A molecular imprinting dual-wavelength portable photoelectrochemical sensor and its preparation method and application

Abstract

The present invention discloses a molecular imprinting dual-wavelength portable photoelectrochemical sensor and its preparation method and application, belonging to the field of sensor technology. The present invention adopts gold nanoparticles (Au NPs) to modify porous silicon and target analyte (2,4-dichlorophenoxyacetic acid (2,4-D)) as photoelectrochemical active substances, and generates non-interfering photocurrent signals at two different excitation wavelengths (560 and 280nm), and uses the falling and rising photocurrent signals generated at different excitation wavelengths under different analyte concentrations as ratio analysis signals, and the differential response between the imprinted polymer and the non-imprinted polymer as the analysis signal, thereby realizing high sensitivity and high selectivity detection of 2,4-D. The ratio differential molecular imprinting photoelectrochemical technology can also be used as an innovative and universal method for detecting other MIPs targets with similar properties.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a molecular imprinting dual-wavelength portable 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, the ratiometric strategy has been widely integrated with various analytical techniques due to its inherent advantages in mitigating environmental interference and its ability to provide more accurate measurements through self-correction capabilities. In terms of selectivity, molecularly imprinted polymers (MIPs), also known as "molecular template technology", provide sites for selective recognition of target molecules and have significant advantages in terms of physical robustness, thermal stability and ease of preparation. Therefore, it is an effective approach to develop ratiometric MIPs technology, which has been successfully combined with various analytical fields such as electrochemistry, fluorescence, electrochemiluminescence and Raman spectroscopy. However, to date, the application of ratiometric MIPs technology in photoelectrochemical (PEC) analysis has been rarely reported.

[0004] Ratio PEC methods usually rely on two selective photoactive materials to achieve different signal labels. In the wavelength-resolved ratio PEC method, one signal from the photoactive material is usually suppressed, while the signal from the other photoactive material is simultaneously amplified in the presence of the target. For example, Yuan et al. (Y. Zheng, W. Liang, C. Xiong, Y. Zhuo, Y. Chai, R. Yuan, Analytical Chemistry 89 (2017) 9445-9451) developed a ratiometric PEC sensor for ultrasensitive detection of microRNA in cells. The ratiometric strategy uses SiO2@methylene blue (623 nm) and CdS quantum dots (460 nm) as wavelength-selective photoactive materials for photocurrent signal ratiometric value. However, the MIPs-PEC strategy usually has only one photoactive material to produce a PEC signal for a single analyte. Achieving two different photocurrent signals in the ratiometric MIPs-PEC strategy remains a huge challenge.

[0005] Although the imprinting sites of MIPs can specifically adsorb template molecules, other interfering substances can also be adsorbed on the surface of MIPs by nonspecific adsorption, which will reduce the recognition selectivity of MIPs. The differential strategy is based on the difference signal between MIPs and NIPs to increase the selectivity and sensitivity of specific analyte determination. At the same time, a weight factor is needed to balance the difference in specific surface area between MIPs and NIPs.

[0006] 2,4-Dichlorophenoxyacetic acid (2,4-D) is a typical phenoxy herbicide, which is very effective in controlling broadleaf weeds in agricultural operations. However, it is toxic and easily accumulates in plants and animals. When the concentration of 2,4-D in the environment exceeds a certain threshold (the concentration required by the U.S. Environmental Protection Agency is 3.17×10 -7 M), it will pose a major threat to the health of humans and animals. Therefore, it is particularly important to develop new molecular imprinting photoelectrochemical biosensing technology to achieve highly selective, highly sensitive and portable analysis and 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 analysis and detection methods, 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

[0007] In view of the problems existing in the above-mentioned prior art, the purpose of the present invention is to propose a molecular imprinting portable photoelectrochemical sensor with a dual-wavelength ratio differential strategy for high sensitivity and high selectivity in detecting 2,4-D. The present invention uses Au NPs / porous silicon with an excitation wavelength of 560nm and 2,4-D with an excitation wavelength of 280nm as two photoactive materials for signal separation for PEC sensors. When 2,4-D is present, MIPs specifically captures 2,4-D. Under 560nm illumination, the Au NPs / porous silicon photocurrent signal is weakened due to steric hindrance. Under 280nm illumination, the photocurrent signal of 2,4-D on the electrode surface is not affected by steric hindrance, and the photocurrent signal of 2,4-D increases. By monitoring the ratio of two different photocurrents and using the response difference between the imprinted polymer and the non-imprinted polymer as the analytical signal, a highly selective and sensitive analytical detection of the 2,4-D concentration in the environment is achieved.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] In the first aspect of the present invention, a molecular imprinting dual-wavelength ratio differential portable photoelectrochemical sensor is provided. The molecular imprinting dual-wavelength ratio differential photoelectrochemical sensor uses MIPs@Au NPs / porous silicon electrode as the first working electrode, NIPs@Au NPs / porous silicon as the second working electrode, a Pt sheet as the counter electrode, an LED lamp as the excitation light source, and a multimeter as the photocurrent signal capture device.

[0010] The MIPs@Au NPs / porous silicon electrode preparation method specifically comprises the following steps:

[0011] S1: Soak the silicon wafer in hydrofluoric acid solution to remove the oxide layer, and then rinse with ultrapure water.

[0012] S2: Use a high vacuum evaporation system to coat a 300nm aluminum film on the back of the silicon wafer.

[0013] S3: Under halogen lamp irradiation, anodize in a mixed solution of hydrofluoric acid and ethanol with constant current, rinse the porous silicon nanostructure with ultrapure water and ethanol in sequence, and then dry it under nitrogen flow. Soak the cleaned porous silicon electrode in a hydrofluoric acid solution to obtain a new H-terminated porous silicon electrode.

[0014] S4: placing the H-terminated porous silicon electrode in a HAuCl4 solution and heating and soaking it to generate Au NPs. Then, the prepared Au NPs / porous silicon electrode is rinsed with ultrapure water and dried for standby use.

[0015] S5: Au NPs / porous silicon were placed in a phosphate buffer solution containing 2,4-D and pyrrole and electropolymerized using cyclic voltammetry for 2,4-D imprinting.

[0016] S6: Using a solvent mixture of methanol and acetic acid to elute 2,4-D in the MIP modified electrode described in step S5, to obtain a MIPs@Au NPs / porous silicon electrode with the target template molecule removed and 2,4-D removed.

[0017] The concentration of the hydrofluoric acid solution in step S1 is 40%wt, and the immersion time is 12min.

[0018] The halogen lamp power in step S3 is 60W, and the constant current density is 30mA cm -2 The hydrofluoric acid and ethanol mixed solution used for anodization is prepared by 40% hydrofluoric acid solution and 95% ethanol solution in a volume ratio of 1:1, and the anodization time is 6 minutes. The cleaned porous silicon electrode is immersed in the hydrofluoric acid solution with a concentration of 5% and an immersion time of 40 minutes.

[0019] The concentration of the HAuCl4 solution in step S4 is 1 mM, the heating temperature is 60°C, and the soaking time is 5 min.

[0020] The concentration of 2,4-D in step S5 is 5 mM, the concentration of pyrrole is 15 mM, and the concentration of phosphate buffer solution pH 7 is 50 mM.

[0021] The 2,4-D imprinting was performed by cyclic voltammetry as described in step S5, with a scan rate of 50 mV / s, 10 cycles, and a voltage range of -0.2 to +1.0 V.

[0022] In the solvent mixture of methanol and acetic acid described in step S6, methanol (concentration ≥ 99.5%) and acetic acid (concentration ≥ 99.5%) are prepared in a volume ratio of 8:1, the elution time is 15 minutes, and the incubation time is 20 minutes.

[0023] The difference between the NIPs@Au NPs / porous silicon electrode preparation method and the MIPs@Au NPs / porous silicon electrode preparation method is that no template molecule is added to the phosphate buffer solution.

[0024] The second aspect of the present invention provides the use of the molecular imprinting dual-wavelength ratio differential portable photoelectrochemical sensor in detecting trace toxic organic matter in the environment.

[0025] The organic matter is 2,4-dichlorophenoxyacetic acid.

[0026] In a third aspect, the present invention provides a method for detecting 2,4-D concentration based on the above-mentioned molecular imprinting dual-wavelength ratio differential portable photoelectrochemical sensor. The method uses porous silicon modified with Au NPs and 2,4-D as photoactive substances to generate the ratio of photocurrents at different excitation wavelengths of 560 and 280 nm, and the response difference between the imprinted polymer and the non-imprinted polymer as analytical signals, thereby realizing the detection of 2,4-D concentration.

[0027] In a fourth aspect, the present invention provides application of the above method in detecting 2,4-D concentration in river water and tap water.

[0028] Beneficial effects of the present invention:

[0029] (1) The present invention provides a molecular imprinting dual-wavelength ratio differential portable photoelectrochemical sensor, which uses the prepared MIPs@Au NPs / porous silicon as the first working electrode. The surface of the working electrode contains a large number of specific cavities that match the 2,4-D results and can selectively adsorb 2,4-D. In addition, the molecular imprinting polymer can form a heterojunction with the photoactive material porous silicon, which greatly enhances the signal strength of the sensor, broadens the detection range of the sensor, and achieves good selectivity of the sensor.

[0030] (2) The present invention provides a method for detecting 2,4-D concentration based on a molecular imprinting dual-wavelength ratio differential photoelectrochemical sensor. The present invention uses Au NPs / porous silicon with a wavelength of 560nm and 2,4-D with a wavelength of 280nm as photoactive materials for PEC sensors. When 2,4-D is present, MIPs specifically captures 2,4-D, and the photocurrent decreases under 560nm illumination and increases under 280nm illumination. By monitoring the ratio of two different photocurrents and using the response difference between the imprinted polymer and the non-imprinted polymer as the analytical signal, the selectivity of the molecular imprinting photoelectrochemical sensor for 2,4-D and the reliability of the detection results are further improved, achieving high-sensitivity detection of 2,4-D. The linear range of the 2,4-D concentration in the environment detected by the method provided by the present invention is 1.0×10 -11 Up to 8.0×10 -8 M, detection limit is 8.9×10 -13 M, the detection effect is superior to the existing technology, the detection mode is shown in the figure Figure 1 shown.

[0031] (3) The molecular imprinting dual-wavelength ratio differential photoelectrochemical sensor provided by the present invention has low preparation cost, is maintenance-free, can be used once, does not require cumbersome pre-treatment processes, and has small differences between electrode batches. The ratio of photocurrents at different excitation wavelengths and the response difference between imprinted polymers and non-imprinted polymers are used as analytical signals, which to a certain extent eliminates the detection error caused by nonspecific adsorption of interferents other than the target molecule, making the detection result more reliable. The method for detecting 2,4-D concentration based on the molecular imprinting dual-wavelength ratio differential photoelectrochemical sensor of the present invention also provides promising applications for detecting other MIPs targets with the same properties, such as atrazine (AT) and triphenyl phosphate (TPhP). BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a model effect diagram of preparing a molecular imprinting dual-wavelength ratio differential photoelectrochemical sensor for 2,4-D concentration detection in the implementation of the present invention.

[0033] Figure 2 This is a SEM image of Au NPs / porous silicon prepared in the practice of the present invention.

[0034] Figure 3 This is a SEM image of MIPs@Au NPs / porous silicon prepared in the practice of the present invention.

[0035] Figure 4 This is the XPS spectrum of Au NPs / porous silicon prepared in the implementation of the present invention.

[0036] Figure 5 This is an infrared spectrum diagram of the sensor in the molecular imprinting process in the implementation of the present invention.

[0037] Figure 6 This is the I-λ curve diagram of (2,4-D)MIPs@Au NPs / PS and Au NPs / PS in the implementation of the present invention.

[0038] Figure 7 The UV-visible absorption spectra of Au NPs / PS, 2,4-D and 2,4-D+Au NPs / PS in the implementation of the present invention.

[0039] Figure 8 This is the photocurrent response curve of the sensor in the molecular imprinting process in the implementation of the present invention.

[0040] Fig. 9 The molecular imprinting dual-wavelength photoelectrochemical sensor (MIPs) prepared in the present invention is 0~1×10 -7 Photocurrent response curve of M 2,4-D.

[0041] Fig.10 The molecular imprinting dual-wavelength photoelectrochemical sensor (MIPs) prepared in the present invention is 560MIPs ,I 280MIPs Linear calibration curve.

[0042] Fig.11 The molecular imprinting dual-wavelength ratio differential photoelectrochemical sensor prepared in the present invention is 280 / I 560 ) MIPs ,(I 280 / I 560 ) NIPs ,(I 280 / I 560 ) MIPs -1.08(I 280 / I 560 ) NIPs Linear calibration curve.

[0043] Fig.12 This is a selectivity test diagram of the molecular imprinting dual-wavelength ratio photoelectrochemical sensor prepared in the implementation of the present invention.

[0044] Fig.13 This is a stability test diagram of the molecular imprinting dual-wavelength ratio photoelectrochemical sensor prepared in the implementation of the present invention.

[0045] Fig.14 This is a repeatability test diagram of the molecular imprinting dual-wavelength ratio photoelectrochemical sensor prepared in the implementation of the present invention.

[0046] Fig.15 1 is an I-λ curve diagram of atrazine (AT) and triphenyl phosphate (TPhP) in the implementation of the present invention.

[0047] Fig.16 It is the UV-visible absorption spectrum of AT and TPhP in the implementation of the present invention.

[0048] Fig.17 The analog (AT) photocurrent response curve of the sensor of the molecular imprinting process in the implementation of the present invention.

[0049] Fig.18 The photocurrent response curve of the analog (TPhP) of the sensor of the molecular imprinting process in the implementation of the present invention. DETAILED DESCRIPTION

[0050] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0051] 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.

[0052] Based on this, the present invention provides a method for detecting 2,4-D concentration based on a molecular imprinting dual-wavelength ratio differential photoelectrochemical sensor. The present invention uses LED lamp as an excitation light source, adopts gold nanoparticles (Au NPs) to modify porous silicon and 2,4-D as photoelectroactive materials with mutually separated excitation light wavelengths, detects the ratio of photoelectrochemical signals at different excitation wavelengths, and uses the differential response between the imprinted polymer and the non-imprinted polymer as the analysis signal, thereby further improving the selectivity of the molecular imprinting photoelectrochemical sensor for 2,4-D, enhancing the reliability of the 2,4-D concentration detection results in the environment, and realizing high-sensitivity detection of 2,4-D, with a detection limit of 8.9×10 -13 M, the detection effect is superior to the existing technology.

[0053] The MIPs@Au NPs / porous silicon electrode prepared by the present invention has a specific recognition cavity on its surface that can selectively adsorb 2,4-D. On the other hand, it can also form a heterojunction with the photoactive material porous silicon. The unique built-in electric field at the interface of the heterojunction material can accelerate the transmission and separation of photogenerated electron / hole pairs, inhibit the recombination of photogenerated carriers, and thus enhance the photocurrent signal. Therefore, the MIPs@Au NPs / porous silicon electrode prepared by the present invention greatly enhances the signal strength of the sensor and broadens the detection range of the sensor.

[0054] Furthermore, the method for detecting 2,4-D concentration based on a molecular imprinting dual-wavelength ratio differential photoelectrochemical sensor provided by the present invention can also be used to detect other MIPs targets with similar properties. When the target molecule to be detected has a photoelectrochemical response and the excitation wavelength can be separated from 560nm, the molecular imprinting dual-wavelength ratio differential photoelectrochemical sensor prepared by the present invention can also be used to achieve high-sensitivity detection of its concentration, and the molecular imprinting dual-wavelength ratio differential photoelectrochemical sensor prepared by the present invention is easy to carry and can meet the needs of on-site detection.

[0055] The following detailed description is for illustrative purposes only and is intended to provide further explanation of the present application, rather than to limit the scope of the present invention.

[0056] Example 1: Preparation of molecularly imprinted dual-wavelength ratiometric photoelectrochemical sensor

[0057] (1) Before preparation, the silicon wafer was immersed in HF (40% wt) solution for 12 min to remove the oxide layer, and then rinsed with ultrapure water. In order to increase the ohmic contact area, a 300 nm aluminum film was coated on the back of the porous silicon wafer using a high vacuum evaporation system. Under 60 W halogen lamp irradiation, 30 mA cm -2 The porous silicon nanostructure was anodized in HF (40% wt) / C2H5OH solution (v / v 1:1) at a constant current density of 1:1 for 6 min, and the porous silicon nanostructure was rinsed with ultrapure water and ethanol in sequence, and then dried under N2 flow. The cleaned porous silicon electrode was immersed in 5% HF solution for 40 min to obtain a new porous silicon electrode.

[0058] (2) The porous silicon electrode prepared in step (1) was placed in a 1 mM HAuCl4 solution and immersed at 60°C for 5 min to generate Au NPs. The prepared Au NPs / porous silicon electrode was rinsed with ultrapure water and dried with N2 for later use.

[0059] (3) MIPs@Au NPs / porous silicon electrodes were prepared by electropolymerization in a phosphate buffer solution (PBS pH 7, 50 mM) containing 2,4-D (5 mM) and pyrrole (15 mM). 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 minutes to obtain a MIPs@Au NPs / porous silicon electrode with 2,4-D removed.

[0060] (4) The preparation method of NIPs@Au NPs / porous silicon electrode is the same as the above-mentioned method for preparing MIPs@Au NPs / porous silicon electrode, except that the 2,4-D template molecule is not added.

[0061] SEM images of Au NPs / porous silicon ( Figure 2 ) It can be seen that Au NPs with a size of 10 to 20 nm have been deposited on the ridges of the porous silicon nanopores. The deposition of Au NPs can prevent photocorrosion, slow down further oxidation and increase the photocurrent signal. After electrochemical polymerization, a layer of polypyrrole film is completely covered on the porous silicon surface, indicating that the MIPs@Au NPs / porous silicon photosensitive electrode has been successfully prepared ( Figure 3 ).

[0062] XPS spectrum of Au NPs / porous silicon confirms the presence of Si, C, Au, and O. The high-resolution spectrum of Au 4f shows two characteristic peaks with binding energies of 83.8 and 87.8 eV, corresponding to Au 4f 7 / 2 and Au 4f 5 / 2 These findings provide evidence for the existence of Au(0) and indicate that Au NPs were successfully modified on the porous silicon surface ( Figure 4 ).

[0063] The FT-IR spectra of porous silicon, Au NPs / porous silicon and MIPs@Au NPs / porous silicon show that the -1 The peak at 2106-2246cm belongs to the vibration mode of Si-Si. -1 The bands in the range are the stretching vibrations of Si-H, Si-H2 and Si-H3, 830cm -1 The existence of the band at 1053 cm is also related to the deformation of Si-H3. -1 The stretching vibration peak of Au NPs shows that the identification of SiOx is observed in the electrochemically etched Si. In addition, the FT-IR spectrum of the Au NPs / porous silicon composite is similar to that of pure porous silicon, indicating that the introduction of Au NPs has no significant effect on the pure porous silicon structure.-1 The peak at can be attributed to the CN vibration mode of polypyrrole, which confirms that polypyrrole is successfully modified on the Au NPs / porous silicon surface ( Figure 5 ).

[0064] Example 2: High-sensitivity detection of 2,4-D concentration

[0065] (1) Detection method

[0066] Water samples were collected from Xiaoqing River in Jinan City. Tap water samples were collected from the laboratory. To eliminate any potential suspended particles, a 0.45 μm microfiltration membrane was used for filtration. Subsequently, the samples were diluted 100 times and a certain concentration of standard 2,4-D solution was added.

[0067] A multimeter two-electrode system was used, with the MIPs@Au NPs / porous silicon electrode prepared in Example 1 as the first working electrode, the NIPs@Au NPs / porous silicon as the second working electrode, the Pt sheet as the counter electrode, and an LED lamp as the excitation light source, with the excitation light being the light source at 560nm and 280nm. 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.

[0068] The spectral distribution of MIPs@Au NPs / porous silicon and NIPs@Au NPs / porous silicon at 560 nm (I 560 ) and 280nm(I 280 ) light. The ratio differential photocurrent signal (ΔI) was calculated, and a standard curve of 2,4-D concentration and photocurrent ratio signal under dual-wavelength light source was established.

[0069] The ratiometric differential photocurrent signal (ΔI) is calculated by the following formula.

[0070] ΔI=(I 280 / I 560 ) MIPs -α(I 280 / I 560 ) NIPs

[0071] The weight factor (α = 1.08) was used to balance the difference between MIPs@Au NPs / PS and NIPs@Au NPs / PS.

[0072] (2) Test results

[0073] (2,4-D)MIPs@Au NPs / PS photoelectrode in photocurrent-excitation light wavelength (I-λ) Figure 6There are two independent and separated photocurrent peaks (560nm and 280nm) in the figure. It can be clearly seen that these two peaks belong to Au NPs / PS and 2,4-D respectively, and the two peaks have little effect on each other. Figure 6 In the experiment, Au NPs / PS showed the maximum photocurrent at 560 nm, which is consistent with the UV-visible absorption results ( Figure 7 ). On the other hand, 2,4-D produces a photocurrent peak at about 280nm ( Figure 6 ), which is consistent with the strongest UV-visible absorption wavelength at 283nm ( Figure 7 ). These two separated photocurrent signals provide an opportunity to develop wavelength-resolved ratiometric PEC methods.

[0074] Depend on Figure 8 It can be seen that under 560nm and 280nm light excitation, the photocurrents of MIPs@Au NPs / porous silicon and NIPs@Au NPs / porous silicon are larger than that of Au NPs / porous silicon. The photocurrent value of MIPs@Au NPs / porous silicon at 560nm is 47.86μA, the photocurrent value of NIPs@Au NPs / porous silicon at 560nm is 44.25μA, the photocurrent value of MIPs@AuNPs / porous silicon at 280nm is 23.02μA, and the photocurrent value of NIPs@Au NPs / porous silicon at 280nm is 20.08μA. When 2,4-D is adsorbed onto MIPs@Au NPs / porous silicon, the photocurrent value of (2,4-D)MIPs@Au NPs / porous silicon at 560nm is 22.90μA, which decreases to 47.8% of MIPs@Au NPs / porous silicon. The weakening of the photocurrent can be attributed to the presence of 2,4-D, which amplifies the steric hindrance at the electrode interface and hinders electron transfer. At 280nm, the PEC signal has a different response, and the photocurrent value of (2,4-D)MIPs@Au NPs / porous silicon at 280nm is 43.05μA, which increases sharply to 1.87 times that of MIPs@Au NPs / porous silicon at 280nm.

[0075] With the increase of 2,4-D concentration (0~1×10 -7 M), under 560nm light, the photocurrent signal intensity of MIPs@Au NPs / porous silicon decreased significantly, while under 280nm light it increased significantly ( Fig. 9 ).

[0076] Fig.10 The results showed that the photocurrent and 2,4-D concentration were 1×10 -11 ~1×10 -7 M and 1×10-11 ~8×10 -8 There is a good linear relationship between them, and the standard curves are 560MIPs (μA / cm 2 )=-2.015lgC+47.8299(R 2 =0.9835) and I 280MIPs (μA / cm 2 )=1.955lgC+23.24(R 2 =0.9864).

[0077] I 280 / I 560 With 2,4-D concentration of 1×10 -11 ~8×10 -8 The linear correlation is good within the range of M ( Fig.11 ), (I 280 / I 560 ) MIPs =0.08482C+0.4759(R 2 =0.9946), and the detection limit (LOD) was 2.5×10 -12 M. (I 280 / I 560 ) MIPs The detection limit is obtained by correction of the 3σ / k formula, where σ is (I 280 / I 560 ) MIPs The standard deviation of the blank measurement value (n = 11), k is (I 280 / I 560 ) MIPs The slope of the calibration curve, the blank measurement sample is pure water.

[0078] Differential photocurrent response (I 280 / I 560 ) MIPs -1.08(I 280 / I 560 ) NIPs ) and 2,4-D concentration was 1×10 -11 ~8×10 -8 M range shows good linear correlation, (I 280 / I 560 ) MIPs -1.08(I 280 / I 560 ) NIPs =0.06442C+0.001534,(R 2 =0.9970), and the LOD is estimated to be 8.9×10 -13 M, even lower than the LOD in normal mode (2.5×10-12 M)(3σ / k). Fig.11 ).

[0079] The test results show that the linear range of the present invention for detecting 2,4-D is 1.0×10 -11 Up to 8.0×10 -8 M, detection limit is 8.9×10 -13 M, when testing samples with unknown 2,4-D concentration, according to (I 280 / I 560 ) MIPs -1.08(I 280 / I 560 ) NIPs =0.06442C+0.001534, (R 2 =0.9970). Therefore, based on the detection method proposed by the present invention, the ratio differential photoelectrochemical sensor prepared by the present invention can achieve high-sensitivity detection of 2,4-D concentration.

[0080] Example 3: Performance detection of dual-wavelength ratiometric photoelectrochemical sensor based on molecular imprinting

[0081] (1) Selective testing:

[0082] 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). Fig.12 As shown, when a differential strategy was adopted to correct these interferences and a weight factor (α = 1.08) was introduced to compensate for the difference between MIPs@Au NPs / porous silicon and NIPs@Au NPs / porous silicon, the PEC signal of the interferences after differentiation was lower compared with that obtained by 2,4-D, indicating that the proposed strategy has good selectivity.

[0083] (2) Stability:

[0084] like Fig.13 As shown, the photocurrent response of MIPs@Au NPs / PS remained at a relative standard deviation (RSD) of 2.12% after 10 repetitions, indicating that the sensor has high stability.

[0085] (3) Repeatability:

[0086] The reproducibility of MIPs@Au NPs / PS electrode is shown in Fig.14 According to the detection method provided by the present invention, 6 modified electrodes are used to repeatedly detect the 2,4-D solution.560 and I 280 The RSDs of I 280 / I 560 The RSD of the ratio was only 1.1%. These results indicate that the ratiometric molecular imprinting photoelectrochemical sensor has good reproducibility.

[0087] Example 4: Detection of other analogs of dual-wavelength ratiometric photoelectrochemical sensor based on molecular imprinting

[0088] Similar to 2,4-D, other common MIP targets, such as AT and TPhP, can also generate photocurrents under UV irradiation. Fig.15 ), AT and TPhP can generate two photocurrent peaks (300nm and 270nm), respectively. These results are consistent with their UV-visible absorption spectra ( Fig.16 The PEC signals of (AT)MIPs@Au NPs / PS and (TPhP)MIPs@Au NPs / PS decreased at 560 nm and increased at 300 and 270 nm ( Fig.17 and 18 ). This indicates that the ratiometric molecular imprinting photoelectrochemical technique can be used as an innovative and universal method to detect other MIPs targets with similar properties, and has good application prospects.

[0089] The present invention provides a novel dual-wavelength ratio differential photoelectrochemical sensor based on molecular imprinting, which is composed of photoactive Au NPs / porous silicon, has excellent 2,4-D detection and analysis performance, and is successfully applied to actual samples. With the increase of 2,4-D concentration, the PEC signal intensity decreases under 560nm irradiation, and increases under 280nm irradiation. The ratio signal of the PEC method is used to effectively improve the sensitivity of the sensor. At the same time, the differential strategy of MIPs and NIPs can greatly improve the selectivity, stability and anti-interference ability of molecular imprinting photoelectrochemical sensors. It is worth noting that this ratio molecular imprinting photoelectrochemical technology provides a general strategy with great application prospects in environmental analysis.

[0090] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0091] Although the above describes the specific implementation methods of the present disclosure in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present disclosure. Technical personnel in the relevant field should understand that on the basis of the technical solution of the present disclosure, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present disclosure.

Claims

1. A method for detecting 2,4-D concentration based on a molecular imprinting dual-wavelength ratio differential portable photoelectrochemical sensor, characterized in that: The method uses Au NPs-modified porous silicon and 2,4-D as photoelectrochemically active materials, and uses the ratio of photocurrents generated at different excitation wavelengths of 560 and 280 nm, and the response difference between the imprinted polymer and the non-imprinted polymer as analytical signals, thereby realizing the detection of 2,4-D concentration; The molecular imprinting dual-wavelength ratio-differential portable photoelectrochemical sensor used in the method uses a multimeter as a photoelectric signal detection device, MIPs@Au NPs / porous silicon electrode as a first working electrode, NIPs@Au NPs / porous silicon as a second working electrode, and a Pt sheet as a counter electrode, and uses 560nm and 280nm LED lights as excitation light sources to obtain ratio differential photocurrent signals; The ratio differential photocurrent signal is calculated by the following formula: ΔI = (I 280 / I 560 ) MIPs -α(I 280 / I 560 ) NIPs ; α = 1.08, α is the weight factor used to balance the difference between MIPs@Au NPs / PS and NIPs@Au NPs / PS; The method for preparing the MIPs@AuNPs / porous silicon electrode of the molecular imprinting dual-wavelength ratio differential portable photoelectrochemical sensor used in the method comprises the following steps: (1) coating an aluminum film on the back of a silicon wafer after removing the oxide layer, anodizing, cleaning, and drying with a nitrogen flow, and then soaking the wafer in a hydrofluoric acid solution to obtain a porous silicon electrode, and then heating and soaking the obtained porous silicon electrode in a HAuCl4 solution to generate Au NPs; (2) Au NPs / porous silicon was placed in a phosphate buffer solution containing template molecules and pyrrole, and electropolymerization was performed using cyclic voltammetry. The template molecules were eluted with a solvent mixture of methanol and acetic acid to obtain MIPs@Au NPs / porous silicon without template molecules.

2. The method according to claim 1, characterized in that The anodizing step in step (1) is as follows: placing the silicon wafer with the oxide layer removed under irradiation of a halogen lamp, and performing anodizing in a mixed solution of hydrofluoric acid and ethanol with a constant current, wherein the power of the halogen lamp is 60 W and the constant current density is 30 mA cm -2 , the volume ratio of hydrofluoric acid solution and ethanol solution is 1:1, and the anodizing time is 6 min.

3. The method according to claim 1, characterized in that: The concentration of the HAuCl4 solution in step (1) is 1 mM, the heating temperature is 60°C, and the soaking time is 5 min.

4. The method according to claim 1, characterized in that: The difference between the NIPs@Au NPs / porous silicon electrode preparation method and the MIPs@Au NPs / porous silicon electrode preparation method is that no template molecule is added to the phosphate buffer solution.

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