A high-performance self-powered wide-spectrum photodetector based on BiVO4 / Bi2S3 / Co3O4 multi-level interface regulation and its application in underwater optical communication

Abstract

The application provides a high-performance self-powered wide-spectrum photodetector based on BiVO4 / Bi2S3 / Co3O4 multi-level interface regulation and submarine optical communication application. The heterojunction with close contact interface is obtained by a method of directly sulfidizing BiVO4 through a solvothermal method, and then a method of photo-deposition is used to modify Co3O4 co-catalyst on the basis of the heterojunction to construct a BiVO4 / Bi2S3 / Co3O4 heterojunction structure, wide-spectrum response from deep ultraviolet to near infrared is realized, and zero-bias self-powered characteristics are possessed. The photodetector exhibits high responsivity (85.32 mA W ‑1 ), fast response time (11.2 / 9.6 ms) and excellent stability under the condition of no hole sacrificial agent, and realizes high-speed optical communication with a-3dB cutoff frequency higher than 1120 Hz in simulated seawater, solving the problems of power supply and stability of submarine communication.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of photoelectric detection, and particularly relates to a high-performance self-powered wide-spectrum photoelectric detector based on BiVO4 / Bi2S3 / Co3O4 multi-level interface regulation and an underwater optical communication application. BACKGROUND

[0002] With the rapid development of marine exploration, seabed resource development, and underwater military communication, the demand for underwater wireless communication technology is increasingly urgent. In traditional underwater communication technology, acoustic communication has the problems of narrow bandwidth, low transmission rate, and high delay, and radio communication is difficult to achieve long-distance transmission due to the severe attenuation of electromagnetic waves in seawater. Underwater optical communication (UOC) has become the core direction of the next generation of underwater wireless communication due to its greater bandwidth, faster transmission rate, lower delay, and higher security.

[0003] The performance of the underwater optical communication system highly depends on the performance of the photoelectric detector, which needs to meet three core requirements: first, wide-spectrum response capability, which needs to cover the waveband with good seawater penetration to adapt to the light transmission characteristics of seawater at different depths and to realize encrypted communication; second, fast response speed, which needs to match the signal modulation frequency of high-speed communication; and third, long-term stability, which needs to withstand the complex environment of high salinity, microbial attachment, and chemical corrosion in seawater, and at the same time, limited by the problem of underwater power supply, the detector also needs to have self-powered characteristics to reduce the dependence on external power supply.

[0004] Two-dimensional (2D) materials provide an ideal platform for constructing high-performance photoelectric detectors due to their extremely high specific surface area, unique layer-dependent electronic structure, and excellent photoelectric properties. The high specific surface area can enhance light absorption efficiency and shorten the carrier diffusion distance, showing broad application prospects in the field of photoelectric detection. Among them, photoelectrochemical (PEC) type devices can spontaneously form a built-in electric field to realize the separation of photo-generated carriers through the redox reaction at the solid-liquid interface, and can operate without external bias, naturally having self-powered characteristics, perfectly meeting the needs of low energy consumption and no power supply in the underwater environment, becoming the preferred structure of underwater optical communication detectors.

[0005] However, current PEC type devices still face three major bottlenecks in underwater optical communication applications, which seriously limit their practical application:

[0006] First, the light absorption range is narrow, which is difficult to cover the wide-spectrum requirement of underwater. The energy band structure of a single semiconductor material is fixed, and the light absorption range is limited. The light transmission characteristics of seawater at different depths are significantly different, and the surface seawater needs to respond to ultraviolet to visible light, and the deep seawater needs near-infrared light to penetrate, so a single semiconductor material is difficult to cover the full-band detection requirement, resulting in limited communication distance and environmental adaptability, and it is difficult to carry out encrypted communication and other applications.

[0007] Second, the semiconductor is susceptible to photo corrosion and chemical corrosion, and has poor stability. When the PEC device is working, the semiconductor is in direct contact with the electrolyte, and the photo-generated holes generated under light irradiation cannot participate in the redox reaction in time, which will gather on the surface of the semiconductor to induce self-oxidation reaction (i.e. photo corrosion); at the same time, Cl - , OH - and other ions in seawater will cause chemical corrosion of the semiconductor, resulting in degradation of the material structure. The prior art often adds Na2S, Na2SO3 and other hole sacrificial agents to consume photo-generated holes to alleviate corrosion, but the sacrificial agent will be gradually consumed with the reaction, which cannot realize long-term stable operation, and will introduce impurities to affect the stability of the communication signal, and it is difficult to solve the corrosion problem from the root.

[0008] Third, the carrier separation efficiency is low, and the response speed and detection performance are insufficient. In the traditional PEC device, the photo-generated electron-hole pairs are easy to recombine in the semiconductor or at the interface, resulting in low carrier separation efficiency, which affects the photocurrent density, response speed and detection sensitivity.

[0009] To solve the above problems, researchers try to optimize the device performance through surface modification, heterostructure construction and other strategies. The existing schemes are mostly limited to single performance optimization, and cannot realize the synergistic improvement of “wide spectral response - fast response - high stability - self-powered”. Moreover, there is a lack of design for complex underwater environment, which leads to the difficulty of the device in balancing the communication rate, distance and long-term reliability in the actual underwater optical communication scene. Therefore, developing a self-powered PEC photodetector that can simultaneously solve the problems of narrow spectrum, poor stability and slow response, and adapt to the high-salt environment under the sea, has become a key breakthrough for promoting the practicalization of underwater optical communication technology. SUMMARY

[0010] In view of the deficiencies in the fields of PEC photodetection and underwater optical communication, the present application aims to provide a high-performance self-powered wide-spectrum photodetector based on BiVO4 / Bi2S3 / Co3O4 multi-level interface regulation and its application in underwater optical communication. The present application discards the complex process that may introduce impurities or cause interface defects in the preparation of traditional heterojunction, and adopts in-situ surface direct sulfidation method. This method makes thiourea directly react with the surface atoms of BiVO4, Bi 3+ and S 2-Bi2S3 nanocrystals are generated in situ on the surface of BiVO4. This in-situ growth mode can minimize the lattice mismatch and interface state density of the heterojunction interface, ultimately forming a BiVO4 / Bi2S3 heterojunction structure with strong interface binding force, large contact area and no obvious interface gap, laying a structural foundation for the subsequent efficient transport of photo-generated carriers. The energy band structure of BiVO4 and Bi2S3 meets the matching conditions of type II heterojunction. When excited by light, the photo-generated holes in the valence band of BiVO4 will transfer to the valence band of Bi2S3, while the photo-generated electrons in the conduction band of Bi2S3 will transfer to the conduction band of BiVO4. This interfacial carrier migration path fundamentally avoids the recombination of photo-generated electron-hole pairs. The contact between the two will form an internal built-in electric field pointing from BiVO4 to Bi2S3, further accelerating the spatial separation of photo-generated carriers and improving the efficiency of photo-generated carrier separation. Moreover, while retaining the high light response of BiVO4 in the visible band, Bi2S3 is used to widen the light absorption to the near-infrared band, achieving a wide spectral response from 254 nm to 950 nm. In order to solve the surface corrosion problem of the PEC device, Co3O4 clusters are directly photodeposited on the surface of the heterojunction to optimize the photo-hole transfer dynamics. Co3O4 clusters can quickly capture holes through energy level coupling, avoiding the accumulation and retention of holes on the surface of the heterojunction, thus alleviating the corrosion problem from the perspective of carrier dynamics, and greatly improving the stability of the BiVO4 / Bi2S3 heterojunction. The Co3O4-modified heterojunction exhibits stronger carrier separation and faster surface reaction kinetics, significantly improving the light response performance and response speed. The BiVO4 / Bi2S3 / Co3O4-based PEC PDs achieve a high response of 85.32 mAW -1 and a fast response time of 11.2 / 9.6 ms under zero bias without a sacrificial agent. Finally, the application in PEC type wide-spectrum photodetection is further explored, and an actual application of an underwater optical communication system is constructed.

[0011] The application provides a high-performance self-powered wide-spectrum photodetector based on BiVO4 / Bi2S3 / Co3O4 multi-level interface regulation, which comprises a BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode.

[0012] The preparation method of the BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode comprises the following steps:

[0013] (1) BiVO4 photoanode preparation: BiOI film is prepared by electrodeposition, and then annealing and alkali washing are performed to convert the BiVO4 photoanode; (2) BiVO4 / Bi2S3 heterojunction preparation: the BiVO4 photoanode obtained in step (1) is placed in a thiourea precursor solution, and is sulfurized at 160 DEG C for 4h by solvent thermal method to obtain a BiVO4 / Bi2S3 heterojunction;

[0014] (3) Co3O4 co-catalyst deposition: the BiVO4 / Bi2S3 heterojunction obtained in step (2) is immersed in a CoCl2-NaIO3 mixed precursor solution, and a BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode is obtained by photo-deposition under ultraviolet light irradiation for 15 min.

[0015] Preferably, in step (1), the voltage for electrodeposition of BiOI is -0.1 V, and the time is 600 s; the annealing rate is 2 ℃ / min, the annealing temperature is 450 ℃, and the time is 2 h; the alkali washing uses a 1 M NaOH solution, and the soaking time is 30 min.

[0016] Preferably, in step (2), the thiourea precursor solution is a mixed solution obtained by dissolving thiourea in water and ethanol, wherein the mass ratio of thiourea, water and ethanol is 115.3:9000:7101.

[0017] Preferably, in step (3), the CoCl2-NaIO3 mixed precursor solution is obtained by mixing a CoCl2 solution with a concentration of 2 mmol / 10 mL and a NaIO3 solution with a concentration of 3.2 mmol / 80 mL, wherein the volume ratio of the CoCl2 solution and the NaIO3 solution is 320 μL:80 mL.

[0018] Preferably, the high-performance self-powered wide-spectrum photodetector comprises a three-electrode system for being arranged in an electrolyte.

[0019] The three-electrode system comprises a working electrode, a counter electrode and a reference electrode; the working electrode is a BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode.

[0020] Preferably, in the three-electrode system, the counter electrode is a Pt wire, and the reference electrode is an Ag / AgCl electrode.

[0021] The electrolyte is arranged in an electrolyte tank, the electrolyte is a 1 M potassium phosphate neutral buffer (KPI), and no sacrificial agent is added in the electrolyte tank; the three-electrode system is suspended in the electrolyte tank and contacts the electrolyte but does not contact the tank bottom; the potassium phosphate neutral buffer (KPI) comprises 1 M dipotassium hydrogen phosphate and 1 M monopotassium phosphate.

[0022] The application further provides an application of the high-performance self-powered wide-spectrum photodetector in underwater optical communication, wherein the photodetector is matched with a TTL-modulated 405 nm laser system to construct an underwater optical communication system, and in the three-electrode system for being arranged in an electrolyte, the electrolyte is seawater.

[0023] The application also provides application of the high-performance self-powered wide-spectrum photodetector in underwater optical communication, comprising the following steps:

[0024] An underwater optical communication system is constructed, and the underwater optical communication system comprises a signal generator, a TTL modulated laser device, an electrochemical workstation, a photodetector and a data display module.

[0025] The BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode has a light response wavelength range of 254 nm to 950 nm, and three single-wavelength lights of the above range are selected, and the signal generator and the TTL modulated laser device are used to compile encrypted light signals according to the image to be transmitted.

[0026] The BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode is loaded into the electrochemical workstation, and the electrochemical workstation is connected to the data display module.

[0027] The BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode receives the encrypted light signals, and the electrochemical workstation converts the encrypted light signals into electrical signals, and the data display module displays the electrical signals.

[0028] Preferably, the three single-wavelength lights are selected by comparing the differences in the photocurrent signals generated by the detector, so as to distinguish the signals of different single-wavelength lights.

[0029] The BiVO4 / Bi2S3 / Co3O4 heterojunction is prepared based on multi-level interface regulation, so as to adjust the energy band structure and broaden the light absorption, and a wide-spectrum PEC type self-powered photodetector based on the BiVO4 / Bi2S3 / Co3O4 heterojunction is further prepared. The construction of the heterojunction of the photodetector improves the separation efficiency of photo-generated carriers, and the modification of the Co3O4 co-catalyst optimizes the carrier dynamics and inhibits photo-corrosion, so that the photodetector has high light response and does not need external bias, and has good stability. Finally, the marine application scene is further expanded, the underwater optical communication application is realized, and the encrypted optical communication is developed. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced below, and some specific embodiments of the present application will be described in detail below with reference to the drawings in an exemplary but non-limiting manner. The same reference signs in the drawings indicate the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0031] Figure 1 are scanning electron microscope images and energy dispersive X-ray spectroscopy of BiVO4, Bi2S3, BiVO4 / Bi2S3, BiVO4 / Bi2S3 / Co3O4 prepared in Inventive Comparative Examples 1, 2, 3 and Example 1.

[0032] Figure 2 are X-ray diffraction (XRD) and Raman spectra of BiVO4, Bi2S3, BiVO4 / Bi2S3, BiVO4 / Bi2S3 / Co3O4 prepared in Inventive Comparative Examples 1, 2, 3 and Example 1.

[0033] Figure 3 are X-ray photoelectron spectroscopy of total spectrum, Bi element of four samples prepared in Inventive Comparative Examples 1, 2, 3 and Example 1.

[0034] Figure 4 are X-ray photoelectron spectroscopy of O, V element of four samples prepared in Inventive Comparative Examples 1, 2, 3 and Example 1.

[0035] Figure 5 are X-ray photoelectron spectroscopy of S, Co element of four samples prepared in Inventive Comparative Examples 1, 2, 3 and Example 1.

[0036] Figure 6 are ultraviolet-visible-near infrared diffuse reflectance spectra, optical band gap and Mott-Schottky curves.

[0037] Figure 7 are energy band structure schematic diagrams of BiVO4 / Bi2S3 / Co3O4 obtained according to energy band characterization in Figure 6

[0038] Figure 8 are chopped photovoltage-ampere characteristic curves, photoelectric conversion efficiency and response time diagrams.

[0039] Figure 9 are monochromatic light transient response curves of BiVO4, Bi2S3, BiVO4 / Bi2S3, BiVO4 / Bi2S3 / Co3O4 prepared in Inventive Comparative Examples 1, 2, 3 and Example 1 under zero bias (0 V (vs. Ag / AgCl)).

[0040] Figure 10 are responsivity, detectivity and performance comparison diagrams.

[0041] Figure 11 are transient optical response behavior diagrams of BiVO4 / Bi2S3 / Co3O4 photodetector prepared in Example 1 of the present application under different light powers at wavelengths of 254-950 nm. ​

[0042] Figure 12 Figure 1 is a schematic diagram of an underwater optical communication system built in Embodiment 3 of the present application.

[0043] Figure 13 Figure 2 is a current response curve and a normalized optical frequency response curve.

[0044] Figure 14 Figure 3 is a stability test diagram of BiVO4 / Bi2S3 and BiVO4 / Bi2S3 / Co3O4 under the conditions of no sacrificial agent and zero bias voltage. DETAILED DESCRIPTION

[0045] In order to make the purposes, technical solutions and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and embodiments. In the present application, the raw materials and equipment used, unless specified, can be purchased from the market or commonly used in the art. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0046] The present application provides a method based on BiVO4 / Bi2S3 / Co3O4 multi-level interface regulation, which comprises three steps of BiVO4 photoanode preparation, Bi2S3 / BiVO4 heterojunction preparation and Co3O4 co-catalyst deposition, and the specific steps are as follows:

[0047] (1) Preparation of BiVO4 photoanode

[0048] Prepare BiOI precursor solution: dissolve 20 mmol KI and 2 mmol Bi (NO3)3·5H2O in 50 mL deionized water, stir for 5 min, and adjust the pH to 1.7 with concentrated nitric acid;

[0049] Prepare p-benzoquinone ethanol solution: dissolve 4.6 mmol p-benzoquinone in 20 mL ethanol and stir until completely dissolved;

[0050] Electrodeposit BiOI film: mix the above two solutions and stir for 15 min, and stand for 5 min; use FTO as the working electrode (deposition area 1 cm 2 ), adopt three-electrode system electrodeposition, deposition voltage -0.1 V, deposition time 600 s, and obtain uniform BiOI film;

[0051] Annealing and converting BiVO4: dissolve 2 mmol vanadyl acetylacetonate in 10 mL dimethyl sulfoxide, take 35 μL to cover the surface of the BiOI film; put the sample into a muffle furnace, heat at 450 ℃ for 2 h; after taking out, immerse in 1 M NaOH solution for 30 min to remove the residues, wash with deionized water and dry at room temperature to obtain BiVO4 photoanode.

[0052] (2) Preparation of BiVO4 / Bi2S3 heterojunction

[0053] The thiourea precursor solution is configured by dissolving 1.5 mmol of thiourea in a mixed solution of 9 mL of water and 9 mL of ethanol, and stirring uniformly;

[0054] The solvothermal sulfuration reaction is performed by transferring the BiVO4 photoanode and the thiourea precursor solution to a 25 mL polytetrafluoroethylene-lined stainless steel high-pressure reaction kettle, and heating at 160°C for 4 h; after the reaction is completed, the sample is washed with deionized water and dried at room temperature to obtain the Bi2S3 / BiVO4 heterojunction.

[0055] (3) Deposition of Co3O4 co-catalyst

[0056] The photodeposition precursor solution is configured by dissolving 2 mmol of CoCl2 in 10 mL of deionized water and 3.2 mmol of NaIO3 in 80 mL of deionized water; 320 μL of the CoCl2 solution is mixed with 80 mL of the NaIO3 solution, and stirred uniformly;

[0057] The in-situ photodeposition is performed by immersing the BiVO4 / Bi2S3 heterojunction in the above precursor solution, and performing photodeposition under the irradiation of a xenon lamp equipped with an ultraviolet filter for 15 min; after the reaction is completed, the sample is thoroughly washed with deionized water and dried at room temperature to obtain the BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode.

[0058] The application also provides a high-performance self-powered wide-spectrum PEC photodetector based on BiVO4 / Bi2S3 / Co3O4 multi-level interface regulation, which comprises the following steps:

[0059] The PEC type self-powered photodetector is constructed, and the BiVO4 / Bi2S3 / Co3O4 heterojunction is used as the working electrode of the PEC type self-powered photodetector;

[0060] The PEC type self-powered photodetector further comprises an electrochemical workstation, an electrolyte tank, a reference electrode and a counter electrode; the electrolyte tank is provided with an electrolyte, the reference electrode, the working electrode and the counter electrode are hung in the electrolyte tank and are in contact with the electrolyte, and none of them contacts the bottom of the electrolyte tank;

[0061] The working electrode is connected to the positive electrode of the power supply of the electrochemical workstation, the counter electrode is connected to the negative electrode of the power supply of the electrochemical workstation, and the reference electrode is connected to the reference potential device of the electrochemical workstation.

[0062] Preferably, the electrolyte in the electrolyte is a 1 M phosphate buffer solution; the reference electrode is an Ag / AgCl electrode; and the counter electrode is a Pt electrode.

[0063] The application also provides an underwater optical communication application based on BiVO4 / Bi2S3 / Co3O4 multi-level interface regulation, comprising the following steps:

[0064] The BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode prepared above is used as a working electrode to assemble a PEC photoelectric detector, cooperate with a TTL modulated 405 nm laser system, and build an underwater optical communication system.

[0065] The underwater optical communication system comprises a signal generator (outputting a modulated signal), a TTL modulated laser device (emitting 405 nm laser pulses), a PEC photoelectric detector (receiving optical signals), an electrochemical workstation (signal processing), and a data display module.

[0066] The underwater optical communication system is operated in a simulated seawater (3.5% NaCl solution) environment under zero bias voltage conditions.

[0067] The laser pulse frequency is modulated from 1 Hz to 500 Hz, the detector can stably receive and convert optical signals into electrical signals, the-3dB cutoff frequency is higher than 730 Hz, the photocurrent retention rate is more than 85% after 6000 s period of light irradiation, and the underwater optical communication is realized with self-power supply, wide spectrum, and high stability. Meanwhile, based on the wide spectrum response from ultraviolet to infrared, an underwater encrypted communication application is designed and realized.

[0068] Preparation method of comparative example 1 BiVO4 photoanode

[0069] (1) The conductive glass FTO is sequentially cleaned with acetone, anhydrous ethanol, deionized water, and anhydrous ethanol for 15 min, and then the FTO is naturally dried in air.

[0070] (2) BiOI precursor solution is prepared: 3353.5 mg (20 mmol) of KI and 980 mg (2 mmol) of Bi (NO3)3·5H2O are dissolved in 50 mL of deionized water, stirred for 5 min, and then adjusted to pH 1.7 with concentrated nitric acid;

[0071] (3) p-benzoquinone ethanol solution is prepared: 502 mg (4.6 mmol) of p-benzoquinone is dissolved in 20 mL of ethanol and stirred until completely dissolved;

[0072] (4) BiOI thin film is electrodeposited: the above two solutions are mixed and stirred for 15 min, and then left to stand for 5 min; the FTO is used as a working electrode (deposition area 1 cm 2 ), a three-electrode system is used for electrodeposition, the deposition voltage is-0.1 V, and the deposition time is 600 s, to obtain a uniform BiOI thin film;

[0073] (5) Annealing transformation of BiVO4: 535.68 mg (2 mmol) of vanadyl acetylacetonate was dissolved in 10 mL of dimethyl sulfoxide, and 35 μL of the solution was coated on the surface of the BiOI thin film; the sample was placed in a muffle furnace and heated at a temperature increasing rate of 2 ℃ / min to 450 ℃ for 2 h; after being taken out, the residual was removed by immersing in 1 M NaOH solution for 30 min, and the sample was washed with deionized water and dried at room temperature to obtain a BiVO4 photoanode.

[0074] (6) The light absorption performance of the BiVO4 photoanode was characterized by using an ultraviolet-visible-near infrared spectrophotometer; the BiVO4 photoanode grown on the FTO glass was directly embedded in a BaSO4 background white plate to form a sample with a flat surface embedded in the BaSO4 background white plate, and the sample was tested; the test range was 200-1100 nm, and the spectral bandwidth was 5 nm.

[0075] (7) The photoelectrochemical and photoelectric detection performances of the BiVO4 photoanode were tested by using a three-electrode system; the BiVO4 photoanode was used as a working electrode, a Pt electrode was used as a counter electrode, and an Ag / AgCl electrode was used as a reference electrode; the electrolyte was 1 M phosphate buffer solution (pH=7). A xenon lamp with AM 1.5G was used to simulate sunlight, and the intensity was about 100 mW / cm 2 ; the potential test range of the linear voltammetric characteristic curve (LSV) was -0.4-0.4 V (vs. Ag / AgCl), and the scanning rate of the voltage was 3 mV / s. The photoelectric performances at different wavelengths were tested by using 355 nm, 400 nm, 450 nm and 550 nm filters, and the power was divided into five levels, namely, I, II, III, IV and V; the period of the transient light response test was 10 s (5 s of irradiation and 5 s of darkness).

[0076] Preparation method of a Bi2S3 photoanode

[0077] (1) Preparation of a thiourea precursor solution: 345.9 mg (4.5 mmol) of thiourea was dissolved in a mixed solution of 9 mL of water and 9 mL of ethanol, and the solution was stirred uniformly;

[0078] (2) Solvothermal sulfurization reaction: the BiVO4 photoanode prepared in Comparative Example 1 was transferred to a 25 mL polytetrafluoroethylene-lined stainless steel high-pressure reaction kettle together with the thiourea precursor solution, and heated at 160 ℃ for 24 h; after the reaction was completed, the sample was washed with deionized water and dried at room temperature to obtain completely sulfurized Bi2S3.

[0079] (3) The light absorption performance of the Bi2S3 photoanode was characterized by a UV-Vis spectrophotometer. The Bi2S3 photoanode grown on the FTO glass was directly embedded in a BaSO4 background whiteboard to form a sample with a uniform surface embedded in the BaSO4 background whiteboard, which was tested. The test range was 200-1100 nm, and the spectral bandwidth was 5 nm.

[0080] (4) The photoelectrochemical and photoelectric detection performances of the Bi2S3 photoanode were tested by a three-electrode system. The Bi2S3 photoanode was used as the working electrode, the Pt electrode was used as the counter electrode, the Ag / AgCl electrode was used as the reference electrode, and the electrolyte was 1 M phosphate buffer (pH=7). The AM1.5G xenon lamp was used to simulate sunlight, and the intensity was about 100 mW / cm 2 . The potential test range of the linear voltammetry characteristic curve (LSV) was -0.4~0.4 V (vs. Ag / AgCl), and the scanning rate was 3 mV / s. The photoelectric performances at different wavelengths were tested by using filters with wavelengths of 355 nm, 400 nm, 450 nm, 550 nm, 650 nm, 765 nm, 850 nm, and 950 nm, and the power sizes were divided into five levels: I, II, III, IV, and V. The transient light response test period was 10 s (5 s illumination and 5 s darkness).

[0081] Preparation method of a BiVO4 / Bi2S3 heterojunction photoanode

[0082] (1) Prepare a thiourea precursor solution: dissolve 115.3 mg (1.5 mmol) of thiourea in a mixed solution of 9 mL of water and 9 mL of ethanol, and stir uniformly;

[0083] (2) Solvothermal sulfurization reaction: transfer the BiVO4 photoanode prepared in the comparative example 1 and the thiourea precursor solution to a 25 mL polytetrafluoroethylene-lined stainless steel high-pressure reaction kettle, heat at 160 ℃ for 4 h; after the reaction is completed, rinse the sample with deionized water, and dry at room temperature to obtain a BiVO4 / Bi2S3 heterojunction.

[0084] (3) The light absorption performance of the BiVO4 / Bi2S3 photoanode was characterized by a UV-Vis spectrophotometer. The Bi2S3 photoanode grown on the FTO glass was directly embedded in a BaSO4 background whiteboard to form a sample with a uniform surface embedded in the BaSO4 background whiteboard, which was tested. The test range was 200-1100 nm, and the spectral bandwidth was 5 nm.

[0085] (4) The photoelectrochemical and photoelectric detection performances of the BiVO4 / Bi2S3 photoanode were tested by a three-electrode system. The BiVO4 / Bi2S3 photoanode was used as the working electrode, the Pt electrode was used as the counter electrode, the Ag / AgCl electrode was used as the reference electrode, and the electrolyte was 1 M phosphate buffer (pH = 7). The AM1.5G xenon lamp was used to simulate sunlight, and the intensity was about 100 mW / cm 2 The potential test range of the linear voltammetry characteristic curve (LSV) was -0.4~0.4 V (vs. Ag / AgCl), and the scanning rate was 3 mV / s. The photoelectric performances under different wavelengths were tested by using the optical filters with wavelengths of 355 nm, 400 nm, 450 nm, 550 nm, 650 nm, 765 nm, 850 nm, and 950 nm, and the power sizes were divided into five energy levels of I, II, III, IV, and V. The transient light response test cycle was 10 s (5 s irradiation and 5 s darkness).

[0086] Example 1 Preparation method of BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode

[0087] (1) Preparation of light deposition precursor solution: 260.46 mg (2 mmol) of CoCl2 was dissolved in 10 mL of deionized water, and 639.64 mg (3.2 mmol) of NaIO3 was dissolved in 80 mL of deionized water; 320 μL of the CoCl2 solution was mixed with 80 mL of the NaIO3 solution, and stirred uniformly;

[0088] (2) In-situ light deposition: the BiVO4 / Bi2S3 heterojunction prepared in Comparative Example 3 was immersed in the above-mentioned precursor solution, and was subjected to light deposition under the irradiation of a xenon lamp equipped with an ultraviolet filter for 15 min; after the reaction was completed, the sample was thoroughly washed with deionized water and dried at room temperature to obtain the BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode.

[0089] (3) The light absorption performance of the BiVO4 / Bi2S3 / Co3O4 photoanode was characterized by an ultraviolet-visible spectrophotometer. The BiVO4 / Bi2S3 photoanode grown on the FTO glass was directly embedded in a BaSO4 background white plate to form a sample with a uniform surface embedded in the BaSO4 background white plate, and the sample was tested. The test range was 200-1100 nm, and the spectral bandwidth was 5 nm.

[0090] (4) The photoelectrochemical and photoelectric detection performance of the BiVO4 / Bi2S3 / Co3O4 photoanode is tested by a three-electrode system, the BiVO4 / Bi2S3 / Co3O4 photoanode is used as a working electrode, a Pt electrode is used as a counter electrode, an Ag / AgCl electrode is used as a reference electrode, and a 1 M phosphate buffer (pH=7) is used as an electrolyte. A xenon lamp with AM1.5G is used to simulate sunlight, and the intensity is about 100 mW / cm 2 , the potential test range of the linear voltammetry characteristic curve (LSV) is-0.4~0.4 V (vs. Ag / AgCl), and the scanning rate is 3 mV / s. The photoelectric performance under different wavelengths is tested by using 355 nm, 400 nm, 450 nm, 550 nm, 650 nm, 765 nm, 850 nm, and 950 nm filters and a 254 nm led lamp, and the power size is divided into five energy levels, namely, I, II, III, IV, and V. The cycle of the transient light response test is 10 s (5 s of irradiation and 5 s of darkness). The following table is the light power value of the I, II, III, IV, and V five energy levels corresponding to the 355 nm, 400 nm, 450 nm, 550 nm, 650 nm, 765 nm, 850 nm, and 950 nm wavelengths in the application.

[0091]

[0092] Example 2: Application of photoelectric detection based on multi-level interface regulated BiVO4 / Bi2S3 / Co3O4 heterojunction

[0093] The method comprises the following steps:

[0094] The PEC type self-powered photoelectric detector is constructed, and the BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode is used as a working electrode of the PEC type self-powered photoelectric detector.

[0095] The PEC type self-powered photoelectric detector further comprises an electrochemical workstation, an electrolyte tank, a reference electrode, and a counter electrode. The electrolyte tank is provided with an electrolyte, and the reference electrode, the working electrode, and the counter electrode are hung in the electrolyte tank and are in contact with the electrolyte, and none of them contacts the bottom of the electrolyte tank. The fixed ends of the reference electrode, the working electrode, and the counter electrode are fixed on the cover of the electrolyte tank through the clamping holes, and the three electrodes are freely hung in the electrolyte tank, about 2-3 cm away from the bottom of the electrolyte tank, so that the photoelectrochemical reaction is more sufficient.

[0096] The connection of the external circuit in the PEC type self-powered photoelectric detector comprises that the working electrode is connected to the positive electrode of the power supply of the electrochemical workstation by a green electrode line, the counter electrode is connected to the negative electrode of the power supply of the electrochemical workstation by a red electrode line, and the reference electrode is connected to the reference potential device by a white electrode line.

[0097] The BiVO4 / Bi2S3 / Co3O4 photoelectric detector exhibits high responsivity (85.32 mAW -1 ), fast response time (11.2 / 9.6 ms) under the condition of no sacrificial agent, and still maintains more than 85% of the original performance after 6000 s of cycle stability test.

[0098] Example 3: Application of underwater optical communication based on multi-level interface regulation of BiVO4 / Bi2S3 / Co3O4 heterojunction

[0099] The Co3O4 / Bi2S3 / BiVO4 heterojunction photoanode PEC photoelectric detector assembled in Example 2 is combined with a TTL modulated 405 nm laser system to build an underwater optical communication system, realizing underwater encrypted communication application.

[0100] The underwater optical communication system includes a signal generator (output modulated signal), a TTL modulated laser device (emits 405 nm laser pulses), a PEC photoelectric detector (receives optical signals), an electrochemical workstation (signal processing), and a data display module.

[0101] The underwater optical communication system test environment is in simulated seawater (3.5% NaCl solution) or KPI electrolyte, and the detector is operated under zero bias voltage.

[0102] The underwater optical communication system is first based on the heterojunction structure of BiVO4 and Bi2S3, which retains the high absorption of BiVO4 in the ultraviolet-visible band, and widens the absorption to the infrared region through Bi2S3, realizing the widening of the detection band, and laying a foundation for realizing multi-channel encrypted underwater optical communication. In addition, the electron-hole spatial separation of the BiVO4 / Bi2S3 heterojunction significantly improves the photo-generated carrier separation efficiency, and the photoresponse performance is improved. Then the deposition of Co3O4 co-catalyst greatly accelerates the photo-hole transfer kinetics, inhibits the surface accumulation of photo-holes, and at the same time improves the surface reaction kinetics, greatly improving the detection light response performance and stability.

[0103] The communication performance test, the laser pulse frequency is modulated from 1 Hz to 500 Hz, the detector can stably receive and convert the optical signal into an electrical signal, the -3 dB cutoff frequency is higher than 730 Hz, and the photocurrent retention rate is more than 85% after 6000 s of cycle illumination, realizing self-powered, wide-spectrum, and high-stability underwater optical communication.

[0104] The encryption communication application of the BiVO4 / Bi2S3 / Co3O4 photoelectric detector prepared in the underwater encryption communication embodiment 1 is demonstrated by selecting an image showing the "HDU" character as an input image. Due to the widening of the detection wave band, the input signal of the selected three single-wavelength lights with light response differentiation can be converted into an electric signal through the photoelectric detector, and the outline of "HDU" can be clearly identified in the final decryption. However, the photoelectric detector capable of detecting only a single wave band cannot accurately decrypt the input matrix due to the inability to distinguish multiple wavelengths, resulting in an incomplete decrypted image. Therefore, the underwater optical communication application can realize efficient and secure information transmission.

[0105] Figure 1 a, b, c, d in FIG. 1 are scanning electron microscope images of BiVO4, Bi2S3, BiVO4 / Bi2S3, and BiVO4 / Bi2S3 / Co3O4 prepared in the present application comparative examples 1, 2, 3, and embodiment 1, respectively. It can be observed that the Bi2S3 nanowires and BiVO4 nanoparticles are distributed in close contact with each other, which proves the formation of the BiVO4 / Bi2S heterojunction with close interface contact from the micro-morphology. Figure 1 e, f in FIG. 2 are energy dispersive X-ray spectroscopy (EDX) images showing the existence and uniform distribution of Bi, V, O, S, and Co elements, which preliminarily proves the realization of the BiVO4 / Bi2S3 / Co3O4 structure.

[0106] Figure 2 a in FIG. 3 is the X-ray diffraction pattern (XRD) of BiVO4, Bi2S3, BiVO4 / Bi2S3, and BiVO4 / Bi2S3 / Co3O4 prepared in the present application comparative examples 1, 2, 3, and embodiment 1. The diffraction peaks of BiVO4 and Bi2S3 match well with the standard monoclinic BiVO4 (JCPDS card No. 14-0668) and orthorhombic Bi2S3 (JCPDS card No. 17-0320). No other secondary phase is detected, and the sharp diffraction peaks indicate good crystallinity. The diffraction peaks of BiVO4 and Bi2S3 are detected in the XRD of BiVO4 / Bi2S3, which proves the successful construction of the heterojunction. The XRD of the heterojunction after photodeposition does not change significantly, and the diffraction peak of Co3O4 may not be detected due to the small amount of Co3O4. For example, Figure 2 The Raman spectrum of b in FIG. 4 shows that the characteristic vibration peaks of BiVO4 and Bi2S3 detected in the range of 100-1000 cm -1 The Raman peaks of BiVO4 / Bi2S3 obviously combine the characteristic peaks of BiVO4 and Bi2S3, especially at 328 and 832.6 cm -1The Raman peaks of the four samples have very obvious broadening. The Raman peaks of the heterojunction after photodeposition have no obvious change, indicating that the photodeposition does not destroy the original heterostructure.

[0107] Figure 3 a and b in the figure are X-ray photoelectron spectrograms of the total spectrum, Bi element of the four samples prepared in the present application comparative example 1, 2, 3 and example 1. Figure 4 a and b in the figure are X-ray photoelectron spectrograms of O and V elements of the four samples prepared in the present application comparative example 1, 2, 3 and example 1. Figure 5 a and b in the figure are X-ray photoelectron spectrograms of S and Co elements of the four samples prepared in the present application comparative example 1, 2, 3 and example 1. It is proved that the BiVO4 / Bi2S3 heterojunction is successfully constructed, and the Co3O4 co-catalyst is successfully wrapped and modified without destroying the heterojunction structure.

[0108] Figure 6 a in the figure is the ultraviolet-visible-near infrared diffuse reflectance spectrum of BiVO4, Bi2S3 and BiVO4 / Bi2S3. The absorption range of BiVO4 / Bi2S3 is greatly red-shifted compared with pure BiVO4, and the absorption edge moves to the near infrared region. Figure 6 b in the figure is the optical band gap of BiVO4 and Bi2S3. Figure 6 c and d in the figure are the Mott-Schottky curves of BiVO4 and Bi2S3, respectively.

[0109] Figure 7 is according to Figure 6 The energy band structure schematic diagram of BiVO4 / Bi2S3 / Co3O4 obtained from the energy band characterization. Under light, electron-hole pairs are generated and separated quickly in BiVO4 and Bi2S3 semiconductors. Then, under the action of built-in electric field, photoelectrons from Bi2S3 are more easily injected into the conduction band of BiVO4, and holes are along the valence band of BiVO4 and Bi2S3. This spatial separation suppresses the recombination of carriers, which can effectively promote the separation and migration of carriers, and is the key to the performance improvement of BiVO4 / Bi2S3 PEC. According to the literature report, the CBM (0.59 eV) of Co3O4 is closer to the Fermi level than the CBM (1.31 eV) of Bi2S3. In this structure, the photo-generated holes can be effectively extracted from Bi2S3 to Co3O4 nanoclusters. Therefore, the BiVO4 / Bi2S3 / Co3O4 heterojunction can further promote the utilization of carriers, reduce the accumulation of holes on the surface of Bi2S3, thereby inhibiting photo-corrosion, and Co3O4 can also accelerate the surface reaction rate and improve the photoelectric performance. The heterojunction with perfect energy band matching provides an opportunity for realizing sacrifice-free and self-powered photoelectric detection applications.

[0110] Figure 8 a and b in FIG. 4 are the photocurrent-voltage curves and the IPCE of BiVO4, Bi2S3, BiVO4 / Bi2S3, BiVO4 / Bi2S3 / Co3O4 prepared in Comparative Examples 1, 2, 3 and Example 1 of the present application. The photocurrent density of the four samples increases with the increase of the applied bias, which can promote the transport of carriers. In addition, due to the efficient charge transport induced by the internal electric field, the photocurrent of the BiVO4 / Bi2S3 heterojunction is improved, especially after Co3O4 modification, the photocurrent of BiVO4 / Bi2S3 / Co3O4 is greatly improved. Figure 8 c and d in FIG. 5 are the response times of BiVO4 / Bi2S3, BiVO4 / Bi2S3 / Co3O4 prepared in Comparative Example 3 and Example 1 of the present application at 450 nm. After depositing Co3O4, the rise time of the heterojunction decreases from 13.7 ms to 11.2 ms, and the decay time significantly decays from 137.7 ms to 9.6 ms, showing ultrafast light response.

[0111] Figure 9 are the monochromatic light transient response curves of BiVO4, Bi2S3, BiVO4 / Bi2S3, BiVO4 / Bi2S3 / Co3O4 prepared in Comparative Examples 1, 2, 3 and Example 1 of the present application at zero bias (0 V (vs. Ag / AgCl)). The light response of pure BiVO4 at 550 nm is almost negligible, while Bi2S3, BiVO4 / Bi2S3, BiVO4 / Bi2S3 / Co3O4 all exhibit a wide spectral response from 355 to 950 nm, which is completely consistent with the results of the absorption spectrum. The photocurrent of the heterojunction after Co3O4 modification is greatly increased, and the photocurrent response of BiVO4 / Bi2S3 / Co3O4 at 355 nm wavelength is 7 times that of BiVO4 / Bi2S3.

[0112] Figure 10 a and b in FIG. 6 are the responsivity and the detectivity of BiVO4, Bi2S3, BiVO4 / Bi2S3, BiVO4 / Bi2S3 / Co3O4 prepared in Comparative Examples 1, 2, 3 and Example 1 of the present application at zero bias (0 V (vs. Ag / AgCl)). Figure 10 c in FIG. 7 is a comparison chart of BiVO4 / Bi2S3 and BiVO4 / Bi2S3 / Co3O4 in photocurrent, responsivity, detectivity and response time performance. The responsivity of BiVO4 / Bi2S3 / Co3O4 PD at zero bias can reach up to 85.32 mAW -1 , and the detectivity can reach up to 8.19 x 10 10Jones, and its D* at 950 nm can still reach 10 10 Compared with BiVO4 / Bi2S3, BiVO4 / Bi2S3 / Co3O4 PD has more excellent and comprehensive photoelectric detection performance.

[0113] Figure 11 a, b, c in FIG. 4 are the transient photoresponse behaviors of BiVO4 / Bi2S3 / Co3O4 photoelectric detector prepared in Example 1 of the present application under different light powers at 254-950 nm wavelengths. BiVO4 / Bi2S3 / Co3O4 has excellent transient photoresponse from 254 nm deep ultraviolet to 950 nm near infrared, and the response intensity continuously increases with the increase of power density.

[0114] Figure 12 FIG. 5 is a schematic diagram of an underwater optical communication system built in Example 3 of the present application. The PEC photoelectric detection device is added to the 405 laser system with TTL modulation to simulate the underwater working environment. The test device includes signal transmission, reception, processing and display.

[0115] Figure 13 a, b, c in FIG. 6 are the current response curves of BiVO4 / Bi2S3 and BiVO4 / Bi2S3 / Co3O4 under zero bias (0 V (vs. Ag / AgCl)) and different light frequencies (10 Hz, 100 Hz, 200 Hz) in simulated seawater and phosphate buffer. Figure 13 d in FIG. 7 is the normalized light frequency response curve of BiVO4 / Bi2S3 and BiVO4 / Bi2S3 / Co3O4 heterojunction under zero bias and 405 nm laser pulse. BiVO4 / Bi2S3 / Co3O4 device shows excellent light response speed and stability in a large frequency range. The obtained PD has a -3 dB cutoff frequency higher than 730 Hz in phosphate buffer and a -3 dB cutoff frequency higher than 1120 Hz in simulated seawater. It exhibits excellent detection bandwidth in the self-powered PEC device.

[0116] Figure 14 BiVO4 / Bi2S3 and BiVO4 / Bi2S3 / Co3O4 are tested for 400 nm monochromatic light stability under the conditions of no sacrificial agent and zero bias. BiVO4 / Bi2S3 shows serious decay in the early stage in the cycle stability test of periodic light (5 s light, 5 s dark), and the photocurrent performance directly decays to 38% of the original current after 6000 s stability test. BiVO4 / Bi2S3 / Co3O4 still maintains more than 85% of the original current after 6000 s of periodic light (5 s light, 5 s dark), showing excellent stability.

[0117] The application of the underwater optical communication system built in Example 3 and the encryption communication application realized by the BiVO4 / Bi2S3 / Co3O4 photoelectric detector prepared in Example 1, the image showing the "HDU" word is selected as the input image as a conceptual demonstration. First, the input image is segmented into a digital matrix: if the pixel is filled with a pattern more than half, the pixel code is "1"; otherwise, the code is "0". Then use 355 nm, 500 nm and 850 nm monochromatic light to transmit different signals (binary coding is used for coding, 10 represents 355 nm bright, 11 represents 500 nm bright, 01 represents 850 nm bright, and 00 represents off), the optical signal is received by the BiVO4 / Bi2S3 / Co3O4 photoelectric detector and converted into a photocurrent with responses of "3", "2", "1" and "0". By comparing with the codebook (response 3 represents 10, response 2 represents 11, response 1 represents 01, and response 0 represents 00), the output current value is decoded back to the "0 / 1" digital matrix. Then fill the pixels to get the image ("1" represents the pixel is filled, and "0" represents not filled), and the outline of "HDU" can be clearly identified. However, the photoelectric detector that can only detect a single waveband cannot accurately decrypt the input matrix due to the inability to distinguish multiple wavelength signals, resulting in incomplete decrypted images. In summary, the BiVO4 / Bi2S3 / Co3O4 underwater optical communication application built by the application can realize efficient and secure information transmission.

[0118] The above is only part of the specific embodiments of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A high-performance, self-powered, broadband photodetector based on multi-level interface modulation of BiVO4 / Bi2S3 / Co3O4, characterized in that, Including BiVO4 / Bi2S3 / Co3O4 heterojunction photoanodes; the high-performance self-powered broadband photodetector described herein is used in underwater optical communication; The high-performance self-powered broadband photodetector includes a three-electrode system disposed in an electrolyte. The three-electrode system includes a working electrode, a counter electrode, and a reference electrode; the working electrode is a BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode; the electrolyte is seawater. The preparation method of the BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode includes the following steps: (1) Preparation of BiVO4 photoanode: BiOI film was electrodeposited and then converted into BiVO4 photoanode by annealing and alkaline washing; (2) Preparation of BiVO4 / Bi2S3 heterojunction: The BiVO4 photoanode obtained in step (1) was placed in thiourea precursor solution and solvothermal sulfurized at 160℃ for 4h to obtain BiVO4 / Bi2S3 heterojunction. (3) Co3O4 co-catalyst deposition: The BiVO4 / Bi2S3 heterojunction obtained in step (2) is immersed in a CoCl2-NaIO3 mixed precursor solution and photodeposited under ultraviolet light for 15 min to obtain a BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode.

2. The high-performance self-powered broadband photodetector according to claim 1, characterized in that, In step (1), the electrodeposition voltage of BiOI is -0.1 V and the time is 600 s; the annealing heating rate is 2 ℃ / min, the annealing temperature is 450 ℃ and the time is 2 h; the alkaline washing uses 1 M NaOH solution and the soaking time is 30 min.

3. The high-performance self-powered broadband photodetector according to claim 1, characterized in that, In step (2), the thiourea precursor solution is a mixed solution obtained by dissolving thiourea in water and ethanol, wherein the mass ratio of thiourea, water and ethanol is 115.3 : 9000 : 7101.

4. The high-performance self-powered broadband photodetector according to claim 1, characterized in that, In step (3), the CoCl2-NaIO3 mixed precursor solution is composed of a CoCl2 solution with a concentration of 2 mmol / 10 mL and a NaIO3 solution with a concentration of 3.2 mmol / 80 mL, wherein the volume ratio of the CoCl2 solution to the NaIO3 solution is 320 μL:80 mL.

5. The high-performance self-powered broadband photodetector as described in claim 1, characterized in that, In the three-electrode system, the counter electrode is a Pt wire, and the reference electrode is an Ag / AgCl electrode; the electrolyte is placed in an electrolyte tank, and the electrolyte is a 1 M phosphate neutral buffer (KPI), without adding a sacrificial agent; the three-electrode system is suspended in the electrolyte tank, all in contact with the electrolyte but not in contact with the bottom of the tank; the phosphate neutral buffer (KPI) includes 1 M dipotassium hydrogen phosphate and 1 M potassium dihydrogen phosphate.

6. The application of the high-performance self-powered broadband photodetector as described in claim 1 in underwater optical communication, characterized in that, The photodetector is combined with a TTL-modulated 405 nm laser system to construct an underwater optical communication system.

7. The application of the high-performance self-powered broadband photodetector as described in claim 1 in underwater optical communication, characterized in that, Includes the following steps: Construct an underwater optical communication system; the underwater optical communication system includes a signal generator, a TTL modulated laser device, an electrochemical workstation, a photodetector, and a data display module; The photoresponse wavelength range of the BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode is 254 nm to 950 nm. Within the above range, three wavelengths of single-wavelength light are selected, and the signal generator and TTL modulated laser device are used to compile and encrypt the optical signal according to the image to be transmitted. The BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode was loaded onto the electrochemical workstation, and the electrochemical workstation was connected to the data display module; The encrypted optical signal is received by the BiVO4 / Bi2S3 / Co3O4 heterojunction photoanode, converted into an electrical signal by an electrochemical workstation, and then displayed on the data display module.

8. The application as described in claim 7, characterized in that, The selection of three wavelengths of single-wavelength light specifically includes: selecting from the three wavelengths of single-wavelength light by comparing the differences in the magnitude of the photocurrent signals generated by the monochromatic light passing through the detector, so as to distinguish the signals of different single-wavelength light.

Images