Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite photoelectric material and preparation method and application thereof

Abstract

The application discloses an Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite photoelectric material and a preparation method and application thereof, belongs to the field of photoelectrochemistry, and is characterized in that a layer of Au film is decorated on an Ag cube, a layer of N-(2-hydroxyphenyl) acetylamino and thiol-modified pillar[5]arene is wrapped on the surface of Ag@Au NCs, Ag@Au@HE / SH-P5 is used as a photoactive material, a signal on-off type photoelectrochemical PEC sensing system is designed, and the system is used for detecting hydroxyl radicals; the excellent conductivity of Ag@Au bimetal, the high mobility of MoS2 and the band gap of Bi2MoO6 are helpful to improving the separation efficiency of photo-generated electrons and holes, reducing the recombination of electron-hole pairs, and based on the multiple signal amplification capacity of Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2, the composite electrode shows an excellent linear range when detecting hydroxyl radicals.

Description

Technical Field

[0001] This invention belongs to the field of photoelectrochemical technology, specifically relating to an Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite photoelectric material, its preparation method, and its application. Background Technology

[0002] Reactive oxygen species (ROS) are a class of highly oxidizing oxygen molecules, including both free radicals and non-free radical oxidants, and are increasingly becoming a research hotspot in areas such as aging, inflammation, cancer, and cell signaling. Among them, hydroxyl radicals (•OH) are the most potent and shortest-lived ROS, capable of damaging proteins, lipids, and DNA. In biological systems, •OH is mainly produced through H₂O₂ conversion and transition metal-mediated Fenton reactions, but its excessive accumulation can disrupt cell metabolism, cause structural damage, and even lead to programmed cell death. Therefore, developing highly sensitive and selective photoelectrochemical (PEC) techniques is crucial for •OH monitoring and helps in understanding related pathophysiological processes. Although various •OH detection methods have been established, including fluorescence sensors / probes, colorimetric methods, and electrochemical techniques, their insufficient sensitivity, selectivity, and stability often affect the accurate measurement of concentration. In contrast, the PEC method significantly improves sensitivity and stability through a unique "photo-electric signal conversion" mechanism. For example, Zhou et al. deposited NH2-MIL-125(Ti) on FTO / TiO2 nanocones using a seed-assisted solvothermal method. By utilizing the quantum effect and tip effect of TiO2 nanocones, combined with the built-in electric field at the heterojunction interface to drive electron transport, they achieved highly sensitive detection of carcinoembryonic antigen (CEA).

[0003] As a core functional component of photoelectrochemical sensors, the properties of the photosensitive material directly determine the detection sensitivity. Bismuth molybdate (Bi₂MoO₆) has shown great potential in PEC applications due to its suitable band gap, excellent chemical stability, and simple synthesis method. However, the rapid recombination of photogenerated electron-hole pairs restricts its practical application. To solve this problem, it can be effectively alleviated by constructing heterojunctions with matched band structures. Among them, MoS₂, with its unique two-dimensional layered structure, can provide abundant active sites for the target analyte, thereby further improving the detection sensitivity. In the MoS₂ / Bi₂MoO₆ heterojunction system, photogenerated electrons transfer from the conduction band of MoS₂ to the conduction band of Bi₂MoO₆, while holes migrate from the valence band of Bi₂MoO₆ to MoS₂. This space charge separation mechanism can effectively suppress carrier recombination, thereby significantly enhancing the photocurrent response.

[0004] Gold and silver nanoparticles have attracted widespread attention due to their unique optical properties. Gold nanoparticles (Au NPs) exhibit excellent optical performance, mainly due to their good chemical stability, biocompatibility, and localized surface plasmon resonance effect. While silver nanoparticles (Ag NPs) are more outstanding in enhancing light absorption and promoting charge separation, the release of silver ions can cause cytotoxicity, which severely limits their practical applications. To overcome this shortcoming, researchers have proposed the silver-core gold-shell (Ag@Au) nanostructure as an effective solution. This structure successfully combines the light absorption capacity of the silver core with the chemical inertness and biocompatibility of the gold shell. However, such core-shell structures still have some drawbacks in practical applications: their high surface energy and nanoscale characteristics make them prone to aggregation under van der Waals forces, thereby weakening light absorption capacity, reducing photogenerated carrier yield, and ultimately affecting detection sensitivity; at the same time, due to the lack of specific recognition groups on the surface, interfering substances are prone to non-specific adsorption, leading to insufficient selectivity and decreased detection accuracy.

[0005] Based on this, columnar aromatics have been introduced into the field of photoelectrochemical detection due to their unique molecular structure. On the one hand, their highly symmetrical columnar cavity structure can achieve precise capture of specific target molecules through size matching and host-guest recognition mechanisms; on the other hand, their electron-rich cavity and modifiable functional groups (such as -NH2, -COOH, -SH, etc.) can be further functionalized to expand recognition sites, thereby significantly improving the specificity and recognition ability of the sensor. For example, Wang et al. constructed columnar aromatics [5] that were modified with both mercapto and borate ester groups. In this case, -SH was combined with Au NPs through Au-S bonds, while the B(OR)3 group reacted with the target analyte H2O2 to achieve the detection of H2O2 concentration. Therefore, we designed a columnar aromatic [5] containing both -SH and N-(2-hydroxyphenyl)acetamide groups, and utilized the N-(2-hydroxyphenyl)acetamide group to react specifically with •OH, thereby achieving sensitive and specific detection of •OH.

[0006] Therefore, it is expected that the designed Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material sensor will open up a completely new way to detect hydroxyl radicals, providing an efficient and sensitive tool for early disease detection and monitoring. Summary of the Invention

[0007] Technical problem solved: This invention provides an Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material, its preparation method, and its application, which solves the core technical problems of existing technologies, such as low detection sensitivity, limited detection range, expensive instruments, need for specialized operators, low efficiency, slow speed, and difficulty in operation.

[0008] To achieve the above objectives, this application provides the following technical solution: A method for preparing Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material involves in-situ growth of Bi2MoO6 to modify MoS2, forming a Bi2MoO6-MoS2 heterojunction. Then, HE / SH-P5 functionalized gold-silver core-shell nanocubes (Ag@Au@HE / SH-P5) are distributed on the Bi2MoO6-MoS2 heterojunction to obtain the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material. The specific steps include: Step 1: Preparation of column-shaped aromatic hydrocarbon HE / SH-P5 modified with N-(2-hydroxyphenyl)acetamido and mercapto groups [5]: ; The second step involves preparing a cubic silver nanoparticle solution (Ag NCs) via thermal reduction: 10–20 mL of a 1,2-propanediol solution containing 173 μM polyvinylpyrrolidone (PVP) with a volume ratio of Mw=58000 is stirred at 140–160 °C for 1–1.5 h. Then, 0.5–1.5 mL of a 1,2-propanediol solution containing 1 mM NaCl is added. After 5–8 min, 3–5 mL of a 1,2-propanediol solution containing 0.15 MAgNO3 is added dropwise. The reaction continues for 35–45 min to obtain a silver-green suspension. The suspension is then centrifuged and washed 3–6 times with ultrapure water at 6000–7000 rpm to obtain pure silver nanocubes. Finally, the centrifuged and washed silver nanocubes are dispersed in 20–30 mL of ultrapure water for storage to obtain a silver nanocube solution. The third step involved synthesizing Ag@Au core-shell nanocubes via a reduction method and an in-situ growth method: First, 80–110 μL of 25.4 mM HAuCl4 was mixed with 2–4 mL of 20 mM NaOH and 17–19 mL of ultrapure water, and stirred at room temperature for 0.5–1.5 h to prepare 0.1 mM Au(OH)4. - Next, take 40-80 mg of PVP, dilute it with 1-2 mL of deionized water, and heat it to 50-60 °C. After 2-5 min, add 500-700 μL of 100 mM ascorbic acid and 500-700 μL of 200 mM NaOH. Incubate for 5-15 min, then add 500-700 μL of silver nanocube solution. After reacting for 10-15 min, add Au(OH)4 dropwise. -The precursor solution was reacted for 5-10 min to obtain the final product. The final product was centrifuged and washed 3-6 times with ultrapure water at 5000-7000 rpm to obtain Ag@Au core-shell nanocubes. The obtained Ag@Au core-shell nanocubes were diluted with 5-10 mL of deionized water to obtain Ag@Au core-shell nanocube solution Ag@Au NCs. The fourth step involves dispersing 2-2.5 mg of HE / SH-P5 in 1-1.2 mL of Ag@Au core-shell nanocube solution (Ag@Au NCs) at a mass-to-volume ratio, followed by sonication for 20-40 minutes to synthesize Ag@Au@HE / SH-P5 composite optoelectronic materials. The fifth step involves preparing flower-like Bi₂MoO₆ using a one-pot hydrothermal method: 0.2–0.4 g of Bi(NO₃)₃·5H₂O and 0.05–0.1 g of Na₂MoO₄·2H₂O are dissolved in a mixed solvent containing 30–40 mL of ethylene glycol and 30–40 mL of ethanol at a mass-to-volume ratio. The mixture is stirred for 30–35 min to obtain a transparent solution, which is then heated in an autoclave at 160–180 °C for 20–24 h. The product is then centrifuged three times at 6000–8000 rpm for 5–10 min, alternating between ethanol and ultrapure water. Finally, the centrifuged sample is vacuum dried, and the yellow Bi₂MoO₆ powder, i.e., flower-like Bi₂MoO₆, is collected for further use. Step 6: Prepare Bi2MoO6-MoS2 heterojunctions via in-situ growth: Dissolve 0.03-0.1 g of sodium molybdate in 30-40 mL of ultrapure water by mass-volume ratio, then add 0.02-0.08 g of thioacetamide, and stir the mixture at 500-800 rpm for 1-1.2 h to ensure homogeneity; add 0.05-0.18 g of Bi2MoO6 to the above mixed solution, and continue stirring at 500-800 rpm for 3-3.5 h, then heat in an autoclave at 180-200℃ for 24-26 h, and centrifuge the product three times at 8000-10000 rpm for 5-10 min with ultrapure water; finally, vacuum dry the sample to obtain Bi2MoO6-MoS2 heterojunctions. Step 7: Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 was synthesized using a physical adsorption method: 2-2.5 mL of the Ag@Au@HE / SH-P5 composite optoelectronic material obtained in step 4 was added dropwise into 1.5-2 mg of the Bi2MoO6-MoS2 heterojunction obtained in step 6 according to the mass-volume ratio. The mixture was stirred at 600-800 rpm for 5-10 min to obtain the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 heterojunction, i.e., the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material.

[0009] Further, in the second step, a cubic silver nanoparticle solution (Ag NCs) was prepared by thermal reduction: 10 mL of a 1,2-propanediol solution containing 173 μM polyvinylpyrrolidone (PVP) with a volume ratio of Mw = 58000 was stirred at 160 °C for 1 hour, followed by the addition of 1 mL of a 1,2-propanediol solution containing 1 mM NaCl. After 5 minutes, 4 mL of a 1,2-propanediol solution containing 0.15 M AgNO3 was added dropwise, and the reaction was continued for 40 minutes to obtain a silver-green suspension. The suspension was then centrifuged and washed 5 times with ultrapure water at 7000 rpm to obtain pure silver nanocubes. Finally, the centrifuged and washed silver nanocubes were dispersed in 20 mL of ultrapure water for storage to obtain a silver nanocube solution.

[0010] Further, the third step is as follows: First, take 100 μL of 25.4 mM HAuCl4, 2 mL of 20 mM NaOH, and 17.9 mL of ultrapure water, mix them, and stir at room temperature for 1 hour to prepare 0.1 mM Au(OH)4. - The precursor solution was prepared by first diluting 1 mL of 40 mg PVP with 1–2 mL of deionized water and heating to 60°C for 2 minutes. Then, 500 μL of 100 mM ascorbic acid and 500 μL of 200 mM NaOH were added and incubated for 10 minutes. Next, 700 μL of silver nanocube solution was added and reacted for 10 minutes. Finally, Au(OH)₄ was added dropwise. - The precursor solution was reacted for 8 min to obtain the final product. The final product was washed 5 times with ultrapure water at 7000 rpm to obtain Ag@Au core-shell nanocubes. The obtained Ag@Au core-shell nanocubes were diluted with 5-10 mL of deionized water to obtain Ag@Au core-shell nanocube solution.

[0011] Further, the fourth step specifically involves dispersing 2.2 mg HE / SH-P5 in 1.1 mL of Ag@Au core-shell nanocube solution (Ag@Au NCs) according to the mass-volume ratio, and sonicating for 30 min to synthesize Ag@Au@HE / SH-P5 composite optoelectronic materials.

[0012] Further, the fifth step specifically involves preparing flower-like Bi2MoO6 using a one-pot hydrothermal method: 0.243 g Bi(NO3)3·5H2O and 0.06 g Na2MoO4·2H2O are dissolved in a mixed solvent containing 40 mL ethylene glycol and 40 mL ethanol according to the mass-to-volume ratio. The mixture is stirred for 30-35 min to obtain a transparent solution, which is then heated in a high-pressure autoclave at 170 °C for 25 h. The product is then centrifuged three times at 7000 rpm for 8 min each time, alternating between ethanol and ultrapure water. Finally, the centrifuged sample is vacuum dried, and the yellow Bi2MoO6 powder, i.e., flower-like Bi2MoO6, is collected for further use.

[0013] An Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material prepared by any of the above preparation methods.

[0014] This application also discloses the application of Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material prepared by any of the above preparation methods in a signal-on-off type photoelectrochemical PEC biosensor system.

[0015] Furthermore, in a surface area of ​​0.07 cm² 2 Ten μL of Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material was dropped onto a glassy carbon electrode GCE to prepare an Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 / GCE nanocomposite electrode.

[0016] Furthermore, the signal-on-off type photoelectrochemical PEC biosensor system uses a traditional three-electrode system, with an Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 / GCE nanocomposite electrode as the working electrode, a platinum mesh as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. A xenon lamp is used to simulate a visible light source to irradiate the surface of the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 / GCE nanocomposite electrode, and the shading interval is controlled as an adjustable "on-off" state. Photoelectrochemical detection is then performed using an electrochemical workstation in an electrolyte containing para-hydroxyl radicals.

[0017] The working principle of the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material described in this application is as follows: Under visible light irradiation, Ag@Au core-shell nanocubes are excited to generate electrons and holes. The conduction band of MoS2 can accept electrons from Ag@Au. Due to the energy level matching between Bi2MoO6 and MoS2, electrons are transferred to Bi2MoO6 and eventually reach the electrode to complete the electron transfer. The excellent conductivity of the Ag@Au bimetallic material, the host-guest complexation between HE / SH-P5 and •OH, the bonding between MoS2 and Bi2MoO6, the high mobility of MoS2, and the moderate band gap of Bi2MoO6 all contribute to improving the separation efficiency of photogenerated electrons and holes and reducing the recombination probability. These materials work synergistically to exhibit excellent detection performance for hydroxyl radicals. This approach provides a novel and effective solution for the detection of •OH and has broad application prospects.

[0018] This application provides an Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material, its preparation method, and its application. Compared with the prior art, it has the following advantages: 1. This application designs AgAu nanoparticles with bimetallic core-shell nanoparticles, which have host-guest complexing ability HE / SH-P5 and excellent photoelectrochemical performance and staggered bandgap structure of Bi2MoO6-MoS2, which can promote carrier separation and be used for photoelectrochemical detection of hydroxyl radicals. 2. This invention solves the technical problems of existing detection technologies, such as low sensitivity, limited detection range, expensive instruments, low efficiency, and difficulty in operation; 3. The detection range of this application is 0.75 μM to 200 μM, and the lowest detection limit is 0.25 μM (S / N=3); 4. The columnar aromatic hydrocarbon synthesized in this application has a good host-guest complexation constant of 47145 with •OH; 5. The detection of •OH in this application has excellent reproducibility, with a relative standard deviation of 3.11% for 5 parallel experiments. Attached Figure Description

[0019] Figure 1 The images shown are SEM images of this application, where A is a scanning electron microscope (SEM) image of Bi2MoO6, B is a scanning electron microscope (SEM) image of MoS2, C is a scanning electron microscope (SEM) image of Ag@Au, D is a transmission electron microscope (TEM) image of Ag@Au, E is an elemental analysis diagram, F is a scanning electron microscope (SEM) image of Bi2MoO6-MoS2, and G is a scanning electron microscope (SEM) image of Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2. The scale bars in D and E are 100 nm. Figure 2These are the X-ray diffraction patterns and ultraviolet-visible absorption spectra of this application, where A is the XRD pattern of Bi2MoO6, MoS2, Bi2MoO6-MoS2, Ag, and Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2, and B is the ultraviolet-visible absorption spectrum of Ag, Au, Ag@Au, Bi2MoO6-MoS2, and Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2; Figure 3 These are the CV curves, impedance curves, it curves, and mechanism diagrams of this application. A represents the CV curves of Ag@Au, HE / SH-P5, Ag@Au@HE / SH-P5, Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2, and Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 in 5 mM K3[Fe(CN)6] / K4[Fe(CN)6] and 0.1 M KCl; B represents the impedance curve; C represents the it curves of the modified Ag@Au in 0.1 M PBS (pH = 2.0) solution containing 1 mM•OH under visible light, where a represents Ag@Au, b represents HE / SH-P5, c represents Ag@Au@HE / SH-P5, d represents Bi2MoO6-MoS2, e represents Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2, and D represents the heterojunction signal amplification mechanism. Figure 4 These are the it curves and linear fitting curves of this application, where A is the it curve of the photoelectrochemical sensor for different concentrations of •OH, and B is the linear fitting curve. Detailed Implementation

[0020] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and equivalent alterations or modifications also fall within the scope defined by the claims of this application.

[0021] Example 1: This example provides a method for preparing Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material. A Bi2MoO6-MoS2 heterojunction is formed by modifying MoS2 on Bi2MoO6 using an in-situ growth method. Then, Ag@Au@HE / SH-P5 core-shell nanocubes with HE / SH-P5 functionalization are distributed on the Bi2MoO6-MoS2 heterojunction to prepare the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material. The specific steps include: The first step was to prepare column-shaped aromatic hydrocarbons [5] HE / SH-P5 modified with N-(2-hydroxyphenyl)acetamido and mercapto groups: ; The second step involves preparing a cubic silver nanoparticle solution (Ag NCs) via thermal reduction: 10 mL of a 1,2-propanediol solution containing 173 μM polyvinylpyrrolidone (PVP) with a volume ratio of Mw=58000 was stirred at 160°C for 1 hour. Then, 1 mL of a 1,2-propanediol solution containing 1 mM NaCl was added. After 5 minutes, 4 mL of a 1,2-propanediol solution containing 0.15 M AgNO3 was added dropwise, and the reaction was continued for 40 minutes to obtain a silver-green suspension. The suspension was then centrifuged and washed five times with ultrapure water at 7000 rpm to obtain pure silver nanocubes. Finally, the centrifuged and washed silver nanocubes were dispersed in 20 mL of ultrapure water for storage to obtain a silver nanocube solution. The third step involved synthesizing Ag@Au core-shell nanocubes via a reduction method and an in-situ growth method: First, 100 μL of 25.4 mM HAuCl4 was mixed with 2 mL of 20 mM NaOH and 17.9 mL of ultrapure water, and stirred at room temperature for 1 hour to prepare 0.1 mM Au(OH)4. - The precursor solution was prepared by first diluting 1 mL of 40 mg PVP with 1–2 mL of deionized water and heating to 60°C for 2 minutes. Then, 500 μL of 100 mM ascorbic acid and 500 μL of 200 mM NaOH were added and incubated for 10 minutes. Next, 700 μL of silver nanocube solution was added and reacted for 10 minutes. Finally, Au(OH)₄ was added dropwise. - The precursor solution was reacted for 8 min to obtain the final product. The final product was centrifuged and washed 5 times with ultrapure water at 7000 rpm to obtain Ag@Au core-shell nanocubes. The obtained Ag@Au core-shell nanocubes were diluted with 5-10 mL of deionized water to obtain Ag@Au core-shell nanocube solution. Step 4: Disperse 2.2 mg HE / SH-P5 in 1.1 mL Ag@Au core-shell nanocube solution Ag@Au NCs according to the mass-volume ratio, and sonicate for 30 min to synthesize Ag@Au@HE / SH-P5 composite optoelectronic material; The fifth step involves preparing flower-like Bi₂MoO₆ using a one-pot hydrothermal method: 0.243 g of Bi(NO₃)₃·5H₂O and 0.06 g of Na₂MoO₄·2H₂O were dissolved in a mixed solvent containing 40 mL of ethylene glycol and 40 mL of ethanol at a mass-to-volume ratio. The mixture was stirred for 30–35 min to obtain a transparent solution, which was then heated in an autoclave at 170 °C for 25 h. The product was then centrifuged three times at 7000 rpm for 8 min each time, alternating between ethanol and ultrapure water. Finally, the centrifuged sample was vacuum dried, and the yellow Bi₂MoO₆ powder, i.e., flower-like Bi₂MoO₆, was collected for further use. Step 6: Prepare Bi2MoO6-MoS2 heterojunctions via in-situ growth: Dissolve 0.03-0.1 g of sodium molybdate in 30-40 mL of ultrapure water by mass-volume ratio, then add 0.02-0.08 g of thioacetamide, and stir the mixture at 500-800 rpm for 1-1.2 h to ensure homogeneity; add 0.05-0.18 g of Bi2MoO6 to the above mixed solution, and continue stirring at 500-800 rpm for 3-3.5 h, then heat in an autoclave at 180-200℃ for 24-26 h, and centrifuge the product three times at 8000-10000 rpm for 5-10 min with ultrapure water; finally, vacuum dry the sample to obtain Bi2MoO6-MoS2 heterojunctions. Step 7: Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 was synthesized using a physical adsorption method: 2~2.5 mL of the Ag@Au@HE / SH-P5 composite optoelectronic material obtained in step 4 was added dropwise to 1.5~2 mg of the Bi2MoO6-MoS2 heterojunction obtained in step 6 according to the mass-volume ratio. The mixture was stirred at 600~800 rpm for 5~10 min to obtain the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 heterojunction, i.e., the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material.

[0022] Example 2: Application of Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material in a signal-switching photoelectrochemical PEC biosensor system with a surface area of ​​0.07 cm². 2 Ten μL of Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material prepared in Example 1 was dropped onto a glassy carbon electrode GCE to prepare an Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 / GCE nanocomposite electrode.

[0023] An application of an Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 nanocomposite electrode in the photoelectric detection of hydroxyl radicals was described. The Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 / GCE nanocomposite electrode was placed in a solution containing •OH for photoelectrochemical detection. All experiments used a conventional three-electrode system, with the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 / GCE nanocomposite electrode as the working electrode, a platinum mesh as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. A xenon lamp was used to simulate a visible light source to irradiate the surface of the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 / GCE electrode, and the shading interval was controlled as an adjustable "on-off" state. Photoelectrochemical detection was then performed using an electrochemical workstation.

[0024] Performance testing: 1. Morphology determination of Ag@Au NCs, Bi2MoO6, MoS2, Bi2MoO6-MoS2 and Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic materials.

[0025] Figure 1 As shown in Figure A, Bi₂MoO₆ exhibits a unique nanoflower structure with a high specific surface area, providing abundant active sites, while MoS₂ exhibits a layered stacked structure, as shown in Figure A. Figure 1 As shown in Figure B, MoS2 nanosheets were uniformly adhered to the surface of Bi2MoO6 nanoflowers through in-situ growth. Figure 1 The F-structure clearly exhibits a layered heterostructure with a tight interface. This heterojunction design effectively promotes interfacial charge separation and transport, significantly improving detection performance. Meanwhile, as... Figure 1 As shown in Figure C, after covering the surface of the silver cube with a gold layer, the material still maintains its complete cubic morphology, with no obvious structural damage. This bimetallic core-shell structure fully utilizes the excellent conductivity of the silver core and the good chemical stability and localized surface plasmon resonance (LSPR) characteristics of the gold shell, achieving synergistic effects. Transmission electron microscopy images and corresponding elemental distribution results are shown in Figure C. Figure 1 China D and Figure 1 Further analysis by E shows that the gold layer uniformly coats the surface of the silver cube, forming a core-shell structure with uniform shell thickness and clear boundaries. Ultimately, Figure 1 The image shows a scanning electron microscope image of the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite material. Ag@Au@HE / SH-P5 is uniformly distributed on the layered structure of Bi2MoO6-MoS2, forming a unified composite structure.

[0026] 2. X-ray diffraction patterns of Bi2MoO6, MoS2, Bi2MoO6-MoS2, Ag, and Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2, and UV-Vis absorption spectra of Ag, Au, Ag@Au, Bi2MoO6-MoS2, and Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2.

[0027] The structure and optical properties of Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 nanocomposites were systematically characterized by X-ray diffraction (XRD) and ultraviolet-visible absorption spectroscopy (UV-Vis). Figure 2 Figure A shows the XRD patterns of different samples. Bi₂MoO₆ (black line) exhibits clear diffraction peaks at a specific 2θ angle, corresponding to the (111), (131), (202), and (133) crystal planes of the orthorhombic crystal system, indicating its good crystallinity. MoS₂ (green line) shows typical diffraction peaks at characteristic positions such as (002), consistent with its layered structure. In the XRD pattern of the Bi₂MoO₆-MoS₂ heterojunction, diffraction signals from both Bi₂MoO₆ and MoS₂ can be identified simultaneously, confirming their successful composite formation. The diffraction peaks of metallic Ag (purple curve) match the face-centered cubic structure, such as the (220) and (311) crystal planes. In the final Ag@Au@HE / SH-P5 / Bi₂MoO₆-MoS₂ composite material (red curve), the characteristic diffraction peaks of Ag, Bi₂MoO₆, and MoS₂ are all clearly visible, indicating that the composite material has been successfully prepared.

[0028] Further through Figure 2 The optical properties were investigated using UV-Vis absorption spectroscopy. As shown in the figure, silver nanoparticles (black line) exhibit a surface plasmon resonance absorption peak at approximately 365 nm, while the characteristic absorption peak of gold nanoparticles (yellow line) is located at 525 nm. The absorption peak of the Ag@Au core-shell structure (blue line) is located at 513 nm, between the elemental absorption peaks of silver and gold, confirming the formation of the core-shell structure. The Bi2MoO6-MoS2 heterojunction (green line) exhibits strong UV absorption at 322 nm, while HE / SH-P5 (violet line) shows characteristic absorption at 307 nm. The final Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite material (red line) exhibits absorption behavior in the ultraviolet-visible region that integrates the characteristics of each component. It retains the plasmon resonance absorption of the Ag@Au core-shell structure and also possesses the ultraviolet absorption characteristics of Bi2MoO6-MoS2 and HE / SH-P5. This confirms that the optical properties of the composite material are effectively integrated, providing important evidence for its application in the field of optoelectronic sensing.

[0029] 3. Photoelectrochemical characterization: like Figure 3 As shown in Figure A, by measuring cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 5.0 mM K3[Fe(CN)6] / K4[Fe(CN)6] and 0.1 M KCl solutions, the oxidation peak current of Ag@Au was significantly higher than that of Ag@Au@HE / SH-P5. This is mainly attributed to the poor conductivity of HE / SH-P5 as an organic polymer material, which partially hinders electron transport at the electrode interface. However, after introducing Bi2MoO6-MoS2, the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite material exhibited the highest oxidation peak current, indicating a significant enhancement in its electron transfer capability. This phenomenon stems from the localized surface plasmon resonance generated by the Ag@Au core-shell structure and the suppression of photogenerated electron-hole recombination by the Bi2MoO6-MoS2 heterojunction, thus enhancing the photocurrent signal; these conclusions were further verified in EIS tests. Figure 3 As shown in Figure B, the charge transfer resistance (Rct) of Ag@Au is less than that of Ag@Au@HE / SH-P5, while the Rct value of the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite material is the smallest, indicating that it has the lowest charge transport resistance, which is consistent with the CV results. The it curve shows the photoelectrochemical behavior of the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite material ( Figure 3 (As shown in Figure C). Under illumination, the photocurrent density of this composite material increases significantly, exhibiting excellent photoelectrochemical response characteristics. Conversely, the photocurrent decays immediately under dark conditions. Compared with single-component Ag@Au / GCE, Ag@Au@HE / SH-P5 / GCE, and Bi2MoO6-MoS2 / GCE, Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 / GCE exhibits the highest photocurrent density. This synergistic effect effectively promotes the separation and migration of photogenerated electron-hole pairs, thereby significantly improving the photoelectrochemical performance of the material. Figure 3 As shown in Figure D, under visible light irradiation, electrons in the valence band of Ag@Au are excited and transition to the conduction band, simultaneously generating holes in the valence band. Subsequently, through the localized surface plasmon resonance effect, electrons transfer from the conduction band of Ag@Au to the conduction band of MoS2, and further migrate to Bi2MoO6; while holes migrate in the opposite direction, achieving effective charge spatial separation. Finally, the holes accumulated on the Ag@Au surface further oxidize the primary oxide species into final-state oxidation products, thereby generating a measurable photocurrent signal. This process effectively promotes the separation and migration of photogenerated carriers, achieving highly selective identification and accurate detection of target analytes.

[0030] 4. Photoelectrochemical detection of •OH: Figure 4Figure A demonstrates the photocurrent response of an Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 / GCE-based photoelectrochemical sensor to different concentrations of •OH. As shown in the figure, the photocurrent density significantly increases with the increase of the •OH concentration gradient, indicating that the sensor has excellent detection sensitivity for •OH. Within the concentration range of 0.75 μM to 200 μM, the photocurrent density exhibits a good linear dependence on the logarithm of the •OH concentration, and the fitting equation is I = 0.5631 lg(C •OH )+ 0.6622 (R 2 = 0.9924) ( Figure 4 (As shown in Figure B). Based on a signal-to-noise ratio (S / N) of 3, the detection limit for •OH was calculated to be 0.25 μM. This is lower than other detection methods, indicating that the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 photoelectrochemical sensor has superior analytical performance.

[0031] Example 3 provides a method for preparing Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material. The method involves modifying Bi2MoO6 with MoS2 to form a Bi2MoO6-MoS2 heterojunction via in-situ growth. Then, HE / SH-P5 functionalized gold-silver core-shell nanocubes (Ag@Au@HE / SH-P5) are distributed on the Bi2MoO6-MoS2 heterojunction to obtain the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material. The specific steps include: The first step was to prepare column-shaped aromatic hydrocarbons [5] HE / SH-P5 modified with N-(2-hydroxyphenyl)acetamido and mercapto groups: ; The second step involves preparing a cubic silver nanoparticle solution (Ag NCs) via thermal reduction: 10 mL of a 1,2-propanediol solution containing 173 μM polyvinylpyrrolidone (PVP) with a volume ratio of 58000 was stirred at 140 °C for 1 h. Then, 0.5 mL of a 1,2-propanediol solution containing 1 mM NaCl was added. After 5 min, 3 mL of a 1,2-propanediol solution containing 0.15 M AgNO3 was added dropwise, and the reaction was continued for 35 min to obtain a silver-green suspension. The suspension was then centrifuged and washed three times with ultrapure water at 6000 rpm to obtain pure silver nanocubes. Finally, the centrifuged and washed silver nanocubes were dispersed in 20 mL of ultrapure water for storage to obtain a silver nanocube solution. The third step involved synthesizing Ag@Au core-shell nanocubes via a reduction method and an in-situ growth method: First, 80 μL of 25.4 mM HAuCl4 was mixed with 2 mL of 20 mM NaOH and 17 mL of ultrapure water, and stirred at room temperature for 0.5 h to prepare 0.1 mM Au(OH)4. - Next, 40 mg of PVP was diluted with 1 mL of deionized water and heated to 50 °C for 2 min. Then, 500 μL of 100 mM ascorbic acid and 500 μL of 200 mM NaOH were added and incubated for 5 min. Then, 500 μL of silver nanocube solution was added and reacted for 10 min. Finally, Au(OH)4 was added dropwise. - The precursor solution was reacted for 5 min to obtain the final product. The final product was centrifuged and washed three times with ultrapure water at 5000 rpm to obtain Ag@Au core-shell nanocubes. The obtained Ag@Au core-shell nanocubes were diluted with 5 mL of deionized water to obtain Ag@Au core-shell nanocube solution Ag@Au NCs. Step 4: Disperse 2 mg HE / SH-P5 in 1 mL Ag@Au core-shell nanocube solution Ag@Au NCs according to the mass-volume ratio, and sonicate for 20 minutes to synthesize Ag@Au@HE / SH-P5 composite optoelectronic material; The fifth step involves preparing flower-like Bi₂MoO₆ using a one-pot hydrothermal method: 0.2 g of Bi(NO₃)₃·5H₂O and 0.05 g of Na₂MoO₄·2H₂O were dissolved in a mixed solvent containing 30 mL of ethylene glycol and 30 mL of ethanol at a mass-to-volume ratio. The mixture was stirred for 30 min to obtain a transparent solution, which was then heated in an autoclave at 160 °C for 20 h. The product was then centrifuged three times at 6000 rpm for 5 min each time, alternating between ethanol and ultrapure water. Finally, the centrifuged sample was vacuum dried, and the yellow Bi₂MoO₆ powder, i.e., flower-like Bi₂MoO₆, was collected for further use. Step 6: Bi2MoO6-MoS2 heterojunction was prepared by in-situ growth method: 0.03 g of sodium molybdate was dissolved in 30 mL of ultrapure water at a mass-to-volume ratio, followed by the addition of 0.02 g of thioacetamide. The mixture was stirred at 500 rpm for 1 h to ensure homogeneity. 0.05 g of Bi2MoO6 was added to the above mixed solution, and the mixture was stirred at 500 rpm for 3 h. Then, it was heated in an autoclave at 180 °C for 24 h. The product was centrifuged three times at 8000 rpm for 5 min each time with ultrapure water. Finally, the sample was vacuum dried to obtain Bi2MoO6-MoS2 heterojunction. Step 7: Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 was synthesized using a physical adsorption method: 2 mL of Ag@Au@HE / SH-P5 composite optoelectronic material obtained in step 4 was added dropwise to 1.5 mg of Bi2MoO6-MoS2 heterojunction obtained in step 6 according to the mass-volume ratio. The mixture was stirred at 600 rpm for 5 min to obtain the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 heterojunction, i.e., the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material.

[0032] Example 4 provides a method for preparing Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material. The method involves modifying Bi2MoO6 with MoS2 to form a Bi2MoO6-MoS2 heterojunction via in-situ growth. Then, HE / SH-P5 functionalized gold-silver core-shell nanocubes (Ag@Au@HE / SH-P5) are distributed on the Bi2MoO6-MoS2 heterojunction to obtain the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material. The specific steps include: The first step was to prepare column-shaped aromatic hydrocarbons [5] HE / SH-P5 modified with N-(2-hydroxyphenyl)acetamido and mercapto groups: ; The second step involved preparing a cubic silver nanoparticle solution (Ag NCs) via thermal reduction: 20 mL of a 1,2-propanediol solution containing 173 μM polyvinylpyrrolidone (PVP) with a volume ratio of 58000 was stirred at 160 °C for 1.5 h. Then, 1.5 mL of a 1,2-propanediol solution containing 1 mM NaCl was added. After 8 min, 5 mL of a 1,2-propanediol solution containing 0.15 M AgNO3 was added dropwise, and the reaction was continued for 45 min to obtain a silver-green suspension. The suspension was then centrifuged and washed 6 times with ultrapure water at 7000 rpm to obtain pure silver nanocubes. Finally, the centrifuged and washed silver nanocubes were dispersed in 30 mL of ultrapure water for storage to obtain a silver nanocube solution. The third step involved synthesizing Ag@Au core-shell nanocubes via a reduction method and an in-situ growth method: First, 110 μL of 25.4 mM HAuCl4 was mixed with 4 mL of 20 mM NaOH and 19 mL of ultrapure water, and stirred at room temperature for 1.5 h to prepare 0.1 mM Au(OH)4. -The precursor solution was prepared by diluting 80 mg of PVP with 2 mL of deionized water and heating to 60°C for 5 min. Then, 700 μL of 100 mM ascorbic acid and 700 μL of 200 mM NaOH were added and incubated for 15 min. Next, 700 μL of silver nanocube solution was added, and the reaction was allowed to proceed for another 15 min. Finally, Au(OH)₄ was added dropwise. - The precursor solution was reacted for 10 min to obtain the final product. The final product was washed 6 times by centrifugation with ultrapure water at 7000 rpm to obtain Ag@Au core-shell nanocubes. The obtained Ag@Au core-shell nanocubes were diluted with 10 mL of deionized water to obtain Ag@Au core-shell nanocube solution Ag@Au NCs. Step 4: Disperse 2.5 mg HE / SH-P5 in 1.2 mL Ag@Au core-shell nanocube solution Ag@Au NCs according to the mass-volume ratio, and sonicate for 40 minutes to synthesize Ag@Au@HE / SH-P5 composite optoelectronic material; The fifth step involves preparing flower-like Bi₂MoO₆ using a one-pot hydrothermal method: 0.4 g Bi(NO₃)₃·5H₂O and 0.1 g Na₂MoO₄·2H₂O were dissolved in a mixed solvent containing 40 mL ethylene glycol and 40 mL ethanol at a mass-to-volume ratio. The mixture was stirred for 35 min to obtain a transparent solution, which was then heated in an autoclave at 180 °C for 24 h. The product was then centrifuged three times at 8000 rpm for 10 min each time, alternating between ethanol and ultrapure water. Finally, the centrifuged sample was vacuum dried, and the yellow Bi₂MoO₆ powder, i.e., flower-like Bi₂MoO₆, was collected for further use. Step 6: Bi2MoO6-MoS2 heterojunctions were prepared by in-situ growth: 0.1 g of sodium molybdate was dissolved in 40 mL of ultrapure water at a mass-to-volume ratio, followed by the addition of 0.08 g of thioacetamide. The mixture was stirred at 800 rpm for 1.2 h to ensure homogeneity. 0.18 g of Bi2MoO6 was added to the above mixed solution, and stirring was continued at 800 rpm for 3.5 h. The mixture was then heated in an autoclave at 200 °C for 26 h. The product was centrifuged three times at 10,000 rpm for 10 min each time with ultrapure water. Finally, the sample was vacuum dried to obtain the Bi2MoO6-MoS2 heterojunction. Step 7: Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 was synthesized using a physical adsorption method: 2.5 mL of the Ag@Au@HE / SH-P5 composite optoelectronic material obtained in step 4 was dropped into 2 mg of the Bi2MoO6-MoS2 heterojunction obtained in step 6 according to the mass-volume ratio, and stirred at 800 rpm for 10 min to obtain the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 heterojunction, i.e., the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material.

[0033] The embodiments selected in the above materials are for ease of understanding and not for limiting the process method. Those skilled in the art can easily modify the process flow or transfer it to other cases without inventive change. If these modifications also fall under the category of similar claims or similar technology of this invention, then the intent of this invention also includes these modifications.

Claims

1. A method for preparing Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material, characterized in that, A Bi2MoO6-MoS2 heterojunction was formed by modifying MoS2 on Bi2MoO6 using an in-situ growth method. Then, gold-silver core-shell nanocubes (Ag@Au@HE / SH-P5) functionalized with HE / SH-P5 were distributed on the Bi2MoO6-MoS2 heterojunction to prepare the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material. Includes the following steps: The first step was to prepare column-shaped aromatic hydrocarbons [5] HE / SH-P5 modified with N-(2-hydroxyphenyl)acetamido and mercapto groups: ； The second step involves preparing a cubic silver nanoparticle solution (Ag NCs) via thermal reduction: 10–20 mL of a 1,2-propanediol solution containing 173 μM polyvinylpyrrolidone (PVP) with a volume ratio of Mw = 58000 is stirred at 140–160 °C for 1–1.5 h. Then, 0.5–1.5 mL of a 1,2-propanediol solution containing 1 mM NaCl is added. After 5–8 min, 3–5 mL of a 1,2-propanediol solution containing 0.15 M AgNO3 is added dropwise. The reaction continues for 35–45 min to obtain a silver-green suspension. The suspension is then centrifuged and washed 3–6 times with ultrapure water at 6000–7000 rpm to obtain pure silver nanocubes. Finally, the centrifuged and washed silver nanocubes are dispersed in 20–30 mL of ultrapure water for storage to obtain a silver nanocube solution. The third step involved synthesizing Ag@Au core-shell nanocubes via a reduction method and an in-situ growth method: First, 80–110 μL of 25.4 mM HAuCl4 was mixed with 2–4 mL of 20 mM NaOH and 17–19 mL of ultrapure water, and stirred at room temperature for 0.5–1.5 h to prepare 0.1 mM Au(OH)4. - Next, take 40-80 mg of PVP, dilute it with 1-2 mL of deionized water, and heat it to 50-60 °C. After 2-5 min, add 500-700 μL of 100 mM ascorbic acid and 500-700 μL of 200 mM NaOH. Incubate for 5-15 min, then add 500-700 μL of silver nanocube solution. After reacting for 10-15 min, add Au(OH)4 dropwise. - The precursor solution was reacted for 5-10 min to obtain the final product. The final product was centrifuged and washed 3-6 times with ultrapure water at 5000-7000 rpm to obtain Ag@Au core-shell nanocubes. The obtained Ag@Au core-shell nanocubes were diluted with 5-10 mL of deionized water to obtain Ag@Au core-shell nanocube solution Ag@Au NCs. The fourth step involves dispersing 2-2.5 mg of HE / SH-P5 in 1-1.2 mL of Ag@Au core-shell nanocube solution (Ag@Au NCs) according to a mass-to-volume ratio, and then sonicating for 20-40 minutes to synthesize Ag@Au@HE / SH-P5 composite optoelectronic materials. The fifth step involves preparing flower-like Bi₂MoO₆ using a one-pot hydrothermal method: 0.2–0.4 g of Bi(NO₃)₃·5H₂O and 0.05–0.1 g of Na₂MoO₄·2H₂O are dissolved in a mixed solvent containing 30–40 mL of ethylene glycol and 30–40 mL of ethanol at a mass-to-volume ratio. The mixture is stirred for 30–35 min to obtain a transparent solution, which is then heated in an autoclave at 160–180 °C for 20–24 h. The product is then centrifuged three times at 6000–8000 rpm for 5–10 min, alternating between ethanol and ultrapure water. Finally, the centrifuged sample is vacuum dried, and the yellow Bi₂MoO₆ powder, i.e., flower-like Bi₂MoO₆, is collected for further use. Step 6: Prepare Bi2MoO6-MoS2 heterojunctions via in-situ growth: Dissolve 0.03-0.1 g of sodium molybdate in 30-40 mL of ultrapure water by mass-volume ratio, then add 0.02-0.08 g of thioacetamide, and stir the mixture at 500-800 rpm for 1-1.2 h to ensure homogeneity; add 0.05-0.18 g of Bi2MoO6 to the above mixed solution, and continue stirring at 500-800 rpm for 3-3.5 h, then heat in an autoclave at 180-200℃ for 24-26 h, and centrifuge the product three times at 8000-10000 rpm for 5-10 min with ultrapure water; finally, vacuum dry the sample to obtain Bi2MoO6-MoS2 heterojunctions. Step 7: Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 was synthesized using a physical adsorption method: 2-2.5 mL of the Ag@Au@HE / SH-P5 composite optoelectronic material obtained in step 4 was added dropwise into 1.5-2 mg of the Bi2MoO6-MoS2 heterojunction obtained in step 6 according to the mass-volume ratio. The mixture was stirred at 600-800 rpm for 5-10 min to obtain the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 heterojunction, i.e., the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material.

2. The preparation method of the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material according to claim 1, characterized in that, The second step involves preparing a cubic silver nanoparticle solution (Ag NCs) via thermal reduction: 10 mL of a 1,2-propanediol solution containing 173 μM polyvinylpyrrolidone (PVP) with a volume ratio of 58000 was stirred at 160°C for 1 hour. Then, 1 mL of a 1,2-propanediol solution containing 1 mM NaCl was added. After 5 minutes, 4 mL of a 1,2-propanediol solution containing 0.15 M AgNO3 was added dropwise, and the reaction was continued for 40 minutes to obtain a silver-green suspension. The suspension was then centrifuged and washed five times with ultrapure water at 7000 rpm to obtain pure silver nanocubes. Finally, the centrifuged and washed silver nanocubes were dispersed in 20 mL of ultrapure water for storage to obtain a silver nanocube solution.

3. The preparation method of the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material according to claim 1, characterized in that, The third step is as follows: First, mix 100 μL of 25.4 mM HAuCl4 with 2 mL of 20 mM NaOH and 17.9 mL of ultrapure water, and stir at room temperature for 1 hour to prepare 0.1 mM Au(OH)4. - The precursor solution was prepared by first diluting 1 mL of 40 mg PVP with 1–2 mL of deionized water and heating to 60°C for 2 minutes. Then, 500 μL of 100 mM ascorbic acid and 500 μL of 200 mM NaOH were added and incubated for 10 minutes. Next, 700 μL of silver nanocube solution was added and reacted for 10 minutes. Finally, Au(OH)₄ was added dropwise. - The precursor solution was reacted for 8 min to obtain the final product. The final product was centrifuged and washed 5 times with ultrapure water at 7000 rpm to obtain Ag@Au core-shell nanocubes. The obtained Ag@Au core-shell nanocubes were diluted with 5-10 mL of deionized water to obtain Ag@Au core-shell nanocube solution.

4. The preparation method of the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material according to claim 1, characterized in that, The fourth step is as follows: 2.2 mg HE / SH-P5 is dispersed in 1.1 mL Ag@Au core-shell nanocube solution Ag@Au NCs according to the mass-volume ratio, and sonicated for 30 min to synthesize Ag@Au@HE / SH-P5 composite optoelectronic material.

5. The preparation method of the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material according to claim 1, characterized in that, The fifth step is as follows: Flower-like Bi₂MoO₆ is prepared using a one-pot hydrothermal method: 0.243 g Bi(NO₃)₃·5H₂O and 0.06 g Na₂MoO₄·2H₂O are dissolved in a mixed solvent containing 40 mL ethylene glycol and 40 mL ethanol according to the mass-to-volume ratio. The solution is stirred for 30-35 min to obtain a transparent solution, heated in a high-pressure autoclave at 170 °C for 25 h, and the product is centrifuged three times at 7000 rpm for 8 min each time, alternating between ethanol and ultrapure water. Finally, the centrifuged sample is vacuum dried, and the yellow Bi₂MoO₆ powder, i.e., flower-like Bi₂MoO₆, is collected for further use.

6. An Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material prepared by any one of the preparation methods described in claims 1-5.

7. The application of the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material prepared by any one of the preparation methods described in claims 1-5 in a signal-switching type photoelectrochemical PEC biosensor system.

8. The application according to claim 7, characterized in that: With a surface area of ​​0.07 cm² 2 A nanocomposite electrode, Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2, was prepared by dropping 10 μL of Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 composite optoelectronic material onto a glassy carbon electrode GCE.

9. The application according to claim 8, characterized in that: The signal-on-off photoelectrochemical PEC biosensor system uses a traditional three-electrode system, with an Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 / GCE nanocomposite electrode as the working electrode, a platinum mesh as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. A xenon lamp is used to simulate a visible light source to irradiate the surface of the Ag@Au@HE / SH-P5 / Bi2MoO6-MoS2 / GCE nanocomposite electrode. The light-blocking interval is controlled as an adjustable "on-off" state, and photoelectrochemical detection is performed using an electrochemical workstation in an electrolyte containing para-hydroxyl radicals.

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