Manganese monatomic modified electrode, preparation method thereof, electrochemical sensor and application

Abstract

The invention belongs to the technical field of electrochemical sensing materials and environmental pollutant detection, and discloses a manganese monatomic modified electrode and a preparation method thereof, an electrochemical sensor and application, and the preparation method comprises the following steps: (1) dissolving manganese acetate and 1, 10-phenanthroline in a solvent, stirring for full complexation reaction to obtain a complex, then adding carbon black, and stirring to obtain a manganese monatomic modified electrode; continuously stirring to uniformly disperse, and heating at a temperature lower than the boiling point of the solvent to obtain a precursor complex; (2) heating the precursor complex to remove the solvent to obtain a black solid, grinding, and calcining in a protective atmosphere to obtain a manganese monatomic catalyst; and (3) loading the manganese monatomic catalyst on a conductive substrate to prepare the manganese monatomic modified electrode. The electrode shows remarkable electrocatalytic response to PFOS, has high sensitivity and selectivity, can realize rapid and stable detection of PFOS, has a detection limit as low as 0.13 nM, and is simple in process and low in cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical sensing materials and environmental pollutant detection, and particularly relates to a manganese monatomic modified electrode and preparation of an electrochemical sensor and application thereof in detection of perfluorooctane sulfonic acid. BACKGROUND

[0002] Perfluorooctane sulfonic acid (PFOS) is a typical perfluoro / polyfluoroalkyl substance (PFAS). Due to its excellent chemical stability, heat resistance and surface activity, PFOS is widely used in industrial fields such as waterproof coating, fire-fighting foam and semiconductor manufacturing. However, PFOS is difficult to degrade in the environment and is easy to accumulate in water bodies and organisms, belonging to persistent organic pollutants. Studies have shown that PFOS has hepatotoxicity, immunotoxicity and reproductive toxicity, and may interfere with the endocrine system, posing a serious threat to the ecosystem and human health. Electrochemical sensors have great potential in the field of environmental pollutant detection due to their rapid response, low cost, simple operation and easy miniaturization. In particular, in terms of working electrode materials, nano materials with high catalytic activity and strong stability are widely studied to improve detection performance.

[0003] Molecularly imprinted polymer (MIPs) electrochemical sensors have become an effective tool for PFOS detection, which realizes target detection through template imprinting-specific recognition-signal conversion. First, a complex of functional monomers (such as pyrrole, acrylic acid) and template molecules (such as PFOS) is electropolymerized on the electrode surface, and after eluting the template, a MIPs film with complementary cavities is formed. During detection, the target molecules selectively bind to the cavities, changing the electrode interface properties, and the quantification is achieved by differential pulse voltammetry (DPV) or electrochemical impedance spectroscopy (EIS). Although this method has good selectivity and low detection limit, there are some defects that cannot be ignored in this type of sensor: first, the preparation process of MIPs film is complex, and the polymerization conditions and template washing requirements are high, and if the template molecules are not completely removed, it may cause false response; second, the conductivity of the polymer imprinting layer itself is poor, and it needs to be combined with conductive materials to enhance the signal response; finally, due to the complexity of the template molecule introduction and elution process in molecular imprinting polymerization, the performance of batch products varies greatly, and more importantly, the recognition sites of this type of sensor are easy to be deactivated due to pollution, structure collapse or target molecule "occupation" during repeated use, resulting in a decrease in response signal and relatively poor cyclic use performance, which is not suitable for batch production and long-term or high-frequency detection applications.

[0004] Chinese patent application with publication number CN 117538394 A develops an ultra-sensitive voltammetric sensor for detecting perfluorooctane sulfonic acid in tap water by modifying AuNS and MIP thin coating, wherein the AuNS coating is used to enhance the redox probe of the selected FcCOOH for Fe 2+The volt-ampere response of the blank signal intensity during oxidation was studied, and the poor reusability of the sensor was addressed by optimizing the MIP electropolymerization process to minimize potential passivation and analyte saturation on the electrode surface. However, the fabrication process is cumbersome, and the cost of the nanofunctionalization modification steps remains high, resulting in high overall production costs, which severely restricts its large-scale and industrial application. Summary of the Invention

[0005] To address the problems of complex preparation processes and poor material stability in existing technologies, the primary objective of this invention is to provide a manganese single-atom modified electrode material. By constructing a manganese single-atom catalyst with atomically dispersed metal sites, the utilization rate of reaction sites and electron transport efficiency can be significantly improved, thereby achieving efficient identification and signal amplification of target pollutants. Specifically, the manganese single-atom catalyst, with a Mn-N4 structure as the active center, is supported on a conductive carbon-based material to form an electrode material layer. Through its highly dispersed single-atom sites and electrochemical activity, it can efficiently catalyze the redox process of PFOS.

[0006] Another object of the present invention is to provide an electrochemical sensor comprising a working electrode, a counter electrode, a reference electrode, an electrolytic cell, and an electrochemical workstation, wherein the working electrode is the aforementioned manganese single-atom modified electrode.

[0007] Another object of the present invention is to provide the application of the above-described electrode and electrochemical sensor in PFOS detection.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preparing a manganese single-atom modified electrode includes the following steps: (1) Dissolve manganese acetate and 1,10-phenanthroline in a solvent, stir to allow them to fully complex and react, and then add carbon black, stir continuously to disperse them evenly, and heat at a temperature below the boiling point of the solvent to obtain the precursor complex. (2) The precursor complex was heated to remove the solvent, and a black solid was obtained. After grinding, it was calcined under a protective atmosphere to obtain a manganese single-atom catalyst (Mn-SAC) with Mn-N4 as the active site. (3) Manganese single-atom catalyst is loaded onto a conductive substrate to form a manganese single-atom modified electrode.

[0009] Preferably, the molar ratio of manganese acetate, 1,10-phenanthroline and carbon black in step (1) is 1:(6±4):(70±20); the calcination conditions in step (2) are: heating to 600±200℃ by programmed temperature increase for 1~4 hours; the programmed temperature increase is 10±5℃ / min.

[0010] Preferably, the concentration of manganese acetate in the solvent in step (1) is 0.02~0.06 mol / L; the calcination conditions in step (2) are: temperature 600±100℃, held for 2-3 hours.

[0011] Preferably, the heating temperature in step (1) is 60±10℃ and the heating time is 4±2h; the solvent is methanol or ethanol; the stirring time for the complexation reaction is 30±10 minutes; and the heating conditions in step (2) are heating at 80-100℃ for 12±2 hours.

[0012] Preferably, the preparation of the manganese single-atom modified electrode in step (3) is as follows: the manganese single-atom catalyst is dispersed in a mixed solution of ethanol and water, then Nafion solution is added, and after ultrasonic dispersion, a suspension is obtained. The suspension is coated on the surface of a conductive substrate and dried to obtain the manganese single-atom modified electrode.

[0013] Preferably, the feed-to-liquid ratio of the manganese single-atom catalyst to the mixed solution of ethanol and water is 0.5–4.0 mg / mL; and the volume ratio of ethanol to water is 1:2 to 2:1.

[0014] Preferably, the volume-to-mass ratio of the Nafion solution to the manganese single-atom catalyst is 5-30 μL / mg, and the mass concentration of the Nafion solution is 1-10%.

[0015] Preferably, the ultrasonic dispersion power is 50~100 W and the time is 1~2 h.

[0016] Preferably, the suspension is prepared at a concentration of 50-150 μL / cm³. 2 The amount applied is coated onto the surface of the conductive substrate, more preferably 70~100 μL / cm. 2 .

[0017] Preferably, the conductive substrate is a glassy carbon electrode, conductive glass, or carbon cloth electrode.

[0018] An electrochemical sensor is prepared by using a manganese single-atom modified electrode obtained by the above method as the working electrode.

[0019] The electrochemical sensor includes the manganese single-atom modified electrode (working electrode), counter electrode (platinum wire), reference electrode (calomel electrode), electrolytic cell, and electrochemical workstation.

[0020] The application of the manganese single-atom modified electrode or the electrochemical sensor described herein in the rapid detection of perfluorinated compounds. Preferably, a PBS buffer solution with a pH of 5-9 is used as the electrolyte for detection.

[0021] The electrode or electrochemical sensor is used in the detection of PFOS. Preferably, a PBS solution with a pH of 5-9 is used as the electrolyte, with a concentration of 0.1 ± 0.05 mol / L.

[0022] This invention utilizes a manganese single-atom catalyst to prepare a highly efficient electrochemical sensor, exhibiting unique advantages in the process. These advantages include: the use of differential pulse voltammetry (DPV) combined with a manganese single-atom modified electrode to achieve highly sensitive detection of PFOS. The core of the detection process lies in the adsorption and electron transfer behavior of PFOS molecules on the working electrode surface, and the high-resolution recognition capability of DPV for weak electrochemical signals. Differential pulse voltammetry is a highly sensitive electrochemical detection technique. Its working principle is as follows: a series of periodic pulse voltages are superimposed on a certain scanning potential, and the current change is measured before and after each pulse. The difference is used to remove interference from non-Radida current (background current), thereby significantly enhancing the electrochemical response signal of the target substance. DPV responds rapidly to weak current changes and is particularly suitable for the quantitative analysis of trace pollutants. In this invention, the manganese single-atom modified electrode surface has abundant electrochemical active sites, possessing good electronic conductivity and interfacial reactivity. When PFOS molecules are introduced into the solution, their sulfonic acid groups and other functional groups adsorb onto the modified electrode surface through electrostatic interactions or hydrogen bonding, resulting in a significant increase in their concentration at the electrode / solution interface. When a pulsed voltage is applied, PFOS molecules undergo an electrochemical response at a specific potential, with electrons being captured or transferred at the active site, forming a measurable current signal. Due to the presence of highly electronegative fluorine and polar groups in the PFOS molecule, this electron exchange process manifests as oxidation or reduction peaks on a manganese single-atom modified electrode, and the intensity of the response signal shows a good linear relationship with the PFOS concentration. Furthermore, the high activity, high dispersibility, and stability of the manganese single-atom catalyst ensure the consistency of the signal output and the repeatability of the detection results. The prepared electrode shows no significant attenuation during multiple cycle tests, making it suitable for long-term applications.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) Compared with traditional molecularly imprinted electrodes, manganese is uniformly distributed on the carbon-based support in the form of single atoms, forming a stable Mn–N4 coordination structure. This structure can greatly improve the electron transfer efficiency and the catalytic oxidation ability of the target molecule, and realize the rapid identification and detection of PFOS.

[0024] (2) The manganese single-atom modified electrode constructed in this invention has efficient electron transport capability and abundant active sites, which can significantly enhance the adsorption of PFOS on the electrode surface and the intensity of the response signal. Combined with DPV to accurately identify current changes, it has high sensitivity and selectivity, and realizes sensitive detection of trace PFOS with a detection limit as low as 0.13 nM, which is superior to most existing electrochemical detection technologies.

[0025] (3) The manganese single-atom catalyst of the present invention has strong thermal stability and good dispersibility, and is not easy to agglomerate and deactivate. The prepared electrode still maintains excellent signal reproducibility in multiple cycle tests, which is suitable for batch preparation and long-term application, and is especially suitable for on-site rapid analysis and high-throughput detection tasks. Attached Figure Description

[0026] Figure 1 TEM image (a) of the manganese single-atom catalyst Mn-SACs prepared in Example 1; XRD patterns of manganese single atoms (catalyst Mn-SACs) and carbon black (b).

[0027] Figure 2 The Mn k-edge XANES spectra (a) and Fourier transform spectra (b) of the manganese single-atom catalysts Mn-SACs, manganese foil, MnO and MnO2 prepared in Example 1 are shown.

[0028] Figure 3 The EXAFS r-space fitting curve is shown for the manganese single-atom catalyst Mn-SACs prepared in Example 1.

[0029] Figure 4 The peak current plots of differential pulse voltammetry curves for detecting PFOS using a manganese single-atom / glassy carbon electrode in different pH buffer solutions are shown in Example 1.

[0030] Figure 5 Cyclic voltammetry curves for PFOS detection using different electrodes.

[0031] Figure 6 Differential pulse voltammetry curves for PFOS detection using different electrodes.

[0032] Figure 7 The differential pulse voltammetry curves (a) and linear relationship graph (b) of the manganese single atom / glassy carbon electrode for detecting different concentrations of PFOS in Example 1 are shown.

[0033] Figure 8 This is a graph showing the reusability test performance of the manganese single-atom / glassy carbon electrode in Example 1.

[0034] Figure 9 Performance test graphs of the four manganese single-atom modified electrodes prepared in Example 1 are shown.

[0035] Figure 10 The peak current diagram of PFOS DPV detected by manganese single atom / glassy carbon electrode in Example 1 under different interfering ion conditions. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. The room temperature described in the present invention is 20~30℃.

[0037] Example 1 (1) 19.8 mg of manganese(II) acetate tetrahydrate and 101.9 mg of 1,10-phenanthroline monohydrate were dissolved in 2 mL of ethanol and stirred at room temperature for 20 min to allow for complete complexation, yielding a complex. Then, 69.6 mg of conductive carbon black was added and stirred at 600 rpm for 20 min to ensure uniform dispersion. Subsequently, the resulting mixture was heated in a 60 °C oil bath for 4 h to form a stable precursor complex. After the reaction, the precursor complex was heated at 80 °C for 12 h to remove the solvent, yielding a black solid. The dried black solid was gently ground and transferred to a ceramic crucible, placed in a tube furnace, and heated to 600 °C under an argon atmosphere with a programmed temperature increase of 10 °C / min, and reacted at this temperature for 2 h. After natural cooling to room temperature, a manganese single-atom catalyst was obtained.

[0038] (2) 4 mg of manganese single-atom catalyst was dispersed in 2 mL of a 1:1 mixture of water and ethanol. 40 μL of 5% Nafion solution was added, and the mixture was ultrasonically dispersed at 100 W for 1 h to obtain a uniform black suspension. 7 μL of this suspension was then dropped onto the surface of a glassy carbon electrode (3 mm in diameter) using a 10 μL micro-injector. The coating amount of the suspension was approximately 100 μL / cm². 2 The manganese single-atom / glassy carbon electrode was prepared by air drying at room temperature.

[0039] In Example 1, the TEM morphology and XRD pattern of the manganese single-atom catalyst are shown in [reference needed]. Figure 1 It can be clearly seen that manganese single atoms appear as irregular granular particles, and no metal or clusters are observed on the surface, indicating that manganese ions exist in Mn-SAC in a single-atom state. Figure 1 Figure (b) shows the XRD patterns of carbon black (CB) and manganese single atoms (i.e., catalyst Mn-SAC). The diffraction peaks of Mn-SAC are almost identical to those of CB. Mn-SAC does not produce any additional peaks based on the carbon black curve; only the peaks at the original carbon black curve increase in size. This indicates that Mn-SAC was successfully prepared without the influence of other impurities.

[0040] Figure 2 The electronic structure and coordination environment of Mn-SACs were analyzed using XANES and EXAFS. Figure 2As shown in (a), Mn-SACs exhibit a higher absorption edge than the Mn foil, indicating an enhanced oxidation state of manganese atoms. The absorption edge of Mn-SACs falls between that of the Mn foil and MnO, indicating the presence of Mn(II). Figure 2 As shown in (b), Mn-SACs do not show a peak at 2.3 Å corresponding to the Mn-Mn bonds in the Mn foil, indicating that Mn is dispersed in a single-atom form. Similarly, comparison with MnO and MnO2 shows that Mn-O bonds are absent in Mn-SACs. Mn-SACs show a peak at around 1.6 Å, indicating the presence of Mn-N bonds.

[0041] Figure 3 Structural features were further extracted through quantitative EXAFS fitting of the Mn K-side. The fitting results showed that the first coordination shell of Mn is mainly composed of 4 N atoms, further confirming the Mn-N4 configuration.

[0042] The application of the electrode prepared in Example 1 in the detection of PFOS is as follows: The detection was performed in a conventional three-electrode system, using a platinum wire electrode as the counter electrode, a calomel electrode as the reference electrode, and the manganese single-atom / glassy carbon electrode prepared in Example 1 as the working electrode. 0.1 mol / L PBS buffer solutions containing 10 nmol / L PFOS at different pH values ​​were used as the electrolyte solution, and an electrochemical workstation was used as the detection instrument. The working electrode was first polished on α-alumina polishing powder with a particle size of 50 nm, and then ultrasonically washed sequentially with anhydrous ethanol and deionized water. During the detection of PFOS, the manganese single-atom modified electrochemical sensor used differential pulse voltammetry to scan the redox reaction of PFOS and record the voltage-current curves of this process.

[0043] from Figure 4 It can be seen that the current density of PFOS detection by differential pulse voltammetry is significantly affected by the pH value of the PBS buffer. The current density measured by differential pulse voltammetry is much higher at pH 7 and 9. Considering the actual pH value of the human body, a PBS buffer with pH=7 was chosen for subsequent experiments.

[0044] Figure 5 Cyclic voltammetry curves of 10 nmol / L PFOS were obtained for a three-electrode system under different working electrode conditions (glassy carbon electrode, carbon black / glassy carbon electrode, and manganese single atom / glassy carbon electrode of Example 1) in 0.1 mol / L PBS buffer (pH=7). The carbon black / glassy carbon electrode was prepared by first preparing a carbon black suspension (method as described in Example 1), which was then drop-coated onto a bare glassy carbon electrode. Figure 5As can be seen, compared with glassy carbon electrode (GCE) and carbon black / glassy carbon electrode, the peak current of manganese single atom / glassy carbon electrode is significantly increased, indicating that Mn-SAC can promote faster electron transfer and significantly enhance the redox peak current signal.

[0045] Figure 6 Differential pulse voltammetry curves of glassy carbon electrode, carbon black / glassy carbon electrode, and manganese single atom / glassy carbon electrode in a solution of 10 nmol / L PFOS + 0.1 mol / L PBS (pH=7) are presented. The specific detection procedure is as follows: In a three-electrode system, a platinum wire electrode is used as the counter electrode, a calomel electrode as the reference electrode, and the glassy carbon electrode, carbon black / glassy carbon electrode, and manganese single atom / glassy carbon electrode of Example 1 are used as working electrodes. A 0.1 mol / L PBS buffer solution containing 10 nmol / L PFOS is used as the electrolyte solution. An electrochemical workstation is used as the detection instrument, and differential pulse voltammetry is employed for potential scanning. Figure 6 As can be seen, the glassy carbon electrode alone and the carbon black / glassy carbon electrode do not respond to PFOS, while the manganese single atom / glassy carbon electrode has a significant PFOS detection peak at around -0.4 V. This phenomenon may be attributed to the excellent separation efficiency of photogenerated carriers by manganese single atoms, thus the manganese single atom modified electrode exhibits excellent differential pulse voltammetry detection signal.

[0046] Figure 7 This is a differential pulse voltammetry curve for the detection of different concentrations of PFOS using a manganese single-atom / glassy carbon electrode in Example 1. The specific detection steps were as follows: In a three-electrode system, a platinum wire electrode was used as the counter electrode, a calomel electrode as the reference electrode, and a glassy carbon electrode, a carbon black / glassy carbon electrode, and a manganese single-atom / glassy carbon electrode as the working electrodes. A 0.1 mol / L PBS buffer (pH=7) containing different concentrations (0-50 nmol / L) of PFOS was used as the electrolyte solution. The detection was performed using a differential pulse voltammetry potential scanning method with an electrochemical workstation as the detection instrument. Figure 7 Image (a) shows that the manganese single-atom / glassy carbon electrode exhibits a stable and clear differential pulse voltammetric response peak to PFOS oxidation in the electrolyte solution. Furthermore, the peak current of the detection peak gradually increases with increasing PFOS concentration, showing different linear relationships across different concentration ranges. Figure 7 As shown in (b), the linear regression equation for PFOS is I1 = 25.671 + 13.696lgC(R²). 2 =0.991), I2=25.318+2.755lgC (R 2 =0.991); where C (nmol / L) is the concentration of PFOS, and I (μA) is the peak current at different concentrations. The signal-to-noise ratio S / N = 3 is used as the detection limit for PFOS detection, calculated using the following formula: Detection limit = 3.3σ / S Where σ is the noise standard deviation of the blank sample response, and S is the slope of the calibration curve, i.e., the rate of change of the response signal of the analyte as its concentration increases. S is taken as the slope of I1, σ=0.536, and the detection limit of PFOS is calculated to be 0.13 nM according to the formula.

[0047] The detection range corresponding to the first linear equation (I1) is 0.15-1 nM, and the detection range corresponding to the second linear equation (I2) is 1-50 nM.

[0048] Depend on Figure 8 As can be seen, after 20 consecutive operations using the same electrode, the peak current of PFOS showed a slight change. Therefore, the manganese single-atom working electrode has excellent recyclability.

[0049] Figure 9 To replicate the detection of 10 nmol / L PFOS using the four manganese single-atom modified electrodes prepared in Example 1, the peak current of PFOS showed a slight change. Therefore, the electrode preparation method of the present invention has good reproducibility and is suitable for mass production.

[0050] Depend on Figure 10 As can be seen, there was no significant change in current response after adding 100 times the concentration of interfering ions to PFOS at a concentration of 10 nmol / L. Therefore, the manganese single-atom working electrode has good anti-interference ability.

[0051] In summary, this invention achieves efficient adsorption, selective recognition, and sensitive response of PFOS by constructing a manganese single-atom modified electrode combined with DPV detection technology, establishing a rapid, stable, and low-cost electrochemical sensing method for environmental pollutants.

[0052] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a manganese single-atom modified electrode, characterized in that, Includes the following steps: (1) Dissolve manganese acetate and 1,10-phenanthroline in a solvent, stir to allow them to fully complex and react, and then add carbon black, stir continuously to disperse them evenly, and heat at a temperature below the boiling point of the solvent to obtain the precursor complex. (2) The precursor complex was heated to remove the solvent, and a black solid was obtained. After grinding, it was calcined under a protective atmosphere to obtain a manganese single-atom catalyst. (3) Manganese single-atom catalyst is loaded onto a conductive substrate to form a manganese single-atom modified electrode.

2. The preparation method according to claim 1, characterized in that, The molar ratio of manganese acetate, 1,10-phenanthroline and carbon black in step (1) is 1:(6±4):(70±20); the calcination conditions in step (2) are: temperature 600±200℃, time 1~4 hours.

3. The preparation method according to claim 2, characterized in that, The concentration of manganese acetate in the solvent in step (1) is 0.02~0.06 mol / L; the calcination conditions in step (2) are: temperature 600±100℃, held for 2-3 hours.

4. The preparation method according to claim 3, characterized in that, Step (1) The heating temperature is 60±10℃ and the heating time is 4±2h; the solvent is methanol or ethanol; the stirring time for the complexation reaction is 30±10 minutes; Step (2) The heating conditions are heating at 80-100℃ for 12±2 hours.

5. The preparation method according to any one of claims 1 to 4, characterized in that, Preparation of the manganese single-atom modified electrode in step (3): The manganese single-atom catalyst is dispersed in a mixed solution of ethanol and water, then Nafion solution is added, and after ultrasonic dispersion, a suspension is obtained. The suspension is coated on the surface of a conductive substrate and dried to obtain the manganese single-atom modified electrode.

6. The preparation method according to claim 5, characterized in that, The feed-to-liquid ratio of the manganese single-atom catalyst to the mixed solution of ethanol and water is 0.5–4.0 mg / mL; the volume ratio of ethanol to water is 1:2 to 2:1; the volume-to-mass ratio of Nafion solution to manganese single-atom catalyst is 5–30 μL / mg, and the mass concentration of Nafion solution is 1–10%. The ultrasonic dispersion power is 50-100 W, and the time is 1-2 h; the suspension concentration is 50-150 μL / cm³. 2 The amount used is coated on the surface of the conductive substrate; The conductive substrate is a glassy carbon electrode, conductive glass, or carbon cloth electrode.

7. The manganese single-atom modified electrode prepared by the preparation method according to any one of claims 1 to 6.

8. An electrochemical sensor, characterized in that, An electrochemical sensor was prepared using the manganese single-atom modified electrode as described in claim 7 as the working electrode.

9. The application of the manganese single-atom modified electrode of claim 7 or the electrochemical sensor of claim 8 in the rapid detection of perfluorinated compounds.

10. The application according to claim 9, characterized in that, PBS buffer with a pH of 5-9 was used as the electrolyte for detection.

Images