and a seed crystal solution into the growth solution; allowing the solution to stand at a constant temperature, and removing excess reducing agent by centrifugal washing; dispersing the collected gold nanorods by using deionized water, and adjusting the concentration of the nanorods through ultraviolet absorption so as to control the SPR absorption peak intensity of the obtained gold nanorod solution to be 0.8-1.2; and finally storing the gold nanorod solution at a low temperature for later use.

4. The method for preparing an electrochromic composite film according to claim 3, characterized in that: in step S1, HAuCl₄The concentration of the aqueous solution was 0.25mmol L^-1(ii) a Concentration of CTAB aqueous solution is 0.1mol L^-1；NaBH₄The concentration of the aqueous solution was 0.1mol L^-1；HAuCl₄Aqueous solution, aqueous CTAB solution and NaBH₄The feeding ratio of the aqueous solution is 10 parts by volume: 10 parts by volume: 0.6 volume part;

in step S2, AgNO₃The concentration of the solution was 4mmol L^-1；HAuCl₄The concentration of the solution was 1.0mmol L^-1(ii) a CTAB, sodium oleate, deionized water, AgNO₃Solution, HAuCl₄The feeding ratio of the solution is 1.8 parts by mass: 0.308 parts by mass: 50 parts by volume: 4.8 parts by volume: 50 parts by volume, wherein the unit of mass part/volume part is g/ml;

in step S3, use 0.1mol L^-1HCl adjusts the pH of the growth solution to 2.0;

the concentration of the ascorbic acid solution is 0.064mol L^-1；

The feeding ratio of the ascorbic acid solution to the seed crystal solution is 0.312 volume part: 0.16 volume portion.

5. The method for producing an electrochromic composite film according to any one of claims 1 to 4, characterized in that:

in step 2.1, the concentration of the chloroauric acid-ethanol solution is 0.2mmol L^-1。

6. The method for preparing an electrochromic composite film according to claim 5, characterized in that: in step 2.2, the mixture is dried at 60 ℃ to prepare AuP/WO₃A film.

7. The method for preparing an electrochromic composite film according to claim 6, characterized in that: in step 3.1, the concentration of the ethanedithiol solution is 2mmol L^-1(ii) a The volume was 10 parts by volume.

8. The method for preparing an electrochromic composite film according to claim 7, characterized in that: step 3.2, AuP/WO with bound thiol₃Immersing the film in the gold nanorod solution, standing for 6 hours, taking out, washing with ethanol for multiple times, and N₂And (5) drying.

9. The method for preparing an electrochromic composite film according to claim 8, characterized in that: cleaning solution in the step 1.1 is acetone, ethanol and deionized water, the FTO glass is sequentially ultrasonically cleaned in the acetone, the ethanol and the deionized water for 15 minutes, and then N is carried out₂Drying for later use;

step 1.2 Na₂WO₄·2H₂The feeding ratio of O to deionized water is as follows: 0.5 parts by mass: 20 parts by volume; wherein the unit of mass part/volume part is g/ml; the concentration of the HCl solution was 1.0mol L^-1；

In step 1.3, 1 part by volume of the suspension solution obtained in step 1.2 is spin-coated on the surface of the FTO glass treated in step 1.1, then the FTO glass is transferred into a tube furnace, oxidized for 10min at 350 ℃, cooled and taken out;

in step 1.6, 0.4 part by mass of WCl₆Dissolved in 20 parts by volume of absolute ethanol and covered with WO₃Soaking FTO glass of seeds into the solution, and reacting for 2h at 180 ℃; under high pressure and temperature, WCl₆Alcoholysis and formation of WO_3-x。

10. An electrochromic composite film prepared by the method of any one of claims 1 to 9.

Technical Field

The invention relates to an electrochromic material, in particular to an electrochromic composite film and a preparation method thereof.

Background

Electrochromism refers to a phenomenon in which optical properties (reflectivity, transmittance, absorption, and the like) of a material undergo a stable and reversible color change under the action of an applied electric field, and is visually represented as a reversible change in color and transparency. The material with electrochromic property is called electrochromic material, and the electrochromic material is a novel functional material and has wide application in the aspects of information, electronics, energy, buildings, national defense and the like. Among the numerous electrochromic materials, WO₃The material is a commonly used inorganic electrochromic material, a large number of oxygen vacancy defects exist in the structure of the material, the defect structure is favorable for the immigration and the immigration of cations, and the optical property of the material can generate relatively durable and reversible color change between the natural color and the blue color after a certain voltage is applied to the material.

Although WO₃Simple preparation, small band gap energy, capability of absorbing visible light with the wavelength less than 500nm and potential photocatalytic capability. But pure WO₃The electrochromic material has certain defects, such as easy light corrosion, low utilization rate of visible light, difficult obtainment of stable photocatalytic performance, low coloring efficiency, slow color changing speed and the like.

The electrochromic material and the multispectral absorbing material based on the composite nanotechnology have working bands covering near ultraviolet, visible light and near infrared, have quick response capability, and have important application requirements in various aspects such as stealth and anti-stealth, automobile coatings, heat-insulating coatings, self-cleaning coatings, seawater desalination and the like.

Disclosure of Invention

To solve the existing WO₃The invention provides a WO, which solves the problems of low coloring efficiency and low color-changing speed of inorganic electrochromic materials₃An inorganic electrochromic composite film and a preparation method thereof, and porous WO with weak reducibility prepared by a solvothermal method_3-xThe film and the gold nanoparticles grow in situ by utilizing the reducibility of the film, and the gold nanoparticles can effectively convert near-infrared light energy intoThe composite film has high light-heat conversion efficiency due to heat energy, and the light response range of the material is expanded to a visible light region. And a gold nanorod with light absorption in a near-infrared region is further introduced, so that the light-heat conversion efficiency of the composite film is further improved, the light response of the composite material can cover the near-infrared spectrum, and the color change of the voltage regulation composite material in a wide spectrum range is realized.

The technical scheme of the invention is to provide a preparation method of an electrochromic composite film, which is characterized by comprising the following steps:

step 1, growing WO₃A two-dimensional nano-film;

step 1.1, FTO glass (SnO doped with fluorine)₂Conductive glass) is sequentially ultrasonically cleaned in a cleaning solution and then dried for standby;

step 1.2, mixing Na₂WO₄·2H₂Dispersing O in deionized water, and after the O is completely dissolved, dropwise adding HCl solution until flocculent precipitate is generated;

step 1.3, spin-coating the suspension solution obtained in the step 1.2 on the surface of the FTO glass treated in the step 1.1, then transferring the FTO glass to a tube furnace, oxidizing at high temperature, cooling and taking out;

step 1.4, spin-coating the suspension solution obtained in the step 1.2 on the surface of the FTO glass treated in the previous step, then transferring the FTO glass into a tube furnace, oxidizing at high temperature, cooling and taking out;

step 1.5, repeating the operation of step 1.4 for a plurality of times to form uniform WO₃A seed-covered substrate;

step 1.6, WCl₆Dissolving in absolute ethanol, and immersing the substrate obtained in step 1.5 in WCl₆Reacting in the solution at high temperature; under high pressure and temperature, WCl₆Alcoholysis and formation of WO_3-x(ii) a Wherein x is 0 or 1, and represents W element with different valence states;

step 2, preparing gold nanoparticle composite WO₃Film AuP/WO₃；

Step 2.1, washing the surface of the FTO glass obtained in the step 1.6 with secondary water, drying, immediately immersing into a chloroauric acid-ethanol solution, and standing for a set time; taking out, washing with ethanol and secondary water respectively, and removing unreacted chloroauric acid on the surface;

step 2.2, placing the sample in an oven to be dried to prepare AuP/WO₃A film.

Further, in order to enable the optical response of the composite material to cover multiple spectra and realize the color change of the voltage regulation composite material in the multispectral range, the step 2 is followed by the following steps:

step 3, preparing gold nanoparticle/rod composite WO₃Film AuPR/WO₃；

Step 3.1, AuP/WO prepared₃Immersing the film in ethanedithiol solution, taking out the film after setting time, and washing the film for multiple times by using ethanol;

step 3.2 preparation of AuP/WO binding thiol₃Immersing the film in the gold nanorod solution, standing for a set time, taking out, washing with ethanol for multiple times, and drying.

Further, the gold nanorod solution in step 3.2 is prepared by the following steps:

s1, preparing a seed crystal solution;

preparation of HAuCl₄And aqueous CTAB; adding fresh NaBH into the solution quickly₄The solution is stirred vigorously and then kept away from light;

s2, preparing a growth solution;

weighing CTAB and sodium oleate into deionized water, adding AgNO after complete dissolution₃Stirring the solution, and adding HAuCl₄Continuing stirring the solution;

s3, directionally growing Au nanorods;

adjusting the pH value of the growth solution to 2.0, and adding an ascorbic acid solution and a seed crystal solution into the growth solution; allowing the solution to stand at a constant temperature, and removing excess reducing agent by centrifugal washing; dispersing the collected gold nanorods by using deionized water, and adjusting the concentration of the nanorods through ultraviolet absorption so as to control the SPR absorption peak intensity of the obtained gold nanorod solution to be 0.8-1.2; and finally storing the gold nanorod solution at a low temperature for later use.

Further, in step S1, HAuCl₄The concentration of the aqueous solution was 0.25mmol L^-1(ii) a Concentration of CTAB aqueous solution is 0.1mol L^-1；NaBH₄The concentration of the aqueous solution was 0.1mol L^-1；HAuCl₄Aqueous solution, aqueous CTAB solution and NaBH₄The feeding ratio of the aqueous solution is 10 parts by volume: 10 parts by volume: 0.6 volume part;

in step S2, AgNO₃The concentration of the solution was 4mmol L^-1；HAuCl₄The concentration of the solution was 1.0mmol L^-1(ii) a CTAB, sodium oleate, deionized water, AgNO₃Solution, HAuCl₄The feeding ratio of the solution is 1.8 parts by mass: 0.308 parts by mass: 50 parts by volume: 4.8 parts by volume: 50 parts by volume, wherein the unit of mass part/volume part is g/ml;

in step S3, use 0.1mol L^-1HCl adjusts the pH of the growth solution to 2.0;

the concentration of the ascorbic acid solution is 0.064mol L^-1；

The feeding ratio of the ascorbic acid solution to the seed crystal solution is 0.312 volume part: 0.16 volume portion.

Further, in step 2.1, the concentration of the chloroauric acid-ethanol solution is 0.2mmol L^-1The volume is not limited.

Further, in step 2.2, drying at 60 ℃ to obtain AuP/WO₃A film.

Further, in step 3.1, the concentration of the ethanedithiol solution is 2mmol L^-1(ii) a The volume was 10 parts by volume.

Further, in step 3.2, AuP/WO with bound thiol₃Immersing the film in the gold nanorod solution, standing for 6 hours, taking out, washing with ethanol for multiple times, and N₂And (5) drying.

Further, the cleaning solution in step 1.1 is acetone, ethanol and deionized water, the FTO glass is sequentially ultrasonically cleaned in the acetone, the ethanol and the deionized water for 15 minutes, and then N is carried out₂Drying for later use;

step 1.2 Na₂WO₄·2H₂The feeding ratio of O to deionized water is as follows: 0.5 parts by mass: 20 parts by volume; wherein the unit of mass part/volume part is g/ml; concentration of HCl solutionDegree of 1.0mol L^-1；

In step 1.3, 1 part by volume of the suspension solution obtained in step 1.2 is spin-coated on the surface of the FTO glass treated in step 1.1, then the FTO glass is transferred into a tube furnace, oxidized for 10min at 350 ℃, cooled and taken out;

in step 1.6, 0.4 part by mass of WCl₆Dissolved in 20 parts by volume of absolute ethanol and covered with WO₃Soaking FTO glass of seeds into the solution, and reacting for 2h at 180 ℃; under high pressure and temperature, WCl₆Alcoholysis and formation of WO_3-x。

The invention also provides an electrochromic composite film prepared by the method.

The invention has the beneficial effects that:

1. the gold nanoparticles and the nanorods which are uniformly dispersed can effectively convert near-infrared light energy into heat energy, so that the composite film has high light-heat conversion efficiency and high color change speed.

2. The invention prepares porous WO with weak reducibility by a solvothermal method_3-xAnd the gold nanoparticles are grown in situ by utilizing the reducibility of the film, so that the photoresponse range of the material is expanded to a visible light region.

3. The invention further introduces the metal nano-rod with light absorption in the near-infrared region, so that the light response of the composite material can cover multiple spectrums, and the color change of the voltage regulation composite material in the multispectral range is realized.

4. WO prepared according to the invention_3-xHas reducing property, and can react with HAuCl₄Oxidation-reduction reaction occurs to generate gold nanoparticles (AuPs) in situ to form AuP/WO₃A film. Using WO_3-xReducing itself without the need for additional reducing agent when HAuCl₄Solution with WO_3-xAfter contact, it is rapidly reduced and is described in WO_3-xForming a tiny gold core on the surface, wherein the gold core is in HAuCl₄The growth continues in the solution, and compared with the traditional preparation method of the gold nanoparticles, the in-situ reduction method can be carried out at normal temperature, the operation is simple, and the reaction time is short. Meanwhile, no additional reducing agent is introduced into the system, so that removal of excessive reducing agent is avoidedAnd (5) carrying out the following steps.

5. The electrochromic film material prepared by the invention basically has no attenuation of the coloring rate in 200 cycles, and has good stability and application prospect.

Drawings

FIG. 1 shows WO modified by Au nanoparticles₃Scanning electron microscope image of the front side of the film;

FIG. 2 is a representation of gold nanorods, (A) is a transmission electron microscope image of the gold nanorods, and (B) is an absorption spectrum of the gold nanorods;

FIG. 3 shows gold nanoparticles and WO modified with gold nanorods₃Scanning electron microscope images of the thin film;

FIG. 4 shows Au-modified WO₃Film (AuPR/WO)₃) X-ray photoelectron spectroscopy; wherein, (A) is a general spectrogram; (B) is W4 f; (C) an electron spectrum for O1s and (D) Au 4 f;

FIG. 5 shows FTO glass and WO₃Films and AuP/WO₃An X-ray diffraction pattern of the film;

FIG. 6 is WO₃A Raman spectrum of the film;

FIG. 7 shows AuP/WO₃A Raman spectrum of the film;

FIG. 8 shows WO under. + -. 0.8V conditions₃、AuP/WO₃And AuPR/WO₃The in-situ spectral transmittance at 630nm of the film changes;

FIG. 9 is an optical photograph of three film samples at different voltage states, i.e., faded state (+0.8V), virgin state (OCP), and colored state (-0.8V), respectively;

FIG. 10 shows the 200 cycling stability tests (635nm) of the electrochromic films between +0.8V and-0.8V;

FIG. 11 is a graph showing the time courses of color change at 1 st, 100 th and 200 th times after 200 cycles of the electrochromic film between the colored state (-0.8V) and the faded state (+ 0.8V);

Detailed Description

The invention is further described with reference to the following figures and specific embodiments.

This example prepares an electrochromic composite film by the following steps:

1、WO₃growing a two-dimensional nano film;

the FTO glass is sequentially ultrasonically cleaned in acetone, ethanol and deionized water for 15 minutes and N is used₂And drying for later use. 0.5g of Na₂WO₄·2H₂O is dispersed in 20mL of deionized water, and 1.0mol L of O is added dropwise after the O is completely dissolved^-11mL of the above suspension solution was spin-coated on the surface of FTO glass, and then transferred to a tube furnace, and oxidized at 350 ℃ for 10 min. The above dropping and oxidizing steps were repeated 3 times to form a uniform WO₃A seed-covered substrate. 0.4g WCl was weighed₆Dissolved in 20mL of absolute ethanol and covered with WO₃The FTO glass of the seed was immersed in the above solution and reacted at 180 ℃ for 2 hours. Under high pressure and temperature, WCl₆Alcoholysis and formation of WO_3-x。

2. Gold nanoparticle composite WO₃Film (AuP/WO)₃) Preparing without reducing agent;

and (3) taking the FTO treated in the step (1) out of the reaction kettle, rapidly washing the surface with secondary water (the surface is controlled to be finished within 10 s), and rapidly drying the surface with nitrogen. Then immediately immersed in the prepared 0.2mmol L^-1Standing in the chloroauric acid-ethanol solution for 10 min. After the sample is taken out, the sample is washed with ethanol and secondary water for three times respectively to remove the unreacted chloroauric acid on the surface. Finally, the sample is dried in an oven at 60 ℃ to prepare AuP/WO₃A film.

Freshly prepared WO_3-xHas reducing property, and can react with HAuCl₄Oxidation-reduction reaction occurs to generate gold nanoparticles (AuPs) in situ to form AuP/WO₃A film. This method utilizes WO_3-xReducing itself without the need for additional reducing agent when HAuCl₄Solution with WO_3-xAfter contact, it is rapidly reduced and is described in WO_3-xForming a tiny gold core on the surface, wherein the gold core is in HAuCl₄The growth continues in the solution, and the size of the generated gold nanoparticles can be controlled according to the reduction time.

As can be seen from fig. 1, the diameter of the gold nanoparticles reduced in situ can reach about 30nm within 10min, and compared with the conventional preparation method of gold nanoparticles, the in situ reduction method can be performed at normal temperature, and is simple to operate and short in reaction time. Meanwhile, no additional reducing agent is introduced into the system, so that the step of removing the excessive reducing agent is avoided.

3. Preparing Au nanorods;

the gold nanorods of the embodiment are prepared by adopting a seed growth method. The method mainly comprises two steps: preparing seed crystal solution and directionally growing the nano rod.

Preparation of seed crystal solution: first, 10mL of 0.25mmol L was prepared^-1HAuCl₄And 0.1mol L^-1Aqueous CTAB solution. To this solution was added rapidly 0.6mL of fresh aqueous NaBH4 solution (0.1mol L)^-1) The solution was stored in the dark after vigorous stirring for 2 min.

Preparation of growth solution: weighing 1.8g CTAB and 0.308g sodium oleate into 50mL deionized water, adding 4.8mL 4mmol L^-1AgNO of₃Stirring the solution for 30min, and adding 50mL of 1.0mmol L^-1HAuCl₄The solution was stirred for another 60 min.

Directional growth of Au nanorods: with 0.1mol L^-1The pH of the growth solution was adjusted to 2.0 with HCl and 0.312mL ascorbic acid solution (0.064mol L) was added to the solution^-1) And 0.16mL of seed solution. The solution was allowed to stand at a constant temperature of 30 ℃ for 12 hours, and excess reducing agent was removed by centrifugal washing. And dispersing the collected gold nanorods by using deionized water, adjusting the concentration of the nanorods through ultraviolet absorption, and controlling the SPR absorption peak intensity of the finally obtained gold nanorod solution to be 0.8-1.2. And finally storing the gold nanorod solution in a refrigerator at 4 ℃ for later use. The transmission electron microscope characterization of the prepared gold nanorods is shown in (a) in fig. 2. The gold nano-rod has the size of 80nm multiplied by 15nm and the length-diameter ratio of about 5.3. Because of the existence of the transverse and longitudinal axes, two plasma resonance absorption peaks, namely a transverse plasma resonance absorption peak and a longitudinal plasma resonance absorption peak, exist in the gold nanorods at the same time, as shown in fig. 2 (B), the gold nanorods used in the experiment have two absorption peaks in an absorption spectrum. The transverse plasma resonance absorption peak and the longitudinal plasma resonance absorption peak are respectively positioned at 550nm and 910nm, which embodies thatThe nano-rod has good absorption potential to near infrared light.

4. Gold nanoparticle/rod composite WO₃Film (AuPR/WO)₃) Preparing;

AuP/WO prepared in step 2₃The membrane was immersed in 10mL of 2mmol L^-1After 12 hours, the reaction solution was taken out and washed with ethanol three times. AuP/WO in combination with mercaptan₃Immersing the film in the solution of gold nano-rod (80nm 15nm), standing for 6h, taking out, washing with ethanol for three times, and N₂And (5) drying.

Gold nanoparticles and gold nanorod-modified WO₃The scanning electron micrograph of the film is shown in FIG. 3. It can be seen that AuPR/WO₃The gold nanoparticles and gold nanorods (marked by arrows) on the film are uniformly distributed, and no obvious agglomeration phenomenon exists. Since the conductivity of the metal conductor is superior to that of the semiconductor substrate WO₃Therefore, the introduction of the gold nano material can accelerate ion transfer and improve the electrochromic performance of the material. Meanwhile, the uniformly dispersed gold nanorods can effectively convert near-infrared light energy into heat energy, so that the composite film has higher light-heat conversion efficiency.

To confirm WO₃Successful preparation of thin film and modification of Au nano material, this example is to prepare composite thin film AuPR/WO₃An X-ray photoelectron spectroscopy (XPS) characterization is carried out, and as shown in FIG. 4, a total spectrum (A in FIG. 4) proves that the film contains four elements of W, O, Au and C, wherein the element C may be derived from organic solvent residues adsorbed on the surface of the material. WO can be further confirmed from the fine XPS peaks of B and C in FIG. 4₃Successful growth. In D in FIG. 4, Au 4f is located at 83.9eV and 87.4eV, and the difference between the two peak positions is 6.5eV, which demonstrates the successful modification of Au (0).

In addition, this example also examined the prepared composite film AuP/WO by X-ray powder diffraction₃A crystalline form of (a). FIG. 5 shows FTO glass and WO₃And AuP/WO₃XRD spectrum of (1). WO₃And AuP/WO₃The spectrum of (A) has obvious WO at 2 theta of 35.1 DEG₃(202) Characteristic diffraction peak of diffraction surface (JCPDS 83-0950); at AuP/WO₃In spectrogramThe characteristic diffraction peak of the Au (200) diffraction surface with the 2 theta being 44.5 degrees further proves that Au is successfully loaded on WO through the in-situ reaction in the experiment₃On the film.

FIGS. 6 and 7 are WO₃And AuP/WO after modification of Au nanoparticles₃Raman spectrum of the film under 532nm laser. Comparing these two figures, it can be seen that WO is applied after modification of Au nanomaterial₃A significant enhancement of the raman peak is obtained, e.g. an increase of one order of magnitude in the intensity of the raman peak. This is because gold nanoparticles are tightly bound to WO₃Surface of (2) resulting in Au and WO₃The electric field at the interface is enhanced, known as surface enhanced raman scattering. Therefore, the Raman spectrum data also proves that the Au nano material is in WO on the other hand₃And (3) successfully modifying the surface of the film.

The response time reflects the response rate of the electrochromic material to voltage changes, WO₃、AuP/WO₃And AuPR/WO₃The electrochromic response time test curve of the film is shown in fig. 8, and the test is performed by cycling between a coloring voltage (-0.8V) and a discoloring voltage (+0.8V) by a multi-potential step method, respectively, a plurality of times. WO was calculated from FIG. 8₃、AuP/WO₃And AuPR/WO₃Time t for coloring film_c12.5s, 3.0s and 3.0s, respectively; time to fade t_b11.4s, 6.0s and 4.4s, respectively. Due to the WO prepared₃The membrane has larger gaps in the 3D honeycomb structure, and can provide effective channels for rapid transmission of ions, so that WO₃The film itself has a relatively fast response rate. The modification of the gold nano material further improves the WO₃The coloring speed and fading speed of the film are due to the fact that gold is a good metal conductor and can accelerate ions in WO₃The conduction rate in the film.

FIG. 9 shows WO₃、AuP/WO₃And AuPR/WO₃Optical photographs corresponding to the open circuit potential state, the colored state and the faded state of the film. It can be observed that the color of the film changes into opaque dark blue after the film lasts for 50s under the voltage of-0.8V, which proves that the film can generate the color change reaction through the voltage regulation, and the color of the discolored film is uniformEven, can exist stably in a colored state. Dark materials absorb light more strongly than light or clear materials, and therefore, films in the colored state may have better light-to-heat conversion.

To confirm WO after modification of gold nanomaterials₃The films do have better conductivity, and WO was measured separately in the examples by the "four-probe" method₃、AuP/WO₃And AuPR/WO₃The resistivity of the film was measured, and the results are shown in Table 1. WO after modification of gold nanoparticles₃The resistivity of the material was reduced from 7.97. cm to 3.39. cm, and the resistivity of the material was reduced to 0.79. cm after further modification of the gold nanorods. The material with lower resistivity has better conductivity, and the resistivity test result shows that WO₃After the gold nano material is introduced into the thin film, the conductivity of the thin film is improved, and ions in the thin film have higher conduction rate. The results of the resistivity test also explain AuP/WO₃And AuPR/WO₃Film comparison with WO₃The film has shorter coloration time and fading time.

TABLE 1 WO test by four-point Probe method₃,AuP/WO₃And AuPR/WO₃Resistivity of thin film

Since the electrochromic process is also an electrochemical reaction process, when voltages under different conditions are applied, the electrochromic material is constantly changed between a coloring state and a fading state, and the film itself also has a tiny physical effect (such as the film falls off from the substrate due to volume expansion), so that the electrochromic performance of the material may gradually decline with the increase of the number of times of recycling, and the electrochromic material in practical application needs to be capable of being recycled for many times. Therefore, the electrochromic stability of the material is particularly important in practical application and is an important evaluation parameter for the performance of the material.

FIG. 10 is a diagram of AuPR/WO₃200 coloring-fading cycles were performed, and as can be seen from the results of the cycle tests, the present practiceThe electrochromic film material prepared in the example has substantially no fading of the coloring rate in 200 cycles, i.e., the color remains stable in the colored state. The prepared material is proved to have good stability and application prospect.

To further investigate the effect of multiple color changes on film performance, the electrochromic data at circles 1, 100 and 200 were extracted and plotted in FIG. 11. From these three curves, AuPR/WO can be seen before and after 200 cycles₃The film has no obvious reduction in coloring effect, basically no change in optical dynamic modulation capacity and only increased fading time. The results show that the prepared film can be stably combined with a substrate and has good cycling stability.