Reversible photoelectrochemical microsensor and hydrogen polysulfide detection method

Abstract

The invention discloses a reversible photoelectrochemical microsensor which is obtained by taking a metal electrode as a substrate and sequentially modifying a Bi2S3-FeIn2S4 heterojunction and a composite nano luminescent probe at one end of the metal electrode, the composite nano light-emitting probe is composed of a small molecule probe and up-conversion nano light-emitting particles. Wherein the small molecule probe is used as a selective recognition unit and an energy receptor, the up-conversion nano light-emitting particles are used as an energy donor and an energy conversion element to activate the Bi2S3-FeIn2S4 heterojunction, and the Bi2S3-FeIn2S4 heterojunction is used as a photoelectric signal converter. The fluorescence resonance energy transfer efficiency between the small-molecule probe and the up-conversion nano light-emitting particles is reduced by utilizing reversible nucleophilic addition reaction of a target H2Sn and the small-molecule probe, so that a light current signal is changed, and the H2Sn is detected. The reversible photoelectrochemical microsensor provided by the invention realizes reversible detection of H2Sn by introducing a small molecule probe capable of reversibly recognizing H2Sn and combining an FRET light regulation mechanism, can monitor fluctuation of H2Sn in a living body in real time, and has high selectivity and anti-interference capability.

Description

Technical Field

[0001] The invention belongs to the technical field of photoelectrochemical sensing, and in particular relates to a reversible photoelectrochemical microsensor, a preparation method thereof, and an application of the microsensor in detecting hydrogen polysulfide. Background Art

[0002] Hydrogen polysulfide (H2S n , n>1) is a type of active sulfur species formed by the polymerization of hydrogen sulfide (H2S) through sulfur-sulfur bonds. Its unique chemical properties and biological functions make it of great research value in the fields of life sciences, environmental monitoring, industrial safety, etc. First, in the field of life sciences, H2S n It is not only a reservoir of H2S, but also an independent signal molecule that participates in key physiological processes such as signal transduction and oxidative stress regulation. n Abnormal concentration is closely related to Alzheimer's disease, cardiovascular disease and cancer progression, and has gradually become an early diagnostic marker for related diseases. n The accurate analysis of biological functions relies on real-time, in-situ detection technology, which poses a severe challenge to existing methods. n As a core indicator of industrial pollution, H2S is widely present in petrochemical wastewater and natural gas desulfurization exhaust. Its oxidation products can cause acid rain and eutrophication of water bodies. In order to control such pollution from the source and formulate precise governance strategies, highly sensitive monitoring methods are needed to support environmental decision-making. Thirdly, focusing on the field of industrial safety, H2S in chemical processes n The accumulation of sulfur will cause equipment corrosion and explosion risks, and its "shuttle effect" in lithium-sulfur batteries is the core bottleneck restricting battery life. Real-time detection becomes the key to optimizing the process and energy storage performance. Despite the urgent need, current n The detection technology of H2S is facing two challenges: on the one hand, traditional in vitro detection methods (such as colorimetry and high performance liquid chromatography) are difficult to detect due to H2S n The rapid decomposition and oxidative inactivation characteristics in the solution cause the test results to deviate seriously from the true physiological state; on the other hand, the large amount of coexisting biological thiols (such as H2S and glutathione) in the complex microenvironment of the living brain puts forward the demand for detection specificity. n Although it has the advantages of non-invasiveness and specificity, it is limited by the light scattering effect of brain tissue and insufficient spatiotemporal resolution, making it difficult to achieve precise positioning between brain regions. Electrochemical sensing technology with high spatiotemporal resolution is difficult to achieve due to the H2S n Electrochemical inertness outside the water splitting potential window makes it impossible to capture effective Faradaic signals. Although photoelectrochemical (PEC) sensors can combine the high selectivity of optical excitation with the sensitivity of electrochemical detection, there is currently no relevant detection method for H2S.n Photoelectrochemical sensors have been developed. However, most sensors rely on irreversible redox reactions between the target and the probe molecule, which results in permanent occupation of the active sites on the electrode surface after detection and the signal cannot be recovered. At the same time, the uncontrollable deposition of sulfides on the electrode surface will cause baseline drift. This irreversibility not only limits the reusability of the sensor, but also makes it difficult to meet the requirements of H2S n Dynamic release process monitoring (such as real-time release of H2S by cells) n ) needs, a reversible detection of H2S n Sensors are yet to be developed. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to propose a reversible photoelectrochemical microsensor and its preparation method in view of the shortcomings of the above-mentioned prior art, which can realize the detection of H2S n Highly selective reversible response and in situ monitoring.

[0004] The technical solution adopted by the present invention to solve the above-mentioned problems is: A reversible photoelectrochemical microsensor for detecting hydrogen polysulfide based on fluorescence resonance energy transfer (FRET) regulation strategy is proposed. It uses a metal electrode as a substrate, and sequentially modifies a Bi2S3-FeIn2S4 heterojunction and a composite nanoluminescent probe (rH2S n / UCNPs); the composite nanoluminescent probe is composed of a small molecule probe (rH2S n ) and upconversion nanoluminescent particles (UCNPs). Among them, rH2S n As a selective recognition unit and energy acceptor, UCNPs act as energy donors and energy conversion elements to activate the Bi2S3-FeIn2S4 heterojunction, which acts as a photoelectric signal converter to convert the optical signal into a detectable electrical signal. The target H2S n With rH2S n Able to undergo reversible nucleophilic addition reaction, affecting rH2S n Fluorescence resonance energy transfer between UCNPs and H2S n Detection.

[0005] According to the above scheme, the base electrode can be made of materials with good conductive properties such as titanium wire, tungsten wire, silver wire, iron wire, platinum wire, etc.; the diameter of the base electrode is preferably 50~150μm, and the length of the modified end is preferably 300~600μm.

[0006] According to the above scheme, the composite nanoluminescent probe (rH2S n / UCNPs) through the positively charged surface of rH2Sn The molecules can be self-assembled with the negatively charged UCNPs through electrostatic attraction.

[0007] According to the above scheme, the composite nanoluminescent probe (rH2S n The preparation method of the UCNPs comprises the following steps: (1) Dispersing UCNPs in water to obtain a UCNPs dispersion with a concentration of 1-10 mg / mL; (2) The small molecule probe rH2S n Dispersed in a mixed solvent of DMSO and water to obtain rH2S n Dispersion; wherein, in the mixed solvent, the volume percentage of DMSO is 1%~5%, rH2S n The concentration in the mixed solvent is 1~100μM; (3) According to the mass of UCNPs and rH2S n The ratio between the amount of substance is 1mg: (0.05-2.5) nmol, UCNPs dispersion and rH2S n The dispersions were mixed and placed in a constant temperature oscillator at 25°C for 12 to 24 hours to allow the rH2S n The UCNPs were fully modified; then, the unbound free rH2S was removed by centrifugation. n molecules, collecting the precipitate, and washing the precipitate until the centrifugal supernatant has no obvious absorption characteristics in the visible light region, thereby obtaining the composite nanoluminescent probe (rH2S n / UCNPs).

[0008] Furthermore, the small molecule probe rH2S n It is: N-(7-(dimethylamino)-10-(4-(hexyloxy)-2-methylphenyl)-5,5-dimethyldibenzo[b,e]silanol-3(5H)-en-3-yl)-N-methylmethanamine, and its chemical structure is: .

[0009] Furthermore, the small molecule probe rH2S n It can be obtained by mixing compound B and compound A in tetrahydrofuran solvent with n-butyl lithium as catalyst at low temperature and then reacting at room temperature. The reaction equation is as follows:

[0010] Wherein, the structural formulas of compound A and compound B are as follows: 、 .

[0011] Furthermore, the chemical composition of the upconversion nanoluminescent particles (UCNPs) is NaYbF4: Er 3+ / Mn 2+ Under the irradiation of excitation light at around 980nm, the main emission peak is at 630~700nm, the diameter is about 20~200nm, and the particle morphology is mostly spherical.

[0012] According to the above scheme, the Bi2S3-FeIn2S4 heterojunction is composed of Bi2S3 and FeIn2S4 in a molar ratio of 1:1 to 4:1. The absorption spectrum of this Bi2S3-FeIn2S4 heterojunction should have strong absorption in the range of 630-700nm, which is a good match with the characteristic emission spectrum of UCNPs, laying the material foundation for the subsequent construction of light-controlled current value.

[0013] Preferably, the Bi2S3-FeIn2S4 heterojunction is prepared by using bismuth nitrate pentahydrate, indium chloride, ferric acetate tetrahydrate, and thioacetamide as raw materials, using water as a solvent, stirring and reacting at 90-120°C for a certain time, and storing in the dark. The raw materials are mixed in a molar ratio of Bi:In:Fe:S = 1:(0.25-1):(0.125-0.5):(2-3.5); the reaction time is generally 1-3 hours.

[0014] According to the above scheme, the preparation method of the reversible photoelectrochemical microsensor includes the following steps: ① Immerse one end of the metal electrode in an etching solution for acid etching, and then ultrasonically clean it with acetone, ethanol, and deionized water to obtain an etched electrode (TiME). The etching solution system consists of 1-10% HF, 1-30% HNO3, and 60-98% ultrapure water by volume, and the etching time is controlled within 1-5 minutes. ② Vertically immerse the etched electrode in a 0.5-10 mg / mL Bi2S3-FeIn2S4 dispersion (water as the solvent) and let it stand at room temperature (generally for 6-24 hours) to achieve the loading of the Bi2S3-FeIn2S4 heterojunction and obtain a Bi2S3-FeIn2S4 / TiME microelectrode; ③ Vertically immerse the Bi2S3-FeIn2S4 / TiME microelectrode in 0.5~3mg / mL rH2S n / UCNPs (with water as solvent) are self-assembled layer by layer in a solution, and the assembly process is allowed to stand at room temperature (generally for 6 to 24 hours) to obtain the FRET-based detection strategy for H2S according to the present invention. n Reversible photoelectrochemical microsensor (abbreviated as rH2S n / UCNPs / Bi2S3-FeIn2S4 / TiME).

[0015] On the basis of the above, the present invention also provides an immobilized reversible photoelectrochemical microsensor. The immobilized reversible photoelectrochemical microsensor comprises a transparent glass capillary and a transparent light-guiding optical fiber, as well as the above rH2S n / UCNPs / Bi2S3-FeIn2S4 / TiME sensor; the rH2S n The / UCNPs / Bi2S3-FeIn2S4 / TiME microsensor is arranged parallel to the transparent light-guiding fiber along the axis and inserted into the cavity of the glass capillary. n The / UCNPs / Bi2S3-FeIn2S4 / TiME microsensor passes through the tip of the narrowed section of the glass capillary, and then the glass capillary is filled with optical glue and UV-cured.

[0016] Furthermore, the inner diameter and outer diameter of the glass capillary are preferably 500-800 μm and 800-1100 μm, respectively. The glass capillary is drawn into a necked section at one end using a drawing instrument, and the diameter of the tip of the necked section is preferably 50-200 μm. The diameter of the transparent light-guiding optical fiber is preferably 100-300 μm.

[0017] The present invention also provides a method for detecting H2S by using the above-mentioned reversible photoelectrochemical microsensor or an immobilized reversible photoelectrochemical microsensor. n H2S2 is a typical representative of polysulfide species, which maintains a dynamic balance with other sulfide species, and H2S2 is present in organisms as HS2 - and S2 2- Therefore, Na2S2 is used as the standard of the target to detect S2 in the target. 2- The content of H2S2 can be determined by the content. The specific steps are as follows: 1) Prepare a gradient concentration of Na2S2 standard solution with a concentration range of 1-15 μM. 2) inserting the reversible photoelectrochemical microsensor or the immobilized reversible photoelectrochemical microsensor into Na2S2 standard solutions of different concentrations, using the microsensor as the working electrode, a silver / silver chloride electrode as the reference electrode, and a platinum wire as the counter electrode, and connecting the microsensor to an electrochemical workstation via a wire, collecting photocurrent data with the electrochemical workstation under near-infrared light excitation; then establishing a standard curve with the Na2S2 concentration in the Na2S2 standard solution as the abscissa and the photocurrent value as the ordinate; 3) Under the conditions parallel to step 2), the reversible photoelectrochemical microsensor or the immobilized reversible photoelectrochemical microsensor is inserted into the sample to be tested, the photocurrent of the sample to be tested is detected, and then the standard curve method is used to realize the target H2S in the sample to be tested. n Detection.

[0018] In the present invention, the sample to be tested can be a living model such as a laboratory mouse, or a complex liquid matrix such as blood, cell culture fluid, or environmental water sample. In particular, the immobilized reversible photoelectrochemical microsensor is obtained by encapsulating it in a capillary glass tube. The microsensor is encapsulated as a working electrode at the tip of the constricted end of the capillary glass tube and can be inserted or implanted as a microprobe into a living body (such as the brain) to achieve real-time H2S detection. n Monitoring and in situ analysis of blood provide the hardware foundation for cross-scale research.

[0019] The technical concept of the present invention is: in the reversible photoelectrochemical microsensor of the present invention, rH2S n As a selective recognition unit and energy acceptor, UCNPs act as energy donors and energy conversion elements to activate the Bi2S3-FeIn2S4 heterojunction, which acts as a photoelectric signal converter. In the initial state, when the near-infrared light output by the 980 nm laser is directed to the microsensor, the rH2S n The strong absorption band at 660 nm effectively overlaps with the upconversion luminescence (UCL) spectrum of UCNPs. n Fluorescence resonance transfer occurs, resulting in UCL quenching. At this time, 980 nm near-infrared excitation cannot generate effective photocurrent. n When present, it reacts with rH2S n A reversible nucleophilic addition reaction occurs to form the compound rH2S n / H2S n , resulting in rH2S n The absorption intensity at 660 nm decreased, the FRET efficiency decreased, and the UCL intensity was expressed as H2S n The released UCL photons activated the Bi2S3-FeIn2S4 heterojunction in a concentration-dependent manner, resulting in a significantly enhanced photocurrent response. n When the concentration decreases, rH2S n Complex with target rH2S n / H2S n When dissociation occurs, the microsensor returns to its initial state and the photocurrent response decreases, achieving true reversible detection.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. The reversible photoelectrochemical microsensor of the present invention first designs and synthesizes rH2S with reversible response characteristics n As the core recognition element of the PEC sensor, the small molecule probe can realize the recognition of H2S through nucleophilic addition. n Specific recognition and dissociation; then, based on the fluorescence resonance energy transfer (FRET) mechanism, upconversion nanoparticles (UCNPs) were used as energy donors to achieve H2S through precise spectral matching. n Dynamic regulation of FRET efficiency by concentration; then using heterojunction engineering to construct a Bi2S3-FeIn2S4 heterojunction with an optimized band gap structure that matches the wavelength of UCNPs, while maintaining excellent optoelectronic properties, it achieves efficient conversion of optical signals to electrical signals.

[0021] Therefore, the reversible photoelectrochemical microsensor of the present invention introduces a reversible recognition of H2S n Small molecule probes, combined with FRET light regulation mechanism, can achieve H2S n Reversible detection, real-time monitoring of H2S in organisms n fluctuations, and has high selectivity and anti-interference capabilities.

[0022] 2. The reversible photoelectrochemical microsensor described in the present invention constructs an energy conversion interface based on UCNPs, uses near-infrared light excitation, and emits visible light (such as 660 nm) through a "photon upconversion" mechanism, which can effectively avoid the stimulation and damage to biological tissues caused by the high radiation energy carried by high-frequency ultraviolet photons.

[0023] 3. The immobilized reversible photoelectrochemical microsensor described in the present invention adopts an integrated light-guiding microelectrode design, which realizes the stable transmission of excitation light along the optical fiber and glass capillary path to the sensor end, and enables the irradiation area to fully cover the entire sensor surface, eliminating the need for complex external optical alignment steps, significantly improving the efficiency of light transmission and the reproducibility and stability of detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the reversible detection principle of the reversible photoelectrochemical microsensor in the present invention.

[0025] Figure 2 The reversible small molecule probe rH2S in the embodiment n Proton spectrum and high-resolution mass spectrometry.

[0026] Figure 3 The reversible small molecule probe rH2S in the embodiment n Reversibility test.

[0027] Figure 4Characterization of UCNPs in the examples; (A) is a TEM image, (B) is a particle size distribution diagram, and (C) is an XRD pattern.

[0028] Figure 5 The XRD pattern of the heterojunction Bi2S3-FeIn2S4 in the embodiment; Figure 6 The XPS spectra of the heterojunction Bi2S3-FeIn2S4 in the embodiment; among them, (A) is the full XPS spectrum, (B) is the high-resolution XPS spectrum of Bi4f and S 2p, (C) is the high-resolution XPS spectrum of In 3d, and (D) is the high-resolution XPS spectrum of Fe 2p.

[0029] Figure 7 In the embodiment, rH2S n Reversible response of UCNPs composite nanoluminescent probe to Na2S2 detection; (A) is the reversible response of UCNPs and rH2S with different concentrations n Fluorescence quenching diagram of binding, (B) rH2S n Fluorescence recovery diagram of rH2S / UCNPs after reaction with different concentrations of Na2S2. (C) is the fluorescence recovery diagram of rH2S after reaction with Na2S2. n Fluorescence response diagram of / UCNPs after reaction with different concentrations of NMM.

[0030] Figure 8 Schematic diagram of the functional modification process of the sensor; TiME is commercial titanium wire, Etched TiME is etched titanium wire, and Etching represents mixed acid etching.

[0031] Figure 9 Schematic diagram and actual picture of the reversible photoelectrochemical microsensor (light-guiding integrated microsensor) prepared in Example 1; (A) is a schematic diagram, and (B) is an actual picture: a magnified image of the exposed titanium wire tip (a) and the optical fiber coupled with optical glue (b) (scale bar 100 μm).

[0032] Figure 10 The reversible photoelectrochemical microsensor prepared in Example 1 is used to detect H2S n Feasibility verification; where (A) is r H2S n and the absorption spectra of Bi2S3-FeIn2S4 and the fluorescence emission spectra of UCNPs under 980 nm excitation. (B) is the photocurrent response diagram of the microsensors with different modified interfaces excited by 980 nm light: (a) TiME, (b) Bi2S3-FeIn2S4 / TiME, (c) UCNPs / Bi2S3-FeIn2S4 / TiME, (d) rH2S n / UCNPs / Bi2S3-FeIn2S4 / TiME and (e)rH2S n / UCNPs / Bi2S3-FeIn2S4 / TiME + Na2S2.

[0033] Figure 11 The photocurrent response diagram (A) and calibration curve (B) of the microsensor in Example 4 to different concentrations of Na2S2.

[0034] Figure 12 This is a test diagram of the reversible performance of the microsensor in Example 5.

[0035] Figure 13 This is a test diagram of the selectivity and competitiveness of the microsensor in Example 6. DETAILED DESCRIPTION

[0036] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with examples, but the present invention is not limited to the following examples.

[0037] 1. In the following examples, the reversible small molecule probe rH2S is used. n , can be synthesized using the following synthetic route:

[0038] In the above synthesis route, serial numbers 1-6 represent corresponding compounds, which are respectively referred to as compounds 1-6 in the following synthesis process.

[0039] The reversible small molecule probe rH2S n The specific synthesis process comprises the following steps: (1) Compounds 1 and 2 were purchased from Aladdin Reagents; (2) Synthesis of Compound 3: 3-Bromo-N,N-dimethylaniline (5.42 g, 27 mmol) and formaldehyde (2.23 g, 27 mmol) were mixed and dissolved in 67 mL of acetic acid. The resulting mixture was stirred at 80°C and refluxed for 12 hours. After the reaction was completed, the mixture was cooled to room temperature and the solvent was removed under vacuum. A large amount of saturated sodium bicarbonate solution was added, and the reaction product was extracted with dichloromethane and separated. Anhydrous sodium sulfate was added to the resulting organic layer for drying. The solvent was removed under vacuum again. Finally, the mixture was purified by chromatography using petroleum ether and ethyl acetate (volume ratio 30:1) as eluent to obtain white solid compound 3 (3.65 g, 67.3%).

[0040] (3) Synthesis of compound 4: Under argon protection, compound 2 (827 mg, 2 mmol) was dissolved in 20 mL of anhydrous tetrahydrofuran, then cooled to -78 °C, n-butyl lithium (1.6 mol / L, 4.375 mL, 7 mmol) was added dropwise, and the resulting mixture was stirred at the same temperature for 2 hours; then dichlorodimethylsilane (387 mg, 3 mmol) was added dropwise and stirred at room temperature for 3 hours, and then dilute hydrochloric acid (10 mL, 20 mmol) was added to quench the reaction. After the reaction was completed, a large amount of saturated sodium bicarbonate solution was added, and the reaction product was extracted with dichloromethane and separated. Anhydrous sodium sulfate was added to the obtained organic layer for drying, and the solvent was removed in vacuo again to obtain a light yellow solution of compound 4 containing impurities (4.07 g).

[0041] (4) Synthesis of Compound 5: The impurity-containing solution of Compound 4 (4.07 g) from the previous step was dissolved in 10 mL of acetone and mixed in a cold trap at -15°C. Potassium permanganate solid (800 mg, 5 mmol) was added thereto in five portions (with a time interval of 30 minutes between the first and fifth additions). The mixture was stirred at -15°C for 2 hours. The resulting mixed solution was filtered to obtain a yellow filtrate. The solvent was removed in vacuo and the mixture was purified by chromatography using dichloromethane and petroleum ether (volume ratio 2:1) as eluent to obtain a yellow-green solid Compound 5 (180 mg, 21.7%).

[0042] (5) Synthesis of compound 6: 4-Bromo-3-methylphenol (1.88 g, 10 mmol), iodohexane (2.52 g, 11.8 mmol), and potassium carbonate (1.68 g, 12.2 mmol) were mixed and dissolved in 16 mL of N,N-dimethylformamide. The resulting mixture was stirred and refluxed at 100 °C for 24 h. Subsequently, the mixture was cooled to room temperature and the solvent was removed under vacuum. The product was then purified by chromatography using petroleum ether and ethyl acetate (volume ratio 50:1) as eluents to obtain oily compound 6 (2.36 g, 87.4%).

[0043] (7) Compounds r H2S nSynthesis: Under argon, compound 6 (410 mg, 1.5 mmol) was dissolved in 5 mL of anhydrous tetrahydrofuran, cooled to -7°C, and n-butyllithium (2.5 mol / L, 2.4 mL, 6 mmol) was added dropwise. The mixture was stirred at -7°C for 2 hours. Compound 5 (98 mg, 0.3 mmol) dissolved in 5 mL of anhydrous tetrahydrofuran was then added dropwise. The mixture was stirred at -7°C for 40 minutes and then allowed to stir at room temperature for 2 hours. Dilute hydrochloric acid (10 mL, 20 mmol) was then added to quench the reaction. After the reaction was complete, a large amount of saturated sodium bicarbonate solution was added, and the reaction product was extracted with dichloromethane. The layers were separated, and the resulting organic layer was dried over anhydrous sodium sulfate. The solvent was again removed in vacuo, and the product was purified by chromatography using dichloromethane and anhydrous methanol (100:1 by volume) as eluents to obtain rH2S as a blue-green solid. n (18mg, 11.9%).

[0044] The prepared rH2S n The hydrogen spectrum and high-resolution mass spectrometry of Figure 2 shown. 1 H NMR (400 MHz, CDCl3) δ 7.16(s, 2H), 7.08 (d, J = 9.4 Hz, 2H), 6.89 (d, J = 8.1 Hz, 1H), 6.79 (d, J = 8.9 Hz,2H), 6.56 (d, J = 9.6 Hz, 2H), 3.97 (t, J = 6.6 Hz, 2H), 3.34 (s, 12H), 1.92 (s, 3H), 1.18 (s, 11H), 0.57 (d, J = 7.8 Hz, 6H). HRMS (ESI): calcd for [C 32 H 43 N2OSi]499.3139, found 499.3142. rH2S n The blue-green solid powder was dissolved in 5% dimethyl sulfoxide aqueous solution to prepare a 20 μM solution (labeled as solution a) to test rH2S n Reversible response performance to H2S2. Figure 3 As shown, the reversible small molecule probe rH2S n The characteristic absorption peak is shown at 660 nm (curve a). nAfter adding 5 μM Na2S2 into the solution (solution b), the absorption peak intensity decreased significantly (curve b), confirming that the probe is sensitive to S2 2- The rH2S2 content has a specific response, so it also has a specific response to H2S2. Subsequently, solution b and solution a were diluted 10 times with PBS buffer to obtain curves c and d. The results showed that the maximum absorption values ​​of curves c and d at 660 nm were reduced to about 1 / 10 of the original value. This phenomenon can be attributed to the dilution causing the concentration of Na2S2 to drop to a negligible level, making the spectral characteristics of the mixed system solution b and the pure probe solution a consistent. It is worth noting that the absorption value of curve c at 660 nm is slightly higher than that of curve d, which may be due to the trace amount of Na2S2 remaining in the dilution solution b. For further verification, solution b was diluted 10 times with PBS buffer containing the same concentration of Na2S2 to obtain solution e. Compared with solution d, the absorption peak of solution e at 660 nm was further weakened. This result not only confirmed that rH2S n The reversibility of the interaction with Na2S2 also showed that the absorption intensity of the probe at 660 nm was dose-dependent with the Na2S2 concentration.

[0045] 2. In the following examples, the upconversion nanoparticles used are specifically NaYbF4: 2%Er 3+ / 5%Mn 2+ , the synthesis process is as follows: Ytterbium nitrate (0.93 mmol), erbium nitrate (0.02 mmol), and manganese chloride (0.05 mmol) were sequentially added to a 20 mL aqueous solution containing 2 mmol of citric acid. The mixture was magnetically stirred for 30 minutes and then sonicated for 30 minutes to obtain a homogeneous lanthanide-citric acid complex precursor solution (designated as Solution A). Simultaneously, sodium hydroxide (2.5 mmol) and ammonium fluoride (6 mmol) were dissolved in 15 mL of ethanol and sonicated until the solution became clear (designated as Solution B). Solution B was slowly added dropwise to Solution A under continuous stirring. Stirring was continued for 30 minutes, until a milky white suspension gradually formed. The mixed solution was then transferred to a 50 mL polytetrafluoroethylene-lined autoclave and reacted in a muffle furnace at 200°C for 8 hours. After the reaction system was naturally cooled to room temperature, the product was separated by centrifugation at a speed of 8000 r / min, and then washed alternately with ultrapure water and anhydrous ethanol four times. The treated solid was placed in a vacuum oven and dried at 60°C to completely lose residual moisture to obtain the target product UCNPs.

[0046] Figure 4The TEM image (A), particle size distribution diagram (B) and XRD pattern (C) of the prepared UCNPs confirm that the synthesized UCNPs have a highly uniform spherical morphology, and the average particle size is approximately 29 nm, with a size range of 25 nm to 35 nm; the XRD spectrum shows a typical hexagonal crystal structure, indicating that the UCNPs have excellent crystalline integrity.

[0047] 3. In the following examples, the Bi2S3-FeIn2S4 heterojunction is composed of Bi2S3 and FeIn2S4 in a molar ratio of 2:1. The synthesis process is as follows: Accurately weighed bismuth nitrate pentahydrate (2 mmol), indium chloride (1 mmol), ferric acetate tetrahydrate (0.5 mmol), and thioacetamide (TAA, 5 mmol) were dispersed in 90 mL of ultrapure water and magnetically stirred for 15 minutes to form a homogeneous mixed solution. The reaction system was then transferred to a preheated oil bath and stirred at 90°C for 2 hours. After the reaction, the black precipitate was collected by centrifugation (8000 rpm, 10 minutes) and washed three times with deionized water and anhydrous ethanol to remove unreacted precursors. Finally, the product was dried in a vacuum oven at 60°C for 12 hours to obtain a composite photoelectrically active Bi2S3-FeIn2S4 heterojunction.

[0048] The XRD and XPS patterns of the prepared Bi2S3-FeIn2S4 are as follows Figure 5 、 6 As shown in the figure, the XRD diffraction pattern shows characteristic diffraction peaks of both Bi2S3 (JCPDS No. 17-0320) and FeIn2S4 (JCPDS No. 80-0608). XPS characterization confirmed the composition and elemental valence of the heterojunction. These results indicate that the Bi2S3-FeIn2S4 heterojunction material has been successfully constructed.

[0049] 4. In the following examples, the composite nanoluminescent probe (rH2S n The preparation method of UCNPs is as follows: UCNPs powder was dispersed in ultrapure water to prepare a UCNPs dispersion with a concentration of 5 mg / mL; Small molecule probe rH2S n Dispersed in a mixed solvent of DMSO and water to obtain rH2S n Dispersion; wherein the volume percentage of DMSO in the mixed solvent is 3%, rH2S nThe concentration in the mixed solvent was 1~100 μM (the specific concentrations were 1, 2, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 μM, and a concentration of 0 was used as a blank control); Take 4 mL of UCNPs dispersion and mix with 1 mL of rH2S of different concentrations. n The dispersions were mixed and then placed in a constant temperature oscillator (25 °C, 150 r / min) for 12 h to ensure that the rH2S n The molecules were fully modified on the surface of UCNPs. Subsequently, the unbound free rH2S was removed by centrifugation (10000 r / min, 15 min). n After collecting the precipitate, it was washed several times with ultrapure water until the supernatant had no obvious absorption characteristics in the visible light region, and finally the composite nanoluminescent probe (rH2S n / UCNPs). Due to rH2S n The concentration of the solution is different to obtain the composite nanoluminescent probe rH2S n rH2S in UCNPs n with different ratios of UCNPs.

[0050] Subsequently, the above rH2S in different proportions n The / UCNPs probes were dispersed in ultrapure water solution, and the concentration of the dispersion was 2.5 mg / mL. The emission spectra were measured under 980 nm excitation light. n As the concentration increases, the upconversion luminescence intensity decreases, such as Figure 7 As shown in A, UCNPs act as energy donors, and their upconversion luminescence (UCL) is converted to rH2S through the FRET pathway. n Effective quenching, the highest quenching efficiency is 90%. Select rH2S with the maximum quenching point of UCL signal n / UCNPs probe dispersion (probe concentration is 100 μM), the target substitute Na2S2 (0~30 μM) was introduced into the system in a gradient manner, such as Figure 7 As shown in B, when Na2S2 exists in the system, rH2S n The characteristic absorption at 660 nm was significantly weakened, resulting in the interaction between the donor (UCNPs) and the acceptor (rH2S n ) spectrum overlap decreased, FRET efficiency decreased, and UCL signal recovered. After further addition of scavenger N-methylmaleimide (NMM), Na2S2 and rH2S n / UCNPs composite probe dissociation, such as Figure 7 As shown in C, the FRET effect is initiated again and causes UCL to be quenched again.

[0051] The above results show that the composite nanoluminescent probe rH2S n / UCNPs show a reversible response to Na2S2 and can also achieve reversible response to H2S n It is worth noting that the dynamic change of the UCL intensity at 660 nm can effectively stimulate the Bi2S3-FeIn2S4 heterojunction to generate a photocurrent signal. This strategy of converting optical signals into electrical signals fully utilizes the technical advantage of the high sensitivity of photoelectrochemical detection.

[0052] Example 1 A method for preparing a reversible photoelectrochemical microsensor, the specific steps are as follows: (1) A capillary with an inner diameter of 500 μm and an outer diameter of 1000 μm was pulled using a pulling apparatus to obtain a tapered glass capillary with a tip diameter of 120 μm; (2) A clean commercial titanium wire with a diameter of 100 μm was used as the base electrode, and a transparent optical fiber with a diameter of 200 μm was used as the light guide component. The titanium wire and the optical fiber were arranged parallel to each other along the axis and inserted into the prefabricated glass capillary cavity. It was important to insert the optical fiber as much as possible into the electrode tip, and at the same time, the exposed length of the titanium wire tip was strictly controlled to be 500 μm. The capillary was then filled with optical glue and cured by UV (wavelength 365 nm, power 30 mW / cm 2 , time 5 min); (3) Mix 3% HF, 6% HNO3, and 91% ultrapure water in a volume ratio to obtain a mixed acid etching solution. Immerse the exposed area of ​​the titanium wire at the tip of the electrode in the mixed acid etching solution and etch for 2 minutes to form a porous rough surface. Immediately after etching, rinse with deionized water to terminate the reaction. Ultrasonic washing is performed three times with acetone, ethanol, and deionized water in sequence. The electrode is then placed in a vacuum drying oven (25°C, -0.1 MPa) for 12 hours to completely remove residual moisture.

[0053] (4) The etched electrode obtained in (3) was vertically immersed in 2 μL of Bi2S3-FeIn2S4 dispersion (the solvent was ultrapure water, the concentration was 2.5 mg / mL), and the electrode was allowed to stand at room temperature for 12 h to achieve Bi2S3-FeIn2S4 heterojunction loading, thereby obtaining a Bi2S3-FeIn2S4 / TiME microelectrode; (5) Transfer the Bi2S3-FeIn2S4 / TiME microelectrode to 2 μL rH2S n / UCNPs dispersion (solvent: ultrapure water, concentration: 2.5 mg / mL) was self-assembled layer by layer. The assembly process lasted for 12 h at room temperature. n Reversible photoelectrochemical microsensor rH2Sn / UCNPs / Bi2S3-FeIn2S4 / TiME.

[0054] like Figure 10 As shown in A, spectral matching analysis shows that the Bi2S3-FeIn2S4 heterojunction exhibits a significant light absorption peak at 660 nm. This characteristic peak forms an effective spectral overlap with the UCL characteristic band of UCNPs, which lays a photophysical foundation for generating photocurrent signals based on UCL excitation.

[0055] Figure 10 B evaluated the photocurrent signal change trend of the electrode interface of different components under 980nm light. The commercial titanium wire almost did not generate a photocurrent signal (curve a); after modifying the Bi2S3-FeIn2S4 heterojunction, a weak photocurrent was generated (curve b, 5 nA). This may be because Bi2S3-FeIn2S4 mainly began to absorb above 800 nm, and the energy of near-infrared light was not enough to effectively excite it to generate photocurrent. When the electrode surface was further modified with UCNPs, the photocurrent signal was significantly enhanced (curve c, 91 nA), indicating that UCNPs can serve as a receiving and conversion medium for near-infrared light, converting 980 nm excitation light into higher energy 660 nm visible light, thereby effectively exciting Bi2S3-FeIn2S4 to generate a photocurrent signal. Subsequently, when the composite nanoluminescent probe rH2S was used n / UCNPs, due to rH2S n After modification to the surface of UCNPs, FRET interaction occurred between the two, resulting in quenching of the UCL of UCNPs, thereby weakening the photocurrent signal (curve d, 15 nA); when 15 μM Na2S2 was added to the system, rH2S n The photocurrent signal of the / UCNPs / Bi2S3-FeIn2S4 / TiME microsensor recovered to 80 nA (curve e). The above results demonstrate that rH2S has molecular reversible recognition function. n / UCNPs / Bi2S3-FeIn2S4 / TiME photoelectrochemical microsensor was successfully constructed.

[0056] Example 2 A method for preparing a reversible photoelectrochemical microsensor, the specific steps are as follows: (1) A capillary with an inner diameter of 500 μm and an outer diameter of 1000 μm was pulled using a pulling apparatus to obtain a tapered glass capillary with a tip diameter of 150 μm; (2) A clean commercial silver wire with a diameter of 120 μm was used as the base electrode, and a transparent optical fiber with a diameter of 250 μm was used as the light guide component. The titanium wire and the optical fiber were arranged parallel to the axis and inserted into the prefabricated glass capillary cavity. Attention was paid to inserting the optical fiber as much as possible into the electrode tip, while strictly controlling the exposed length of the titanium wire tip to 400 μm. The capillary was then filled with optical glue and cured by UV (wavelength 365 nm, power 30 mW / cm 2 , time 5 min); (3) Mix 8% HF, 20% HNO3, and 72% ultrapure water in a volume ratio to obtain a mixed acid etching solution. Immerse the exposed area of ​​the titanium wire at the tip of the electrode in the mixed acid etching solution and etch for 1 min to form a porous rough surface. Immediately after etching, rinse with deionized water to terminate the reaction. Ultrasonic washing is performed three times with acetone, ethanol, and deionized water in sequence. The electrode is then placed in a vacuum drying oven (25°C, -0.1 MPa) for 12 h to completely remove residual moisture.

[0057] (4) The etched electrode obtained in (3) was vertically immersed in 2 μL of Bi2S3-FeIn2S4 dispersion (the solvent was ultrapure water, the concentration was 8 mg / mL), and the electrode was allowed to stand at room temperature for 6 h to achieve Bi2S3-FeIn2S4 heterojunction loading, thereby obtaining a Bi2S3-FeIn2S4 / TiME microelectrode; (5) Transfer the Bi2S3-FeIn2S4 / TiME microelectrode to 2 μL 1.5 mg / mL rH2S n / UCNPs dispersion was self-assembled layer by layer, and the assembly process was allowed to stand at room temperature for 10 h to obtain the detection of H2S n Reversible photoelectrochemical microsensor rH2S n / UCNPs / Bi2S3-FeIn2S4 / TiME.

[0058] Example 3 A method for preparing a reversible photoelectrochemical microsensor, the specific steps are as follows: (1) A capillary with an inner diameter of 500 μm and an outer diameter of 1000 μm was pulled using a pulling apparatus to obtain a tapered glass capillary with a tip diameter of 100 μm; (2) A clean commercial platinum wire with a diameter of 80 μm was used as the metal electrode, and a transparent optical fiber with a diameter of 150 μm was used as the light guide component. The titanium wire and the optical fiber were arranged parallel to the axis and inserted into the prefabricated glass capillary cavity. Attention was paid to inserting the optical fiber as much as possible into the electrode tip, while strictly controlling the exposed length of the titanium wire tip to 600 μm. The capillary was then filled with optical glue and cured by UV (wavelength 365 nm, power 30 mW / cm 2 , time 5 min); (3) Mix 5% HF, 10% HNO3, and 85% ultrapure water in a volume ratio to obtain a mixed acid etching solution. Immerse the exposed area of ​​the titanium wire at the tip of the electrode in the mixed acid etching solution and etch for 3 minutes to form a porous rough surface. Immediately after etching, rinse with deionized water to terminate the reaction. Ultrasonic washing is performed three times with acetone, ethanol, and deionized water in sequence. The electrode is then placed in a vacuum drying oven (25°C, -0.1 MPa) for 12 hours to completely remove residual moisture.

[0059] (4) The etched electrode obtained in (3) was vertically immersed in 2 μL of Bi2S3-FeIn2S4 dispersion (the solvent was ultrapure water, the concentration was 5 mg / mL), and the electrode was allowed to stand at room temperature for 24 h to achieve Bi2S3-FeIn2S4 heterojunction loading, thereby obtaining a Bi2S3-FeIn2S4 / TiME microelectrode; (5) Transfer the Bi2S3-FeIn2S4 / TiME microelectrode to 2 μL 2 mg / mL rH2S n / UCNPs dispersion was self-assembled layer by layer, and the assembly process was allowed to stand at room temperature for 20 h to obtain the detection of H2S n Reversible photoelectrochemical microsensor rH2S n / UCNPs / Bi2S3-FeIn2S4 / TiME.

[0060] Example 4 This embodiment provides a method for detecting H2S using a reversible photoelectrochemical microsensor. n The method used artificial cerebrospinal fluid (containing 200 μM ascorbic acid) as the detection object, and the specific process is as follows: Test conditions: The test was carried out on a CHI 660E electrochemical workstation using a standard three-electrode system. The reversible photoelectrochemical microsensor rH2S prepared in Example 1 was used. nA / UCNPs / Bi2S3-FeIn2S4 / TiME electrode was used as the working electrode, a silver / silver chloride electrode as the reference electrode, and a platinum wire as the counter electrode. A 980 nm near-infrared laser was used as the excitation light source. All measurements were performed under zero bias conditions. The reversible photoelectrochemical microsensor was inserted into solutions containing varying concentrations of Na2S2 (0, 1, 2, 3, 4, 5, 6, 8, 10, 12, and 15 μM). After a 2-minute incubation, the photocurrent signal was acquired. A standardized signal acquisition method was used: the last stable potential point before photoexcitation was used as the baseline, and the steady-state value 10 s after photoexcitation was used as the response endpoint. The current difference between the two was defined as the photocurrent response.

[0061] Figure 11 A shows that as the concentration of Na2S2 increases, the photocurrent of the reversible photoelectrochemical microsensor is significantly enhanced, and in the linear range of 1~15 μM, the photocurrent response shows a good linear correlation with the target concentration. A standard curve is established with the Na2S2 concentration as the horizontal axis and the photocurrent value as the vertical axis, as shown in FIG. Figure 11 As shown in B, the regression equation of the standard curve is I PEC =4.34 c (μmol / L) + 15.55( R 2 = 0.9982)( I PEC :nA; c : μmol / L), with a limit of detection (LOD) of 0.387 μM (3σ / k, n=10), which further demonstrated that the reversible photoelectrochemical microsensor has excellent quantitative detection capability for Na2S2.

[0062] Subsequently, a Na2S2 standard solution with a concentration of 7.7 μM was prepared under the aforementioned test conditions, generating a photocurrent signal of 48.92 nA. Substituting this photocurrent signal into the aforementioned standard curve, the concentration was calculated to be 7.689 μM. The absolute deviation between this measured and calculated value and the prepared concentration was 0.011 μM (relative error 0.14%), confirming the excellent detection accuracy of the reversible photoelectrochemical microsensor.

[0063] Example 5 Under the same test conditions as in Example 4, the reversible photoelectrochemical microsensor rH2S prepared in Example 1 was n / UCNPs / Bi2S3-FeIn2S4 / TiME were alternately immersed in artificial cerebrospinal fluid containing Na2S2 (10 μM) and artificial cerebrospinal fluid without Na2S2 to test the reversible detection performance of the sensor. The steady-state photocurrent signal was collected after each incubation for 2 minutes. Figure 12As shown, the reversible photoelectrochemical microsensor exhibited highly reversible photoelectric response in four sets of continuous cycles, and was able to maintain the consistency and reproducibility of the photoelectric signal response under different Na2S2 concentrations, confirming the good reversibility of the electrode interface reaction and the long-term stability of the detection system, and at least four cycles of continuous repeated measurements could be performed.

[0064] Example 6 Under the same test conditions as in Example 4, the selectivity and anti-interference performance of the sensor were evaluated. Interferors were divided into the following three groups: (A) Anions and sulfur-containing substances: Cys, GSH, NO3 - 、Cl - 、HCO3 - 、Hcy、S2O3 2- 、Na2S2、SO3 2- 、SO4 2- , Na2S, Na2S2 (Na2S2 is 10 μM, GSH is 1 mM, NO3 - 20 μM, Cl - 150 mM HCO3 - 50 mM, other substances were 20 μM, water was used as solvent, and each anion was prepared as its sodium salt); (B) Amino acids and metal ions: Glu, Leu, Try, Gly, His, Arg, Lys, NE, 5-HT, K + 、Na + , Ca 2+ (Lys is 50 μM, K + 3 mM, Na + 150 mM Ca 2+ 1 mM, other substances were 20 μM, prepared in water as solvent, and all cations were prepared as their chloride salts); (C) Other biological species and neurotransmitters: H2O2, 1 O2, •OH, ONOO - , ClO - AA, DA, UA, glucose, ATP, Lact (AA is 200 μM, DA is 20 nM, glucose is 500 μM, ATP is 10 nM, Lact is 1 mM, other substances are 10 μM, prepared with water as solvent; 1 O2 is generated in situ by adding HClO to an excess H2O2 solution (ClO - / H2O2=1:5); •OH is generated in situ by adding FeCl2 to the excess H2O2 solution (Fe 2+ / H2O2=1:6);ONOO- ClO was generated in situ by adding HCl to a solution of NaNO2 and excess H2O2 at 0°C and then quickly adding NaOH (HCl / NaNO2 / H2O2 / NaOH=6:6:7:3); - Made from NaClO).

[0065] Perform the anti-interference experiment by following the steps below: 1. Baseline measurement: Steady-state photocurrent signal is collected in blank artificial cerebrospinal fluid (aCSF) ( I 0); 2. Control assay: Incubate in aCSF containing 10 μM Na2S2 for 15 min and record the signal ( ) 3. Interference experiment: Each interfering substance in each group was added to aCSF separately, and the signal was recorded after incubation for 15 min ( I 干扰 ); 4. Competitive assay: Add 10 μM Na2S2 to the aCSF containing interfering substances and measure the mixed signal ( I 混合 ).

[0066] like Figure 13 As shown, the photocurrent signal fluctuation caused by the addition of interfering substances is less than 3.9% ( ΔI / ΔI 0= ( I 干扰 - I 0) / ( - I 0)×100%), in the competitive detection experiment, even if the concentration of some interfering substances is much higher than that of Na2S2, the response signal of the reversible photoelectrochemical microsensor to Na2S2 changes by less than 3.3% ( ΔI / ΔI 0= ( I 混合 - I 干扰 ) / ( - I 干扰 )×100%). This indicates that the sensor still has high selectivity and anti-interference ability in complex biological systems.

[0067] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A reversible photoelectrochemical microsensor, characterized in that: It uses a metal electrode as a substrate, and sequentially modifies a Bi2S3-FeIn2S4 heterojunction and a composite nanoluminescent probe at one end thereof; the composite nanoluminescent probe is composed of a small molecule probe and an upconversion nanoluminescent particle; wherein the small molecule probe serves as a selective recognition unit and energy acceptor, and the upconversion nanoluminescent particle serves as an energy donor and energy conversion element to activate the Bi2S3-FeIn2S4 heterojunction; the Bi2S3-FeIn2S4 heterojunction serves as a photoelectric signal converter, and utilizes a reversible nucleophilic addition reaction between the target and the small molecule probe to reduce the fluorescence resonance energy transfer efficiency between the small molecule probe and the upconversion nanoluminescent particle, thereby changing the photocurrent signal and realizing the detection of the target.

2. A reversible photoelectrochemical microsensor according to claim 1, characterized in that: The composite nanoluminescent probe is a positively charged rH2S n The molecules are self-assembled with the negatively charged UCNPs through electrostatic attraction; the target is H2S n , small molecule probe rH2S n It is N-(7-(dimethylamino)-10-(4-(hexyloxy)-2-methylphenyl)-5,5-dimethyldibenzo[b,e]silanol-3(5H)-en-3-yl)-N-methylmethanamine, and its chemical structure is 。 3. A reversible photoelectrochemical microsensor according to claim 2, characterized in that: The preparation method of the composite nanoluminescent probe comprises the following steps: (1) Dispersing UCNPs in water to obtain a UCNPs dispersion with a concentration of 1-10 mg / mL; (2) The small molecule probe rH2S n Dispersed in a mixed solvent of DMSO and water to obtain rH2S n dispersion; wherein the volume percentage of DMSO in the mixed solvent is 1%~5%; rH2S n The concentration in the mixed solvent is 1~100μM; (3) According to the mass of UCNPs and rH2S n The ratio between the amount of substance is 1mg: (0.05-2.5) nmol, UCNPs dispersion and rH2S n The dispersion was mixed and shaken at room temperature to make rH2S n The UCNPs were fully modified; then, the unbound free rH2S was removed by centrifugation. n The precipitate was collected and washed until the supernatant had no obvious absorption characteristics in the visible light region, thereby obtaining the composite nanoluminescent probe rH2S. n / UCNPs.

4. A reversible photoelectrochemical microsensor according to claim 1, characterized in that: The chemical composition of the upconversion nanoluminescent particles is NaYbF4: Er 3+ / Mn 2+ , which are nano-scale particles, have characteristic emission peaks in the wavelength range of 630~700nm under near-infrared light excitation.

5. The reversible photoelectrochemical microsensor according to claim 1, characterized in that: The Bi2S3-FeIn2S4 heterojunction is composed of Bi2S3 and FeIn2S4 in a molar ratio of 1:1 to 4:1; and the absorption spectrum of the Bi2S3-FeIn2S4 heterojunction has a characteristic absorption peak at 630 to 700 nm, which matches the characteristic emission peak of UCNPs.

6. A reversible photoelectrochemical microsensor according to claim 1, characterized in that: The preparation method of the Bi2S3-FeIn2S4 heterojunction is as follows: using bismuth nitrate pentahydrate, indium chloride, ferric acetate tetrahydrate and thioacetamide as raw materials, using water as solvent, stirring and reacting at 90~120°C for a certain time, and storing in the dark; wherein, the raw materials are mixed according to the molar ratio of Bi: In: Fe: S = 1: (0.25~1): (0.125~0.5): (2~3.5), and the reaction time is 1~3h.

7. The reversible photoelectrochemical microsensor according to claim 1, characterized in that: The diameter of the metal electrode is in the range of 50~150μm, and the length of the modified end is in the range of 300~600μm.

8. The method for preparing the reversible photoelectrochemical microsensor according to claim 2, wherein: The steps include: ① Immerse one end of the metal electrode in an etching solution for acid etching, and after washing, obtain the etched electrode TiME; ② Immerse the etched TiME electrode in a Bi2S3-FeIn2S4 dispersion and let it stand to achieve the loading of the Bi2S3-FeIn2S4 heterojunction and obtain a Bi2S3-FeIn2S4 / TiME microelectrode; ③Immerse the Bi2S3-FeIn2S4 / TiME microelectrode in rH2S n / UCNPs were allowed to self-assemble in the solution to detect H2S n Reversible photoelectrochemical microsensor.

9. The method for preparing a reversible photoelectrochemical microsensor according to claim 8, wherein: The etching solution system is composed of 1~10% HF, 1~30% HNO3 and 60~98% water by volume, and the etching time is controlled at 1~5min; the Bi2S3-FeIn2S4 dispersion liquid uses water as the solvent and the concentration is 0.5~10mg / mL; rH2S n / UCNPs solution uses water as solvent and the concentration is 0.5~3mg / mL.

10. An immobilized reversible photoelectrochemical microsensor, characterized in that: The invention comprises the reversible photoelectrochemical microsensor according to claim 1, and also comprises a transparent glass capillary and a transparent light-guiding optical fiber; the reversible photoelectrochemical microsensor according to claim 1 and the transparent light-guiding optical fiber are arranged axially parallel and inserted into the cavity of the glass capillary, and the reversible photoelectrochemical microsensor according to claim 1 passes through the tip of the necked section of the glass capillary, and the inner cavity of the glass capillary is filled with optical glue and ultraviolet curing is performed.

11. The immobilized reversible photoelectrochemical sensor according to claim 10, characterized in that The inner diameter and outer diameter of the glass capillary are respectively in the range of 500-800 μm and 800-1100 μm. The glass capillary is drawn into a necked section at one end by a drawing instrument, and the diameter of the necked section tip is 50-200 μm. The diameter of the transparent light-guiding optical fiber is 100-300 μm.

12. Detection of H2S using the reversible photoelectrochemical microsensor according to claim 2 or the immobilized reversible photoelectrochemical microsensor according to claim 10 n The method is characterized in that The steps include: 1) Prepare a Na2S2 standard solution with gradient concentrations using a Na2S2 standard sample; 2) inserting the reversible photoelectrochemical microsensor according to claim 2 or the immobilized reversible photoelectrochemical microsensor according to claim 10 into Na2S2 standard solutions of different concentrations, and collecting photocurrent data using a three-electrode system under near-infrared light excitation with the aid of an electrochemical workstation; then establishing a standard curve with the Na2S2 concentration in the Na2S2 standard solution as the abscissa and the photocurrent value as the ordinate; 3) Under conditions parallel to step 2), the reversible photoelectrochemical microsensor according to claim 2 or the immobilized reversible photoelectrochemical microsensor according to claim 10 is inserted into the sample to be tested, the photocurrent of the sample to be tested is detected, and then the standard curve method is used to realize the target H2S in the sample to be tested. n Detection.

13. The method according to claim 12, characterized in that The samples to be tested include organisms, blood, cell culture fluid and environmental water samples.

Images