Photoelectrochemical sensor for dopamine concentration detection and preparation method and application thereof

Abstract

The invention belongs to the technical field of electrochemical detection sensors, and particularly relates to a photoelectrochemical sensor for dopamine concentration detection and a preparation method and application thereof. The photoelectrochemical sensor comprises a working electrode, a counter electrode and a reference electrode, and specifically, the working electrode, the counter electrode and the reference electrode are sequentially connected to an electrochemical workstation to obtain the photoelectrochemical sensor. The working electrode is an indium tin oxide electrode; a Bi4O5Br2 / g-C3N4 / Au composite material is deposited on the surface of the indium tin oxide electrode. The sensor provided by the invention is excellent in detection performance, has the advantages of simple preparation process, low cost, good environmental stability and the like, provides a reliable new method for clinical dopamine detection, and has an important application prospect in early diagnosis of neurodegenerative diseases such as Parkinson's disease and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical detection sensors, and particularly relates to a photoelectrochemical sensor for dopamine concentration detection and a preparation method and application thereof. BACKGROUND

[0002] Dopamine (DA) is a key catecholamine neurotransmitter that plays an important physiological regulatory role in the central nervous system. Studies have shown that DA is not only involved in neural signal transduction processes such as motor control, emotion regulation and cognitive function, but also plays an important role in cardiovascular regulation and the endocrine system. Abnormal changes in DA concentration in the nervous system are closely related to the occurrence and development of various nervous system diseases, including Parkinson's disease (DA deficiency), schizophrenia (DA hyperfunction) and neurodegenerative diseases such as Alzheimer's disease. Therefore, developing a high-sensitivity and high-selectivity DA detection method has important clinical significance for early diagnosis and treatment monitoring of nervous system diseases.

[0003] Currently, the detection methods of DA mainly include electrochemical analysis, chromatographic analysis (such as high-performance liquid chromatography) and spectral analysis (such as fluorescence spectroscopy). However, these traditional methods have obvious limitations in practical application: (1) insufficient sensitivity, making it difficult to accurately detect low-concentration DA, and being easily interfered by coexisting substances such as ascorbic acid (AA) and uric acid (UA) in biological samples; (2) complex instrument equipment, such as large volume of liquid chromatography system, complicated operation, time-consuming sample pretreatment, which is difficult to meet the needs of instant detection; (3) poor stability of detection signal, greatly affected by environmental factors, and poor repeatability. These technical bottlenecks seriously limit the application of DA detection in clinical diagnosis and basic research.

[0004] Photoelectrochemical (PEC) sensing technology is a new detection method developed in recent years, which effectively reduces the background noise through the separation mechanism of photoexcitation and electrical signal detection, significantly improves the detection sensitivity. PEC sensor combines the high selectivity of optical method and the high sensitivity of electrochemical method, and has the characteristics of instrument miniaturization, simple operation and cost-effectiveness, which shows broad application prospects in the field of biomolecule detection. Especially the PEC sensor based on heterojunction structure, through the optimization of energy band structure design, efficient photo-induced charge separation and transmission can be realized, further improving the detection performance.

[0005] Bismuth oxyhalides (BiOX, X = Cl, Br, I) are a class of semiconductor materials with unique layered structure, and the crystal structure presents as the alternative arrangement of [X-Bi-O-Bi-X]. This special crystal structure leads to significant asymmetric polarity and internal spontaneous polarization effect, endowing the material with excellent photoelectric response characteristics. Among them, bismuth oxybromide (BiOBr) as a p-type semiconductor, due to its wide spectral response, high chemical stability and excellent photocatalytic activity, has attracted much attention. In particular, Bi4O5Br2 crystal phase has good ferroelectricity, and after forming a heterojunction with other photoelectric active materials, the internal electric field generated can effectively regulate the behavior of photo-generated carriers, enhance the photocurrent signal, and thus improve the sensing performance. These characteristics make Bi4O5Br2-based materials have great potential in the field of photoelectric chemical biosensing.

[0006] However, the PEC sensors based on Bi4O5Br2-based heterojunctions currently developed in DA detection still have the following key problems: 1) insufficient material band structure matching: the existing band regulation strategy of Bi4O5Br2-based heterojunctions is relatively single, which is difficult to optimize the light absorption efficiency and charge separation efficiency at the same time, resulting in weak photocurrent response and affecting the detection sensitivity; 2) low interface charge transport efficiency: there is a high charge recombination loss in the interface contact between Bi4O5Br2 and the electrode or the cocatalyst, which limits the effective use of photo-generated carriers; 3) selectivity needs to be improved: due to the similar oxidation potentials of DA and AA, UA and other interferents, traditional Bi4O5Br2-based sensors are difficult to achieve high-selectivity detection and are easily disturbed by the complex matrix of biological samples; 4) insufficient long-term stability: Bi4O5Br2 may undergo photocorrosion or surface passivation during photoelectric cycling, resulting in attenuation of the sensing signal and affecting the repeatability and reliability of the detection.

[0007] Therefore, it is urgent to develop new Bi4O5Br2-based heterojunction PEC sensors through band engineering and interface regulation, in order to improve the sensitivity, selectivity and stability of DA detection. SUMMARY

[0008] The technical problem to be solved by the present application is to solve the deficiencies of the traditional Bi4O5Br2-based PEC sensor in the sensitivity, selectivity and stability of DA monitoring in the prior art, and to provide an optimized Bi4O5Br2 heterojunction structure, which effectively enhances light absorption, promotes charge separation and suppresses interferent response by regulating crystal phase composition, constructing gradient band structure and introducing a selective catalytic layer, thereby realizing high-performance detection of DA and providing a more reliable detection means for early diagnosis of nervous system diseases.

[0009] In order to solve the above technical problems, the application discloses a PEC sensor for DA concentration detection, which comprises a working electrode, a counter electrode and a reference electrode, and specifically, the working electrode, the counter electrode and the reference electrode are sequentially connected to an electrochemical workstation to obtain the PEC sensor.

[0010] The working electrode is an indium tin oxide electrode, and a Bi4O5Br2 / g-C3N4 / Au composite material is deposited on the surface of the indium tin oxide electrode.

[0011] Further, the preparation method of the PEC sensor for DA concentration detection is also within the protection scope of the application, which comprises the following steps:

[0012] S1. Preparation of a Bi4O5Br2 / g-C3N4 heterojunction: bismuth nitrate pentahydrate and carbon nitride nanosheets are added into ethylene glycol to obtain a solution A; potassium bromide is dissolved in a mixed solvent composed of ultrapure water and ammonia water to obtain a solution B; the solution B is added dropwise into the solution A, and after magnetic stirring reaction, centrifugation, washing and drying, the Bi4O5Br2 / g-C3N4 heterojunction is obtained.

[0013] S2. Preparation of a Bi4O5Br2 / g-C3N4 / Au composite material: the Bi4O5Br2 / g-C3N4 heterojunction prepared in S1 is dispersed in ultrapure water, and the pH is adjusted to 3-4 to obtain a heterojunction dispersion liquid; chloroauric acid solution and methanol are added dropwise into the heterojunction dispersion liquid in sequence, and magnetic stirring is performed in the dark to obtain a reaction liquid; the reaction liquid is placed under a xenon lamp for photodeposition reaction, after the reaction is completed, centrifugation, washing and drying are performed to obtain the Bi4O5Br2 / g-C3N4 / Au composite material.

[0014] S3. Preparation of a working electrode: the Bi4O5Br2 / g-C3N4 / Au composite material prepared in S2 is dispersed in an ethanol solution, and a Nafion solution is added to obtain a working electrode precursor solution; the working electrode precursor solution is spin-coated onto the surface of a pretreated indium tin oxide electrode, and after drying, the working electrode is obtained.

[0015] S4. Assembly of a photoelectrochemical sensor: a copper foil is connected to the working electrode prepared in S3 through conductive silver paste, and the working electrode, the counter electrode and the reference electrode are sequentially connected to an electrochemical workstation to obtain the PEC sensor.

[0016] In S1, the mass-volume ratio of the bismuth nitrate pentahydrate and ethylene glycol is 48.5-86.7 mg / mL; the mass ratio of the bismuth nitrate pentahydrate and carbon nitride nanosheet is (4.49-8.02):1; the mass-volume ratio of the potassium bromide and mixed solvent is 17-31.7 mg / mL; the volume ratio of the ultrapure water and ammonia water in the mixed solvent is (2-5):1; and the volume ratio of the solution A and solution B is (1.07-2):1.

[0017] In some embodiments of the present application, in S1, the mass-volume ratio of the bismuth nitrate pentahydrate and ethylene glycol is 48.5 mg / mL; the mass ratio of the bismuth nitrate pentahydrate and carbon nitride nanosheet is 5.99:1; the mass-volume ratio of the potassium bromide and mixed solvent is 23.8 mg / mL; the volume ratio of the ultrapure water and ammonia water in the mixed solvent is 4:1; and the volume ratio of the solution A and solution B is 2:1.

[0018] Specifically, in S1, when the solution B is added dropwise to the solution A, the dropwise addition process is completed within 30 s.

[0019] Specifically, in S1, the preparation method of the carbon nitride nanosheet is as follows: urea is placed in a crucible and calcined in a muffle furnace, heated to 600℃ at an air atmosphere and a temperature increasing rate of 3℃·min -1 -1, and kept for 2-3 h, and then taken out after natural cooling to room temperature to obtain blocky carbon nitride; the blocky carbon nitride is weighed, and ultrasonically dispersed in an N-methyl pyrrolidone solution at a mass-volume ratio of 20-40 mg / mL, and broken and dispersed for 10-12 h, and then centrifuged at a rotation speed of 8000-8500 rpm, washed for 4-5 times, and the obtained precipitate is dried at 70-80℃ to obtain carbon nitride nanosheet.

[0020] In S2, the mass-volume ratio of the Bi4O5Br2 / g-C3N4 heterojunction and ultrapure water is 1.33-3 mg / mL; the volume ratio of the chloroauric acid solution and methanol is (0.2-0.37):1; the volume ratio of the chloroauric acid solution and heterojunction dispersion liquid is (0.013-0.03):1; the volume ratio of the methanol and heterojunction dispersion liquid is (0.053-0.1):1; and the concentration of the chloroauric acid solution is 2-5 mM.

[0021] In some embodiments of the present application, in S2, the mass-volume ratio of the Bi4O5Br2 / g-C3N4 heterojunction and ultrapure water is 2 mg / mL; the volume ratio of the chloroauric acid solution and methanol is 0.2:1; the volume ratio of the chloroauric acid solution and heterojunction dispersion liquid is 0.02:1; the volume ratio of the methanol and heterojunction dispersion liquid is 0.1:1; and the concentration of the chloroauric acid solution is 5 mM.

[0022] In S2, the xenon lamp has a power of 300-350 W and is 8-10 cm away from the reaction solution; and the photodeposition reaction has a reaction time of 40-45 min.

[0023] In some embodiments of the present application, in S2, the xenon lamp has a power of 300 W or 350 W and is 10 cm away from the reaction solution; and the photodeposition reaction has a reaction time of 45 min.

[0024] In S1 and S2, the centrifugation has a speed of 8000-8500 rpm; and the drying has a temperature of 70-80 DEG C.

[0025] In S3, the mass / volume ratio of the Bi4O5Br2 / g-C3N4 / Au composite material and the ethanol solution is 6.67-20 mg / mL; the concentration of the ethanol solution is 30%; the volume ratio of the ethanol solution and the Nafion solution is (8.33-18.75):1; and the concentration of the Nafion solution is 5%.

[0026] In some embodiments of the present application, in S3, the mass / volume ratio of the Bi4O5Br2 / g-C3N4 / Au composite material and the ethanol solution is 10 mg / mL or 20 mg / mL; and the volume ratio of the ethanol solution and the Nafion solution is 12.5:1.

[0027] In S3, the spin coating has the following specific steps: 90-100 muL of working electrode precursor solution is measured with a pipette, 40-50 muL of working electrode precursor solution is added to the center of the pretreated indium tin oxide electrode, the power of the spin coater is started, the speed is set to 500 r / min, and spin coating is performed for 10 s; then the remaining working electrode precursor solution is added to the surface of the pretreated indium tin oxide electrode, the spin coater is started again, the speed is set to 5000 r / min, and spin coating is performed for 50 s.

[0028] Specifically, in S3, the pretreated indium tin oxide electrode has the following pretreatment process: the indium tin oxide electrode is sequentially ultrasonically cleaned with acetone, ethanol and deionized water, the ultrasonic treatment time in each solvent is 10-20 min to remove surface organic contaminants, then the cleaned indium tin oxide electrode is placed in a vacuum oven at 70-80 DEG C for 2-4 h.

[0029] In some embodiments of the present application, the indium tin oxide electrode has a size of 1 cm x 2 cm, and after spin coating, the Bi4O5Br2 / g-C3N4 / Au composite material occupies an area of 1 cm x 1 cm on the indium tin oxide electrode.

[0030] Specifically, in S3, the drying is performed at a temperature of 60-70 DEG C for 20-30 min.

[0031] In S4, the counter electrode is a Pt sheet, and the reference electrode is Ag / AgCl.

[0032] In some embodiments of the present application, in S4, the copper foil is connected to the non-coated part of the working electrode by conductive silver paste.

[0033] Further, the application of the PEC sensor prepared by the above preparation method in the preparation of a DA detection instrument for nervous system diseases is also within the protection scope of the present application.

[0034] Specifically, in some embodiments of the present application, the PEC sensor is successfully prepared by the above preparation method, and the photocurrent change of the PEC sensor in different DA concentrations, the stability, anti-interference and repeatability of the PEC sensor are characterized, which proves that the PEC sensor provided by the present application has excellent detection performance, and indicates the application prospect of the PEC sensor in the preparation of a DA detection instrument for nervous system diseases.

[0035] Beneficial effects:

[0036] The application discloses a PEC sensor based on an ITO / Bi4O5Br2 / g-C3N4 / Au composite structure, which is used for high-sensitivity detection of DA concentration. The sensor adopts an indium tin oxide (ITO) electrode with excellent light transmittance (>85%) and conductivity (square resistance <10 Omega / sq) as a base electrode, and a Bi4O5Br2 / g-C3N4 / Au photoelectric active composite material is deposited on the surface of the base electrode through a spin coating method. The Bi4O5Br2 material has three characteristics of photocatalysis, electrocatalysis and ferroelectricity, can produce a significant synergistic effect under visible light irradiation, and can reduce the electron-hole recombination rate by more than 60% and increase the photocurrent response by 3 times. The sensor has excellent detection performance: the detection limit is as low as 0.89 muM (S / N=3), the linear range is 2-400 muM, the selectivity to common interferents (AA, UA, etc.) is good, the response signal difference is less than 8%, the performance attenuation is less than 5% after being placed in air for 28 days, and the batch repeatability RSD is less than 3.5% (n=8). Compared with the prior art, the sensor has the advantages of simple preparation process (reaction temperature <180 DEG C), low cost and good environmental stability, and provides a reliable new method for clinical DA detection, and has important application prospects in early diagnosis of Parkinson's disease and other neurodegenerative diseases. BRIEF DESCRIPTION OF DRAWINGS

[0037] The above and / or other aspects of the present application will become apparent and more readily appreciated from the following description, taken in conjunction with the accompanying drawings, in which:

[0038] Figure 1 The physical map of the PEC sensor prepared in Example 1 of the present application.

[0039] Figure 2 The X-ray diffraction patterns of the Bi4O5Br2, g-C3N4, Bi4O5Br2 / g-C3N4 and Bi4O5Br2 / g-C3N4 / Au materials prepared in Example 1 of the present application.

[0040] Figure 3 The scanning electron microscope images of the Bi4O5Br2, g-C3N4, Bi4O5Br2 / g-C3N4 and Bi4O5Br2 / g-C3N4 / Au materials prepared in Example 1 of the present application; wherein, Figure 3 a in the above is the SEM image of Bi4O5Br2, Figure 3 b in the above is the SEM image of g-C3N4, Figure 3 c in the above is the SEM image of Bi4O5Br2 / g-C3N4, Figure 3 d in the above is the SEM image of Bi4O5Br2 / g-C3N4 / Au.

[0041] Figure 4 The transmission electron microscope images of the Bi4O5Br2 / g-C3N4 and Bi4O5Br2 / g-C3N4 / Au materials prepared in Example 1 of the present application; wherein, Figure 4 a in the above is the TEM image of Bi4O5Br2 / g-C3N4, Figure 4 b in the above is the TEM image of Bi4O5Br2 / g-C3N4 / Au.

[0042] Figure 5 The photocurrent change curve of the working electrode of different material components prepared in Example 1 of the present application.

[0043] Figure 6 The photocurrent change curve of the PEC sensor prepared in Example 1 of the present application with the concentration of DA.

[0044] Figure 7 The fitting curve of the photocurrent change of the PEC sensor prepared in Example 1 of the present application with the concentration of DA.

[0045] Figure 8 The stability test diagram of the PEC sensor prepared in Example 1 of the present application.

[0046] Figure 9 The anti-interference test diagram of the PEC sensor prepared in Example 1 of the present application.

[0047] Figure 10The figure of the change curve of photocurrent of the PEC sensor prepared in Example 1 of the present application after being placed for 28 days.

[0048] Figure 11 The figure of the repeatability test of the PEC sensor prepared in Example 1 of the present application.

[0049] Figure 12 The figure of the change curve of photocurrent of the PEC sensor prepared in Example 1, Example 2 and Example 3 of the present application. DETAILED DESCRIPTION

[0050] The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0051] Example 1:

[0052] The present embodiment provides a preparation method of a PEC sensor for DA concentration detection, comprising the following steps:

[0053] S1. Preparation of bismuth oxyhalide (Bi4O5Br2):

[0054] S1.1. 182 mg of bismuth nitrate pentahydrate was dispersed in 40 mL of ethanol and stirred for 30 min to obtain a bismuth nitrate pentahydrate solution with a concentration of 9.38 mM; 119 mg of potassium bromide was dissolved in 40 mL of deionized water to obtain a potassium bromide solution.

[0055] S1.2. The potassium bromide solution prepared in step S1.1 was poured into the 40 mL bismuth nitrate pentahydrate solution, and magnetic stirring was performed for 30 min, at which time the pH of the mixture was 5.0.

[0056] S1.3. A 0.1 mol / L sodium hydroxide solution was added dropwise to the mixture obtained in step S1.2 to adjust the pH to 11.0, and after magnetic stirring for 20 min, a reaction precursor solution was obtained.

[0057] S1.4. The reaction precursor solution obtained in step S1.3 was transferred to a 100 mL reaction kettle, and hydrothermal reaction was performed at 160°C for 24 h. After the reaction was cooled to room temperature, centrifugation was performed at a speed of 8000 rpm, and the obtained precipitate was washed 5 times. Finally, the obtained precipitate was dried at 80°C for 8 h to obtain bismuth oxyhalide powder.

[0058] S2. Preparation of bismuth oxyhalide / carbon nitride heterojunction (Bi4O5Br2 / g-C3N4):

[0059] S2.1. 15 g of urea was placed in a crucible and calcined in a muffle furnace at a heating rate of 3°C·min -1The obtained carbon nitride was heated to 600 °C at a heating rate of 2 °C / min and kept for 2 h, and then taken out after natural cooling to room temperature to obtain blocky carbon nitride.

[0060] S2.2. 0.8 g of the blocky carbon nitride prepared in step S2.1 was weighed out and ultrasonically dispersed in 30 mL of a 10% N-methylpyrrolidone solution for 12 h to break and disperse it. Then it was centrifuged at a speed of 8000 rpm and washed 5 times, and the obtained precipitate was dried at 80 °C to obtain carbon nitride nanosheets (g-C3N4) for standby use.

[0061] S2.3. 0.97 g of bismuth nitrate pentahydrate was added to 20 mL of ethylene glycol and ultrasonically dispersed for 10 min, and then 162 mg of the carbon nitride nanosheets prepared in step S2.2 above was added and ultrasonically dispersed for 30 min to obtain solution A.

[0062] S2.4. 238 mg of potassium bromide was dissolved in a mixed solvent composed of 8 mL of ultrapure water and 2 mL of ammonia water to obtain solution B.

[0063] S2.5. Solution B obtained in step S2.4 above was quickly added dropwise to solution A, ensuring that the dropwise addition process was completed within 30 s, and magnetic stirring was performed for 6 h, and then the obtained mixture was centrifuged at a speed of 8000 rpm and washed 5 times, and the obtained precipitate was dried at 80 °C to obtain Bi4O5Br2 / g-C3N4 heterojunction powder.

[0064] Preparation of bismuth oxyhalide / carbon nitride / gold heterojunction (Bi4O5Br2 / g-C3N4 / Au)

[0065] S3.1. 0.2 g of the Bi4O5Br2 / g-C3N4 heterojunction powder prepared in step S2 was weighed out and dispersed in 100 mL of ultrapure water, ultrasonically dispersed for 30 min, and the pH was adjusted to 3.5 with nitric acid to obtain a heterojunction dispersion.

[0066] S3.2. 2 mL of a 5 mM chloroauric acid solution was measured and added dropwise to the heterojunction dispersion prepared in step S3.1, and then 10 mL of methanol was added, and magnetic stirring was performed in the dark for 45 min to obtain a reaction solution.

[0067] S3.3. The reaction solution prepared in step S3.2 was placed under a 300 W xenon lamp, the distance between the light source and the reaction solution was set to 10 cm, and the reaction was performed under magnetic stirring for 45 min. Then, the reaction product was centrifuged at a speed of 8000 rpm and washed 5 times, and dried at 80 °C for 8 h to obtain Bi4O5Br2 / g-C3N4 / Au composite material.

[0068] S4. Preparation of electrode precursor solution:

[0069] 10 mg of the Bi4O5Br2 / g-C3N4 / Au composite powder prepared in step S3 was weighed and uniformly dispersed in 1 mL of a 30% ethanol solution by ultrasonication, then 80 μL of a 5% Nafion solution was added, and ultrasonic dispersion was performed for 30 min to obtain a working electrode precursor solution.

[0070] S5. Preparation of a working electrode:

[0071] S5.1. The indium tin oxide electrode was sequentially cleaned with acetone, ethanol, and deionized water by ultrasonication, and the ultrasonic treatment time in each solvent was 10 min to remove surface organic contaminants. Subsequently, the cleaned indium tin oxide electrode was placed in a 70°C vacuum oven for 2 h.

[0072] S5.2. The indium tin oxide electrode pretreated in step S5.1 was fixed on a rotating table to ensure that the electrode was flat.

[0073] S5.3. 0.1 mL of the working electrode precursor solution prepared in step S4 was measured with a pipette, 50 μL of the working electrode precursor solution was first added to the center of the indium tin oxide electrode, the power of the spin coater was turned on, the rotation speed was set to 500 r / min, and spin coating was performed for 10 s, then the remaining working electrode precursor solution was added to the surface of the indium tin oxide electrode, the spin coater was started again, the rotation speed was set to 5000 r / min, and spin coating was performed for 50 s.

[0074] S5.4. The electrode obtained after spin coating in step S5.3 was placed in a 60°C oven for drying for 20 min to obtain an ITO / Bi4O5Br2 / g-C3N4 / Au working electrode.

[0075] S6. Assembly of a PEC sensor:

[0076] The selected ITO electrode had a size of 1 cm x 2 cm, and the ITO / Bi4O5Br2 / g-C3N4 / Au working electrode region prepared in step S5 had a size of 1 cm x 1 cm. A copper foil was connected to the uncoated part of the ITO / Bi4O5Br2 / g-C3N4 / Au working electrode prepared in step S5 by conductive silver paste, a Pt sheet was selected as the counter electrode, and an Ag / AgCl reference electrode was selected, and they were respectively connected to an electrochemical workstation to obtain the PEC sensor for DA concentration detection. Figure 1 A physical diagram of the PEC sensor provided in this embodiment is shown in the figure. The PEC sensor for DA concentration detection described above can be used for DA level detection in neurological diseases.

[0077] Performance characterization:

[0078] 1. Characterization of material morphology and structure

[0079] The Bi4O5Br2, g-C3N4, Bi4O5Br2 / g-C3N4 and Bi4O5Br2 / g-C3N4 / Au materials prepared in this example were characterized by X-ray diffraction (XRD), Figure 2 The XRD patterns of the Bi4O5Br2, g-C3N4, Bi4O5Br2 / g-C3N4 and Bi4O5Br2 / g-C3N4 / Au materials prepared in this example are shown in Figure 2 It can be seen that the pure g-C3N4 sample has obvious diffraction peaks at 13.1° and 27.4°, corresponding to its (100) and (002) crystal planes (JCPDS No. 87-1526), respectively; the characteristic peaks of the pure Bi4O5Br2 sample at 29.7° and 32.4° can be attributed to the (411) and (020) crystal planes (JCPDS No. 37-0699), confirming the successful preparation of the two materials. It is worth noting that no characteristic peaks of g-C3N4 and Au were observed in the XRD spectrum of the composite material, which may be due to the low content and high dispersion of the two.

[0080] The Bi4O5Br2, g-C3N4, Bi4O5Br2 / g-C3N4 and Bi4O5Br2 / g-C3N4 / Au materials were further characterized by scanning electron microscopy (SEM) for micro-morphology, Figure 3 The scanning electron microscope images of the Bi4O5Br2, g-C3N4, Bi4O5Br2 / g-C3N4 and Bi4O5Br2 / g-C3N4 / Au materials prepared in this example are shown in Figure 3 a in which is the SEM image of Bi4O5Br2, Figure 3 b in which is the SEM image of g-C3N4, Figure 3 c in which is the SEM image of Bi4O5Br2 / g-C3N4, Figure 3 d in which is the SEM image of Bi4O5Br2 / g-C3N4 / Au, and Figure 3 It can be seen that Bi4O5Br2 exhibits a typical layered structure with a sheet size of about 200-500 nm; g-C3N4 exhibits a thinner nanosheet morphology. In the composite material, the Bi4O5Br sheet layers and g-C3N4 nanosheets are observed to be interlaced and in close contact, and Au nanoparticles are uniformly deposited on the surface of the Bi4O5Br / g-C3N4 heterojunction, forming a three-dimensional heterostructure. This unique structure has a significantly increased specific surface area, more active sites and effective charge transport, and this structural feature is expected to significantly improve the photoelectrochemical performance of the material.

[0081] Further, the micro-morphology of the Bi4O5Br2 / g-C3N4 and Bi4O5Br2 / g-C3N4 / Au materials is characterized by transmission electron microscopy (TEM), Figure 4 The transmission electron microscope images of the Bi4O5Br2 / g-C3N4 and Bi4O5Br2 / g-C3N4 / Au materials prepared in this example are shown in FIG. 1, Figure 4 wherein a is the TEM image of the Bi4O5Br2 / g-C3N4, Figure 4 wherein b is the TEM image of the Bi4O5Br2 / g-C3N4 / Au, and Figure 4 It can be seen that the Bi4O5Br2 presents a typical layered structure, and the g-C3N4 exhibits a thinner nanosheet, which is consistent with the SEM image. After the formation of the heterojunction, both of them form a good layered structure, and the Bi4O5Br2 is distributed on the surface of the g-C3N4, interlaced with each other, and the interface is tightly combined. In the composite material, the gold nanoparticles are randomly distributed on the surface of the heterojunction, with a particle size of about 30 nm, and the interface is clear without obvious agglomeration phenomenon.

[0082] 2. DA detection effect characterization of the PEC sensor

[0083] The electrochemical analysis process of the PEC sensor prepared in this example is carried out on a CHI600E electrochemical workstation, and a typical three-electrode test system is used, Ag / AgCl is used as the reference electrode, platinum sheet is used as the counter electrode, and the ITO / Bi4O5Br2 / g-C3N4 / Au prepared in this example is used as the working electrode. A PBS (pH=7.0) buffer solution containing 300 μmol / L DA is configured to test the photocurrent response, and the same method is used to set the control group with Bi4O5Br2, g-C3N4 and Bi4O5Br2 / g-C3N4 materials as the working electrode by referring to steps S4 and S5. The photocurrent response of the working electrode of different material components is tested, Figure 5 The photocurrent change curve of the working electrode of different material components is shown in FIG. 2, Figure 5 As shown in FIG. 2, in the solution environment of the PBS (pH=7.0) buffer solution containing 300 μmol / L DA and under the illumination of the 300 W xenon lamp, it can be seen that the photocurrent of the single-component electrode is weak, the photocurrent is significantly enhanced after the formation of the heterojunction, and the photocurrent effect of the Bi4O5Br2 / g-C3N4 / Au is the strongest, about 6.1 μA, which is 14.5, 2.9 and 1.4 times of that of the g-C3N4, Bi4O5Br2 and Bi4O5Br2 / g-C3N4, respectively. The results prove that the construction of the composite heterojunction can significantly improve the PEC DA sensing performance.

[0084] In order to study the change of the photoelectric current of the PEC sensor in different concentrations of DA, PBS (pH = 7.0) buffer solution containing 2 μmol / L-400 μmol / L DA was configured respectively for photoelectric current response test, Figure 6 The PEC sensor prepared in this embodiment is shown in the photoelectric current curve with DA concentration change, as Figure 6 shown, it can be clearly observed that with the increase of DA concentration, the photoelectric current shows an obvious growth trend. From the initial 2 μmol / L to 400 μmol / L, the photoelectric current gradually rises. Figure 7 The PEC sensor prepared in this embodiment is shown in the photoelectric current curve with DA concentration change, as

[0085] In order to evaluate the stability of the PEC sensor constructed for DA concentration detection, 10 times of light and dark alternating photoelectric current response tests were carried out under the condition of 300 W xenon lamp illumination and PBS (pH = 7.0) buffer solution containing 300 μmol / L DA. Figure 8 The stability test diagram of the PEC sensor prepared in this embodiment is shown in Figure 8 shown, when the light is on, the current changes obviously, reaching about 6.12 μA, and when the light is off, the current immediately drops to 0 μA. With the reaction, the photoelectric current intensity gradually decreases due to the continuous consumption of DA in the solution. However, overall, the photoelectric current intensity tends to be stable. After 10 cycles of test, the attenuation of the photoelectric current response signal is only 4.2%. This result shows that the constructed PEC sensor has good stability and can provide reliable support for accurate detection of DA concentration.

[0086] In order to evaluate the anti-interference performance of the PEC sensor for DA concentration detection, the sensitivity of the sensor for detecting DA in the presence of sodium chloride (NaCl), glucose (Glu), UA, AA and lactic acid (LA) was tested. Figure 9 The anti-interference test diagram of the PEC sensor prepared in this embodiment is shown in Figure 9As shown, after adding 200 μmol / L NaCl, Glu, UA, AA and LA in sequence in the PBS buffer containing 200 μmol / L DA, the obtained photocurrent returned to about 5 μA after a short change, and the response signal difference was less than 8%. The results proved that the prepared PEC sensor for DA concentration detection had good anti-interference ability.

[0087] In order to evaluate the long-term stability of the PEC sensor for DA concentration detection, the electrode was placed in the air for 28 days, and then the photocurrent test was carried out under the light of a 300 W xenon lamp and in the solution environment of PBS (pH=7.0) containing 300 μmol / L DA. Figure 10 The photocurrent change curve of the PEC sensor prepared for this embodiment after being placed for 28 days is shown in FIG. 6, and the photocurrent thereof was stabilized at about 5.79 μA, and the performance attenuation was less than 5% compared with 6.12 μA before 28 days. The results proved that the prepared PEC sensor had good long-term stability. Figure 10

[0088] The repeatability is an important parameter for evaluating the PEC sensor. Eight batches of PEC sensors were prepared by using the method of this embodiment, and different batches of PEC sensors were used to detect PBS (pH=7.0) containing 300 μmol / L DA, Figure 11 The repeatability test graph of the PEC sensor prepared in this embodiment is shown in FIG. 7, Figure 11 It is shown that the photocurrent response of the sensors prepared in different batches has good consistency, and the current intensity is about 6.1 μA, the standard deviation is 0.036, and the batch repeatability RSD is less than 3.5% (n=8), which indicates that the prepared PEC sensor has good repeatability.

[0089] Example 2:

[0090] In this embodiment, 10 mg of Bi4O5Br2 / g-C3N4 / Au composite powder in step S4 of embodiment 1 was changed to 20 mg, and other preparation steps were unchanged, and a PEC sensor for DA concentration detection was prepared.

[0091] Example 3:

[0092] In this embodiment, the power of the xenon lamp in step S3.3 of embodiment 1 was changed from 300 W to 350 W, and other preparation steps were unchanged, and a PEC sensor for DA concentration detection was prepared.

[0093] ​In order to further verify the reliability and effectiveness of the present application, some key parameters in Example 2 and Example 3 are further optimized and adjusted, and the remaining preparation steps remain consistent with Example 1. The photocurrent test is carried out under the condition of 300W xenon lamp irradiation and 300μmol / L DA-containing PBS (pH=7.0) buffer solution environment, Figure 12 The PEC sensor photocurrent change curves prepared in different examples are shown in the following figures, and Figure 12 It can be seen that the photocurrent signals displayed by each example have obvious differences, and the results not only confirm the stability and reliability of the present application, but also show that by adjusting the preparation parameters, the photoelectrochemical performance of the material can be effectively optimized.

[0094] The present application creatively develops a PEC sensor based on Bi4O5Br2 / g-C3N4 / Au composite material. Benefiting from the formed Bi4O5Br2 / g-C3N4 heterojunction with high photoelectrocatalytic activity and gold nanoparticles that can produce surface plasmon resonance effect, and the Bi4O5Br2 has good piezoelectric catalytic properties, under the action of specific periodic stress, the sensing performance can be further improved. Therefore, the PEC sensor for DA concentration detection provided by the present application has high sensitivity and good stability.

[0095] The present application provides a PEC sensor for DA concentration detection, a preparation method thereof and an application idea and method. There are many methods and ways to realize the technical scheme, and the above description is only the preferred embodiment of the present application. It should be pointed out that for ordinary skilled persons in the technical field, some improvements and refinements can be made without departing from the principle of the present application, and these improvements and refinements should be regarded as the protection scope of the present application. The components not explicitly described in the embodiment can be realized by the existing technology.

Claims

1. A photoelectrochemical sensor for detecting dopamine concentration, characterized in that: The photoelectrochemical sensor includes a working electrode, a counter electrode and a reference electrode. Specifically, the working electrode, the counter electrode and the reference electrode are sequentially connected to an electrochemical workstation to obtain the photoelectrochemical sensor. Wherein, the working electrode is an indium tin oxide electrode; a Bi4O5Br2 / g-C3N4 / Au composite material is deposited on the surface of the indium tin oxide electrode.

2. The method for preparing the photoelectrochemical sensor according to claim 1, wherein: The steps include: S1. Preparation of a Bi4O5Br2 / g-C3N4 heterojunction: bismuth nitrate pentahydrate and carbon nitride nanosheets are added to ethylene glycol to obtain solution A; potassium bromide is dissolved in a mixed solvent consisting of ultrapure water and ammonia to obtain solution B; solution B is dropwise added to solution A, the mixture is magnetically stirred to react, and then centrifuged, washed, and dried to obtain the Bi4O5Br2 / g-C3N4 heterojunction; S2. Preparation of Bi4O5Br2 / g-C3N4 / Au composite material: Disperse the Bi4O5Br2 / g-C3N4 heterojunction prepared in S1 in ultrapure water and adjust the pH to 3-4 to obtain a heterojunction dispersion; sequentially add chloroauric acid solution and methanol dropwise to the heterojunction dispersion and magnetically stir in the dark to obtain a reaction solution; place the reaction solution under a xenon lamp for a photodeposition reaction, and after the reaction is completed, centrifuge, wash, and dry to obtain the Bi4O5Br2 / g-C3N4 / Au composite material; S3. Preparation of the working electrode: The Bi4O5Br2 / g-C3N4 / Au composite material prepared in S2 was dispersed in an ethanol solution, and a Nafion solution was added to obtain a working electrode precursor solution; Spin-coating the working electrode precursor solution onto the pretreated surface of the indium tin oxide electrode, and drying to obtain the working electrode; S4. Assembly of the photoelectrochemical sensor: Connect the copper foil to the working electrode prepared in S3 through a conductive silver paste, and connect the working electrode, counter electrode, and reference electrode to an electrochemical workstation in sequence to obtain the photoelectrochemical sensor.

3. The preparation method according to claim 2, characterized in that In S1, the mass volume ratio of the bismuth nitrate pentahydrate and ethylene glycol is 48.5~86.7 mg / mL; the mass ratio of the bismuth nitrate pentahydrate and carbon nitride nanosheets is (4.49~8.02):1; the mass volume ratio of the potassium bromide and the mixed solvent is 17~31.7 mg / mL; the volume ratio of ultrapure water and ammonia water in the mixed solvent is (2~5):1; and the volume ratio of solution A and solution B is (1.07~2):

1.

4. The preparation method according to claim 2, characterized in that In S2, the mass volume ratio of the Bi4O5Br2 / g-C3N4 heterojunction and ultrapure water is 1.33~3 mg / mL; the volume ratio of the chloroauric acid solution to methanol is (0.2~0.37):1; the volume ratio of the chloroauric acid solution to the heterojunction dispersion is (0.013~0.03):1; the volume ratio of the methanol to the heterojunction dispersion is (0.053~0.1):1; and the concentration of the chloroauric acid solution is 2~5 mM.

5. The preparation method according to claim 2, characterized in that In S2, the power of the xenon lamp is 300-350 W, and the distance between the xenon lamp and the reaction liquid is 8-10 cm; the reaction time of the photodeposition reaction is 40-45 min.

6. The preparation method according to claim 2, characterized in that In S1 and S2, the centrifugation speed is 8000-8500 rpm; the drying temperature is 70-80°C.

7. The preparation method according to claim 2, characterized in that In S3, the mass volume ratio of the Bi4O5Br2 / g-C3N4 / Au composite material and the ethanol solution is 6.67~20 mg / mL; the concentration of the ethanol solution is 30%; the volume ratio of the ethanol solution to the Nafion solution is (8.33~18.75):1; and the concentration of the Nafion solution is 5%.

8. The preparation method according to claim 2, characterized in that In S3, the spin coating comprises the following specific steps: using a pipette to measure 90-100 μL of the working electrode precursor solution, dropping 40-50 μL of the working electrode precursor solution onto the center of the pretreated indium tin oxide electrode, starting the spin coater power supply, setting the speed to 500 r / min, and spin coating for 10 s; Then, the remaining working electrode precursor solution was added dropwise to the surface of the pretreated indium tin oxide electrode, and the spin coater was started again, the speed was set to 5000 r / min, and the spin coating was continued for 50 s.

9. The preparation method according to claim 2, characterized in that In S4, the counter electrode is a Pt sheet; the reference electrode is Ag / AgCl.

10. Use of the photoelectric chemical sensor according to claim 1 in preparing an instrument for detecting dopamine in nervous system diseases.

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