A portable potential-resolving ratiometric molecular imprinting photoelectrochemical sensor and its preparation method and application

Abstract

The present invention discloses a portable potential resolution ratio molecular imprinting photoelectrochemical sensor and its preparation method and application, belonging to the field of sensor technology. The sensor is based on MIPs / Ru(bpy)3 2+ The BiOBr / ITO electrode is used as the working electrode, the Pt sheet is used as the counter electrode, and the LED lamp is used as the excitation light source. The present invention is applied to the detection of trace toxic organic matter in the environment and food, improves the anti-interference ability of molecular imprinting photoelectrochemical sensing technology, and realizes sensitive and specific detection of target molecules.

Description

Technical Field

[0001] The invention belongs to the field of sensor technology, and in particular relates to a portable potential-resolving ratiometric molecular imprinting photoelectrochemical sensor and a preparation method and application thereof. Background Art

[0002] Photoelectrochemical (PEC) sensor is a branch of electrochemical biosensor. Its detection principle is to use the photoelectric characteristics to generate photocurrent to detect the concentration of the analyte in the biochemical reaction related to the current, and convert the light signal into an electrical signal during the detection process. PEC sensor has the advantages of simple instrumentation and high sensitivity, but due to the poor selectivity of photocatalytic reaction, the selectivity of pure PEC sensor detection is not high.

[0003] The main challenges for the practical application of photoelectrochemical sensing focus on the development of its sensitivity and selectivity. In terms of sensitivity, ratiometric analysis has been widely used in various analytical techniques due to its higher measurement accuracy with built-in self-calibration and the advantage of mitigating environmental interference. In terms of selectivity, molecular imprinted polymers (MIPs) have significant advantages in terms of specific recognition ability, cost-effectiveness, high reliability, and ease of preparation. Therefore, it is considered to be an effective method for the preparation of ratiometric MIPs sensors, which have been successfully applied to various analytical methods (fluorescence, electrochemistry, electrochemiluminescence, and Raman spectroscopy). However, to date, there has been no report on the application of ratiometric MIPs methods in photoelectrochemical (PEC) analysis. Ratiometric PEC strategies usually rely on two selective photoactive materials to achieve different signal labels by adjusting the wavelength of the incident light, applying voltage, etc. In the voltage-resolved strategy, one signal from the photoactive material is usually attenuated, while the signals from the other photoactive materials are simultaneously amplified in the presence of the target at different voltages. For example, Wang et al. (N. Hao, R. Hua, K. Zhang, J. Lu, K. Wang, Analytical Chemistry 90 (2018) 13207−13211) developed a potential-resolved ratiometric PEC sensor for ultrasensitive detection of aflatoxin B1. Carbon nitride nanosheets (CNNSs) and Ag / TiO2 / 3DNGH hydrogel were used as two photoactive materials, and the photocurrent signal ratio under different bias voltages was calculated.

[0004] In terms of portability, the photocurrent of the MIPs-PEC strategy can be measured by a digital multimeter (DMM, two-electrode system), which is considered to be a simple, low-cost and portable platform compared to the expensive electrochemical workstation (three-electrode system). In addition, the new DMM can not only display the results by itself, but also record the data by connecting to a computer. At the same time, the bias voltage is increased by a voltage-current signal generator (VCSG), which is cheaper and more portable than traditional voltage-applying equipment (such as electrochemical workstations and DC regulated power supplies).

[0005] 2,4-Dichlorophenoxyacetic acid (2,4-D) is a typical phenoxy herbicide that is widely used to control the growth of broad-leaved weeds in food crops. Since 2,4-D accumulates in agricultural products and the human body through contact with the skin and other pathways, it can lead to food safety and a variety of diseases (such as chronic kidney disease and Alzheimer's disease, etc.). Considering its harmful effects on human health and environmental pollution, the detection of 2,4-D in environmental monitoring poses a major challenge. It is particularly important to develop a new molecular imprinting photoelectrochemical biosensor technology to achieve highly selective, highly sensitive and portable analytical detection of 2,4-D. Therefore, it is an urgent problem to be solved in the field of molecular imprinting photoelectrochemical sensing to construct a dual-wavelength ratio differential photoelectrochemical sensor based on molecular imprinting, optimize the analytical detection method, and realize sensitive and specific detection of target molecules while improving the anti-interference ability of molecular imprinting photoelectrochemical sensing technology. Summary of the invention

[0006] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to improve the anti-interference ability of molecular imprinting photoelectrochemical sensing technology and realize sensitive and specific detection of target molecules. A portable potential-resolved ratiometric molecular imprinting strategy is proposed for the molecular imprinting photoelectrochemical sensor with high sensitivity and high selectivity for detecting 2,4-D, as well as its preparation method and application.

[0007] In order to solve the technical problem, the technical solution adopted by the present invention is:

[0008] In one aspect, the present invention provides a sensor, wherein the sensor is MIPs / Ru(bpy)3 2+ -BiOBr / ITO electrode is used as the working electrode, Pt sheet is used as the counter electrode, and LED lamp is used as the excitation light source.

[0009] Another aspect of the present invention provides a method for preparing the above sensor, comprising MIPs / Ru(bpy)3 2+ -BiOBr / ITO electrode preparation steps, the MIPs / Ru(bpy)3 2+ -BiOBr / ITO electrode preparation steps include:

[0010] S1: Bi(NO3)3•5H2O, polyvinyl pyrrolidone and KBr are added to ethylene glycol solution, kept at a constant temperature, and then transferred to a reactor for heating to obtain BiOBr;

[0011] S2: BiOBr and Ru(bpy)3 2+ Mix and stir to obtain Ru(bpy)3 2+ -BiOBr;

[0012] S3: Coating Ru(bpy)3 on ITO surface 2+ -BiOBr solution, dried under infrared irradiation to obtain Ru(bpy)3 2+ -BiOBr / ITO;

[0013] S4: Ru(bpy)3 2+ -BiOBr / ITO was placed in a phosphate buffer solution containing template molecules and pyrrole, and electropolymerized using cyclic voltammetry to perform template molecular imprinting;

[0014] S5: The template molecule is eluted with a solvent mixture of methanol and acetic acid to obtain the MIPs / Ru(bpy)3 of the de-templated molecule 2+ -BiOBr / ITO.

[0015] Preferably, the masses of Bi(NO3)3•5H2O, polyvinyl pyrrolidone and KBr in S1 are 1.6247 g, 0.1362 g and 0.5756 g respectively, the constant temperature is 50°C, the holding time is 15 min, the heating temperature is 120°C, the heating time is 3 h, and the obtained BiOBr is dried at 40°C and the drying time is 12 h.

[0016] Preferably, the BiOBr in S2 accounts for BiOBr and Ru(bpy)3 2+ The weight ratio of the total weight is 40%, and the obtained Ru(bpy)3 2+ -BiOBr was dried at a drying temperature of 50°C.

[0017] Preferably, Ru(bpy)3 in S3 2+ -BiOBr solution concentration was 2 mg / mL, coated with Ru(bpy)3 2+ The volume of the -BiOBr solution was 20 μL.

[0018] Preferably, in S4, cyclic voltammetry is used for template molecular imprinting, the template molecule is 2,4-D, the scan rate is 50 mV / s, 10 cycles are performed, and the voltage range is -0.2-+1.0 V; the concentration of 2,4-D is 5 mM, the concentration of pyrrole is 15 mM, the pH of the phosphate buffer solution is 7, and the concentration of the phosphate buffer solution is 50 mM; in S5, in the solvent mixture of methanol and acetic acid, the volume ratio of methanol to acetic acid is 8:1, the elution time is 15 min, and the incubation time is 20 min.

[0019] The present invention also provides the use of the sensor described in the above technical solution in detecting trace toxic organic matter in the environment and food, wherein the trace toxic organic matter is a template molecule.

[0020] Preferably, the trace toxic organic matter is 2,4-D.

[0021] Preferably, Ru(bpy)3 is used 2+ -BiOBr heterojunction is a photoactive material, and its heterojunction type can be switched between type II and type Z by changing the applied bias voltage of +0.1 V and -0.2 V; when 2,4-D is present, the molecular imprinting polymer specifically captures 2,4-D. As the concentration of 2,4-D increases, the PEC signal of the type II heterojunction is positive and decreases at a bias voltage of +0.1 V, while the PEC signal of the Z-type heterojunction is negative and increases at a bias voltage of -0.2 V. 2,4-D is detected by monitoring the ratio of two different photocurrents and the selectivity of the molecular imprinting method.

[0022] Preferably, Ru(bpy)3 is used 2+ -BiOBr heterojunction as a photoactive material to detect 2,4-D concentrations in river water, milk, beef, and lettuce.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention provides a sensor, using the prepared MIPs / Ru(bpy)3 2+ -BiOBr / ITO is the working electrode, which contains a large number of specific cavities matching the results of 2,4-D and can selectively adsorb 2,4-D, and Ru(bpy)3 2+ The heterojunction formed with BiOBr greatly enhances the signal strength of the sensor, broadens the detection range of the sensor, and achieves good selectivity of the sensor;

[0025] The present invention provides a method for preparing the above sensor, which has low preparation cost, is maintenance-free, can be used once, has no cumbersome pre-treatment process, has small differences between electrode batches, and uses the ratio of photocurrents under different bias voltages as an analytical signal to make the detection result more sensitive and reliable. The method for detecting 2,4-D concentration based on a portable potential-resolved ratio molecular imprinting photoelectrochemical sensor of the present invention also provides a promising application for detecting other MIPs targets with the same properties.

[0026] The present invention also provides the use of the portable potential-resolved ratiometric molecular imprinting photoelectrochemical sensor in detecting trace toxic organic matter in the environment and food, wherein two different external bias voltages (+0.1 V and -0.2 V) are applied to the PEC sensor, Ru(bpy)3 2+ -BiOBr heterojunction as a photoactive material, its heterojunction type can be switched between type II and type Z by changing the applied bias voltage (+0.1 V and -0.2 V). When 2,4-D exists, MIPs specifically captures 2,4-D. With the increase of 2,4-D concentration, type II heterojunction ( I +0.1 ) is positive and decreases at a bias voltage of +0.1 V, while the Z-type heterojunction ( I -0.2 ) is negative and increases at a bias voltage of -0.2 V. By monitoring the ratio of two different photocurrents, coupled with the selectivity of the molecular imprinting photoelectrochemical sensor for 2,4-D and the reliability of the detection results, a high-sensitivity detection of 2,4-D is achieved. The linear range of the 2,4-D concentration in the environment detected by the method provided by the present invention is 5.0×10 -12 to 1.0×10 -8 M, detection limit is 1.2×10 -12 M, the detection effect is superior to the existing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Ru(bpy)3 prepared in the practice of the present invention 2+ -SEM image of BiOBr;

[0028] Figure 2 Ru(bpy)3 prepared in the practice of the present invention 2+ -XPS spectrum of BiOBr;

[0029] Figure 3 BiOBr and Ru(bpy)3 prepared in the present invention 2+ -Infrared spectrum of BiOBr;

[0030] Figure 4The photocurrent response curve of the sensor in the molecular imprinting process in the implementation of the present invention;

[0031] Figure 5 The portable ratiometric molecular imprinting photoelectrochemical sensor (MIPs) prepared in the present invention is 5.0×10 -12 -1×10 -7 Photocurrent response curve of M 2,4-D;

[0032] Figure 6 The portable ratiometric molecular imprinting photoelectrochemical sensor (MIPs) prepared in the present invention is ( I +0.1 ) MIPs 、( I -0.2 ) MIPs Linear calibration curve of

[0033] Figure 7 is a linear calibration curve of the portable ratiometric molecular imprinting photoelectrochemical sensor (I-0.2 / I+0.1) prepared in the embodiment of the present invention;

[0034] Figure 8 This is a selectivity test diagram of a portable ratiometric molecular imprinting photoelectrochemical sensor prepared in the implementation of the present invention;

[0035] Fig. 9 This is a stability test diagram of a portable ratiometric molecular imprinting photoelectrochemical sensor prepared in the implementation of the present invention;

[0036] Fig.10 This is a repeatability test diagram of a portable ratiometric molecular imprinting photoelectrochemical sensor prepared in the implementation of the present invention;

[0037] Fig.11 A flow chart of the preparation process of the sensor provided for the implementation of the present invention. DETAILED DESCRIPTION

[0038] The technical scheme in the specific embodiment of the present invention is described in detail and completely below. Obviously, the described embodiment is only a part of the specific implementation of the overall technical scheme of the present invention, rather than all implementations. Based on the overall concept of the present invention, all other embodiments obtained by ordinary technicians in this field fall within the scope of protection of the present invention.

[0039] On the one hand, the present invention provides a portable potential-resolved ratio molecular imprinting photoelectrochemical sensor, wherein the portable potential-resolved ratio molecular imprinting photoelectrochemical sensor is respectively based on MIPs / Ru(bpy)3 2+-BiOBr / ITO electrode is used as the working electrode and Pt sheet is used as the counter electrode, LED lamp is used as the excitation light source, and digital multimeter is used as the photocurrent capture device. 2+ -BiOBr heterojunction as a photoactive material, its heterojunction type can be switched between type II and type Z by changing the applied bias voltage (+0.1 V and -0.2 V). When 2,4-D is present, MIPs specifically capture 2,4-D, and with the increase of 2,4-D concentration, type II heterojunction ( I +0.1 ) is positive and decreases at a bias voltage of +0.1 V, while the Z-type heterojunction ( I -0.2 ) is negative and increases at a bias voltage of -0.2 V. By monitoring the ratio of two different photocurrents and the selectivity of the molecular imprinting (MIPs) method, high sensitivity and high selectivity for 2,4-D detection are achieved. The linear range of the portable ratiometric molecular imprinting photoelectrochemical sensor for detecting 2,4-D is 5.0×10 -12 to 1.0×10 -7 M, detection limit is 1.2×10 -12 As an important extension, this ratiometric molecular imprinting photoelectrochemical technique can be used as an innovative and general method to detect other MIPs targets with similar properties.

[0040] The MIPs / Ru(bpy)3 2+ -BiOBr / ITO electrode preparation method, Fig.11 As shown, the specific steps include:

[0041] S1: Bi(NO3)3·5H2O, polyvinyl pyrrolidone and KBr are added to ethylene glycol solution, maintained at a constant temperature, and then transferred to a reactor for heating, and the obtained BiOBr sample is collected and dried.

[0042] S2: BiOBr and Ru(bpy)3 2+ Mix and stir to obtain Ru(bpy)3 2+ -BiOBr sample drying.

[0043] S3: Coating Ru(bpy)3 on ITO surface 2+ -BiOBr solution, dried under infrared irradiation to obtain Ru(bpy)3 2+ -BiOBr / ITO.

[0044] S4: Ru(bpy)3 2+-BiOBr / ITO was placed in a phosphate buffer solution containing 2,4-D and pyrrole and electropolymerized using cyclic voltammetry for 2,4-D imprinting.

[0045] S5: eluting the 2,4-D in the MIPs modified electrode in step S4 with a solvent mixture of methanol and acetic acid to obtain MIPs / Ru(bpy)3 with the target template molecule removed from 2,4-D 2+ -BiOBr / ITO electrode.

[0046] The masses of Bi(NO3)3·5H2O, polyvinyl pyrrolidone and KBr described in step S1 are 1.6247 g, 0.1362 g and 0.5756 g respectively, the volume of ethylene glycol is 30 mL, the constant temperature is 50°C, the holding time is 15 min, the heating temperature is 120°C, the heating time is 3 h, the drying temperature is 40°C, and the drying time is 12 h.

[0047] Step S2 described in the step of mixing BiOBr with Ru(bpy)3 2+ The mixture is mixed and stirred and then dried. The weight ratio of BiOBr is 40% and the drying temperature is 50°C.

[0048] Ru(bpy)3 described in step S3 2+ -BiOBr solution concentration was 2 mg / mL, coated with Ru(bpy)3 2+ The volume of the -BiOBr solution was 20 μL.

[0049] The concentration of 2,4-D in step S4 is 5 mM, the concentration of pyrrole is 15 mM, and the concentration of phosphate buffer solution pH 7 is 50 mM.

[0050] Cyclic voltammetry was used for 2,4-D imprinting as described in step S4, with a scan rate of 50 mV / s, 10 cycles, and a voltage range of -0.2 to +1.0 V.

[0051] In the solvent mixture of methanol and acetic acid described in step S5, methanol (concentration ≥ 99.5%) and acetic acid (concentration ≥ 99.5%) are prepared in a volume ratio of 8:1, the elution time is 15 min, and the incubation time is 20 min.

[0052] The NIPs / Ru(bpy)3 2+ -BiOBr / ITO electrode preparation method and MIPs / Ru(bpy)3 2+ -BiOBr / ITO electrode preparation method is different only in that no template molecules are added to the phosphate buffer solution.

[0053] The present invention also provides the use of the portable potential-resolved ratio molecular imprinting photoelectrochemical sensor in detecting trace toxic organic matter in environmental water and food, wherein the organic matter is 2,4-dichlorophenoxyacetic acid.

[0054] The present invention also provides a method for detecting 2,4-D concentration based on the portable potential-resolved ratiometric molecular imprinting photoelectrochemical sensor, wherein the method uses Ru(bpy)3 2+ -BiOBr is a photoactive material, and its heterojunction type can be switched between type II and type Z by changing the applied bias voltage (+0.1 V and -0.2 V). When 2,4-D is present, MIPs specifically captures 2,4-D. With the increase of 2,4-D concentration, type II heterojunction ( I +0.1 ) is positive and decreases at a bias voltage of +0.1 V, while the Z-type heterojunction ( I -0.2 ) is negative and increases at a bias voltage of -0.2 V. By monitoring the ratio of two different photocurrents and combining the selectivity of the molecular imprinting (MIPs) strategy for 2,4-D, high sensitivity and high selectivity for 2,4-D can be achieved.

[0055] Another aspect of the present invention provides application of the above method in detecting 2,4-D concentration in river water, milk, beef and lettuce.

[0056] As mentioned above, the photoelectrochemical sensing detection method is an analytical technology that combines photoelectric technology with sensors. The photoelectrochemical sensor based on molecular imprinting is a good tool for biomolecule detection. 2,4-D is a widely used herbicide and is toxic. When the concentration of 2,4-D in the environment exceeds a certain threshold, it will pose a major threat to the health of humans and animals. The development of a highly selective and sensitive analytical detection method for 2,4-D concentration is currently a hot topic of research.

[0057] Based on this, the present invention provides a method for detecting 2,4-D concentration using a portable ratiometric molecular imprinting photoelectrochemical sensor. The present invention uses an LED lamp as an excitation light source and adopts Ru(bpy)3 2+ -BiOBr was used as a photoactive substance. By detecting the ratio of photoactive substances at different bias voltages and using imprinted polymers, the selectivity of molecular imprinted photoelectrochemical sensors for 2,4-D was further improved, the reliability of the detection results of 2,4-D concentration in the environment was enhanced, and high-sensitivity detection of 2,4-D was achieved, with a detection limit of 1.2×10 -12 M, the detection effect is superior to the existing technology.

[0058] MIPs / Ru(bpy)3 prepared by the present invention 2+ -BiOBr electrode, on the one hand, contains specific cavities on its surface, which can selectively adsorb 2,4-D, and on the other hand, Ru(bpy)3 2+ -BiOBr heterojunction is used as a photoactive material, and its heterojunction type can be switched between type II and type Z by changing the applied bias voltage (+0.1 and -0.2 V). By monitoring the ratio of two different photocurrents, coupled with the selectivity of molecular imprinting photoelectrochemical sensors for 2,4-D and the reliability of the detection results, high-sensitivity detection of 2,4-D was achieved.

[0059] Furthermore, the method for detecting 2,4-D concentration using a portable ratio molecular imprinting photoelectrochemical sensor provided by the present invention can also be used to detect other organic pollutants (including analogs of 2,4-D) in the environment. The portable ratio molecular imprinting photoelectrochemical sensor prepared by the present invention is easy to carry and can meet the needs of on-site detection.

[0060] In order to more clearly and in detail introduce the sensor provided by the embodiments of the present invention, its preparation method and application, the following will be described in conjunction with specific embodiments.

[0061] Example 1: Preparation of molecularly imprinted ratiometric photoelectrochemical sensor

[0062] (1) 0.1362 g of polyvinyl pyrrolidone and 0.5756 g of KBr were added to 30 mL of ethylene glycol solution (containing 1.6247 g of Bi(NO3)3·5H2O), kept at 50°C for 15 min, and then transferred to 50 mL of polytetrafluoroethylene and washed at 120°C for 3 h. The obtained product was washed with ethanol and ultrapure water for 5 times, respectively. Finally, the collected BiOBr sample was dried at 40°C for 12 h.

[0063] (2) BiOBr with a weight ratio of 60% and Ru(bpy)3 2+ Mix and stir for 15 h to prepare Ru(bpy)3 2+ -BiOBr. Finally, it was dried at 50°C before use.

[0064] (3) Wash the ITO electrode with acetone, ethanol and ultrapure water respectively. 2 ) coated with Ru(bpy)3 2+ -BiOBr solution (20 μL, 2 mg / mL) was dried under infrared irradiation to obtain Ru(bpy)3 2+ -BiOBr / ITO.

[0065] (4) MIPs / Ru(bpy)3 were prepared by electropolymerization in phosphate buffer solution (PBS pH 7, 50 mM) containing 2,4-D (5 mM) and pyrrole (15 mM). 2+ -BiOBr electrode. 2,4-D imprinting was performed by cyclic voltammetry with a scan rate of 50 mV / s and a voltage range of −0.2 to +1.0 V. After 10 cycles, the 2,4-D imprinted electrode was removed and washed with a solvent mixture of methanol and acetic acid (v / v 8:1) for 10 min to obtain MIPs / Ru(bpy)3 2+ -BiOBr electrode.

[0066] (5) NIPs / Ru(bpy)3 2+ The preparation method of -BiOBr electrode is the same as the preparation of MIPs / Ru(bpy)3 except that 2,4-D template molecules are not added. 2+ -BiOBr electrode in the same way.

[0067] Ru(bpy)3 2+ -SEM image of BiOBr ( Figure 1 )It can be seen that Ru(bpy)3 2+ -BiOBr has a complete hierarchical microsphere structure, and the smooth surface increases the binding sites. 2+ The introduction of has no effect on the structure of pure BiOBr.

[0068] Ru(bpy)3 2+ -XPS spectrum of BiOBr Figure 2 As shown, it contains C, O, N, Bi, Br and Ru elements. The three characteristic peaks of Ru 3d are 280.8 eV, 284.6 eV and 285.6 eV, corresponding to Ru 3d 5 / 2 and Ru 3d 3 / 2 The results showed that Ru was successfully modified on the BiOBr surface.

[0069] Ru(bpy)3 2+ FT-IR spectrum of -BiOBr ( Figure 3 ) It can be seen that 514 cm -1 and 772 cm -1 The peak at 1616 cm -1 The peak at 3443 cm is responsible for the OH stretching vibration. -1 The existence of the band is also consistent with the absorption vibration of the OH functional group. 2+The FT-IR spectrum of the Ru(bpy)-BiOBr composite is similar to that of pure BiOBr, indicating that 2+ The introduction of has no obvious effect on the structure of pure BiOBr.

[0070] Example 2: High-sensitivity detection of 2,4-D concentration

[0071] (1) Detection method

[0072] Water samples were collected from Xiaoqing River in Jinan City. To eliminate any potential suspended particles, the samples were filtered using a 0.45 µm microfiltration membrane. Subsequently, the samples were diluted 100 times and spiked with a certain concentration of standard 2,4-D solution. Milk, beef, cabbage, and lettuce were purchased from a local supermarket (Jinan) as authentic samples. 5 mL of milk sample was mixed with 20 mL of acetonitrile and 5 mL of EDTA (0.5%) in a polypropylene centrifuge tube and rotated for 30 s. Then 1.25 g of MgSO4 was added and rotated for 30 s. After centrifugation at 10000 rpm for 10 min, the supernatant was collected and filtered and evaporated under a stream of nitrogen. The resulting sample was re-dissolved in 1 mL of ultrapure water. 1.0 g of beef sample was transferred to a polypropylene centrifuge tube containing 3 mL of acetonitrile. A certain concentration of 2,4-D standard solution was added to the tube and retained for 15 min for spiking. The mixture was sonicated for 15 min and the acetonitrile was transferred to another tube. After three repetitions, the acetonitrile supernatant was centrifuged at 6000 rpm for 10 min, the supernatant was evaporated with nitrogen, and the resulting sample was dissolved in 10 mL of ultrapure water for 2,4-D determination. The pretreatment process of Chinese cabbage and lettuce is as follows. First, the sample was crushed into small pieces, 10 g of sample was weighed, and 10 mL of acetonitrile was added for ultrasonic extraction. Finally, the extracted sample was centrifuged at 8000 rpm for 20 min, the residue was discarded, and the supernatant was collected. Subsequently, the sample was diluted 100 times and a certain concentration of standard 2,4-D solution was added.

[0073] Using a two-electrode system, the MIPs / Ru(bpy)3 prepared in Example 1 2+ -BiOBr / ITO electrode was used as the working electrode, and Pt sheet was used as the counter electrode, and LED light was used as the excitation light source. The working electrode was then incubated in a 10% ethanol solution containing different concentrations of 2,4-D for 15 minutes, and then the electrode was removed and rinsed with ultrapure water.

[0074] Record MIPs / Ru(bpy)3 separately 2+ -BiOBr / ITO at +0.1 V ( I +0.1 ) and -0.2 V ( I -0.2) Photocurrent response under bias voltage. A standard curve of 2,4-D concentration and photocurrent ratio signal under different bias voltages was established.

[0075] (2) Test results

[0076] Depend on Figure 4 It can be seen that BiOBr / ITO exhibits obvious PEC responses (0.137 μA, -0.180 μA) at +0.1 V and -0.2 V. In addition, Ru(bpy)3 2+ The photocurrent of -BiOBr / ITO at +0.1 V and -0.2 V increases to 7.3 times and 8.7 times that of BiOBr / ITO, respectively. This is because Ru(bpy)3 2+ Integration on the BiOBr surface can not only facilitate the separation of electrons and holes, but also enhance the photocurrent response. 2+ -After electropolymerization of PPy film on BiOBr / ITO electrode, MIPs / Ru(bpy)3 2+ -BiOBr / ITO and NIPs / Ru(bpy)3 2+ -BiOBr / ITO has a higher photocurrent than Ru(bpy)3 at +0.1 V and -0.2 V. 2+ -BiOBr / ITO increases. When 2,4-D rebounds to MIPs / Ru(bpy)3 2+ -BiOBr / ITO, (2,4-D) MIPs / Ru(bpy)3 2+ -The photocurrent of BiOBr / ITO decreases to that of MIPs / Ru(bpy)3 at +0.1 V 2+ -BiOBr / ITO is about 38.4%. The weakening of PEC signal can be attributed to the presence of 2,4-D, which blocks the electron transfer and increases the steric hindrance of the ITO interface. However, at -0.2 V, the PEC signal has a different response, which increases sharply to -0.2 V MIPs / Ru(bpy)3 2+ -BiOBr / ITO by 2.16 times. These results indicate that the applied bias voltage is an important parameter associated with this MIPs-PEC sensor.

[0077] At +0.1 V and -0.2 V, the photocurrent is a function of the 2,4-D concentration (from 5 × 10 -12 M to 1×10 -7 M) is related to Figure 5 As the concentration of 2,4-D increases, the photocurrent signal intensity of MIPs and NIPs decreases at +0.1 V and increases at -0.2 V.

[0078] Figure 6 The results showed that the photocurrent and 2,4-D concentration were 5×10 -12 ~ 1×10 -7 There is a good linear relationship between M, and the standard curves are ( I +0.1 ) MIPs (μA)=-0.5323lgC+0.1549 (R 2 =0.9581) and ( I -0.2 ) MIPs (μA)=-0.4556lgC–6.964 (R 2 =0.9893).

[0079] ( I -0.2 / I +0.1 ) MIPs The relationship with 2,4-D concentration is as follows Figure 7 The results show that ( I -0.2 / I +0.1 ) MIPs With 2,4-D concentration of 5×10 -12 ~ 1×10 -7 There is a good linear correlation within the range of M, ( I -0.2 / I +0.1 ) MIPs =-1.055lgC–13.15 (R 2 =0.9946), and the detection limit (LOD) was 1.2×10 -12 M (S / N=3). I -0.2 / I +0.1 ) MIPs The detection limit is obtained by correction of the 3σ / k formula, where σ is ( I -0.2 / I +0.1 ) MIPs The standard deviation of the blank measurements (n = 11), k is ( I -0.2 / I +0.1 ) MIPs The slope of the calibration curve, the blank measurement sample is pure water.

[0080] The test results show that the linear range of the present invention for detecting 2,4-D is 5×10 -12 Up to 1×10-7 M, detection limit is 1.2×10 -12 M, when testing samples with unknown 2,4-D concentration, according to ( I -0.2 / I +0.1 ) MIPs =-1.055lgC–13.15, (R 2 =0.9946). Therefore, based on the detection method proposed by the present invention, the portable ratio molecular imprinting photoelectrochemical sensor prepared by the present invention can achieve high-sensitivity detection of 2,4-D concentration.

[0081] Example 3: Performance detection based on portable ratiometric molecular imprinting photoelectrochemical sensor

[0082] (1) Selective testing:

[0083] The sensor was compared with 10 nM 2,4-D, 4-dichlorophenylacetic acid (2,4-DCPA), 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB), 2,4-dichlorophenol (2,4-DCP) and 2,4-dichlorobenzoic acid (2,4-DCB). Figure 8 As shown, the interfering PEC signal ratio is significantly lower compared with that obtained from 2,4-D, which indicates that the proposed MIPs-PEC sensor has good selectivity for the determination of 2,4-D.

[0084] (2) Stability:

[0085] like Fig. 9 As shown, MIPs / Ru(bpy)3 2+ The photocurrent response of -BiOBr / ITO remained within a relative standard deviation (RSD) of 2.15% after 10 repetitions, indicating that the sensor has high stability.

[0086] (3) Repeatability:

[0087] MIPs / Ru(bpy)3 2+ -Reproducibility of BiOBr / ITO electrodes Fig.10 According to the detection method provided by the present invention, 6 modified electrodes are used to repeatedly detect the 2,4-D solution. I +0.1 and I -0.2 The RSDs were 2.68% and 2.56% respectively. It is worth noting that I -0.2 / I +0.1The RSD of the ratio was only 1.3%. These results indicate that the ratiometric molecular imprinting photoelectrochemical sensor has good reproducibility.

[0088] The present invention discloses a novel portable ratiometric molecular imprinting photoelectrochemical sensor, which uses Ru(bpy)3 2+ -BiOBr heterojunction as a photoactive material, its heterojunction type can be switched between type II and type Z by changing the applied bias voltage (+0.1 and -0.2 V). When 2,4-D is present, MIPs specifically captures 2,4-D, and with the increase of 2,4-D concentration, type II heterojunction ( I +0.1 ) is positive and decreases at a bias voltage of +0.1 V, while the Z-type heterojunction ( I -0.2 ) is negative and increases under a bias voltage of -0.2 V. By monitoring the ratio of two different photocurrents, the sensitivity of the sensor is effectively improved. At the same time, the MIPs strategy can greatly improve the selectivity and anti-interference ability of molecular imprinting photoelectrochemical sensors, and achieve high-sensitivity detection of 2,4-D. It is worth noting that this ratiometric molecular imprinting photoelectrochemical technology provides a general strategy with great application prospects in environmental analysis.

Claims

1. A portable potential-resolved ratiometric molecular imprinted photoelectrochemical sensor, characterized in that: Sensor based on MIPs / Ru(bpy)3 2+ -BiOBr / ITO electrode is used as the working electrode, Pt sheet is used as the counter electrode, and LED lamp is used as the excitation light source.

2. A method for preparing a portable potential-resolved ratiometric molecular imprinted photoelectrochemical sensor according to claim 1, characterized in that: Including MIPs / Ru(bpy)3 2+ -BiOBr / ITO electrode preparation steps, the MIPs / Ru(bpy)3 2+ -BiOBr / ITO electrode preparation steps include: S1: Bi(NO3)3·5H2O, polyvinyl pyrrolidone and KBr are added to ethylene glycol solution, kept at a constant temperature, and then transferred to a reactor for heating to obtain BiOBr; S2: BiOBr and Ru(bpy)3 2+ Mix and stir to obtain Ru(bpy)3 2+ -BiOBr; S3: Coating Ru(bpy)3 on ITO surface 2+ -BiOBr solution, dried under infrared irradiation to obtain Ru(bpy)3 2+ -BiOBr / ITO; S4: Ru(bpy)3 2+ -BiOBr / ITO was placed in a phosphate buffer solution containing template molecules and pyrrole, and electropolymerized using cyclic voltammetry to perform template molecular imprinting; S5: The template molecule is eluted with a solvent mixture of methanol and acetic acid to obtain the MIPs / Ru(bpy)3 without the template molecule. 2+ -BiOBr / ITO.

3. The preparation method according to claim 2, characterized in that: The masses of Bi(NO3)3·5H2O, polyvinyl pyrrolidone and KBr in S1 are 1.6247g, 0.1362g and 0.5756g respectively. The constant temperature is 50℃, the holding time is 15min, the heating temperature is 120℃, the heating time is 3h, and the obtained BiOBr is dried at 40℃ and the drying time is 12h.

4. The preparation method according to claim 2, characterized in that: BiOBr in S2 accounts for the proportion of BiOBr and Ru(bpy)3 2+ The weight ratio of the total weight is 40%, and the obtained Ru(bpy)3 2+ -BiOBr was dried at a drying temperature of 50°C.

5. The preparation method according to claim 2, characterized in that: Ru(bpy)3 in S3 2+ -BiOBr solution concentration was 2 mg / mL, coated with Ru(bpy)3 2+ The volume of the -BiOBr solution was 20 μL.

6. The preparation method according to claim 2, characterized in that: In S4, cyclic voltammetry was used for template molecular imprinting, the template molecule was 2,4-D, the scanning rate was 50 mV / s, 10 cycles were performed, and the voltage range was -0.2-+1.0 V; the concentration of 2,4-D was 5 mM, the concentration of pyrrole was 15 mM, the pH of the phosphate buffer solution was 7, and the concentration of the phosphate buffer solution was 50 mM; in S5, the solvent mixture of methanol and acetic acid had a volume ratio of 8:1, the elution time was 15 min, and the incubation time was 20 min.

7. The use of the portable potential-resolved ratiometric molecular imprinted photoelectrochemical sensor according to claim 1 in detecting trace toxic organic matter in the environment and food, characterized in that: The trace toxic organic substance is 2,4-D.

8. The use of the portable potential-resolved ratiometric molecular imprinted photoelectrochemical sensor according to claim 7 in detecting trace toxic organic matter in the environment and food, characterized in that: Using Ru(bpy)3 2+ -BiOBr heterojunction is a photoactive material, and its heterojunction type can be switched between type II and type Z by changing the external bias voltage of +0.1V and -0.2V; when 2,4-D is present, the molecular imprinting polymer specifically captures 2,4-D. As the concentration of 2,4-D increases, the PEC signal of the type II heterojunction is positive and decreases at a bias voltage of +0.1V, while the PEC signal of the Z-type heterojunction is negative and increases at a bias voltage of -0.2V. 2,4-D is detected by monitoring the ratio of two different photocurrents and the selectivity of the molecular imprinting method.

9. The use of the portable potential-resolved ratiometric molecular imprinted photoelectrochemical sensor according to claim 7 in detecting trace toxic organic matter in the environment and food, characterized in that: Using Ru(bpy)3 2+ -BiOBr heterojunction as a photoactive material to detect 2,4-D concentrations in river water, milk, beef, and lettuce.

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