Preparation of Bi (at) C / BiOCl heterojunction dispersion liquid, construction of photoelectrochemical sensor and method for detecting chloramphenicol

Abstract

The invention provides preparation of Bi (at) C / BiOCl heterojunction dispersion liquid, construction of a photoelectrochemical sensor and a method for detecting chloramphenicol. The preparation method comprises the following steps: mixing a BiOCl dispersion liquid and a Bi (at) C dispersion liquid, and performing ultrasonic dispersion to obtain a Bi (at) C / BiOCl heterojunction dispersion liquid; biOCl and Bi (at) C are compounded to prepare the Bi (at) C / BiOCl heterojunction photoelectric material, so that the spectral absorption range and the photon-generated carrier separation efficiency of a single material can be remarkably improved, and charge recombination is inhibited; the prepared Bi (at) C / BiOCl heterojunction material is used for electrode modification, and a photo-electrochemical sensor based on the Bi (at) C / BiOCl material, which is good in photoelectric property and stable in response signal, is obtained. The photoelectrochemical sensor provided by the invention realizes the detection of chloramphenicol, the adopted instrument is cheap and portable, the preparation method of the sensor is simple and feasible, the signal response is fast, the sensitivity is higher, and the detection limit is as low as 9.6 mu M.

Description

Technical Field

[0001] This invention relates to the field of photoelectrochemical analysis and food environment monitoring technology, and particularly to the preparation of Bi@C / BiOCl heterojunction dispersion, the construction of photoelectrochemical sensor, and a method for detecting chloramphenicol. Background Technology

[0002] Chloramphenicol (CAP) is a broad-spectrum antibiotic with advantages such as easy synthesis, low cost, and strong anti-infective properties, and is widely used in clinical medicine and animal husbandry. However, studies have found that the improper use of CAP can cause serious health risks and ecological harm. Considering the toxicity and illegal use of CAP, the development of simple and efficient detection techniques remains an urgent need.

[0003] Current methods for detecting CAP mainly rely on large-scale instrumental analytical techniques such as high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS), and gas chromatography-mass spectrometry (GC-MS). While these methods offer advantages such as high detection accuracy and specificity, they also suffer from drawbacks such as expensive equipment, complex sample pretreatment, long detection cycles, and reliance on specialized operators, making them unsuitable for rapid on-site screening.

[0004] Compared to traditional detection methods that rely on large instruments (such as high-performance liquid chromatography and mass spectrometry), photoelectrochemical detection, as an emerging analytical technique, not only inherits the advantages of rapid response, low cost, and miniaturization of electrochemistry, but also utilizes light signals as the excitation source and electricity as the output signal. These two separate energy forms result in photoelectrochemical detection with lower background and higher sensitivity, making it highly promising in sensor analysis. The photoelectric conversion unit is a crucial core component of a photoelectrochemical sensor. The key lies in the rational design and fabrication of photoactive materials, primarily semiconductors, to construct photoelectrodes and achieve efficient photoelectric conversion to generate a stable photoelectric signal output. However, current photoactive materials such as BiOCl have insufficient photoelectric performance; therefore, improvements are necessary. Summary of the Invention

[0005] To address the shortcomings of existing technologies in chloramphenicol detection, such as high equipment costs and complex operation, this invention provides a method for preparing Bi@C / BiOCl heterojunction dispersions, constructing photoelectrochemical sensors, and detecting chloramphenicol.

[0006] The present invention adopts the following technical solution:

[0007] This invention provides a method for preparing a Bi@C / BiOCl heterojunction dispersion, comprising the following steps:

[0008] Preparation of bismuth oxychloride nanosheets;

[0009] Preparation of bismuth metal-organic framework (Bi-MOF) materials;

[0010] Bismuth metal-organic framework (Bi-MOF) materials were calcined to obtain Bi@C materials.

[0011] Bi@C material was dispersed in water to obtain a Bi@C dispersion.

[0012] Bismuth oxychloride nanosheets were dispersed in water to obtain a BiOCl dispersion;

[0013] After mixing BiOCl dispersion and Bi@C dispersion, ultrasonic dispersion was obtained to obtain Bi@C / BiOCl heterojunction dispersion.

[0014] Preferably, the method for preparing the bismuth oxychloride nanosheets is as follows:

[0015] KCl solution was added to Bi(NO3)3 solution and stirred to obtain the first mixed solution;

[0016] The first mixed solution was reacted at 180~190℃ for 12~13h, the precipitate was collected by centrifugation, washed and dried to obtain BiOCl nanosheets.

[0017] Preferably, the preparation method of the bismuth metal-organic framework (Bi-MOF) material is as follows:

[0018] Bi(NO3)3·5H2O was dissolved in ethylene glycol to obtain a Bi(NO3)3·5H2O solution.

[0019] Terephthalic acid was dissolved in N,N-dimethylformamide to obtain a terephthalic acid solution;

[0020] Add terephthalic acid solution to Bi(NO3)3·5H2O solution and stir to obtain a second mixed solution;

[0021] The second mixed solution was reacted at 150~160 ℃ for 16~17 h to obtain Bi-MOF, which is the bismuth metal-organic framework Bi-MOF material;

[0022] And / or, the preparation method of the Bi@C material is as follows:

[0023] Bismuth metal-organic framework (Bi-MOF) materials were calcined at 600-650℃ for 0.5-1h under an inert atmosphere to obtain Bi@C materials.

[0024] Preferably, the concentration of the BiOCl dispersion is 10 mg / mL;

[0025] The concentration of the Bi@C dispersion is 5 mg / mL;

[0026] The volume ratio of the BiOCl dispersion to the Bi@C dispersion is 1 mL:(10~60) μL.

[0027] Preferably, KCl is dissolved in water to obtain a KCl solution, wherein the mass-to-volume ratio of KCl to water is (0.7~0.8) g: 25 mL;

[0028] Bi(NO3)3·5H2O is dissolved in water to obtain a Bi(NO3)3 solution, wherein the mass-volume ratio of Bi(NO3)3·5H2O to water is (4.5~5) g: 100 mL.

[0029] Preferably, in the step of dissolving Bi(NO3)3·5H2O in ethylene glycol, the molar volume ratio of Bi(NO3)3·5H2O to ethylene glycol is (2~3) mmol:(40~50) mL.

[0030] In the step of dissolving terephthalic acid in N,N-dimethylformamide, the molar volume ratio of terephthalic acid to N,N-dimethylformamide is (3~4) mmol:(30~40) mL;

[0031] Bismuth metal-organic framework (Bi-MOF) materials were heated to 600-650℃ at a rate of 2-3℃ / min under an inert atmosphere and then calcined at 600-650℃ for 0.5-1h to obtain Bi@C materials.

[0032] Secondly, the present invention also provides a photoelectrochemical sensor, comprising:

[0033] The photoelectrode is prepared by adding the Bi@C / BiOCl heterojunction dispersion obtained by the above preparation method onto the electrode and drying it to obtain the photoelectrode.

[0034] Reference electrode;

[0035] Counter electrode.

[0036] 100-200 μL of Bi@C / BiOCl heterojunction dispersion was dropped onto the electrode and dried at 60-70 °C for 2-3 h to obtain the photoelectrode; the electrode was an ITO electrode.

[0037] The reference electrode is Ag / AgCl.

[0038] The counter electrode is a Pt counter electrode.

[0039] Thirdly, the present invention also provides an application of the aforementioned photoelectrochemical sensor in the detection of chloramphenicol.

[0040] Fourthly, the present invention also provides a method for detecting chloramphenicol, using the aforementioned photoelectrochemical sensor, comprising the following steps:

[0041] The photoelectrode, reference electrode, and counter electrode were placed in the test solution containing chloramphenicol, respectively.

[0042] The photoelectrode serves as the working electrode, and the working electrode, reference electrode, and counter electrode are respectively connected to the electrochemical workstation.

[0043] Irradiate the solution to be tested with light;

[0044] A voltage was applied to the working electrode using an electrochemical workstation, and the current-time curve was measured. The concentration of chloramphenicol was then determined based on the current.

[0045] The preparation method of Bi@C / BiOCl heterojunction dispersion, the photoelectrochemical sensor, and the method for detecting chloramphenicol of the present invention have the following advantages compared with the prior art:

[0046] 1. The preparation method of the Bi@C / BiOCl heterojunction dispersion of the present invention includes the following steps: Bismuth oxychloride (BiOCl) nanosheets and bismuth metal-organic framework (Bi-MOF) materials are prepared by a solvothermal method; the Bi-MOF materials are then calcined to degenerate Bi@C; finally, the BiOCl dispersion and the Bi@C dispersion are mixed and ultrasonically dispersed to obtain the Bi@C / BiOCl heterojunction dispersion; the preparation of Bi@C / BiOCl heterojunction optoelectronic materials by combining BiOCl and Bi@C can significantly improve the spectral absorption range and photogenerated carrier separation efficiency of the single material, and suppress charge recombination; the prepared Bi@C / BiOCl heterojunction material is used for electrode modification to obtain a photoelectrochemical sensor based on Bi@C / BiOCl material with good photoelectric performance and stable response signal;

[0047] 2. The photoelectrochemical sensor of this invention enables the detection of chloramphenicol. The instrument used is inexpensive and portable, the sensor fabrication method is simple and easy to implement, and it exhibits rapid signal response and high sensitivity, with a detection limit as low as 9.6 μM. This photoelectrochemical sensor can be used for the detection of actual samples, and the design concept of its fabrication method greatly assists in the development of similar sensors for the detection of other target analytes, demonstrating excellent application prospects. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This invention describes the process of preparing the sensor and its application in detection.

[0050] Figure 2 The images are scanning electron microscope (SEM) images of (a) BiOCl nanosheets and (b) Bi@C / BiOCl heterostructures prepared in Example 1.

[0051] Figure 3 In the figures (a) and (b), the effect of Bi@C loading on the photocurrent of Bi@C / BiOCl / ITO is shown; in the figures (c) and (d), the effect of applied potential on the photocurrent of Bi@C / BiOCl / ITO is shown. The test electrolyte was 5 mL of 0.1 mol / L PBS (pH=7.4) solution.

[0052] Figure 4 (a) shows the electrochemical impedance spectra of BiOCl / ITO, Bi@C / ITO, and Bi@C / BiOCl / ITO, with the electrolyte being 5 mL of 5 mmol / L Fe(CN)6. 3- / 4- (a) Solution containing 0.1 M KCl; (b) Stability test of Bi@C / BiOCl / ITO, the test electrolyte is 5 mL 0.1 mol / L PBS (pH=7.4) solution;

[0053] Figure 5 Comparison of photocurrents for BiOCl / ITO, Bi@C / ITO, and Bi@C / BiOCl / ITO;

[0054] Figure 6 (a) shows the UV-Vis diffuse reflectance spectra of BiOCl, Bi@C and Bi@C / BiOCl, (b) shows the band gap of BiOCl, Bi@C and Bi@C / BiOCl, (c) shows the Mott-Schottky test of Bi@C / BiOCl, and (d) shows the charge transfer diagram of Bi@C / BiOCl.

[0055] Figure 7 The photocurrent response diagrams and corresponding linear graphs are shown for PBS buffer solutions containing different concentrations of CAP. Detailed Implementation

[0056] To facilitate understanding of the present invention, a more comprehensive description of the invention will be provided below in conjunction with specific embodiments. Preferred embodiments of the invention are given in the specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0057] The order in which the embodiments are described below is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0058] This invention provides a method for preparing a Bi@C / BiOCl heterojunction dispersion, comprising the following steps:

[0059] S1. Preparation of bismuth oxychloride nanosheets;

[0060] S2. Preparation of bismuth metal-organic framework (Bi-MOF) materials;

[0061] S3. The bismuth metal-organic framework (Bi-MOF) material was calcined to obtain Bi@C material;

[0062] S4. Disperse the Bi@C material in water to obtain a Bi@C dispersion;

[0063] S5. Bismuth oxychloride nanosheets are dispersed in water to obtain a BiOCl dispersion;

[0064] S6. After mixing the BiOCl dispersion and the Bi@C dispersion, ultrasonic dispersion is performed to obtain the Bi@C / BiOCl heterojunction dispersion.

[0065] The preparation method of the Bi@C / BiOCl heterojunction dispersion of the present invention includes the following steps: Bismuth oxychloride (BiOCl) nanosheets and bismuth metal-organic framework (Bi-MOF) materials are prepared by a solvothermal method; the Bi-MOF materials are then calcined to degenerate Bi@C; finally, the BiOCl dispersion and the Bi@C dispersion are mixed and ultrasonically dispersed to obtain the Bi@C / BiOCl heterojunction dispersion; the preparation of Bi@C / BiOCl heterojunction optoelectronic materials by combining BiOCl and Bi@C can significantly improve the spectral absorption range and photogenerated carrier separation efficiency of the single material, and suppress charge recombination; the prepared Bi@C / BiOCl heterojunction material is used for electrode modification to obtain a photoelectrochemical sensor based on Bi@C / BiOCl material with good photoelectric performance and stable response signal.

[0066] Specifically, this invention uses a Bi@C / BiOCl heterostructure formed by Bi@C nanospheres and BiOCl nanosheets as a photoelectric conversion layer. The introduction of Bi@C can effectively broaden the spectral absorption range of a single BiOCl, improve the separation and transfer efficiency of photogenerated electrons and holes, and provide an enhanced and stable photocurrent response.

[0067] In some embodiments, the method for preparing bismuth oxychloride nanosheets is as follows:

[0068] KCl solution was added to Bi(NO3)3 solution and stirred to obtain the first mixed solution;

[0069] The first mixed solution was reacted at 180~190℃ for 12~13h, the precipitate was collected by centrifugation, washed and dried to obtain BiOCl nanosheets.

[0070] In some embodiments, the preparation method of bismuth metal-organic framework (Bi-MOF) materials is as follows:

[0071] Bi(NO3)3·5H2O was dissolved in ethylene glycol to obtain a Bi(NO3)3·5H2O solution.

[0072] Terephthalic acid was dissolved in N,N-dimethylformamide to obtain a terephthalic acid solution;

[0073] Add terephthalic acid solution to Bi(NO3)3·5H2O solution and stir to obtain a second mixed solution;

[0074] The second mixed solution was reacted at 150~160 ℃ for 16~17 h to obtain Bi-MOF, which is the bismuth metal-organic framework Bi-MOF material;

[0075] In some embodiments, the preparation method of Bi@C material is as follows:

[0076] Bismuth metal-organic framework (Bi-MOF) materials were calcined at 600-650°C for 0.5-1 h under an inert atmosphere (including but not limited to nitrogen, helium, neon, argon, etc.) to obtain Bi@C materials.

[0077] In some embodiments, the concentration of the BiOCl dispersion is 10 mg / mL;

[0078] The concentration of the Bi@C dispersion was 5 mg / mL;

[0079] The volume ratio of BiOCl dispersion to Bi@C dispersion is 1 mL:(10~60) μL.

[0080] In some embodiments, KCl is dissolved in water to obtain a KCl solution, wherein the mass-to-volume ratio of KCl to water is (0.7~0.8) g: 25 mL;

[0081] Bi(NO3)3·5H2O is dissolved in water to obtain a Bi(NO3)3 solution, wherein the mass-volume ratio of Bi(NO3)3·5H2O to water is (4.5~5) g: 100 mL.

[0082] In some embodiments, in the step of dissolving Bi(NO3)3·5H2O in ethylene glycol, the molar volume ratio of Bi(NO3)3·5H2O to ethylene glycol is (2~3) mmol:(40~50) mL.

[0083] In the step of dissolving terephthalic acid in N,N-dimethylformamide, the molar volume ratio of terephthalic acid to N,N-dimethylformamide is (3~4) mmol:(30~40) mL;

[0084] Bismuth metal-organic framework (Bi-MOF) materials were heated to 600-650℃ at a rate of 2-3℃ / min under an inert atmosphere and then calcined at 600-650℃ for 0.5-1h to obtain Bi@C materials.

[0085] In some embodiments, the BiOCl dispersion and the Bi@C dispersion are mixed and then ultrasonically dispersed to obtain a Bi@C / BiOCl heterojunction dispersion, wherein the ultrasonic power is 100~200W, the frequency is 20~40KHz, and the time is 1~2h.

[0086] Based on the same inventive concept, the present invention also provides a photoelectrochemical sensor, comprising:

[0087] The photoelectrode is prepared by adding the Bi@C / BiOCl heterojunction dispersion obtained by the above preparation method onto the electrode and drying it to obtain the photoelectrode.

[0088] Reference electrode;

[0089] Counter electrode.

[0090] In some embodiments, 100-200 μL of Bi@C / BiOCl heterojunction dispersion is dropped onto the electrode and dried at 60-70 °C for 2-3 h to obtain a photoelectrode; the electrode is an ITO electrode.

[0091] The reference electrode is Ag / AgCl.

[0092] The counter electrode is a Pt counter electrode.

[0093] In some embodiments, a Bi@C / BiOCl heterojunction dispersion is dropped onto the surface of an ITO electrode to obtain a photoelectrochemical sensor based on the Bi@C / BiOCl composite material.

[0094] Based on the same inventive concept, the present invention also provides an application of the above-mentioned photoelectrochemical sensor in the detection of chloramphenicol.

[0095] Based on the same inventive concept, the present invention also provides a method for detecting chloramphenicol, which uses the above-mentioned photoelectrochemical sensor for detection, and includes the following steps:

[0096] The photoelectrode, reference electrode, and counter electrode were placed in the test solution containing chloramphenicol, respectively.

[0097] The photoelectrode serves as the working electrode, and the working electrode, reference electrode, and counter electrode are connected to the electrochemical workstation, respectively.

[0098] Irradiate the solution to be tested with light;

[0099] A voltage was applied to the working electrode using an electrochemical workstation, and the current-time curve was measured. The concentration of chloramphenicol was then determined based on the current.

[0100] In some embodiments, the voltage range is -0.2 to 0.05V.

[0101] In some embodiments, the working electrode, reference electrode, and counter electrode are immersed in a phosphate buffer solution (PBS, pH=7.4) containing different concentrations of chloramphenicol, and the photocurrent response at different chloramphenicol concentrations is measured. A standard curve of photocurrent intensity versus chloramphenicol concentration is plotted, thereby realizing the application of chloramphenicol detection.

[0102] In some embodiments, an indium tin oxide (ITO) electrode is ultrasonically cleaned with acetone, ethanol and water respectively, and then dried. 100 μL of Bi@C / BiOCl dispersion is dropped onto the clean electrode surface and dried in a drying oven at 60 °C for 2 to 3 hours and then cooled to room temperature to obtain a Bi@C / BiOCl / ITO photoelectrode.

[0103] In some embodiments, the photocurrent test includes: using a 500 W xenon lamp (cutoff filter λ ≥ 400 nm) as the excitation source, and employing an electrochemical workstation equipped with a three-electrode system (photoelectrode as the working electrode, Ag / AgCl as the reference electrode, and Pt as the counter electrode) to test the photocurrent. The electrolyte solution is phosphate buffered saline (PBS, 0.1 mol / L, pH = 7.4). The photoelectrochemical testing conditions are: periodic illumination of 20 s with the lamp on and 20 s with the lamp off.

[0104] In some embodiments, the Bi@C loading was optimized by changing the added volume of the Bi@C dispersion to 10 μL, 20 μL, 30 μL, 40 μL, and 60 μL, and recording the photocurrent signals under different loadings (0.5%, 1.0%, 1.5%, 2.0%, 3%) to investigate the effect of Bi@C loading on the photocurrent of the Bi@C / BiOCl / ITO photoelectrode.

[0105] In some embodiments, the applied potential is optimized by changing the applied potential in step (2) to 0.05 V, 0 V, -0.05 V, -0.1 V, and -0.2 V, respectively, recording the photocurrent signal under different applied potentials, and exploring the effect of the applied potential on the photocurrent of the Bi@C / BiOCl / ITO photoelectrode.

[0106] In some embodiments, a clean conductive glass (ITO) electrode was prepared, and 100 μL of a Bi@C (1%) / BiOCl mixed solution was drop-coated onto the surface, covering an area of ​​1.00 square centimeters. The electrode was then dried in an oven at 60 °C for 2 hours to obtain a Bi@C / BiOCl heterostructure modified electrode. The first photocurrent response signal was obtained by current-time measurement using a photoelectrochemical reactor and an electrochemical workstation in 5 mL of 0.1 mol / L PBS (pH=7.4). Due to the surface plasmon resonance between metallic Bi and semiconductor BiOCl, as well as the doping of conductive carbon, the resulting composite material exhibited a good cathodic photocurrent response. Different concentrations of CAP were added to the PBS substrate. Since CAP is a typical nitrobenzene derivative, it can effectively receive photogenerated electrons from Bi@C / BiOCl, thereby enhancing the cathodic photocurrent response and generating a second photocurrent signal. The changes in the photocurrent signal caused by different concentrations of CAP were used to determine the CAP signal.

[0107] In some embodiments, the band structure of the Bi@C / BiOCl heterostructure is calculated. The UV-Vis absorption spectrum of Bi@C / BiOCl is obtained by UV-Vis diffuse reflectance spectroscopy (UV-vis DRS) according to the formula αhν = A(hν−E). g )n / 2 The band gap E can be calculated. g (where α, h, ν, A, E) g and n represent the absorption index and Planck's constant (6.63 × 10⁻⁶), respectively. -34 (Incident light frequency, band gap, and optical transition type). In 0.5 M Na2SO4 solution, the flat band potential of Bi@C / BiOCl was obtained by Mott-Schottky test, and then the conduction band potential was calculated according to E. VB = E CB + E g The valence band position was calculated, thus explaining the mechanism of photocurrent generation.

[0108] In some embodiments, a Bi@C / BiOCl heterostructure modified electrode is used as the working electrode, Ag / AgCl as the reference electrode, Pt as the counter electrode, and a phosphate buffer solution (PBS, 0.1 mol / L, pH=7.4) containing different concentrations of chloramphenicol (CAP) is used as the supporting electrolyte. Current-time (it) scanning is performed to obtain the changes in photocurrent signals at different concentrations, and detection is achieved based on the linear relationship between the photocurrent signal and the CAP concentration.

[0109] In some embodiments, the chloramphenicol concentrations are 0.1 mM, 0.2 mM, 0.4 mM, 0.8 mM, and 1.2 mM, respectively. The it scan parameters are: Init E (initial potential, applied potential) = -0.1 V, Sample Interval = 0.1 s, Run Time = 150 s, Quiet Time = 0 s, Scales during Run = 1, and Sensitivity = 1 × 10⁻⁶. -5 .

[0110] The photoelectrochemical sensor of this invention enables the detection of chloramphenicol. The instrument used is inexpensive and portable, the sensor fabrication method is simple and easy to implement, and it exhibits rapid signal response and high sensitivity, with a detection limit as low as 9.6 μM. This photoelectrochemical sensor can be used for the detection of actual samples, and the design concept of its fabrication method greatly assists in the development of similar sensors for the detection of other target analytes, demonstrating excellent application prospects.

[0111] Further reference Figure 1As shown, it illustrates the process of preparing the sensor and the application detection process of the present invention; specifically, Bi@C / BiOCl heterostructure material (purple spherical, combining the conductivity and plasma effect of Bi@C and the photoelectric activity of BiOCl) is modified onto the surface of indium tin oxide (ITO) conductive electrode to obtain a functionalized working electrode—Bi@C / BiOCl / ITO electrode.

[0112] When visible light (hv) irradiates the modified electrode, the following process occurs:

[0113] Photogenerated carrier separation: Bi@C / BiOCl absorbs photon energy, exciting valence band (VB) electrons to the conduction band (CB), generating photogenerated electrons (e⁻) and holes (h⁺). Because Bi@C and BiOCl form a heterojunction (band matching), they effectively suppress the recombination of photogenerated electrons and holes, promoting carrier separation.

[0114] Electron capture and signal output of chloramphenicol (CAP): CAP in the system acts as an "electron acceptor," preferentially capturing photogenerated electrons (e⁻) in the conduction band and undergoing a reduction reaction (generating product Product). This electron transfer process generates a detectable photocurrent signal (the current peak on the right); the higher the CAP concentration, the more electrons are captured, and the more significant the photocurrent enhancement, thus enabling quantitative detection of CAP. In short, this figure visually presents the complete photoelectrochemical detection process: "material-modified electrode → photo-excited carriers → CAP captures electrons to generate a current signal." The core is to utilize the photoelectric properties of the Bi@C / BiOCl heterojunction and the CAP's ability to capture photogenerated electrons to convert the CAP concentration into a measurable current signal.

[0115] The following further describes the preparation method of the Bi@C / BiOCl heterojunction dispersion, the photoelectrochemical sensor, and the method for detecting chloramphenicol according to the present invention. This section further illustrates the content of the present invention with reference to specific embodiments, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0116] Example 1

[0117] This embodiment provides a method for preparing bismuth oxychloride (BiOCl) nanosheets, including the following steps:

[0118] S1. Dissolve 0.7438g KCl in 25 mL of deionized water to obtain a KCl solution;

[0119] S2. Dissolve 4.8321g of Bi(NO3)3·5H2O in 100 mL of deionized water to obtain a Bi(NO3)3·5H2O solution;

[0120] S3. Add KCl solution to Bi(NO3)3·5H2O solution and stir to obtain the first mixed solution;

[0121] S4. Place the first mixed solution in a reaction vessel and react at 180 °C for 12 h. After centrifugation to collect the precipitate, wash it three times with deionized water and ethanol respectively, and then vacuum dry to obtain bismuth oxychloride (BiOCl) nanosheets.

[0122] Scanning electron microscope (SEM) image of the bismuth oxychloride (BiOCl) nanosheets prepared in Example 1 is shown below. Figure 2 As shown in (a), from Figure 2 As can be seen in (a), the scanning electron microscope image shows that it is in the form of a thin sheet, about 1.4 μm long.

[0123] Example 2

[0124] This embodiment provides a method for preparing a Bi@C / BiOCl heterojunction dispersion, including the following steps:

[0125] S1. Preparation of bismuth metal-organic framework (Bi-MOF) materials, specifically including the following steps:

[0126] S11. Dissolve 2 mmol Bi(NO3)3·5H2O in 40 mL of ethylene glycol to obtain a Bi(NO3)3·5H2O solution;

[0127] S12. Dissolve 3 mmol of terephthalic acid in 30 mL of N,N-dimethylformamide (DMF) to obtain a terephthalic acid solution;

[0128] S13. Add terephthalic acid solution to Bi(NO3)3·5H2O solution and stir for 2 hours to obtain a second mixed solution;

[0129] S14. The second mixed solution is reacted at 150℃ for 16h to obtain Bi-MOF, which is the bismuth metal-organic framework Bi-MOF material.

[0130] S2. Preparation of Bi@C materials, specifically including the following steps:

[0131] S21. The bismuth metal-organic framework (Bi-MOF) material was placed in a tube furnace under a nitrogen atmosphere, heated to 600 °C at a rate of 2 °C / min, and calcined for 60 min to obtain the Bi@C material.

[0132] The preparation of S3, Bi@C / BiOCl heterojunction dispersion includes the following steps:

[0133] S31. Add 10 mg of bismuth oxychloride (BiOCl) nanosheets prepared in Example 1 to 1 mL of deionized water and sonicate for 30 minutes to obtain a 10 mg / mL BiOCl dispersion;

[0134] S32. Add 5 mg of the Bi@C material prepared in step S2 above to 1 mL of deionized water and sonicate for 30 minutes to obtain a 5 mg / mL Bi@C dispersion.

[0135] S33, 20 μL of 5 mg / mL Bi@C dispersion was added to 1 mL of 10 mg / mL BiOCl dispersion, and the mixture was sonicated at 300 W and 40 kHz for 2 h to obtain Bi@C / BiOCl heterojunction dispersion.

[0136] The scanning electron microscope image of the Bi@C / BiOCl heterojunction dispersion prepared in Example 2 is shown below. Figure 2 As shown in (b), from Figure 2 As can be seen in (b), the scanning electron microscope image shows that Bi@C is spherical with Bi particles distributed on its surface, and BiOCl nanosheets are in close contact with Bi@C.

[0137] Example 3

[0138] This embodiment optimizes the Bi@C loading and applied potential, as follows:

[0139] 10 μL, 20 μL, 30 μL, 40 μL, and 60 μL of 5 mg / mL Bi@C dispersion (prepared according to step S32 in Example 2) were added to 1 mL of 10 mg / mL BiOCl dispersion (prepared according to step S31 in Example 2), respectively, and the mixture was sonicated at an ultrasonic power of 100 W and a frequency of 40 kHz for 2 h to obtain Bi@C / BiOCl heterojunction dispersions with Bi@C loadings of 0.5%, 1.0%, 1.5%, 2.0%, and 3%, respectively.

[0140] Indium tin oxide (ITO) electrodes were ultrasonically cleaned with acetone, ethanol, and water, respectively, and then dried. 100 μL of Bi@C / BiOCl dispersions at different loading levels were drop-coated onto the clean electrode surface and dried in a drying oven at 60 °C for 3 h, then cooled to room temperature to obtain Bi@C / BiOCl / ITO photoelectrodes.

[0141] The photoelectrode was used as the working electrode, Ag / AgCl as the reference electrode, Pt as the counter electrode, a 500 W xenon lamp as the excitation source, and phosphate buffered solution (PBS, 0.1 mol / L, pH = 7.4) as the electrolyte solution. Current-time (it) curves were measured using an electrochemical workstation. Periodic illumination was used as the lamp-on (…). Figure 3 (Light on) 20 seconds and turn off the lights ( Figure 3 (Light off) for 20 seconds, with the control voltage at -0.1V during the test; the test results are as follows. Figure 3 As shown.

[0142] Specifically, Figure 3 (a) shows the effect of Bi@C loading on photocurrent in different periods; Figure 3 (b) shows the calculation and average of the differences in photocurrent over multiple cycles in (a) (i.e., the difference between the photocurrent when the light is on and when the light is off), thus obtaining the relationship between the Bi@C load and the difference in photocurrent; Figure 3 As shown in (a) and (b), as the Bi@C loading increases from 0.5% to 3%, the photocurrent difference first increases and then decreases, indicating that excessive Bi@C may become a new recombination site, causing a decrease in photocurrent. Therefore, the optimal loading is 1%.

[0143] Under optimal load, the applied potential during the test is varied from 0.05 to -0.2 V, such as... Figure 3 As shown in (c) and (d), the photocurrent difference first increases and then decreases, reaching its maximum at -0.1 V. Therefore, the optimal applied potential is -0.1 V.

[0144] Example 4

[0145] This embodiment tests the charge transfer impedance and stability of the photoelectrode, and the process is as follows:

[0146] 100 μL of 10 mg / mL BiOCl dispersion (prepared according to step S31 in Example 2), 100 μL of 10 mg / mL Bi@C dispersion (prepared by adding 10 mg of Bi@C material prepared in step S2 of Example 2 to 1 mL of deionized water and sonicating for 30 minutes to obtain 10 mg / mL Bi@C dispersion), and 100 μL of 10 mg / mL Bi@C (1%) / BiOCl dispersion (prepared according to step S33 in Example 2) were respectively drop-coated onto clean electrode surfaces, dried in a drying oven at 60 °C for 3 h and cooled to room temperature to obtain BiOCl / ITO, Bi@C / ITO, and Bi@C (1%) / BiOCl / ITO photoelectrodes.

[0147] Three different photoelectrodes were immersed in 5 mM [Fe(CN)6] containing 0.1 M KCl. 3− / 4− Electrochemical impedance spectroscopy (EIS) tests were performed in solution, such as... Figure 4 As shown in Figure (a), compared to BiOCl / ITO and Bi@C / ITO, Bi@C (1%) / BiOCl / ITO has a smaller charge transfer impedance, indicating that the composite of BiOCl and Bi@C helps to improve the charge transfer capability of the single material and enhance its photoelectric activity.

[0148] The Bi@C (1%) / BiOCl / ITO photoelectrode was used as the working electrode and immersed in phosphate buffer solution (PBS, 0.1 mol / L, pH = 7.4). Ag / AgCl was used as the reference electrode, Pt was used as the counter electrode, and a 500 W xenon lamp was used as the excitation source. Ten cycles of lamp-on-off were performed using an electrochemical workstation. Figure 4 (b) In this test, "on" means the light is on and "off" means the light is off. The test current-time (it) curve is measured, and the applied potential is -0.1V. The test results are as follows: Figure 4 As shown in (b); from Figure 4 As can be seen in (b), the photocurrent difference was small during the 10-cycle lamp-on-off test, and the RSD (relative standard deviation) was 2.2%, indicating that the prepared Bi@C (1%) / BiOCl / ITO has excellent stability.

[0149] Example 5

[0150] This embodiment provides a photoelectrochemical sensor for chloramphenicol detection, and the process is as follows:

[0151] A Bi@C(1%) / BiOCl / ITO photoelectrode (prepared according to the method in Example 4) was used as the working electrode, Ag / AgCl as the reference electrode, a platinum electrode as the counter electrode, and a 500 W xenon lamp as the excitation source. It was performed using PBS buffer solutions containing and without 0.8 mM CAP as the electrolyte solution. The potential during the test was -0.1 V, and the periodic illumination was achieved by turning the lamp on. Figure 5 (Light on) 20 seconds and turn off the lights ( Figure 5 (Light off) 20 s; Test results are as follows Figure 5 As shown, Figure 5 Bi@C / BiOCl indicates that it does not contain CAP, while Bi@C / BiOCl+0.80.8mM CAP indicates that it contains CAP.

[0152] like Figure 5As shown, under illumination, Bi@C(1%) / BiOCl / ITO exhibits a significant cathode photocurrent response. The addition of CAP increases the photocurrent by 2.9 μA, demonstrating a significant photocurrent enhancement effect.

[0153] Example 6

[0154] This embodiment provides a study on the photocurrent generation mechanism of Bi@C / BiOCl / ITO, as follows:

[0155] First, the UV-Vis diffuse reflectance spectra (UV-vis DRS) of BiOCl (prepared according to the method in step S31 of Example 2), Bi@C (prepared according to the method in step S32 of Example 2), and Bi@C / BiOCl (prepared according to the method in step S33 of Example 2) were tested, such as... Figure 6 As shown in (a), the absorption edge of BiOCl nanosheets is located at 375 nm, exhibiting almost no absorption in the visible light region. Bi@C, on the other hand, has an absorption edge at 576 nm, demonstrating significant absorption in the visible light region. When Bi@C is combined with BiOCl, the absorption edge of the composite material is at 442 nm, showing a significant redshift compared to BiOCl alone, and the light absorption intensity also increases. This indicates that the introduction of Bi@C can effectively broaden the spectral absorption range of BiOCl and improve its photoresponse capability, thereby enhancing the photoelectric conversion efficiency. The Kubellka-Munk function transform is used to estimate the bandgap energy of the semiconductor, such as... Figure 6 As shown in Figure (b), the band gaps of BiOCl, Bi@C, and Bi@C / BiOCl are 3.20 eV, 1.54 eV, and 1.88 eV, respectively. Furthermore, Figure 6 The Mott-Schottky test in (c) yielded a flat band potential of -0.53 V for Bi@C / BiOCl (approximately equal to the conduction band potential). Based on the band gap and conduction band values, the valence band of Bi@C / BiOCl can be calculated to be 1.55 V, allowing for the creation of a schematic diagram of the band structure, as shown below. Figure 6 As shown in (d), when illuminated, the photogenerated electron-hole pairs of Bi@C / BiOCl separate, and the electrons jump to the conduction band and are captured by CAP in the solution to undergo a reduction reaction, resulting in an enhanced cathode photocurrent response.

[0156] Example 7

[0157] This embodiment provides the sensor's sensitivity detection for different concentrations of CAP. The detection process is as follows:

[0158] A Bi@C(1%) / BiOCl / ITO photoelectrode (prepared according to the method in Example 4) was prepared by modifying the ITO surface with 100 μL of 10 mg / mL Bi@C(1%) / BiOCl material. This photoelectrode served as the working electrode, Ag / AgCl as the reference electrode, and a platinum electrode as the counter electrode. A 500 W xenon lamp was used as the excitation source. It was tested in PBS buffer solution (0.1 mol / L, pH = 7.4) containing different concentrations of CAP. The potential during the test was -0.1 V, and the periodic illumination consisted of 20 s with the lamp on and 20 s with the lamp off. The test results are as follows: Figure 7 As shown; Figure 7 As shown in Figure (a), the concentrations of CAP (a to f) are 0, 0.1, 0.2, 0.4, 0.8, and 1.2 mM, respectively. The current response increases with increasing CAP concentration, as shown in Figure (a). Figure 7 As shown in (b), the corresponding linear relationship is ΔI = -3.54c - 0.55, and its detection limit is as low as 9.6 μM. ΔI is the difference between the photocurrent when the light is on and the photocurrent when the light is off.

[0159] In summary, the photoelectrochemical sensor based on the Bi@C / BiOCl composite material designed in this embodiment has the advantages of high sensitivity and fast response, and it can be used to detect the antibiotic chloramphenicol. Therefore, the design concept provided by this invention may greatly assist in the development of ultrasensitive photoelectrochemical sensors for identifying other target analytes.

[0160] It is understood that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0161] The above are merely preferred embodiments of this application, and only specifically describe the technical principles of this application. These descriptions are only for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, as well as other specific embodiments of this application that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of this application.

Claims

1. A method for preparing a Bi@C / BiOCl heterojunction dispersion, characterized in that, Includes the following steps: Preparation of bismuth oxychloride nanosheets; Preparation of bismuth metal-organic framework (Bi-MOF) materials; Bismuth metal-organic framework (Bi-MOF) materials were calcined to obtain Bi@C materials. Bi@C material was dispersed in water to obtain a Bi@C dispersion. Bismuth oxychloride nanosheets were dispersed in water to obtain a BiOCl dispersion; After mixing BiOCl dispersion and Bi@C dispersion, ultrasonic dispersion was obtained to obtain Bi@C / BiOCl heterojunction dispersion.

2. The method for preparing the Bi@C / BiOCl heterojunction dispersion as described in claim 1, characterized in that, The method for preparing the bismuth oxychloride nanosheets is as follows: KCl solution was added to Bi(NO3)3 solution and stirred to obtain the first mixed solution; The first mixed solution was reacted at 180~190℃ for 12~13h, the precipitate was collected by centrifugation, washed and dried to obtain BiOCl nanosheets.

3. The method for preparing the Bi@C / BiOCl heterojunction dispersion as described in claim 1, characterized in that, The preparation method of the bismuth metal-organic framework (Bi-MOF) material is as follows: Bi(NO3)3·5H2O was dissolved in ethylene glycol to obtain a Bi(NO3)3·5H2O solution. Terephthalic acid was dissolved in N,N-dimethylformamide to obtain a terephthalic acid solution; Add terephthalic acid solution to Bi(NO3)3·5H2O solution and stir to obtain a second mixed solution; The second mixed solution was reacted at 150~160 ℃ for 16~17 h to obtain Bi-MOF, which is the bismuth metal-organic framework Bi-MOF material; And / or, the preparation method of the Bi@C material is as follows: Bismuth metal-organic framework (Bi-MOF) materials were calcined at 600-650℃ for 0.5-1h under an inert atmosphere to obtain Bi@C materials.

4. The method for preparing the Bi@C / BiOCl heterojunction dispersion as described in claim 1, characterized in that, The concentration of the BiOCl dispersion is 10 mg / mL; The concentration of the Bi@C dispersion is 5 mg / mL; The volume ratio of the BiOCl dispersion to the Bi@C dispersion is 1 mL:(10~60) μL.

5. The method for preparing the Bi@C / BiOCl heterojunction dispersion as described in claim 2, characterized in that, KCl is dissolved in water to obtain a KCl solution, wherein the mass-to-volume ratio of KCl to water is (0.7~0.8) g: 25 mL; Bi(NO3)3·5H2O is dissolved in water to obtain a Bi(NO3)3 solution, wherein the mass-volume ratio of Bi(NO3)3·5H2O to water is (4.5~5) g: 100 mL.

6. The method for preparing the Bi@C / BiOCl heterojunction dispersion as described in claim 3, characterized in that, In the step of dissolving Bi(NO3)3·5H2O in ethylene glycol, the molar volume ratio of Bi(NO3)3·5H2O to ethylene glycol is (2~3) mmol:(40~50) mL. In the step of dissolving terephthalic acid in N,N-dimethylformamide, the molar volume ratio of terephthalic acid to N,N-dimethylformamide is (3~4) mmol:(30~40) mL; Bismuth metal-organic framework (Bi-MOF) materials were heated to 600-650℃ at a rate of 2-3℃ / min under an inert atmosphere and then calcined at 600-650℃ for 0.5-1h to obtain Bi@C materials.

7. A photoelectrochemical sensor, characterized in that, include: The photoelectrode is prepared by dropping the Bi@C / BiOCl heterojunction dispersion prepared by any one of the preparation methods described in claims 1 to 6 onto the electrode and drying it to obtain the photoelectrode. Reference electrode; Counter electrode.

8. The photoelectrochemical sensor as described in claim 7, characterized in that, 100-200 μL of Bi@C / BiOCl heterojunction dispersion was dropped onto the electrode and dried at 60-70 °C for 2-3 h to obtain the photoelectrode; the electrode was an ITO electrode. The reference electrode is Ag / AgCl. The counter electrode is a Pt counter electrode.

9. The application of a photoelectrochemical sensor as described in any one of claims 7-8 in the detection of chloramphenicol.

10. A method for detecting chloramphenicol, comprising using a photoelectrochemical sensor as described in any one of claims 7-8, characterized in that, Includes the following steps: The photoelectrode, reference electrode, and counter electrode were placed in the test solution containing chloramphenicol, respectively. The photoelectrode serves as the working electrode, and the working electrode, reference electrode, and counter electrode are respectively connected to the electrochemical workstation. Irradiate the solution to be tested with light; A voltage was applied to the working electrode using an electrochemical workstation, and the current-time curve was measured. The concentration of chloramphenicol was then determined based on the current.

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