Photoelectrochemistry and colorimetric method dual-mode bisphenol A detection method

Abstract

The invention discloses a method for detecting bisphenol A in dual modes of photo-induced electrochemistry and a colorimetric method. A Fe-doped ZnIn2S4 (FZIS) and NH2-UiO-66 (NU66) compound is selected as a photoelectric interface, and the photoelectric response of the interface is improved by forming a heterojunction and doping metal elements. And anchoring the 5 '-phosphorylated aptamer DNA on the surface of the electrode through a Zr-O-P coordinate bond. And simple and convenient dual-mode detection is realized through the reduction of the light current and the increase of the colorimetric signal after the target bisphenol A is added.

Description

Technical Field

[0001] The present invention relates to the technical field of analytical detection, and specifically relates to a preparation method and application of a photoelectrochemical-colorimetric dual-mode sensor. Background Art

[0002] Bisphenol A (BPA) is an important raw material for the production of polycarbonate, epoxy resin and flame retardant, and is widely used in daily necessities such as food packaging, beverage can linings, baby bottles, tableware, dental sealants, etc. However, BPA can seep into the environment through wastewater during the production and processing process. In addition, BPA in food packaging may directly migrate into food and then enter the human body. BPA can cause a variety of diseases, including various inflammatory reactions, abnormal body behavior, reduced reproductive and immune capabilities, etc. Relevant research shows that even at low-dose exposure levels, BPA can induce malignant tumors such as prostate cancer and breast cancer. Currently, the commonly used BPA detection methods include high performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS). However, due to reasons such as expensive equipment, complex sample pretreatment procedures, and the need for professional operation, these methods cannot meet the requirements of on-site detection.

[0003] Compared with other measurement techniques, photoelectrochemistry (PEC) has the advantages of low background, high sensitivity, fast response, portability, low price, etc., and is one of the most reliable analytical methods for rapid detection of environmental pollutants. The selection of photoelectric materials is the key to preparing photoelectric sensors. In order to improve the photoelectric response of semiconductor materials, the most effective method is to construct a heterojunction to improve the separation of photogenerated electrons and holes, thereby improving the photoelectric conversion efficiency. In addition, doping with metal elements can effectively reduce the band gap and enhance charge transfer. At the same time, doping can also improve the absorption efficiency of visible light, which is beneficial to the separation of photogenerated carriers.

[0004] In order to achieve highly sensitive and dual-mode detection, a photoelectric sensing interface with excellent performance is constructed by forming a heterojunction and doping with metal elements, and through the recognition of aptamers, dual-mode detection of BPA by photoelectrochemistry and colorimetry is realized.

[0005] The closest prior art currently:

[0006] Prior art 1: (Jia L.; Wang Y.; Jiang M.; Yuan W.; Jin Y.; Yan W.; Ze X; Chen Y.; Niu L. An ultrasensitive dual-mode stagey for 17β-estradiol assay: Photoelectrochemical and colorimetric biosensor based on a WSe2 / TiO2-modified electrode coupled with nucleic acid amplification. Analytica Chimica Acta 2024, 1319, 342966) proposed using WSe2 / TiO2 as the optoelectronic substrate material, and assembling double-stranded DNA with G-quadruplex / heme at one end through gold nanoparticles. G-quadruplex / heme can not only reduce the photocurrent through a bioprecipitation reaction, but also catalyze the oxidation of ABTS by hydrogen peroxide to produce color. At the same time, nucleic acid isothermal amplification under the action of aptamer recognition and exonuclease III generates a large amount of single-stranded DNA that can displace the G-quadruplex / heme structure, resulting in an increase in the optoelectronic signal and a decrease in the colorimetric signal. However, this method uses multiple DNAs and exonuclease III for isothermal amplification, with a long detection time, high cost, and complex operation.

[0007] Prior Art 2: (Wang Z., Shen Y., Xu M., Zhu J., Ma C., Hu X., Xu Q. Self-powered sandwich-type dual-mode sensor built on open bipolar electrode. Sensors & Actuators: B. Chemical 2024, 414, 135924) constructed a self-powered bipolar electrode sensor for the dual-mode detection of bisphenol A through electrochromism and photoelectrochemistry. An open bipolar electrode was constructed on an indium tin oxide glass substrate, with its electron injection region modified with molecularly imprinted polymers (MIPs), and the electrochromic region coated with a Prussian blue (PB) film. An aptamer DNA was modified on a zirconium-based metal-organic framework material (UiO-66) coated titanium dioxide heterojunction (TiO2@UiO-66) as a photoelectric probe. Bisphenol A was first selectively enriched by MIPs, and then specifically recognized with TiO2@UiO-66-Apt to form a "MIPs / BPA / Apt-TiO2@UiO-66" sandwich structure. Under ultraviolet light excitation, the captured TiO2@UiO-66 generated photogenerated electrons to achieve photoelectrochemical detection. At the same time, the photogenerated electrons were injected into the PB film to trigger a color reaction, thus realizing self-powered electrochromic visual detection. However, this method requires the preparation of bipolar electrodes and the synthesis of photoelectric probes and electrochromic films, and the operation process is cumbersome.

[0008] Prior Art 3: (Deiminiat B., Rounaghi G.H. A novel visible light photoelectrochemical aptasensor for determination of bisphenol A based on surface plasmon resonance of gold nanoparticles activated g-C3N4 nanosheets. Journal of Electroanalytical Chemistry 2021, 886, 115122) mentioned using g-C3N4 and gold nanoparticles as photoelectric substrate materials, and assembling thiol aptamer DNA through Au-S bonds. After the aptamer binds to the target BPA, it will block the irradiation of light and change the direction of electron transfer at the same time, resulting in a decrease in photocurrent, thus realizing photoelectrochemical detection. However, this method cannot achieve dual-mode detection and can only perform single photoelectric detection, reducing the accuracy.

[0009] In summary, the prior art has the following deficiencies:

[0010] (1) The existing technology requires isothermal amplification of nucleic acids, which takes a long time to detect and is complicated to operate.

[0011] (2) The existing technology requires the use of bipolar electrodes, which is complicated to operate and has high experimental costs.

[0012] (3) Existing technologies cannot achieve dual-mode detection and are prone to produce false positive results. Summary of the invention

[0013] In view of the problems existing in the prior art, the present invention provides a dual-mode (photoelectrochemical and colorimetric) method for detecting bisphenol A.

[0014] In order to achieve the above object, the present invention adopts the following technical solutions:

[0015] The heterojunction composed of Fe-doped ZnIn2S4 (FZIS) and metal organic framework NH2-UIO-66 (NU66) was selected as the optoelectronic material. 2+ The radius (76 pm) and Zn 2+ The radius of Fe is similar to that of Fe (74 pm). 2+ Partially replace Zn 2+ It will not cause significant changes in the ZnIn2S4 lattice structure. 2+ The difference is that Fe has two valence states, Fe(II) and Fe(III), which are easily interconvertible and can act as an "electron trap" in FZIS, thereby promoting the separation of photogenerated electron-hole pairs, which is beneficial for photoelectrochemical detection. At the same time, the presence of iron in the material FZIS@NU66 gives the material peroxidase (POD)-like activity, which can catalyze color development reactions and thus achieve dual-mode detection. In this experiment, the 5'-phosphorylated BPA aptamer was fixed on the surface of the photoelectric material FZIS@NU66 through the Zr-OP coordination bond. The purpose of dual detection was achieved by measuring the changes in photocurrent and solution color before and after the aptamer binds to the target BPA.

[0016] Further, the method for detecting bisphenol A by photoelectrochemical and colorimetric dual modes comprises the following steps:

[0017] The first step is the preparation of nanomaterial FZIS@NU66;

[0018] The second step is the preparation of the optoelectronic sensing interface and the assembly of aptamer DNA;

[0019] The third step is photoelectrochemical detection of BPA;

[0020] The fourth step is the colorimetric detection of BPA.

[0021] Further, for the synthesis of NH2-UiO-66 (NU66), 1 mmol of ZrCl4 and 1 mmol of 2-aminoterephthalic acid were dissolved in 60 mL of DMF, and then 8 mL of acetic acid was added. The mixture was sonicated for 30 minutes and heated in a 100 mL Teflon-lined autoclave at 120 °C for 24 hours. The precipitate was collected by centrifugation and washed three times with absolute ethanol to obtain NU66. The product was fully activated in methanol for subsequent use.

[0022] Further, for the synthesis of the FZIS@NU66 composite, 0.5 mmol of (NH4)2Fe(SO4)2·12H2O, 0.5 mmol of Zn(CH3COO)2, 2 mmol of InCl3·4H2O, and 4 mmol of thioacetamide were dissolved in 60 mL of deionized water. Then, 30 mg of the above-prepared NU66 was added, and the mixture was sonicated and stirred for 30 minutes. The resulting suspension was transferred to a 100 mL Teflon-lined autoclave and heated at 120 °C for 12 hours. The precipitate was collected by centrifugation and washed three times with deionized water and absolute ethanol. Finally, it was dried overnight in a vacuum oven at 60 °C to obtain the yellow powder FZIS@NU66.

[0023] Further, for the preparation of the photoelectric sensing interface and the assembly of aptamer DNA, the 1 mg / mL FZIS@NU66 was ultrasonically dispersed. Then, 20 μL of the dispersion was dropped onto the ITO electrode. After drying, 20 μL of a 5'-phosphate-modified BPA aptamer DNA solution was added to the electrode and incubated at 4 °C for 18 hours, followed by washing with deionized water to obtain the ITO / FZIS@NU66-apt electrode.

[0024] Specifically, the bisphenol A aptamer DNA sequence: 5’P-CCG GTG GGT GGT CAG GTG GGA TAG CGT TCCGCG TAT GGC CCA GCG CAT CAC GGG TTC GCA CCA 3’

[0025] Further, for the photoelectrochemical detection of bisphenol A, the obtained working electrode was immersed in 1 mL of a solution containing different concentrations of BPA, incubated for 20 minutes, washed with deionized water, and then used for PEC detection. The electrolyte was a 20 mM Tris-HCl buffer (pH 7.4) containing 100 mM NaCl and ascorbic acid. The light source was a 20 W white LED lamp, which was switched on and off every 20 seconds. The bias voltage was 0 V.

[0026] Further, for the colorimetric detection of bisphenol A, after incubation with different concentrations of BPA, the working electrode was immersed in the newly prepared colorimetric solution for 30 minutes. Subsequently, the working electrode was removed and the colorimetric solution was immediately measured at 652 nm using a UV-visible spectrophotometer. The colorimetric solution consisted of 650 μL HAc / NaAc buffer (200 mM, pH 4.0), 200 μL 3,3',5,5'-tetramethylbenzidine (TMB) dissolved in DMSO (4 mM), and 100 μL H2O2 (0.3 M).

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) In the FZIS@NU66 composite material synthesized in the present invention, a heterojunction is formed between different semiconductor materials, reducing the recombination of electrons and holes. At the same time, Fe has two valence states, Fe(II) and Fe(III), and these two valence states can easily convert into each other, which can act as "electron traps" in FZIS, thus promoting the separation of photo-generated electron-hole pairs. All of these are beneficial to improving the optoelectronic activity of the interface for photoelectrochemical detection.

[0029] (2) The presence of iron in the FZIS@NU66 synthesized in the present invention endows the material with peroxidase (POD)-like activity, which enables the sensor to be used for colorimetric detection.

[0030] (3) The present invention has universality. By simply changing the type of aptamer DNA, the detection of other target substances can be achieved. Description of the Drawings

[0031] Figure 1 is the schematic diagram of the synthesis process of FZIS@NU66 and the PEC-colorimetric dual-mode aptasensor involved in Example 1.

[0032] Figure 2 are the (A) TEM and (B) HRTEM images of FZIS@NU66 involved in Example 1.

[0033] Figure 3 is the feasibility analysis of the dual-mode sensor involved in Example 1. (A and B) Photocurrent responses of different modified electrodes. (C) UV-visible spectra of colorimetric solutions treated with different electrodes. Inset: Photos of the corresponding colorimetric solutions.

[0034] Figure 4 is the detection performance of the dual-mode sensor involved in Example 1. (A) Photocurrent responses of different concentrations of BPA. The concentrations of BPA range from a to i: 1.0×10 -15 、1.0×10 -14 、1.0×10 -13 、1.0×10 -12, 1.0×10 -11 , 1.0×10 -10 , 1.0×10 -9 , 1.0×10 -8 and 1.0×10 -7 M; (B) Linear relationship between PEC signal and logarithm of BPA concentration; (C) UV-vis spectra generated by different concentrations of BPA. Concentrations of BPA from a to i: 1.0×10 -10 , 5.0×10 -10 , 1.0×10 -9 , 5.0×10 -9 , 1.0×10 -8 , 5.0×10 -8 , 1.0×10 -7 , 5.0×10 -7 , 1.0×10 -6 M (Insert: Photos of corresponding colorimetric solutions); (D) Linear relationship between ultraviolet absorption intensity and logarithm of BPA concentration. Detailed implementation manners

[0035] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] Embodiment 1

[0037] The aptamer DNA sequence of bisphenol A used in this embodiment is: 5’P-CCG GTG GGT GGT CAG GTG GGA TAGCGT TCC GCG TAT GGC CCA GCG CAT CAC GGG TTC GCA CCA 3’

[0038] As Figure 1 shown, a method for dual-mode detection of bisphenol A by photoelectrochemistry and colorimetry provided by an embodiment of the present invention includes the following steps:

[0039] I. Synthesis of materials

[0040] (1) Synthesis of NH2-UiO-66 (NU66):

[0041] Dissolve 1 mmol of ZrCl4 and 1 mmol of 2-aminoterephthalic acid in 60 mL of DMF, and then add 8 mL of acetic acid. Ultrasonically treat the mixture for 30 minutes and heat it in a 100 mL Teflon-lined autoclave at 120 °C for 24 hours. The precipitate is collected by centrifugation and washed three times with absolute ethanol to obtain NU66. This product is fully activated in methanol for subsequent use.

[0042] (2) Synthesis of FZIS@NU66 composite:

[0043] Dissolve 0.5 mmol of (NH4)2Fe(SO4)2·12H2O, 0.5 mmol of Zn(CH3COO)2, 2 mmol of InCl3·4H2O and 4 mmol of thioacetamide in 60 mL of deionized water. Then add 30 mg of NU66 prepared above and stir ultrasonically for 30 minutes. Transfer the resulting suspension to a 100 mL Teflon-lined autoclave, heat at 120 °C for 12 hours, centrifuge to collect the precipitate, and wash it three times with deionized water and absolute ethanol. Finally, dry it overnight in a vacuum oven at 60 °C,

[0044] to obtain the yellow powder FZIS@NU66.

[0045] Figure 2 For the transmission electron microscopy characterization of the material FZIS@NU66. From Figure 2 Figure A, it can be seen that the FZIS@NU66 composite synthesized in this experiment forms a flower-like structure due to the aggregation of FZIS flakes, with a diameter of about 2.5 μm. Figure 2 Figure B is a high-resolution transmission electron microscopy image of the local area of FZIS@NU66. Two obvious lattice fringe spacings can be seen. Among them, 0.947 nm belongs to the lattice plane spacing of the (110) plane of NU66, and 0.333 nm belongs to the lattice plane spacing of the (102) plane of FZIS.

[0046] II. Preparation of the optoelectrochemical sensing interface and assembly of aptamer DNA:

[0047] Ultrasonically disperse 1 mg / mL of FZIS@NU66. Then drop 20 μL of the dispersion on the ITO electrode. After drying, add 20 μL of the 5'-phosphate-modified BPA aptamer DNA solution to the electrode and incubate at 4 °C for 18 hours. Wash with deionized water to obtain the ITO / FZIS@NU66-apt electrode.

[0048] III. Photoelectrochemical detection of bisphenol A:

[0049] Immerse the obtained working electrode ITO / FZIS@NU66-apt in 1 mL of a solution containing different concentrations of BPA, incubate for 20 minutes, wash with deionized water, and then use it for PEC detection. The electrolyte is 20 mM Tris-HCl buffer (pH 7.4) containing 100 mM NaCl and ascorbic acid. The light source is a 20 W white LED lamp, which is switched on and off every 20 seconds. The bias voltage is 0 V. IV. Colorimetric detection of bisphenol A:

[0050] After incubation with different concentrations of BPA, the working electrode was immersed in the freshly prepared colorimetric solution for 30 minutes. Subsequently, the working electrode was removed and the colorimetric solution was immediately measured at 652 nm using a UV-visible spectrophotometer. The colorimetric solution consisted of 650 μL HAc / NaAc buffer (200 mM, pH 4.0), 200 μL 3,3',5,5'-tetramethylbenzidine (TMB) dissolved in DMSO (4 mM), and 100 μL H2O2 (0.3 M).

[0051] Figure 3 The feasibility of the detection was investigated. As Figure 3 shown in A, under 20 W white light illumination, the anodic photocurrent generated by the ITO electrode coated only with NU66 was as low as 0.75 μA (curve a). When ZIS was coated alone, the photocurrent signal was approximately 7.1 μA (curve b). After Fe 2+ doping, Fe has multiple valence states and can act as an "electron trap" to improve the electron transfer efficiency. Thus, the photocurrent of the electrode coated with FZIS increased to 15.89 μA (curve c). The application of the FZIS@NU66 composite increased the photocurrent to 24.02 μA (curve d), approximately 150% of that when using FZIS alone, indicating that the formation of the heterojunction promoted the separation and transfer of photogenerated carriers.

[0052] When the 5'-end modified phosphate aptamer DNA was assembled onto the ITO / FZIS@NU66 electrode, the 5'-end phosphate group coordinated with Zr 4+ on the surface of / FZIS@NU66 and was assembled onto the electrode surface. At this time, the photocurrent increased from 24 μA ( Figure 3 curve a in B) to 32.1 μA ( Figure 3 curve b in B). When 1.0×10 -8 M bisphenol A solution was added, due to the blocking effect of the complex formed by the aptamer and the target and the change in the electron transfer direction caused by bisphenol A, the photocurrent decreased to 10.8 μA ( Figure 3 curve c in B), indicating that the developed PEC sensor can be used for the detection of bisphenol A.

[0053] Due to the mutual conversion between iron(II) and iron(III) in the substrate material, the material is endowed with POD enzyme-like activity. Therefore, FZIS@NU66 can catalyze the oxidation of TMB by H2O2, showing blue ( Figure 3 curve a and the inset in C). Anchoring the 5'-phosphate group modified aptamer led to a significant decrease in the catalytic activity of FZIS@NU66 ( Figure 3C curve b and the illustration). This is because the phosphate groups of the aptamer DNA backbone interact with iron in the substrate material, thus shielding the catalytic active sites. When BPA is added, the binding of the aptamer DNA to the target BPA causes one end of the DNA strand to attach to the surface of FZIS@NU66, and the other parts to dissociate from the material surface, thereby exposing the catalytic active center and restoring the catalytic activity of the substrate material ( Figure 3 C curve c and the illustration). Therefore, colorimetry can be used to detect bisphenol A.

[0054] The detection performance of BPA was evaluated using the developed dual-mode aptamer sensor. As Figure 4 shown in Figures 4A and 4B, the photocurrent signal of the sensor has a good linear relationship with the BPA concentration in the range of 1 fM to 100 nM. The corresponding linear equation is I = -3.807 - 1.856 lg CBPA, R 2 with a correlation coefficient of 0.992. In the colorimetric mode, the absorbance of the TMB solution has a good linear relationship with the BPA concentration in the range of 0.1 nM - 1 μM. The linear equation is A = 3.127 + 0.267 lg CBPA, R 2 is 0.987 ( Figure 4 Figures 4C and 4D).

[0055] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for dual-mode detection of bisphenol A (BPA) by photoelectrochemistry and colorimetry, characterized in that: The Fe-doped ZnIn2S4 (FZIS) and NH2-UiO-66 (NU66) composite was selected as the optoelectronic interface to improve the photocurrent response through Fe doping and the formation of heterojunctions. The 5'-phosphorylated aptamer DNA was anchored on the electrode surface through Zr-O-P coordination. At this time, the optoelectronic response was further enhanced by the interaction between Fe and the phosphate groups on the DNA backbone. Meanwhile, since the DNA strand shielded the Fe species on the surface of FZIS@NU66, the peroxidase-like activity of the substrate material was masked. After adding the target BPA, the aptamer bound to the target, disrupting the interaction between Fe and the phosphate groups on the DNA backbone, resulting in one end of the DNA strand being connected to the surface of FZIS@NU66 and the other part dissociating from the material surface, thus exposing the catalytic active center and realizing colorimetric detection. At the same time, due to the shielding effect of the complex formed by the binding of the aptamer and the target and the change in the direction of electron transfer caused by BPA, the photocurrent decreased, and photoelectrochemical detection could also be achieved.

2. The method for dual-mode detection of bisphenol A by photoelectrochemistry and colorimetry according to claim 1, characterized in that The operation steps are as follows: (1) Preparation of the FZIS@NU66 composite. (2) Assembly of the sensor. (3) Photoelectrochemical detection. (4) Colorimetric detection.

3. The method for dual-mode detection of bisphenol A by photoelectrochemistry and colorimetry according to claim 2, wherein, The preparation steps of step (1) FZIS@NU66 are as follows: Dissolve 1 mmol of ZrCl4 and 1 mmol of 2-aminoterephthalic acid in 60 mL of DMF, and then add 8 mL of acetic acid. The mixture was ultrasonically treated for 30 minutes and heated in a 100 mL Teflon-lined autoclave at 120 °C for 24 hours. The precipitate was collected by centrifugation and washed three times with absolute ethanol to obtain NU66. The product was fully activated in methanol for subsequent use. Dissolve 0.5 mmol of (NH4)2Fe(SO4)2·12H2O, 0.5 mmol of Zn(CH3COO)2, 2 mmol of InCl3·4H2O, and 4 mmol of thioacetamide in 60 mL of deionized water. Then add 30 mg of the above-prepared NU66 and ultrasonically stir for 30 minutes. Transfer the resulting suspension to a 100 mL Teflon-lined autoclave, heat at 120 °C for 12 hours, collect the precipitate by centrifugation, and wash it 3 times with deionized water and absolute ethanol. Finally, dry it overnight in a vacuum oven at 60 °C to obtain the yellow powder FZIS@NU66.

4. The method for dual-mode detection of bisphenol A by photoelectrochemistry and colorimetry according to claim 2, wherein, The assembly steps of step (2) the sensor are as follows: Ultrasonically disperse 1 mg / mL of FZIS@NU66. Then, add 20 μL of the dispersion onto the ITO electrode. After drying, add 20 μL of the 5'-phosphate-modified bisphenol A aptamer DNA solution onto the electrode and incubate at 4 °C for 18 hours, and wash with deionized water to obtain the ITO / FZIS@NU66-apt electrode.

5. The method for dual-mode detection of bisphenol A by photoelectrochemistry and colorimetry according to claim 2, wherein, Step (3) The photoelectrochemical detection steps are as follows: Immerse the obtained working electrode in 1 mL of solution containing different concentrations of BPA, incubate for 20 minutes, wash with deionized water, and then use it for PEC detection. The electrolyte is 20 mM Tris-HCl buffer (pH 7.4) containing 100 mM NaCl and ascorbic acid. The light source is a 20 W white LED lamp, which is switched on and off every 20 seconds. The bias voltage is 0 V.

6. A method for dual-mode detection of bisphenol A by photoelectrochemistry and colorimetry according to claim 2, characterized in that, Step (4) The photoelectrochemical detection steps are as follows: After incubation with different concentrations of BPA, immerse the working electrode in the newly prepared colorimetric solution for 30 minutes. Subsequently, remove the working electrode and immediately measure the colorimetric solution at 652 nm using a UV-visible spectrophotometer. The colorimetric solution is composed of 650 μL of HAc / NaAc buffer (200 mM, pH 4.0), 200 μL of 3,3',5,5'-tetramethylbenzidine (TMB) dissolved in DMSO (4 mM), and 100 μL of H2O2 (0.3 M).

7. A method for dual-mode detection of bisphenol A by photoelectrochemistry and colorimetry according to claim 2, characterized in that Using the same substrate material FZIS@NU66, simply replacing it with other aptamer DNAs modified with phosphate groups at the end can perform dual-mode detection of other targets by photoelectrochemistry and colorimetry.

8. A method for dual-mode detection of bisphenol A by photoelectrochemical and colorimetric methods according to any one of claims 1 to 7.

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