Carbon quantum dot-wolfram oxide-bismuth oxyhalide composite material, preparation method and application, working electrode, photoelectrochemical detection system

Abstract

The application provides a carbon quantum dot-wolfram oxide-halogenated bismuth oxide composite material and a preparation method and application thereof, a working electrode and a photoelectrochemical detection system, and relates to the technical field of photoelectric detection. 18 O 49 / BiOX and carbon quantum dots (CQD) loaded on the W 18 O 49 / BiOX; X in the W 18 O 49 / BiOX is a halogen element. The CQD is coupled with the W 18 O 49 / BiOX, so that the solar spectrum utilization efficiency can be effectively improved, the built-in electric field between the two can be enhanced, and the electron-hole separation is promoted; the CQD also has good conductivity, so that the charge transfer resistance can be reduced, the migration of photoexcited carriers is accelerated, and the photoelectric response capability of the photoelectrochemical detection system using the W 18 O 49 / BiOX as a photoactive material and the self-powered detection capability are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection technology, specifically relating to a carbon quantum dot-tungsten oxide-bismuth oxide composite material and its preparation method and application, a working electrode and its application, and a photoelectrochemical detection system. Background Technology

[0002] A photodetector is an electronic device that converts light signals into electrical signals, based on the photoelectric effect within semiconductor materials. Among these, photoelectrochemical detection systems (PECs) have attracted widespread attention and research due to their advantages such as fast response speed, self-powered operation, high cost-effectiveness, and environmental friendliness. Generally, the active semiconductor material on the photoanode of a PEC detector directly affects the actual working capability of the device; therefore, the simple and efficient preparation of active semiconductor materials for the photoanode is crucial for obtaining excellent PEC detectors.

[0003] Tungsten oxide (BiOBr) is a visible light semiconductor material with a narrow bandgap (2.5 eV), exhibiting good visible light absorption efficiency and stability. Its suitable bandgap, unique layered structure, and natural interlayer built-in electric field also make BiOBr an increasingly popular visible light semiconductor material. However, these single semiconductor materials all suffer from drawbacks such as high photogenerated electron-hole recombination efficiency and unsatisfactory photogenerated electron-hole separation ability.

[0004] Among various methods to improve the separation efficiency of photogenerated electron-hole pairs, heterostructure construction strategies are considered an effective approach. Numerous studies have shown that constructing heterostructure semiconductors using semiconductors with suitable band gaps can create a stepped band gap between the two materials. When photogenerated electrons are generated, electrons can transfer from the higher conduction band to the lower conduction band, while holes can transfer from the lower valence band to the higher valence band, thus effectively improving the problem of high electron-hole recombination efficiency in single semiconductor materials. For example, Chinese patent CN111589460A discloses a W... 18 O 49 / BiOX composite photocatalyst material, wherein X is chlorine, bromine or iodine, and W 18 O 49 / BiOX composite photocatalysts can effectively separate photogenerated carriers and improve catalytic efficiency. However, based on the above W 18 O 49 The photodetector of the / BiOX composite photocatalytic material does not have good photoelectric response in a wide spectral range (375-800 nm). Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a carbon quantum dot-tungsten oxide-bismuth oxide composite material (CQD / W).18 O 49 The invention relates to CQD / W (BiOX) and its preparation method and applications, working electrode and its applications, and photoelectrochemical detection system. 18 O 49 / BiOX exhibits excellent photoelectric response in a wide spectral range (375–800 nm).

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a carbon quantum dot-tungsten oxide-bismuth oxide composite material, comprising W 18 O 49 / BiOX and load in the W 18 O 49 Carbon quantum dots on / BiOX; the W 18 O 49 In / BiOX, X represents a halogen.

[0008] Preferably, the loading of the carbon quantum dots is 40–60 wt%.

[0009] This invention provides a method for preparing the carbon quantum dot-tungsten oxide-bismuth oxyhalide composite material described in the above technical solution, comprising the following steps:

[0010] W 18 O 49 BiOX, carbon quantum dots, and water are mixed and heat-treated to obtain a carbon quantum dot-tungsten oxide-bismuth oxide composite material; the W 18 O 49 In / BiOX, X represents a halogen.

[0011] Preferably, the W 18 O 49 The mass ratio of BiOX to carbon quantum dots is 1:0.4–0.6;

[0012] The solid-liquid ratio of the carbon quantum dots to water is 1–1.5 g: 1 L;

[0013] The heat treatment is performed at a temperature of 60–80°C for a duration of 6–12 hours.

[0014] Preferably, the W 18 O 49 The preparation method of / BiOX includes the following steps:

[0015] W 18 O 49 A mixture of hexadecyltrimethylammonium halide and an organic solvent yields an organic phase;

[0016] A bismuth source, acid, and water are mixed to obtain an aqueous phase;

[0017] The organic phase and aqueous phase are mixed and subjected to an interfacial emulsion reaction to obtain W. 18 O 49 / BiOX.

[0018] Preferably, the method for preparing the carbon quantum dots includes the following steps: mixing an acidic carbon source, an organic amine, and water, and carrying out a hydrothermal reaction to obtain carbon quantum dots.

[0019] This invention provides a working electrode, characterized in that it includes a photoactive material layer on the surface of a conductive substrate; the photoactive material layer is made of carbon quantum dot-tungsten oxide-bismuth oxyhalide composite material as described in the above technical solution or carbon quantum dot-tungsten oxide-bismuth oxyhalide composite material prepared by the preparation method described in the above technical solution.

[0020] Preferably, the thickness of the photoactive material layer is 10–50 μm.

[0021] This invention provides the application of the carbon quantum dot-tungsten oxide-bismuth oxyhalide composite material, the carbon quantum dot-tungsten oxide-bismuth oxyhalide composite material prepared by the preparation method described in the above technical solution, or the working electrode described in the above technical solution in photochemical detectors or photoelectrochemical detectors.

[0022] This invention provides a photoelectrochemical detection system, characterized in that it includes an electrolytic cell, a three-electrode system and an electrolyte located in the electrolytic cell; the three-electrode system includes a reference electrode, a counter electrode and the working electrode described in the above technical solution, and the light source used is a xenon lamp or sunlight.

[0023] This invention provides a carbon quantum dot-tungsten oxide-bismuth oxide composite material, comprising W 18 O 49 / BiOX and load in the W 18 O 49 Carbon quantum dots on / BiOX; the W 18 O 49 In / BiOX, X represents a halogen. This invention combines carbon quantum dots (CQDs) with W... 18 O 49 Coupling with / BiOX can effectively improve the utilization efficiency of the solar spectrum and enhance the built-in electric field between them, thereby promoting electron-hole separation; moreover, CQD has good conductivity, which can reduce charge transfer resistance, thereby accelerating the migration of photoexcited carriers and significantly improving W. 18 O 49 / BiOX serves as a photochemical or photoelectrochemical detector using photoactive materials, exhibiting photoelectric response capability and self-powered detection capability.

[0024] The present invention provides a CQD / W-based 18 O 49 / BiOX photoelectrochemical detection system, as a photoactive material, exhibits excellent photoelectric response detection capability in a wide spectral range (375–800 nm). Furthermore, this photoelectrochemical detection system can achieve self-powered operation without an external voltage, providing a key technology for low-cost, self-powered photoelectrochemical photodetectors. This has significant theoretical and practical implications for promoting the industrial application of self-powered photoelectrochemical photodetectors.

[0025] As shown in the test results of the embodiments, based on the CQD / W provided by the present invention 18 O 49 The / BiOBr composite photodetector exhibits excellent photoelectric response over a wide spectral range. Under illumination, the current density is generally higher than under no-illumination conditions when biased at 0–1V. Specifically, at a bias voltage of 0.4V, the relative photocurrent density is 80.3 nA·cm⁻¹. -2 The light responsivity is a single W. 18 O 49 5.3 times that of W 18 O 49 / BiOBr is 2.7 times that of BiOBr; at 0V, the relative response current density is 164 nA·cm. -2 The responsivity is 1.64 μA·W. -1 Meanwhile, this photochemical photodetector CQD / W 18 O 49 / BiOBr photocurrent rise time (t) at a bias voltage of 0.4V rise ) and fall time (t fall The times were 1.59s and 2.53s, respectively, while W 18 O 49 W 18 O 49 The rise and fall times of / BiOBr were 3.25s and 3.40s, and 3.89s and 4.39s, respectively, showing significant improvements in both rise and fall times; particularly important is CQD / W. 18 O 49 / BiOBr at no bias voltage t rise and t fall The response rise and fall times are 0.36s and 0.47s respectively, indicating faster response times. Furthermore, the photocurrent density remains relatively stable under both zero bias and 0.4V conditions, demonstrating that the CQD / W provided by this invention… 18 O 49 / BiOBr exhibits good stability in the fabrication of photochemical or photoelectrochemical detectors.

[0026] This invention provides a method for preparing the carbon quantum dot-tungsten oxide-bismuth oxyhalide composite material described in the above technical solution. The preparation method provided by this invention is simple, efficient, low-cost, environmentally friendly, and suitable for industrial production. Attached Figure Description

[0027] Figure 1 TEM image of the carbon quantum dots (CQDs) prepared in Example 1;

[0028] Figure 2 BiOBr and W prepared in Example 1 18 O 49 and CQD / W 18 O 49 XRD pattern of / BiOBr;

[0029] Figure 3 CQD and W prepared in Example 1 18 O 49 W 18 O 49 / BiOBr and CQD / W 18 O 49 FT-IR spectrum of / BiOBr;

[0030] Figure 4 W prepared in Example 1 18 O 49 W 18 O 49 / BiOBr and CQD / W 18 O 49 / BiOBr's UV diffuse reflectance spectrum;

[0031] Figure 5 W prepared in Example 1 18 O 49 (above), W 18 O 49 / BiOBr (middle) and CQD / W 18 O 49 Scanning electron microscope image of / BiOBr (below);

[0032] Figure 6 W prepared based on Example 1 18 O 49 W 18 O 49 / BiOBr and CQD / W 18 O 49 The transient photocurrent response (IT) curves of the photoelectrochemical photodetector of / BiOBr are shown, where (a) is the photocurrent response at 0.4V and (b) is the photocurrent response at 0 to 0.2V.

[0033] Figure 7 For CQD / W 18 O 49 The graph shows the photoresponse speed of the photoelectrochemical photodetector made of / BiOBr composite material, where (a) is the W 18 O 49 The rise and fall times at a bias voltage of 0.4V, (b) is W 18 O 49 The rise and fall times of / BiOBr at a bias voltage of 0.4V, (c) is CQD / W 18 O 49 The rise and fall times of / BiOBr at a bias voltage of 0.4V, (d) is CQD / W 18 O 49 / BiOBr rise and fall times at a bias voltage of 0 to 1V;

[0034] Figure 8 The stability test curve of the photodetector device prepared in Example 3 is shown. Detailed Implementation

[0035] This invention provides a carbon quantum dot-tungsten oxide-bismuth oxide composite material, comprising W 18 O 49 / BiOX and load in the W 18 O 49 Carbon quantum dots on / BiOX; the W 18 O 49 In / BiOX, X represents a halogen. In this invention, the halogen preferably includes chlorine, bromine, or iodine, more preferably bromine. In this invention, the loading amount of the carbon quantum dots (i.e., the percentage of carbon quantum dots in W) is... 18 O 49 The mass ratio of BiOX is preferably 40-60 wt%, more preferably 45-55 wt%, and even more preferably 50 wt%; the particle size of the carbon quantum dots is preferably 4-6 nm.

[0036] This invention provides a method for preparing the carbon quantum dot-tungsten oxide-bismuth oxyhalide composite material described in the above technical solution, comprising the following steps: W 18 O 49 BiOX, carbon quantum dots, and water are mixed and heat-treated to obtain a carbon quantum dot-tungsten oxide-bismuth oxide composite material; the W 18 O 49 In / BiOX, X represents a halogen.

[0037] Unless otherwise specified, all materials and equipment used in this invention are commercially available products in the field.

[0038] In this invention, the W 18 O 49 The mass ratio of BiOX to carbon quantum dots is preferably 1:0.4 to 0.6, more preferably 1:0.45 to 0.55, and even more preferably 1:0.5. In this invention, the W... 18 O 49 In / BiOX, X is a halogen, preferably including chlorine, bromine, or iodine, and more preferably bromine.

[0039] In this invention, the solid-liquid ratio of the carbon quantum dots to water is preferably 1-1.5 g:1 L, more preferably 1.1-1.4 g:1 L, and even more preferably 1.2-1.3 g:1 L.

[0040] In this invention, the mixing is preferably performed by: dispersing carbon quantum dots in water to obtain a carbon quantum dot dispersion; and mixing the carbon quantum dot dispersion with W. 18 O 49 / BiOX is subjected to ultrasonic mixing and stirring mixing in sequence; the ultrasonic mixing temperature is preferably room temperature, and the ultrasonic mixing time is preferably 30-60 min, more preferably 30-40 min; the ultrasonic mixing power is preferably <800W, more preferably 300W; the stirring mixing temperature is preferably room temperature, and the stirring mixing time is preferably 2-4 h, more preferably 3 h; the present invention does not have special limitations on the ultrasonic mixing power and stirring speed, as long as the raw materials are mixed evenly.

[0041] In this invention, the heat treatment temperature is preferably 60-80°C, more preferably 65-75°C, and even more preferably 70°C; the heat treatment time is preferably 6-12 hours, more preferably 6-10 hours, and even more preferably 6-8 hours; the heat treatment is preferably carried out in an oven.

[0042] This invention utilizes ultrasonic and low-temperature heat treatment techniques to process the aforementioned W... 18 O 49 / BiOX materials are effectively coupled with carbon quantum dots to construct CQD / W 18 O 49 The preparation method of the / BiOX composite material provided by this invention is simple in process, easy to operate, low in production cost, green and environmentally friendly, and suitable for industrial production.

[0043] Following the heat treatment, the present invention preferably further includes solid-liquid separation of the obtained heat treatment reaction solution, washing the obtained solid product with water, and drying it to obtain a carbon quantum dot-tungsten oxide-bismuth oxide composite material. The present invention does not have specific limitations on the solid-liquid separation; any solid-liquid separation method well known to those skilled in the art can be used, such as filtration, vacuum filtration, or centrifugation. In the present invention, the water used for washing preferably includes deionized water; the number of washings is preferably 4 to 5 times, and the washing is preferably centrifugal washing. In the present invention, the drying temperature is preferably 50 to 100°C, more preferably 60 to 80°C; the present invention does not have specific limitations on the drying time, drying to constant weight is sufficient.

[0044] In this invention, the W 18 O 49 The preparation method of / BiOX includes the following steps:

[0045] W 18 O 49 A mixture of hexadecyltrimethylammonium halide and an organic solvent yields an organic phase;

[0046] A bismuth source, acid, and water are mixed to obtain an aqueous phase;

[0047] The organic phase and aqueous phase are mixed and subjected to an interfacial emulsion reaction to obtain W. 18 O 49 / BiOX.

[0048] This invention will W 18 O 49 A mixture of hexadecyltrimethylammonium halide and an organic solvent yields an organic phase. In this invention, W in the organic phase... 18 O 49 The concentration of W is preferably 8–40 g / L, more preferably 10–30 g / L, and even more preferably 20 g / L; 18 O 49 W is preferred 18 O 49 Nanowires, the W 18 O 49The diameter is preferably 25–35 nm, and the length is preferably 600–1000 nm. In this invention, the concentration of hexadecyltrimethylammonium halide in the organic phase is preferably 15–45 g / L, more preferably 20–40 g / L, and even more preferably 30–35 g / L; the hexadecyltrimethylammonium halide preferably includes hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, or hexadecyltrimethylammonium iodide, more preferably hexadecyltrimethylammonium bromide; the function of the hexadecyltrimethylammonium halide is to provide a halogen source and to act as a selective adsorption site to regulate the morphology of BiOX. In this invention, the organic solvent preferably includes one or more of n-octane, chloroform, and n-hexane, more preferably n-octane.

[0049] In this invention, the W 18 O 49 The preparation method includes the following steps: dissolving a tungsten source in an alcohol solvent and carrying out a solvothermal reaction to obtain W. 18 O 49 In this invention, the tungsten source preferably includes tungsten chloride. In this invention, the alcohol solvent preferably includes anhydrous ethanol. In this invention, the solid-liquid ratio of the tungsten source to the alcohol solvent is preferably 0.075–0.15 g:30 mL, more preferably 0.08–0.12 g:30 mL, and even more preferably 0.1 g:30 mL. In this invention, the temperature of the solvothermal reaction is preferably 180–200 °C, more preferably 185–195 °C, and even more preferably 190 °C; the time of the solvothermal reaction is preferably 5–20 h, more preferably 6–10 h, and even more preferably 6–8 h. After the solvothermal reaction, this invention preferably further includes: performing solid-liquid separation on the obtained solvothermal reaction liquid, washing and drying the obtained solid product to obtain W. 18 O 49 This invention does not specifically limit the solid-liquid separation; any solid-liquid separation method well-known to those skilled in the art can be used, such as centrifugation, filtration, or vacuum filtration. In this invention, the washing solvent preferably includes an aqueous solution of ethanol or methanol, wherein the volume fraction of methanol in the aqueous ethanol solution is preferably 20-70%, more preferably 40-50%. In this invention, the drying temperature is preferably 50-80°C, more preferably 60-70°C; the drying time is preferably 20-48 hours, more preferably 24-30 hours; and the drying is preferably vacuum drying. This invention uses a one-step solvothermal method to prepare W... 18 O 49 The process is simple, the operation is easy, the cost is low, it is green and environmentally friendly, and it is suitable for industrial production.

[0050] This invention involves mixing a bismuth source, an acid, and water to obtain an aqueous phase. In this invention, the concentration of the bismuth source in the aqueous phase is preferably 30–90 g / L, more preferably 40–80 g / L, and even more preferably 50–60 g / L; the bismuth source preferably includes bismuth nitrate and / or bismuth halide, and the bismuth halide preferably includes bismuth chloride, bismuth bromide, or bismuth iodide. In this invention, the concentration of the acid in the aqueous phase is preferably 5–10 g / L, more preferably 6–9 g / L, and even more preferably 7–8 g / L; the acid preferably includes citric acid and / or boric acid. In this invention, the water preferably includes deionized water.

[0051] After obtaining the organic phase and the aqueous phase, the present invention mixes the organic phase and the aqueous phase and performs an interfacial emulsion reaction to obtain W. 18 O 49 / BiOX. In this invention, W in the organic phase 18 O 49 The mass ratio of the bismuth source in the aqueous phase to the organic phase is preferably 2-4:3-9, more preferably 2.5-3:4-6. In this invention, the mixing is preferably performed by adding the aqueous phase dropwise to the organic phase. This invention does not have a specific limitation on the dropping rate; uniform dropwise addition is acceptable. In this invention, the temperature of the interfacial emulsion reaction is preferably 10-30°C, more preferably 20-25°C; the reaction time is preferably 30-60 min, more preferably 30-50 min, and even more preferably 30-40 min. After the interfacial emulsion reaction, this invention preferably further includes: solid-liquid separation of the obtained interfacial emulsion reaction solution, washing and drying the obtained solid product to obtain W. 18 O 49 / BiOX. This invention does not specifically limit the solid-liquid separation; any solid-liquid separation method well-known to those skilled in the art can be used, such as centrifugation, filtration, or vacuum filtration. In this invention, the washing solvent preferably includes water and / or ethanol, and the water is preferably deionized water. In this invention, the drying temperature is preferably 60–80°C, more preferably 60–70°C; the drying time is preferably 24–48 h, more preferably 24–30 h; and the drying is preferably vacuum drying.

[0052] In this invention, the method for preparing carbon quantum dots preferably includes the following steps: mixing an acidic carbon source, an organic amine, and water, and performing a hydrothermal reaction to obtain carbon quantum dots. In this invention, the acidic carbon source preferably includes citric acid and / or boric acid. In this invention, the organic amine preferably includes ethylenediamine and / or 1,3-propylenediamine. In this invention, the mass ratio of the acidic carbon source to the volume of the organic amine is preferably 3g:0.75-1mL, more preferably 3g:0.8-1mL, and even more preferably 3g:0.9-1mL. In this invention, the solid-liquid ratio of the acidic carbon source to water is preferably 3g:10-30mL, more preferably 3g:15-20mL; the water preferably includes deionized water. In this invention, the mixing preferably involves mixing citric acid and water, adding the organic amine dropwise under stirring conditions, and continuing stirring and mixing. This invention does not have a specific limitation on the dropwise addition; it can be added dropwise at a uniform rate. The time for continuing stirring and mixing is preferably 10-30 minutes, more preferably 15-20 minutes. In this invention, the hydrothermal reaction temperature is preferably 180–200°C, more preferably 185–195°C, and even more preferably 190°C; the hydrothermal reaction time is preferably 8–12 h, more preferably 8–10 h, and even more preferably 8–9 h. After the hydrothermal reaction, this invention preferably further includes: cooling the obtained hydrothermal reaction solution to room temperature and then dialyzing it, and drying the obtained carbon quantum dot solution to obtain carbon quantum dots. This invention does not have a specific limitation on the cooling process; any cooling method well known to those skilled in the art can be used, such as natural cooling. In this invention, the molecular weight cutoff of the dialysis bag used for dialysis is preferably 6000–8000 Da, more preferably 7000 Da; the dialysis time is preferably 48–72 h, more preferably 48–55 h. In this invention, the drying is preferably freeze-drying, and the freeze-drying temperature is preferably -30–-40°C, more preferably -35°C. This invention does not have a specific limitation on the drying time; drying to constant weight is sufficient.

[0053] This invention provides a working electrode comprising a photoactive material layer on the surface of a conductive substrate; the photoactive material layer is made of the carbon quantum dot-tungsten oxide-bismuth oxide composite material described in the above-described technical solution or a carbon quantum dot-tungsten oxide-bismuth oxide composite material prepared by the preparation method described in the above-described technical solution. In this invention, the conductive substrate preferably comprises ITO conductive glass or FTO conductive glass. In this invention, the thickness of the photoactive material layer is preferably 10–50 μm, more preferably 20–40 μm, and even more preferably 20–30 μm.

[0054] In this invention, the preferred method for preparing the working electrode includes the following steps: pretreating a conductive substrate to obtain a pretreated conductive substrate; mixing a carbon quantum dot-tungsten oxide-bismuth oxide composite material with an organic solvent to obtain a slurry; coating the slurry onto the surface of the pretreated conductive substrate and then drying it to obtain the working electrode. In this invention, the pretreatment preferably includes sequential water washing, alcohol washing, and drying; the water used for water washing is preferably deionized water, and the water washing is preferably ultrasonic water washing; the alcohol used for alcohol washing preferably includes ethanol; the alcohol washing is preferably ultrasonic alcohol washing; the ultrasonic water washing and ultrasonic alcohol washing times are preferably 10–20 min, more preferably 10–15 min; the drying temperature (drying during the pretreatment process) is preferably 80–100 °C, more preferably 90 °C; this invention does not have a specific limitation on the drying time, drying to constant weight is sufficient; the drying is preferably carried out in an oven. In this invention, the concentration of the carbon quantum dot-tungsten oxide-bismuth oxide composite material in the slurry is preferably 4-5 wt%, more preferably 4.4-4.6 wt%; the organic solvent preferably includes one or more of N-methylpyrrolidone, N / N dimethylformamide, and N / N dimethylacetamide. In this invention, the drying temperature (drying after coating) is preferably 60-70°C, more preferably 65°C. This invention does not have a specific limitation on the drying time; drying to constant weight is sufficient.

[0055] This invention provides the application of the carbon quantum dot-tungsten oxide-bismuth oxyhalide composite material, the carbon quantum dot-tungsten oxide-bismuth oxyhalide composite material prepared by the preparation method described in the above technical solution, or the working electrode described in the above technical solution in photochemical detectors or photoelectrochemical detectors.

[0056] This invention also provides a photoelectrochemical detection system, comprising an electrolytic cell, a three-electrode system within the electrolytic cell, and an electrolyte; the three-electrode system includes a reference electrode, a counter electrode, and the working electrode described in the above-described technical solution, using a xenon lamp or sunlight as the light source. In this invention, the electrolytic cell preferably comprises a quartz photoelectrolytic cell that is transparent on all four sides. In this invention, the reference electrode preferably comprises an Ag / AgCl electrode. In this invention, the counter electrode preferably comprises Pt. In this invention, the electrolyte preferably comprises a Na₂SO₄ solution; the concentration of the electrolyte is preferably 0.5 mol / L.

[0057] In this invention, the preferred application conditions for the photoelectrochemical detection system include: the light source is a xenon lamp or simulated sunlight, and the irradiance of the light source is 100 mA·cm. -2The light source switching interval is 20s, the applied bias voltage is 0 to 1V (relative to the Ag / AgCl reference electrode), the bias voltage application time is 400s, the linear sweep voltammetry (LSV) test range is -0.4V to 1.6V, and the preferred scan range is 10mV / s.

[0058] To further illustrate the present invention, the carbon quantum dot-tungsten oxide-bismuth oxide composite material, its preparation method and application, working electrode, and photoelectrochemical detection system are described in detail below with reference to the accompanying drawings and embodiments. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0059] Example 1

[0060] CQD / W 18 O 49 Preparation of / BiOBr

[0061] (1) 0.1 g of tungsten chloride was placed in a reaction vessel, and 30 mL of anhydrous ethanol was added under stirring. After complete dissolution, the mixture was reacted at 200 °C for 6 h. After the reaction was completed, the reaction solution was filtered through a 0.25 μm filter membrane, washed with deionized water and ethanol respectively, and dried under vacuum at 60 °C for 24 h to obtain tungsten oxide powder (W). 18 O 49 ).

[0062] (2) Dissolve 0.485 g of bismuth nitrate pentahydrate and 0.072 g of citric acid in 7.5 mL of deionized water to obtain an aqueous phase. Add 0.25 g of the W... 18 O 49 Dispersed in 12.5 mL of n-octane containing 0.364 g of hexadecyltrimethylammonium bromide, the aqueous phase was added dropwise, and the reaction was carried out for 30 min. After centrifugation, the resulting solid product was washed and dried under vacuum at 60 °C for 24 h to obtain tungsten oxide / bismuth oxybromide (W). 18 O 49 / BiOBr, abbreviated as WB).

[0063] (3) Place 3g of citric acid in the liner of a 50mL reaction vessel, add 15mL of deionized water, and add 0.8mL of ethylenediamine dropwise while stirring. After stirring for 15min, react at 190℃ for 8h. After the reaction is complete, wait for the reaction vessel to cool to room temperature, remove the liner, dialyze the resulting solution through a dialysis bag with a molecular weight cutoff of 6000~8000Da for 48h, and freeze-dry at -30~-40℃ to obtain carbon quantum dot powder.

[0064] (4) The W 18 O 49BiOBr (50 mg) was dispersed in 20 mL of deionized water with a carbon quantum dot concentration of 1.3 mg / mL, sonicated for 0.5 h, stirred for 3 h, and heat-treated in an oven at 70 °C for 6 h. After centrifugation, the resulting solid product was washed with deionized water and centrifuged 4–5 times, and then vacuum dried at 60 °C to constant weight to obtain the carbon quantum dot-tungsten oxide-bismuth oxybromide composite material (CQD / W). 18 O 49 / BiOBr, abbreviated as CWB).

[0065] Example 2

[0066] CQD / W was prepared according to the method in Example 1. 18 O 49 / BiOBr differs from Example 1 only in that: the reaction temperature in step (1) is 180°C; the ultrasonic time in step (4) is 0.2h, the stirring time is 2h, and the reaction temperature is 60~70°C.

[0067] Example 3

[0068] Fabrication of photoelectrochemical photodetectors

[0069] (1) Clean the 1.5×1.5cm ITO conductive glass by ultrasonic cleaning in deionized water and ethanol for 10 min respectively, dry it in an oven at 90℃, and leave a 1cm margin. 2 Used for sample preparation; 50 mg of CQD / W prepared in Example 1 was used. 18 O 49 / BiOBr is mixed evenly with 1 mL of N-methylpyrrolidone, and 50 μL of the slurry is coated onto a pretreated ITO conductive glass with an area of ​​1.0 × 1.0 cm. The mixture is then dried at 60 °C to obtain the working electrode.

[0070] (2) At room temperature, using Ag / AgCl as the reference electrode, a Pt sheet as the counter electrode, and 0.5 mol / L Na₂SO₄ aqueous solution as the electrolyte, the above three-electrode system was placed in a four-sided transparent quartz photoelectrolysis cell to construct a photoelectric optical detector. The working electrode of the obtained photoelectric optical detector was illuminated with parallel light from a xenon lamp source, with a light-off / light-on time interval of 20 s. All applied bias voltages were relative to the Ag / AgCl reference electrode. At room temperature, the required light source was simulated sunlight (irradiance of 100 mA·cm⁻¹). -2 A bias voltage was applied to the assembled device, relative to the Ag / AgCl reference electrode. Linear sweep voltammetry (LSV) was performed over a range of -0.4V to 1.6V (vs. Ag / AgCl) at a scan rate of 10 mV·s. -1The bias voltage applied to the photocurrent curve (it) ranged from 0V to 1V (vs. Ag / AgCl) for 400s, with a switching interval of 20s between xenon lamps.

[0071] Example 4

[0072] The photoelectrochemical photodetector was prepared according to the method of Example 3, the only difference being the CQD / W used. 18 O 49 / BiOBr was prepared in Example 2.

[0073] Comparative Example 1

[0074] The photoelectrochemical photodetector was prepared according to the method of Example 3, the only difference being that the CQD / W... 18 O 49 / BiOBr is replaced with W prepared in Example 1 18 O 49 .

[0075] Comparative Example 2

[0076] The photoelectrochemical photodetector was prepared according to the method of Example 3, the only difference being that the CQD / W... 18 O 49 / BiOBr is replaced with W prepared in Example 1 18 O 49 / BiOBr (denoted as WB).

[0077] Figure 1 TEM image of the carbon quantum dots (CQDs) prepared in Example 1. Figure 1 It can be seen that CQDs exhibit quasi-spherical and monodisperse nanoparticle morphology, with a diameter range of approximately 4–6 nm.

[0078] Figure 2 BiOBr and W prepared in Example 1 18 O 49 and CQD / W 18 O 49 XRD pattern of / BiOBr. Figure 2 It can be seen that pure W 18 O 49 At 23.5 respectively ° 47.9 ° The presence of diffraction peaks corresponding to the (010) and (020) crystal planes corresponds to that of the standard card (JCPDS No. 732061), and the absence of impurity peaks indicates that the prepared sample is W. 18 O 49The purity is high; pure BiOBr exhibits diffraction peaks at 10.9°, 25.3°, 32.3°, 39.4°, 46.3°, 57.3°, 67.6°, and 76.9° corresponding to the (001), (011), (110), (112), (020), (212), (220), and (130) crystal planes of BiOBr, respectively, which are consistent with the standard card (JCPDS NO. 732061), indicating that the BiOBr prepared in this invention is pure BiOBr; while CQD, W 18 O 49 After being combined with BiOBr, its XRD pattern not only showed the corresponding W... 18 O 49 The diffraction peaks of BiOBr also showed characteristic diffraction peaks around 22°, possibly corresponding to the (002) crystal plane of carbon quantum dots, indicating that the present invention successfully synthesized CQD and W through reaction. 18 O 49 It is assembled together with BiOBr.

[0079] Figure 3 CQD and W prepared in Example 1 18 O 49 W 18 O 49 / BiOBr and CQD / W 18 O 49 FT-IR spectrum of / BiOBr. (By...) Figure 3 It can be seen that pure W 18 O 49 At 600-800cm -1 The presence of characteristic peaks caused by WO bond vibrations indicates that the product is tungsten oxide; in W... 18 O 49 / BiOBr and CQD / W 18 O 49 In the spectral curves of the two materials / BiOBr, at approximately 520 cm⁻¹ -1 Characteristic peaks caused by Bi-O vibrations appeared in all regions, which is evident in pure W. 18 O 49 It was not found in the sample, and it was present at a depth of 600–800 cm. -1 Both samples also showed characteristic peaks corresponding to Bi-O vibrations, indicating that W exists in both samples. 18 O 49 And BiOBr; meanwhile, pure CQD at approximately 1560 cm -1 and 1770cm -1 Characteristic peaks caused by CO and C=O vibrations appeared at [location], and the same characteristic peaks also appeared at CQD / W. 18 O 49In / BiOBr, it is shown that the reaction successfully loaded CQD onto W under the action of ultrasound and heat treatment. 18 O 49 / BiOBr, combined with XRD, indicates CQD, W 18 O 49 It was successfully combined with BiOBr to create a new type of CQD / W 18 O 49 / BiOBr composite material.

[0080] Figure 4 W prepared in Example 1 18 O 49 W 18 O 49 / BiOBr and CQD / W 18 O 49 The UV diffuse reflectance spectrum of / BiOBr is derived from... Figure 4 It can be seen that, with W 18 O 49 and W 18 O 49 Compared to / BiOBr, CQD / W 18 O 49 / BiOBr exhibits good light absorption efficiency from 375 to 800 nm (ultraviolet and visible light regions), indicating that CQD / W 18 O 49 / BiOX, as a photoelectrochemical detection system based on photoactive materials, exhibits excellent photoelectric response detection capabilities across a wide spectral range (375–800 nm).

[0081] Figure 5 W prepared in Example 1 18 O 49 (above), W 18 O 49 / BiOBr (middle) and CQD / W 18 O 49 Scanning electron micrograph of / BiOBr (bottom). (From...) Figure 5 It can be seen that W 18 O 49 It exhibits a one-dimensional nanowire structure with relatively uniform thickness, a diameter of approximately 30 nm, and a length ranging from approximately 600 nm to 1 μm; after being combined with BiOBr, the resulting two-dimensional BiOBr nanosheets and one-dimensional W 18 O 49 Nanowires interact to form a wire-sheet composite structure; W 18 O 49 After being combined with CQD under heat treatment, / BiOBr exhibits a linear-sheet composite structure that aggregates with each other, often presenting a linear-sheet stacked structure.

[0082] To further understand the sample's light response performance to sunlight, the responsivity (R) is obtained from the following formula: R = I / J light Where I is the relative photocurrent density (unit mA·cm²). -2 ), J Light It is the irradiance of the light source. The relative photocurrent intensity is the photocurrent when the light is on minus the photocurrent when the light is off. The photocurrent density is the relative photocurrent intensity divided by the area of ​​the active material. Figure 6 W prepared based on Example 1 18 O 49 W 18 O 49 / BiOBr and CQD / W 18 O 49 The transient photocurrent response (IT) curves of the / BiOBr photoelectrochemical photodetector are shown, where (a) is the photocurrent response at 0.4V and (b) is the photocurrent response from 0 to 0.2V. Figure 6 It can be seen that a single W 18 O 49 The response under simulated sunlight is very weak, with a photocurrent density of approximately 15.2 nA·cm⁻¹. -2 Moreover, it is generally unstable, with a response time of 152 nA·W. -1 W after compounding BiOBr 18 O 49 The / BiOBr material exhibits a photocurrent density of 32.7 nA·cm under the same simulated sunlight. -2 The response time is 372 nA·W. -1 , with W 18 O 49 Compared to the previous version, the response capability was improved by approximately 2 times; for CQD / W modified by CQD 18 O 49 / BiOBr significantly improves the responsiveness and stability to simulated sunlight, achieving a photocurrent density of 80.3 nA·cm⁻¹. -2 The response time is 814 nA·W. -1 CQD / W 18 O 49 / BiOBr's responsiveness is W 18 O 49 5.3 times that of W 18 O 49 2.3 times that of / BiOBr.

[0083] Photoresponse speed is an important indicator for evaluating photodetectors. It refers to the time required to effectively detect a light signal and assesses the sensitivity of a photodetector to light signals. A photodetector with a fast response speed can achieve efficient light detection. Taking the photocurrent response under a bias voltage of 0.4V as an example, the photocurrent rise time (t...) rise ) and fall time (t fall ) refers to the time interval between the rise and fall of the photoresponse current (from 10% to 90% and 90% to 10% of the peak value of the photocurrent intensity). Figure 7 The graph shows the photoresponse speed of a series of materials, where (a) is W. 18 O 49 The rise and fall times at a bias voltage of 0.4V, (b) is W 18 O 49 The rise and fall times of / BiOBr at a bias voltage of 0.4V, (c) is CQD / W 18 O 49 The rise and fall times of / BiOBr at a bias voltage of 0.4V, (d) is CQD / W 18 O 49 / BiOBr's rise and fall times at a bias voltage of 0–1V. Figure 7 It can be seen that, based on CQD / W 18 O 49 A photoelectrochemical photodetector made of / BiOBr composite material under a bias voltage of 0.4V t rise and t fall The values ​​are 1.59s and 2.53s, respectively. Using the same method, calculate the t values ​​for the same time intervals from 0 to 1V. rise and t fall Overall t rise It must be faster than t fall The response time is fastest when no power is required. rise and t fall The times were 0.36s and 0.47s, respectively.

[0084] The switching light response of the CWB-based photoelectrochemical photodetector was tested for up to 1000 seconds. Figure 8 This is a stability test curve of the photodetector device prepared in Example 3. Figure 8 It can be seen that after 1000 seconds of testing, the photocurrent intensity remained relatively stable under both zero bias and 0.4V conditions, without significant changes, indicating that the CQD / W 18 O 49 / BiOBr exhibits good stability in the fabrication of photoelectrochemical detection systems.

[0085] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. The application of a carbon quantum dot-tungsten oxide-bismuth oxide composite material in a photoelectrochemical detector, characterized in that, The carbon quantum dot-tungsten oxide-bismuth oxide composite material includes W 18 O 49 / BiOBr and load in the W 18 O 49 Carbon quantum dots on / BiOBr; The W 18 O 49 The preparation method of / BiOBr includes the following steps: W 18 O 49 A mixture of hexadecyltrimethylammonium bromide and an organic solvent yields an organic phase. A bismuth source, acid, and water are mixed to obtain an aqueous phase; The organic phase and aqueous phase are mixed and subjected to an interfacial emulsion reaction to obtain W. 18 O 49 / BiOBr.

2. The application according to claim 1, characterized in that, The loading of the carbon quantum dots is 40~60wt%.

3. The application according to claim 1 or 2, characterized in that, The preparation method of the carbon quantum dot-tungsten oxide-bismuth oxide composite material includes the following steps: W 18 O 49 BiOBr, carbon quantum dots, and water are mixed and heat-treated to obtain a carbon quantum dot-tungsten oxide-bismuth oxide composite material.

4. The application according to claim 3, characterized in that, The W 18 O 49 The mass ratio of BiOBr to carbon quantum dots is 1:0.4~0.6; The solid-liquid ratio of the carbon quantum dots to water is 1~1.5g:1L; The heat treatment is performed at a temperature of 60-80°C for 6-12 hours.

5. The application according to claim 2 or 4, characterized in that, The method for preparing carbon quantum dots includes the following steps: mixing an acidic carbon source, an organic amine, and water, and carrying out a hydrothermal reaction to obtain carbon quantum dots.

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