Preparation method and application of tungsten oxide-carbon dot-polyacrylic acid composite material

Abstract

The invention relates to a preparation method and application of a tungsten oxide-carbon dot-polyacrylic acid composite material. A carboxyl-containing compound and an amino-containing compound are used as a carbon source and a nitrogen source, and nitrogen-doped carbon dots are synthesized through a solvothermal method; the preparation method comprises the following steps: precipitating soluble tungstate under the condition that the pH value is 1.2-3 to obtain a tungsten oxide precursor; adding the obtained carbon dots into the obtained tungsten oxide precursor, mixing, and reacting at 120 DEG C for 2 hours to obtain a tungsten oxide / carbon dot composite material; carbomer with the concentration of 1 wt% is dissolved in water to form a solution, 0.5 wt% of the tungsten oxide / carbon dot composite material is added, and nanometer ink is formed through dispersion; the surface of a conductive flexible substrate is coated with the nano ink, a carbomer substrate flexible thin film is obtained after drying, and the carbomer substrate flexible thin film is a tungsten oxide-carbon dot-polyacrylic acid composite material, has efficient photochromic and electrochromic properties, and shows the characteristics of high transmissivity modulation amplitude and rapid response. And an innovative material scheme is provided for development and multi-scene application of flexible photoelectric devices, and the method has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of electrochromic / photochromic sensor technology, and particularly to a method for preparing and applying a tungsten oxide-carbon dot-polyacrylic acid composite material with dual photochromic and electrochromic functions. Background Technology

[0002] Research on electrochromic phenomena began in the 1960s. In 1969, Deb first reported the reversible color change of WO3 thin films under an applied electric field, a discovery that laid the foundation for electrochromic technology research. As a star material possessing both electrochromic and photochromic (E / PC) dual-response properties, WO3, with its excellent physicochemical stability, weather resistance, open ion-accommodating channels, and high photocatalytic activity, has significant application value in fields such as smart windows for energy-efficient buildings, automotive rearview mirrors, and wearable flexible smart display devices. The open ion channels allow WO3 to reversibly switch between a transparent state and a deep blue state under an applied electric field through ion-electron insertion / extraction processes; while its narrow bandgap and high photocatalytic activity endow it with photochromic response capabilities to ultraviolet and even visible light. These characteristics make it an ideal choice for constructing E / PC dual-response materials.

[0003] However, the practical application of WO3 still faces several challenges. First, its photoelectric / chromatic efficiency is low, and the color change is slow and limited. Due to its loosely packed amorphous structure, α-WO3 lacks long-range order, leading to localized stress accumulation during repeated ion insertion / extraction, which can cause structural collapse and disrupt the insertion of H+. + As H accumulates continuously in the a-WO3 film, partially irreversible H is generated. x WO3. Ultimately, this leads to a severe degradation of the optical controllability and electrochromic activity of WO3. Secondly, the photochromic self-fading process of WO3 thin films relies on oxidation, which takes several days at room temperature. Although heating can accelerate fading, it causes the oxygen vacancies to disappear, causing the material to lose its color-changing ability. In addition, the photochromic reaction usually requires the participation of hydrogen donor molecules (such as water and methanol), and these substances may negatively affect the ion-based electrolyte performance of electrochromic devices.

[0004] Color-changing polymers (CDs) exhibit great potential in the field of electrode materials due to their advantages of low cost, easy synthesis, and modifiability. Their significant quantum size effect shortens the diffusion path of ions and electrons, improving charge transport efficiency. Carbomer, as a cross-linked acrylic resin, possesses excellent thickening and stability. Its gelation process, activated by hydration and pH neutralization, can form a three-dimensional network structure, effectively inhibiting film peeling and delamination, providing a new strategy for improving the stability of color-changing films and enhancing process compatibility. Summary of the Invention

[0005] To address the problems of low photochromic and electrochromic response efficiency and easy delamination between flexible films in existing WO3 thin film preparation technologies, a method for preparing and applying tungsten oxide-carbon dots-polyacrylic acid composite materials is proposed. The research will explore composite materials combining WO3, CDs, and carbomer to achieve more efficient electrochromic and photochromic properties, providing new solutions for related fields.

[0006] The technical solution of this invention is: a method for preparing tungsten oxide-carbon dots-polyacrylic acid composite materials, specifically including the following steps:

[0007] S1. Soluble tungstate is precipitated at pH 1.2–3 to obtain tungsten oxide precursor;

[0008] S2. Carbon dots are synthesized by a solvothermal method using carboxyl-containing compounds and amino-containing compounds as carbon sources;

[0009] S3. Add the tungsten oxide precursor obtained in step S1 to the carbon dots obtained in S2 and mix them. React at 120°C for 2 hours to obtain tungsten oxide / carbon dot composite material.

[0010] S4. Dissolve carbomer in water at a concentration of 1 wt% to form a solution, add 0.5 wt% tungsten oxide / carbon dot composite material, and disperse to form nano ink;

[0011] S5. The nano-ink is coated on the surface of a conductive flexible substrate and dried to obtain a carbomer-based flexible film. The carbomer-based flexible film is a tungsten oxide-carbon dot-polyacrylic acid composite material, which has both high-efficiency photochromic and electrochromic properties, and exhibits high transmittance modulation amplitude and fast response characteristics.

[0012] Furthermore, in step S2, the carboxyl compound is selected from citric acid or L(+)-ascorbic acid; the amino compound is selected from ethylenediamine, m-phenylenediamine, or a combination of o-phenylenediamine and catechol.

[0013] Further, the specific implementation method of step S1 is as follows: 4.125g of sodium tungstate is dissolved in 12.5mL of deionized water to prepare a Na2WO4 solution. The Na2WO4 solution is adjusted to pH=1.2 with 12M hydrochloric acid solution at room temperature, and a white precipitate is immediately formed. The precipitate is washed with deionized water until the eluent pH=3. 30ml of ethanol is added to the eluent at pH=3 and the mixture is sonicated for 30min to obtain the tungsten oxide precursor.

[0014] The specific implementation method of step S3 is as follows: 25 mg of carbon dots are mixed with the tungsten oxide precursor in S1, ultrasonicated at 50 Hz for 10 min, transferred to a 50 mL reaction vessel and heated to 120 ℃ at 10 ℃ / min for 2 h; the product is washed by centrifugation with deionized water and ethanol and then vacuum dried at 60 ℃ for 8 h to obtain the tungsten oxide / carbon dot composite material.

[0015] Furthermore, by adjusting the ratio of tungsten oxide / carbon dots in step S3 to carbomer in step S4, and adapting the spin coating and spray coating film formation process parameters, a film can be rapidly formed on any substrate surface, including plastics, fabrics, glass, ceramics, metals, and skin, exhibiting stable photochromic properties and the advantage of easy cleaning.

[0016] A tungsten oxide-carbon dot-polyacrylic acid composite material is obtained by a preparation method. In this composite material, the carboxyl, hydroxyl and carbonyl groups on the surface of the carbon dots stabilize the network structure of WO3 through hydrogen bonding and synergistically construct ion transport channels with the carboxyl groups in the carbomer, thereby improving the electron migration rate and high charge transfer efficiency.

[0017] A method for selecting the optimal tungsten oxide-carbon dot-polyacrylic acid composite material is disclosed. The method uses a conductive flexible substrate of the tungsten oxide-carbon dot-polyacrylic acid composite material as the working electrode, a platinum plate as the counter electrode, Ag / AgCl (1M KCl) as the reference electrode, and a 1M AlCl3·6H2O aqueous solution as the electrolyte for electrochemical testing. Cyclic voltammetry curves are obtained at 10, 20, 50, 80, and 100 mVs. -1 The scanning range was between -1.0 and 1.0 V (vs. SCE); the CV curve was fitted and the charge capacity was calculated to study the reversible charge storage capacity and electrochemical activity; the transmission spectrum of the electrochromic thin film was fitted and the optical modulation range was calculated to study the spectral modulation capability, thereby obtaining a tungsten oxide-carbon dot-polyacrylic acid composite material with optimal ion transport performance and electrochromic optical modulation amplitude capability.

[0018] An application of a tungsten oxide-carbon dot-polyacrylic acid composite material is disclosed, in which a sandwich-structured electrochromic device is prepared using the tungsten oxide-carbon dot-polyacrylic acid composite material and integrated with a piezoelectric thin film to form a self-powered electrochromic device. When the finger is bent, it exhibits high transmittance modulation amplitude and fast response color-changing characteristics on the surface of a conductive substrate.

[0019] The beneficial effects of this invention are as follows: The preparation method and application of the tungsten oxide-carbon dot-polyacrylic acid composite material of this invention significantly improve the electrochromic and photochromic properties, exhibiting high transmittance modulation amplitude and fast response characteristics, providing an innovative material solution for the development and multi-scenario application of flexible optoelectronic devices, and has broad application prospects. Attached Figure Description

[0020] Figure 1 High-resolution X-ray photoelectron spectra of (a)C 1s, (b)O 1s and (c)W 4f of a-WO3 and a-WO3@CDs;

[0021] Figure 2 Scanning electron microscope images of a-WO3@carbomer and a-WO3@CDs@carbomer;

[0022] Figure 3 Cyclic voltammetry plots of a-WO3 and a-WO3@CDs;

[0023] Figure 4 Cyclic voltammetry plots of a-WO3, a-WO3 / CD-1-0.1%, a-WO3 / CD-1-0.25%, and a-WO3 / CD-1-0.5% (inset shows ion diffusion rate values);

[0024] Figure 5 Electrochemical impedance spectroscopy for a-WO3, a-WO3 / CD-1-0.1%, a-WO3 / CD-1-0.25%, and a-WO3 / CD-1-0.5%;

[0025] Figure 6 Mott-Schottky plots of a-WO3, a-WO3 / CD-1-0.1%, a-WO3 / CD-1-0.25%, and a-WO3 / CD-1-0.5%;

[0026] Figure 7 Photochromic images of a-WO3 and a-WO3@CDs after ultraviolet light irradiation (recorded every 15 seconds) and their corresponding transmission spectra;

[0027] Figure 8 Photochromic images of a-WO3@CDs@carbomer film on (a) plastic, (b) wall and (c) glass substrates before and after ultraviolet light irradiation;

[0028] Figure 9 Optical transmission spectra of colored and faded states of (a) a-WO3@carbomer and (b) a-WO3@CDs@carbomer films under ultraviolet light irradiation;

[0029] Figure 10 :(a) In-situ transmittance variation curves of a-WO3@carbomer and (b) a-WO3@CDs@carbomer films at a wavelength of 633nm under potentials of -0.1V (coloring) and 1V (bleaching);

[0030] Figure 11 : Circuit diagram and physical image of PVDF piezoelectric material and electrochromic device integrated through a rectifier;

[0031] Figure 12 Color switching behavior of the device driven by finger bending: (a) bleached state, (b) colored state;

[0032] Figure 13 Schematic diagram of the electro / photochromic mechanism of a-WO3@CDs. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0034] This invention provides a method for preparing a tungsten oxide-carbon dot-polyacrylic acid composite material with dual photochromic and electrochromic functions, specifically including the following steps:

[0035] S1. Preparation of tungsten oxide / carbon dot composite materials using a solvothermal method:

[0036] S11. Dissolve 4.125 g of sodium tungstate (Na2WO4) in 12.5 mL of deionized water to prepare a Na2WO4 solution. Adjust the pH of the Na2WO4 solution to 1.2 with hydrochloric acid (12M) solution at room temperature, and a white precipitate will immediately form. Wash the precipitate with deionized water until the eluent pH is 3. Add 30 mL of ethanol to the eluent at pH 3 and sonicate for 30 min to obtain the tungsten oxide precursor.

[0037] Preparation of S12-1 and CD-1 type carbon dots.

[0038] 1344.84 mg of CA was weighed and dissolved in 25 mL of DMF. 468 μL of EDA was added to the solution, using citric acid and ethylenediamine as precursors. The mixture was then sonicated for 25 min. The solution was then transferred to a 50 mL polytetrafluoroethylene-lined reactor and heated in an oven at 160 °C for 8 h. After natural cooling to room temperature, the product was filtered through a 0.22 μm filter to obtain a brownish-red solution, which was then dialyzed against a cellulose membrane for 24 h. Finally, the solution was freeze-dried to obtain a yellowish-brown carbon dot powder.

[0039] Preparation of S12-2 and CD-2 type carbon dots.

[0040] 0.1 M ascorbic acid solution (0.8 mL) and 0.1 M m-phenylenediamine solution (0.8 mL) were added to 10.4 mL of deionized water, stirred for 5 min, and then transferred to a 50 mL reaction vessel. The mixture was reacted at 160 °C for 6 h. The product was centrifuged at 8000 rpm for 20 min, dialyzed against a cellulose membrane with a molecular weight cutoff of 35-3000 D for 24 h, and then freeze-dried to obtain a yellow-brown powder.

[0041] Preparation of S12-3 and CD-3 type carbon dots

[0042] 0.54 g of o-phenylenediamine (oPD), 0.55 g of catechol (CAT), and 0.08 g of AlCl3·6H2O were ground for 10 min and transferred to a 30 mL reactor, where they were reacted at 200 °C for 12 h. The product was dissolved in ethanol, filtered through a 0.22 μm filter, dialyzed against a cellulose membrane with a molecular weight cutoff of 35-3500 D for 7 days (with water changed every 12 h), and then freeze-dried to obtain a black powder.

[0043] S13. Take 25 mg of the carbon dots obtained from S12-1, S12-2, and S12-3 respectively and mix them one by one with the tungsten oxide precursor obtained from S11. Sonicate at 50 Hz for 10 min, transfer to a 50 mL reactor, and react at 120 ℃ for 2 h by heating at 10 ℃ / min. After centrifugation and washing with deionized water and ethanol, dry under vacuum at 60 ℃ for 8 h to obtain the tungsten oxide / carbon dot composite material.

[0044] S2. A flexible carbomer substrate film was prepared based on a tungsten oxide / carbon dot composite material. The flexible carbomer substrate film is a tungsten oxide-carbon dot-polyacrylic acid composite material, which has both high efficiency photochromic and electrochromic properties, and exhibits high transmittance modulation amplitude and fast response characteristics.

[0045] S21. Add 50 mg of tungsten oxide / carbon dot composite material powder to a 1:1 solution of 20 mL deionized water and ethanol, and stir for 10 min to obtain a uniform nano-ink. Drop-coat the nano-ink onto an ITO film preheated to 80 °C. Dry in a vacuum oven at 60 °C for 1 h to obtain a flexible tungsten oxide / carbon dot composite material film.

[0046] S22. Using the ITO film in the tungsten oxide / carbon dot composite flexible film obtained in S21 as the working electrode, a platinum plate as the counter electrode, Ag / AgCl (1M KCl) as the reference electrode, and 1M AlCl3·6H2O aqueous solution as the electrolyte, electrochemical tests were performed. Cyclic voltammetry curves were obtained at 10, 20, 50, 80, and 100 mV s. -1 The voltage was scanned between -1.0 and 1.0 V (vs. SCE). CV curves were fitted and charge capacity was calculated to investigate reversible charge storage capacity and electrochemical activity.

[0047] S23. Fit the transmission spectrum of the electrochromic thin film and calculate the optical modulation range to study its spectral modulation capability. See [link / reference] Figure 1 and Figure 2 Cyclic voltammetry curves of a-WO3 and a-WO3 / CDs (inset shows ion diffusion rate values) and optical transmission spectra of their colored and faded thin film states are shown. a-WO3 / CD-1 exhibits the best ion transport performance and electrochromic optical modulation amplitude capability.

[0048] S24. Add CD-1 at mass fractions of 0.1%, 0.25%, and 0.5% to the tungsten oxide precursor obtained in S11 and mix. Repeat the other steps to complete S13, S21-S23. Figure 3 .exist Figure 3 In the XRD patterns of a-WO3, a-WO3 / CD-1-0.1%, a-WO3 / CD-1-0.25%, and a-WO3 / CD-1-0.5%, the diffraction peaks showed a trend towards higher angles with increasing CD1 content. According to the Bragg equation (nλ = 2dsinθ), this shift may originate from the interaction between the carboxyl and hydroxyl groups on the carbon dot surface and W. 6+ The strong coordination effect of WO3 shortens the bond distance of WO3, thereby inducing local lattice shrinkage of α-WO3.

[0049] S25. Preparation of flexible carbomer-based films based on a-WO3 / CD-1 composite materials.

[0050] 75 mL of carbomer was dissolved in 10 mL of deionized water and stirred for 30 min to obtain a carbomer aqueous solution. Three identical portions of the carbomer aqueous solution were then added to 50 mg of a-WO3 / CD-1-0.1%, a-WO3 / CD-1-0.25%, and a-WO3 / CD-1-0.5% composite material powder, respectively, and stirred for 10 min to obtain three uniform nano-inks. The three nano-inks were then drop-coated onto three ITO films preheated to 80 °C (ITO film was used as the substrate; flexible polymer films or metal foils could also be used). The films were dried in a vacuum oven at 60 °C for 1 h to obtain flexible carbomer-based films prepared from a-WO3 / CD-1-0.1%, a-WO3 / CD-1-0.25%, and a-WO3 / CD-1-0.5% composite materials.

[0051] S26. Using the ITO film in the prepared carbomer-based flexible thin film as the working electrode, a platinum plate as the counter electrode, Ag / AgCl (1M KCl) as the reference electrode, and 1M AlCl3 aqueous solution as the electrolyte, electrochemical tests were performed. Cyclic voltammetry curves were scanned between -1.0 and 1.0 V (vs. SCE) at 10, 20, 50, 80, and 100 mV s⁻¹. CV curves were fitted and charge capacity was calculated to study the reversible charge storage capacity and electrochemical activity. EIS Nyquist plots were also fitted to investigate the charge transfer process. Figure 4 Cyclic voltammetry of a-WO3 and a-WO3 / CDs and Figure 5In the electrochemical impedance spectroscopy (EIS) plots of a-WO3 and a-WO3 / CD-1, as the CD-1 doping concentration gradually increases, the peak redox current rises to its maximum in a-WO3 / CD-1-0.1% and then gradually decreases, resulting in a smaller area of ​​the integral curve. This indicates a gradual weakening of the redox reaction, making ion implantation and extraction more difficult, and reducing charge storage capacity. To more accurately study the kinetics of ion transport in the electrochemical reaction, the diffusion coefficient of H+ during insertion and extraction was calculated: Da-WO3 / CD-1-0.1%... H (4.38×10- 9 cm 2 s -1 All were 0.25% (3.33×10⁻⁶) lower than α-WO₃ / CD⁻¹. 9 cm 2 s -1 ) and a-WO3 / CD-1-0.5% (2.57×10-9cm 2 s -1 The value is high, and it is a-WO3 (9.91×10- 10 cm 2 ·s -1 The charge transport resistance is 4.4 times that of WO3 / CD-0.1%, indicating that the ions exhibit the least migration resistance and the best rapid charge transport kinetics at the α-WO3 / CD-0.1% interface. Experiments have verified that CD-1 type carbon dots exhibit the best charge transport performance at a mass fraction of 0.1%. Figure 5 The semicircle in the high-frequency region of the EIS Nyquist plot represents the charge transfer process at the electrode / electrolyte interface, and its radius is equal to the charge transfer resistance. The a-WO3 / CD-1-0.1% composite sample shows the smallest Nyquist plot radius, indicating that it has the smallest charge transfer resistance.

[0052] S27. Electrochemical impedance spectroscopy was performed on two thin films, a-WO3 and a-WO3 / CD-1-0.1% (hereinafter referred to as a-WO3 / CDs), in AC open-circuit voltage mode over a frequency range of 0.01 to 10 kHz, and Mott-Schottky plots were obtained at a frequency of 1500 Hz. Figure 6 The Mott-Schottky diagrams for a-WO3 and a-WO3 / CDs are shown. The band gap of pure a-WO3 is 3.21 eV, and that of a-WO3 / CDs is 3.15 eV. This is due to the formation of oxygen vacancies and W vacancies by the introduction of CDs. 5+ The defect, oxygen vacancies, introduce donor levels into the band gap, resulting in a narrower band gap, thereby enhancing light absorption, electrical conductivity, and ion transport performance.

[0053] S28. Fit the transmission spectrum of the electrochromic thin film and calculate the optical modulation range to study the spectral modulation capability. Figure 7The color changes of a-WO3 / carbomer and a-WO3 / CDs / carbomer during photochromism were demonstrated. When a-WO3 / carbomer and a-WO3 / CDs / carbomer were irradiated with ultraviolet light for 15s, 30s, 45s, 60s, 100s, and 180s, the a-WO3 / carbomer and a-WO3 / CDs / carbomer films changed from pale yellow to deep blue. Figure 7 In (b), after 180 s of UV irradiation, the transmittance of the a-WO3 / carbomer film at 633 nm decreased from 96.9% to 32.4%, while the transmittance of the a-WO3 / CDs / carbomer film at 633 nm decreased from 96.4% to 16.3%. The results indicate that the a-WO3 / CDs / carbomer film exhibits a larger optical modulation amplitude before and after the color change, and thus better color conversion and fading rates. Figure 8 As shown, a-WO3 / CDs / carbomer coatings can create different patterns on various substrates, such as plastics, walls, glass, and skin. After 60 seconds of UV irradiation, all substrates changed from colorless to a distinct blue. Further research was conducted on the electrochromic tone modulation amplitude and response time of a-WO3 / carbomer and a-WO3 / CDs / carbomer. Figure 9 (b) The optical modulation amplitude of a-WO3 / CDs / Carbomer reached 76.8%. This indicates that a-WO3 / CDs / Carbomer has a more transparent fading state and excellent broadband modulation capability in the visible light region. Furthermore... Figure 10 The α-WO3 / CDs / carbomer exhibits faster photochromic and electrochromic rates (2.6s and 1.9s, respectively). Experiments have verified that CD-1 type carbon dots exhibit the best photochromic and electrochromic properties at a mass fraction of 0.1%.

[0054] S3. Fabrication of electrochromic devices with sandwich structures using flexible thin films on a carbomer substrate: By integrating piezoelectric thin films and electrochromic devices through rectifiers, the application scenarios of the devices can be broadened.

[0055] Piezoelectric-driven electrochromic device integrated system such as Figure 11 This exhibit showcases the structural principle of a piezoelectric-driven electrochromic integrated system and provides photographs of actual piezoelectric-driven EC devices. The system utilizes an LDT0-028K piezoelectric film as an energy harvesting unit, converting mechanical deformations such as finger taps and bending into electrical energy to power the EC display devices. A rectifier circuit converts the AC signal generated by the piezoelectric material into a DC signal output.

[0056] S31. An electrochromic device is constructed using a sandwich model of transparent conductive substrate (ITO thin film) / electrochromic layer / electrolyte layer / transparent conductive substrate. A flexible thin film on a carbomer substrate is used as the electrochromic layer, and a 1M AlCl3 solution is used as the electrolyte. The device is encapsulated with UV adhesive.

[0057] S32. Using LDT0-028K piezoelectric film as an energy harvesting unit, mechanical deformations such as finger tapping and bending are converted into electrical energy, which then powers the electrochromic display device.

[0058] S33, the rectifier circuit converts the AC signal generated by the piezoelectric material into a DC signal output.

[0059] S34 drives the electrochromic device to undergo an oxidation-reduction reaction, thereby achieving optical modulation.

[0060] The tungsten oxide / carbon dot / carbomer composite material provided by this invention significantly improves both electrochromic and photochromic properties, exhibiting high transmittance modulation amplitude and fast response characteristics. Figure 12 The Chinese team integrated materials with piezoelectric thin films to construct a self-driven electrochromic device. Experiments have shown that the mechanical energy (2V) generated by bending a finger can trigger a significant color change (colorless (a) → blue (b)). This characteristic provides an innovative material solution for the development and multi-scenario application of flexible optoelectronic devices.

[0061] like Figure 13 The schematic diagram of the electro / photochromic mechanism of a-WO3 / CDs shows that in the composite system, the carboxyl, hydroxyl, and carbonyl groups on the carbon dot surface effectively stabilize the WO3 network structure through hydrogen bonding and synergistically construct ion transport channels with the carboxyl groups in the carbomer, thereby significantly improving electron mobility and high charge transfer efficiency. This composite film exhibits the following excellent properties: in terms of electrochromism, it displays high transmittance modulation amplitude and fast response characteristics (short switching time) on conductive substrates; in terms of fabrication process flexibility, by adjusting the carbon dot to carbomer content ratio, it can be adapted to spin-coating, spray-coating, and other film-forming process parameters; in terms of application compatibility, this film can be rapidly formed on diverse substrate surfaces such as plastics, fabrics, glass, ceramics, metals, and skin, exhibiting stable photochromic properties and easy cleaning, providing an innovative material solution for the development and multi-scenario applications of flexible optoelectronic devices.

[0062] The embodiments described above merely illustrate specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a tungsten oxide-carbon dot-polyacrylic acid composite material, characterized in that, Specifically, the steps include the following: S1. Soluble tungstate is precipitated at pH 1.2–3 to obtain tungsten oxide precursor; S2. Carbon dots are synthesized by a solvothermal method using carboxyl-containing compounds and amino-containing compounds as carbon sources; S3. Add the tungsten oxide precursor obtained in step S1 to the carbon dots obtained in S2 and mix them. React at 120°C for 2 hours to obtain tungsten oxide / carbon dot composite material. S4. Dissolve carbomer in water at a concentration of 1 wt% to form a solution, add 0.5 wt% tungsten oxide / carbon dot composite material, and disperse to form nano ink; S5. The nano-ink is coated on the surface of a conductive flexible substrate and dried to obtain a carbomer-based flexible film. The carbomer-based flexible film is a tungsten oxide-carbon dot-polyacrylic acid composite material, which has both high-efficiency photochromic and electrochromic properties, and exhibits high transmittance modulation amplitude and fast response characteristics.

2. The method for preparing tungsten oxide-carbon dot-polyacrylic acid composite material according to claim 1, characterized in that, In step S2, the carboxyl compound is selected from citric acid or L(+)-ascorbic acid; The amino-containing compound is selected from ethylenediamine, m-phenylenediamine, or a combination of o-phenylenediamine and catechol.

3. The method for preparing tungsten oxide-carbon dot-polyacrylic acid composite material according to claim 2, characterized in that, The specific implementation method of step S1 is as follows: Dissolve 4.125g of sodium tungstate in 12.5mL of deionized water to prepare a Na2WO4 solution. Adjust the pH of the Na2WO4 solution to 1.2 with 12M hydrochloric acid solution at room temperature, and a white precipitate will be generated immediately. Rinse the precipitate with deionized water until the eluent pH is 3. Add 30mL of ethanol to the eluent at pH 3 and sonicate for 30min to obtain the tungsten oxide precursor. The specific implementation method of step S3 is as follows: 25 mg of carbon dots are mixed with the tungsten oxide precursor in S1, ultrasonicated at 50 Hz for 10 min, transferred to a 50 mL reaction vessel and heated to 120 ℃ at 10 ℃ / min for 2 h; the product is washed by centrifugation with deionized water and ethanol and then vacuum dried at 60 ℃ for 8 h to obtain the tungsten oxide / carbon dot composite material.

4. The method for preparing tungsten oxide-carbon dot-polyacrylic acid composite material according to claim 2, characterized in that, By adjusting the ratio of tungsten oxide / carbon dots in step S3 to carbomer in step S4, and adapting it to spin coating and spray coating film formation process parameters, a film can be rapidly formed on any substrate surface, including plastics, fabrics, glass, ceramics, metals, and skin, exhibiting stable photochromic properties and the advantage of easy cleaning.

5. A tungsten oxide-carbon dot-polyacrylic acid composite material, characterized in that, A tungsten oxide-carbon dot-polyacrylic acid composite material is obtained by any one of the preparation methods in claims 1 to 4. In this composite material, the carboxyl, hydroxyl and carbonyl groups on the surface of the carbon dots stabilize the network structure of WO3 through hydrogen bonding and synergistically construct ion transport channels with the carboxyl groups in the carbomer, thereby improving the electron migration rate and high charge transfer efficiency.

6. A method for testing and selecting the best tungsten oxide-carbon dot-polyacrylic acid composite materials, characterized in that, Electrochemical tests were performed using the conductive flexible substrate of the tungsten oxide-carbon dot-polyacrylic acid composite material described in claim 5 as the working electrode, a platinum plate as the counter electrode, Ag / AgCl (1M KCl) as the reference electrode, and a 1M AlCl3·6H2O aqueous solution as the electrolyte; cyclic voltammetry curves were obtained at 10, 20, 50, 80, and 100 mV s. -1 The scanning range was between -1.0 and 1.0 V (vs. SCE); the CV curve was fitted and the charge capacity was calculated to study the reversible charge storage capacity and electrochemical activity; the transmission spectrum of the electrochromic thin film was fitted and the optical modulation range was calculated to study the spectral modulation capability, thereby obtaining a tungsten oxide-carbon dot-polyacrylic acid composite material with optimal ion transport performance and electrochromic optical modulation amplitude capability.

7. An application of a tungsten oxide-carbon dot-polyacrylic acid composite material, characterized in that, An electrochromic device with a sandwich structure was prepared using the tungsten oxide-carbon dot-polyacrylic acid composite material described in claim 5, and integrated with a piezoelectric thin film to form a self-powered electrochromic device. When the finger is bent, it exhibits high transmittance modulation amplitude and fast response color-changing characteristics on the surface of a conductive substrate.

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