Preparation of a bimetallic MOF material functionalized transistor sensor for BPA detection

Abstract

The application provides a preparation method of a double-metal MOF material functionalized transistor sensor for BPA detection, and the material uses ZIF-8 as a carbon source, and a carbon material (Ce@ZIF8 / C) with rich mesoporous structures and good dispersed metal active sites embedded with Ce and Zn double metals is successfully prepared by using a direct pyrolysis method. The Ce@ZIF8 / C material prepared by the application can be applied to the functionalization of a gate electrode of an SGGT sensor, and an electrochemical sensor for real-time monitoring of an organic pollutant BPA in water can be successfully constructed. The electrochemical sensor constructed by the material synthesized by the application has good detection performance on BPA.

Description

Technical Field

[0001] This invention relates to the field of gated graphene field-effect transistor sensors, and more specifically to a method for fabricating a bimetallic MOF material functionalized transistor sensor for BPA detection. Background Technology

[0002] Bisphenol A (BPA) is a synthetic organic pollutant widely used in the synthesis of polycarbonates, epoxy resins, medical devices, food packaging materials, and thermal paper. Due to its widespread presence, BPA can enter the human body primarily through oral ingestion and skin contact. Because of its diverse sources, BPA readily accumulates in the human body. BPA not only causes endocrine disorders, metabolic disturbances, and harms the reproductive system, but it is also believed to be linked to cancer and obesity.

[0003] Traditional detection methods, such as gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), optical analysis, and electrochemical analysis, offer advantages such as strong separation capabilities and reliable results. However, the expensive instruments and time-consuming nature of these methods limit their application. Electrochemical and optical analysis methods, including spectrophotometry, offer advantages such as low cost, good reproducibility, and ease of operation, but suffer from slow detection speed and discontinuous measurements. In contrast, electrochemical methods are widely used in various fields due to their speed, high accuracy, high sensitivity, good selectivity, simple instrumentation, and ease of automation. These applications include toxicity testing in food safety, detection of harmful components in water for environmental monitoring, and real-time detection in medical diagnostics. Compared to other electrochemical analysis techniques, SGGT offers higher sensitivity and the ability to perform real-time detection. Metal-organic frameworks (MOFs) can serve as precursors for porous nanostructured carbon, especially bimetallic MOFs (particularly zinc), which are ideal precursors for obtaining porous carbon materials with high specific surface area and high catalytic activity. Because most zinc evaporates during high-temperature pyrolysis, it inhibits the aggregation of metal oxides, thus ensuring uniform loading of metal oxides onto porous carbon materials. Furthermore, cerium (Ce) is widely used in various catalytic reactions due to its ability to change ionic valence states. These properties make Ce-doped MOFs porous carbon nanomaterials a promising material for electrochemical analysis. Summary of the Invention

[0004] The technical problem to be solved: The purpose of this invention is to provide a method for fabricating a bimetallic MOF material functionalized transistor sensor for BPA detection. The Ce@ZIF8 / C modified gate SGGT sensor prepared by this invention has excellent BPA detection capability, with a detection limit as low as 30 nM and a linear range of 30 nM-1 μM. This detection limit fully meets the sensitivity required for actual detection. In addition, the sensor also exhibits excellent selectivity.

[0005] Technical solution: A method for fabricating a bimetallic MOF material functionalized transistor sensor for BPA detection, the specific fabrication steps are as follows:

[0006] (1) Mix Zn(NO3)2·6H2O, Ce(NO3)3·6H2O and hexadecyltrimethylammonium bromide uniformly in methanol solution and stir for 10-15 min to obtain mixed solution A, which is set aside. At the same time, dissolve 2-methylimidazolium in methanol solution and stir thoroughly for 10-15 min to obtain mixed solution B. Add mixed solution A to mixed solution B in a volume ratio of (20:1)-(1:10) and allow it to react fully at room temperature for 6-10 h to obtain mixed solution.

[0007] (2) Centrifuge the mixed solution obtained in step (1) at 5000-12000 rpm for 3-15 min, take the precipitate after centrifugation and wash it with methanol 5-8 times, and finally vacuum dry the precipitate to obtain Ce@ZIF8 powder.

[0008] (3) Place Ce@ZIF8 in a tube furnace, fill with nitrogen for 10-60 min, and heat to 600-900℃ under nitrogen atmosphere protection for 2-5 h, then cool down and wait until room temperature to obtain Ce@ZIF8 / C powder.

[0009] (4) Clean the silicon-based carrier and cut it into a substrate for the sensor. Fix the substrate on the photomask and deposit 10 nm of Cr and 100 nm of Au on the substrate surface. Cut the CVD monolayer graphene into an appropriate size and cover it flat in the area between the source and drain. Anneal the transferred device for a period of time and then immerse it in acetone at 50-70°C until the PMMA on the surface of the CVD monolayer graphene is completely removed. Encapsulate the sensor with waterproof glue and silver paste.

[0010] (5) Dissolve chitosan powder in 0.5-5 w / v acetic acid solution and stir thoroughly until the solution is completely clear to obtain acetic acid chitosan solution. Finally, dissolve Ce@ZIF8 / C powder prepared in step (3) in acetic acid chitosan solution and sonicate to obtain electrode modification solution.

[0011] (6) Polish the glassy carbon electrode to a mirror finish, then sonicate to remove surface impurities, dry the glassy carbon electrode surface, add a modification solution, and then dry to obtain the Ce@ZIF8 / C modified SGGT sensor.

[0012] Preferably, in step (1), the mass-to-volume ratio of Zn(NO3)2·6H2O, Ce(NO3)3·6H2O, hexadecyltrimethylammonium bromide and methanol solution is (1-30g):1g:(0.01-0.3g):(20-100mL).

[0013] Preferably, in step (1), the mass-to-volume ratio of 2-methylimidazole to methanol solution is 1 g: (10-30 mL).

[0014] Preferably, the vacuum drying conditions in step (2) are 40-100℃ for 8-12 hours.

[0015] Preferably, in step (3), the heating rate is 3-5℃ / min and the cooling rate is 5-20℃ / min.

[0016] Preferably, the specific steps for cleaning the silicon-based carrier in step (4) are as follows: the silicon-based carrier is cleaned three times in an ultrasonic bath with acetone, ethanol and ultrapure water in sequence, and then dried with high-purity nitrogen gas for later use.

[0017] Preferably, in step (5), the mass-to-volume ratio of chitosan powder to acetic acid solution is 1 mg: (3-20 mL).

[0018] Preferably, the transistor sensor prepared by the method described above for preparing a bimetallic MOF material functionalized transistor sensor for BPA detection is used in the detection of bisphenol A.

[0019] Beneficial effects: The present invention has the following advantages:

[0020] 1. In the synthesis of Ce@ZIF8 / C, this invention adds hexadecyltrimethylammonium bromide. The long alkane chain of hexadecyltrimethylammonium bromide can be adsorbed on the hydrophobic surface of ZIF8, acting as a protective agent to reduce the growth rate of ZIF8 crystals, effectively control its morphology, and ensure that the morphology and size of the generated MOF carbon material meet the ideal standard.

[0021] 2. In this invention, the use of ZIF8 not only facilitates the formation of Ce@ZIF8 / C structure, but also makes zinc an ideal precursor for obtaining porous carbon materials with high specific surface area and high catalytic activity. Most zinc evaporates during high-temperature pyrolysis, inhibiting the aggregation of metal oxides and allowing them to be uniformly loaded onto the porous carbon material. These characteristics enable Ce@ZIF8 / C to have a richer mesoporous structure and good charge transfer ability. At the same time, the cerium uniformly loaded on the material surface has multiple valence states, which is conducive to the catalytic reaction of the material.

[0022] 3. The cerium (Ce) in the Ce@ZIF8 / C material synthesized in this invention can change its ionic valence state in the catalytic reaction and can serve as the active center of the catalytic reaction. The structure of the MOF material can provide it with better catalytic properties and stability. Attached Figure Description

[0023] Figure 1The preparation process for Ce@ZIF8 / C;

[0024] Figure 2 Electron micrographs of Ce@ZIF8 / C powder prepared in Example 1 and corresponding elemental distribution diagrams of C, N, and Ce, where (a) is a scanning electron microscope image and (b) is a transmission electron microscope image.

[0025] Figure 3 The adsorption isotherm curve of Ce@ZIF8 / C powder prepared in Example 1;

[0026] Figure 4 A comparison graph showing the electrochemical impedance measurement results of Example 1 and Comparative Examples 1, 2, and 3;

[0027] Figure 5 This is a schematic diagram illustrating the working principle of the sensor prepared according to the present invention.

[0028] Figure 6 This is a verification diagram showing that the sensor prepared in Example 1 has a selective response to BPA;

[0029] Figure 7 The transfer characteristic curves (V) of the sensors prepared for Comparative Example 1 and Example 1 were measured in 1×PBS solution. G -I Ds ), of which (a) Comparative Example 1 and (b) Example 1;

[0030] Figure 8 The effective gate voltage change (Δ) of the SGGT sensor in Comparative Example 1 and Example 1 The relationship between BPA concentration and the logarithm of BPA concentration. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments. The following embodiments are illustrative of the present invention, but the present invention is not limited to the following embodiments:

[0032] Example 1

[0033] A method for fabricating a transistor sensor based on bimetallic MOF material, the specific steps of which are as follows:

[0034] (1) Zn(NO3)2·6H2O, Ce(NO3)3·6H2O and hexadecyltrimethylammonium bromide were uniformly mixed in a methanol solution, wherein the mass-to-volume ratio of Zn(NO3)2·6H2O, Ce(NO3)3·6H2O, hexadecyltrimethylammonium bromide and methanol solution was 10 g:1 g:0.1 g:30 mL. The mixture was stirred for 10 min to obtain mixed solution A, which was set aside. At the same time, 2-methylimidazole was dissolved in a methanol solution, wherein the mass-to-volume ratio of 2-methylimidazole and methanol solution was 1 g:24.35 mL. The mixture was stirred thoroughly for 10 min to obtain mixed solution B. Mixed solution A was added to mixed solution B at a volume ratio of 1:1, and the mixture was allowed to react fully at room temperature for 6 h to obtain a mixed solution.

[0035] (2) The mixed solution obtained in step (1) was centrifuged at 8000 rpm for 3 min. The precipitate after centrifugation was washed with methanol 5 times. Finally, the precipitate was vacuum dried at 40℃ for 8 h to obtain Ce@ZIF8 powder.

[0036] (3) Place Ce@ZIF8 in a tube furnace and fill it with nitrogen for 30 min. Under the protection of nitrogen atmosphere, the heating rate is 3℃ / min. After heating to 900℃ and holding for 3 h, the cooling rate is 5℃ / min. After cooling to room temperature, Ce@ZIF8 / C powder is obtained.

[0037] (4) The silicon-based carrier was cleaned three times in the ultrasonic process with acetone, ethanol and ultrapure water in sequence. It was dried with high-purity nitrogen and cut into 1×1.2cm as the substrate of the sensor. The substrate was fixed on the photomask and 10nm of Cr and 100nm of Au were deposited on the surface of the substrate in sequence. The CVD monolayer graphene was cut into appropriate size and flatly covered the area between the source and drain. The transferred device was annealed for a period of time and then immersed in acetone at 55°C until the PMMA on the surface of the CVD monolayer graphene was completely removed. The sensor was encapsulated with waterproof glue and silver paste.

[0038] (5) Dissolve chitosan powder in 1 w / v acetic acid solution and stir thoroughly until the solution is completely clear to obtain acetic acid chitosan solution. The mass-volume ratio of chitosan powder to acetic acid solution is 1 mg: 10 mL. Finally, dissolve Ce@ZIF8 / C powder prepared in step (3) in acetic acid chitosan solution and sonicate to obtain electrode modification solution.

[0039] (6) Polish the glassy carbon electrode to a mirror finish, then sonicate to remove surface impurities, dry the glassy carbon electrode surface, add a modification solution, and then dry to obtain the Ce@ZIF8 / C modified SGGT sensor.

[0040] Example 2

[0041] A method for fabricating a transistor sensor based on bimetallic MOF material, the specific steps of which are as follows:

[0042] (1) Zn(NO3)2·6H2O, Ce(NO3)3·6H2O and hexadecyltrimethylammonium bromide are uniformly mixed in methanol solution and stirred for 12 min to obtain mixed solution A, which is set aside. The mass-volume ratio of Zn(NO3)2·6H2O, Ce(NO3)3·6H2O, hexadecyltrimethylammonium bromide and methanol solution is 15 g: 1 g: 0.2 g: 50 mL. At the same time, 2-methylimidazole is dissolved in methanol solution and stirred thoroughly for 12 min to obtain mixed solution B. The mass-volume ratio of 2-methylimidazole and methanol solution is 1 g: 20 mL. Mixed solution A is added to mixed solution B at a volume ratio of 2:5 and allowed to react fully at room temperature for 8 h to obtain mixed solution.

[0043] (2) The mixed solution obtained in step (1) was centrifuged at 10,000 rpm for 10 min. The precipitate after centrifugation was washed with methanol 7 times. Finally, the precipitate was vacuum dried at 80℃ for 10 h to obtain Ce@ZIF8 powder.

[0044] (3) Place Ce@ZIF8 in a tube furnace and fill it with nitrogen for 30 min. Under the protection of nitrogen atmosphere, the heating rate is 4℃ / min. After heating to 750℃ and holding for 4 h, the cooling rate is 10℃ / min. After cooling to room temperature, Ce@ZIF8 / C powder is obtained.

[0045] (4) The silicon-based carrier was cleaned three times in the ultrasonic process with acetone, ethanol and ultrapure water in sequence. It was dried with high-purity nitrogen and cut into 1×1.2cm as the substrate of the sensor. The substrate was fixed on the photomask and 10nm of Cr and 100nm of Au were deposited on the surface of the substrate in sequence. The CVD monolayer graphene was cut into appropriate size and flatly covered the area between the source and drain. The transferred device was annealed for a period of time and then immersed in acetone at 55°C until the PMMA on the surface of the CVD monolayer graphene was completely removed. The sensor was encapsulated with waterproof glue and silver paste.

[0046] (5) Dissolve chitosan powder in 1 w / v acetic acid solution and stir thoroughly until the solution is completely clear to obtain acetic acid chitosan solution. The mass-volume ratio of chitosan powder to acetic acid solution is 1 mg: 10 mL. Finally, dissolve Ce@ZIF8 / C powder prepared in step (3) in acetic acid chitosan solution and sonicate to obtain electrode modification solution.

[0047] (6) Polish the glassy carbon electrode to a mirror finish, then sonicate to remove surface impurities, dry the glassy carbon electrode surface, add a modification solution, and then dry to obtain the Ce@ZIF8 / C modified SGGT sensor.

[0048] Example 3

[0049] A method for fabricating a transistor sensor based on bimetallic MOF material, the specific steps of which are as follows:

[0050] (1) Zn(NO3)2·6H2O, Ce(NO3)3·6H2O and hexadecyltrimethylammonium bromide are uniformly mixed in methanol solution and stirred for 15 min to obtain mixed solution A, which is set aside. The mass-volume ratio of Zn(NO3)2·6H2O, Ce(NO3)3·6H2O, hexadecyltrimethylammonium bromide and methanol solution is 30 g: 1 g: 0.3 g: 100 mL. At the same time, 2-methylimidazole is dissolved in methanol solution and stirred thoroughly for 15 min to obtain mixed solution B. The mass-volume ratio of 2-methylimidazole and methanol solution is 1 g: 30 mL. Mixed solution A is added to mixed solution B at a volume ratio of 1:10 and allowed to react fully at room temperature for 10 h to obtain mixed solution.

[0051] (2) The mixed solution obtained in step (1) was centrifuged at 12000 rpm for 15 min. The precipitate after centrifugation was washed with methanol 8 times. Finally, the precipitate was vacuum dried at 100℃ for 12 h to obtain Ce@ZIF8 powder.

[0052] (3) Place Ce@ZIF8 in a tube furnace and fill it with nitrogen for 60 min. Under the protection of nitrogen atmosphere, the heating rate is 5℃ / min. After heating to 800℃ and holding for 2 h, the cooling rate is 10℃ / min. After cooling to room temperature, Ce@ZIF8 / C powder is obtained.

[0053] (4) The silicon-based carrier was cleaned three times in the ultrasonic process with acetone, ethanol and ultrapure water in sequence. It was dried with high-purity nitrogen and cut into 1×1.2cm as the substrate of the sensor. The substrate was fixed on the photomask and 10nm of Cr and 100nm of Au were deposited on the surface of the substrate in sequence. The CVD monolayer graphene was cut into appropriate size and flatly covered the area between the source and drain. The transferred device was annealed for a period of time and then immersed in acetone at 55°C until the PMMA on the surface of the CVD monolayer graphene was completely removed. The sensor was encapsulated with waterproof glue and silver paste.

[0054] (5) Dissolve chitosan powder in 1 w / v acetic acid solution and stir thoroughly until the solution is completely clear to obtain acetic acid chitosan solution. The mass-volume ratio of chitosan powder to acetic acid solution is 1 mg: 10 mL. Finally, dissolve Ce@ZIF8 / C powder prepared in step (3) in acetic acid chitosan solution and sonicate to obtain electrode modification solution.

[0055] (6) Polish the glassy carbon electrode to a mirror finish, then sonicate to remove surface impurities, dry the glassy carbon electrode surface, add a modification solution, and then dry to obtain the Ce@ZIF8 / C modified SGGT sensor.

[0056] Comparative Example 1

[0057] The sensor in this comparative example is unmodified; specifically:

[0058] A method for fabricating a transistor sensor based on bimetallic MOF material, the specific steps of which are as follows:

[0059] (1) Clean the glass slide and cut it into 1×1.2cm as the substrate of the sensor. Fix the glass substrate on the photomask with high temperature tape. Deposit 10nm Cr and 100nm Au on the surface of the glass substrate by magnetron sputtering. Cut the CVD monolayer graphene into appropriate size using wet transfer method and cover it flat in the area between the source and drain. Anneal the transferred device at 120℃ for 15min, and then immerse it in acetone at 55℃ for 1h. Repeat 3 times until the PMMA on the surface of the CVD monolayer graphene is completely removed. Encapsulate the sensor with waterproof glue and silver paste.

[0060] (2) Place alumina powder with a particle size of 0.05 μm on a chamois, add an appropriate amount of deionized water to wet the chamois, polish the glassy carbon electrode to a mirror finish, and then sonicate it in a 50% ethanol solution to remove surface impurities. After drying the glassy carbon electrode, use it directly as an SGGT sensor.

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 1 is that cetyltrimethylammonium bromide was not added during the synthesis of the bimetallic MOF material used in the sensor. Specifically:

[0063] A method for fabricating a transistor sensor based on bimetallic MOF material, the specific steps of which are as follows:

[0064] (1) Zn(NO3)2·6H2O and Ce(NO3)3·6H2O are uniformly mixed in methanol solution and stirred for 10 min to obtain mixed solution A, which is set aside. The mass-volume ratio of Zn(NO3)2·6H2O, Ce(NO3)3·6H2O to methanol solution is 10 g: 1 g: 30 mL. At the same time, 2-methylimidazole is dissolved in methanol solution and stirred thoroughly for 10 min to obtain mixed solution B. The mass-volume ratio of 2-methylimidazole to methanol solution is 1 g: 24.35 mL. Mixed solution A is added to mixed solution B at a volume ratio of 1:1 and allowed to react fully at room temperature for 6 h to obtain mixed solution.

[0065] (2) Centrifuge the mixed solution obtained in step (1) at 8000 rpm for 3 min, take the precipitate after centrifugation and wash it with methanol 5 times. Finally, dry the precipitate under vacuum at 80℃ for 10 h to obtain Ce@ZIF8 powder.

[0066] (3) Place Ce@ZIF8 in a tube furnace and fill it with nitrogen for 30 min. Under the protection of nitrogen atmosphere, the heating rate is 5℃ / min. After heating to 900℃ and holding for 3 h, the cooling rate is 5℃ / min. After cooling to room temperature, Ce@ZIF8 / C powder is obtained.

[0067] (4) The silicon-based carrier was cleaned three times in the ultrasonic process with acetone, ethanol and ultrapure water in sequence. It was dried with high-purity nitrogen and cut into 1×1.2cm as the substrate of the sensor. The substrate was fixed on the photomask and 10nm of Cr and 100nm of Au were deposited on the surface of the substrate in sequence. The CVD monolayer graphene was cut into appropriate size and flatly covered the area between the source and drain. The transferred device was annealed for a period of time and then immersed in acetone at 55°C until the PMMA on the surface of the CVD monolayer graphene was completely removed. The sensor was encapsulated with waterproof glue and silver paste.

[0068] (5) Dissolve chitosan powder in 1 w / v acetic acid solution and stir thoroughly until the solution is completely clear to obtain acetic acid chitosan solution. The mass-volume ratio of chitosan powder to acetic acid solution is 1 mg: 10 mL. Finally, dissolve Ce@ZIF8 / C powder prepared in step (3) in acetic acid chitosan solution and sonicate to obtain electrode modification solution.

[0069] (6) Polish the glassy carbon electrode to a mirror finish, then sonicate to remove surface impurities, dry the glassy carbon electrode surface, add a modification solution, and then dry to obtain the Ce@ZIF8 / C modified SGGT sensor.

[0070] Comparative Example 3

[0071] The difference between this comparative example and Example 1 is that Zn(NO3)2·6H2O was replaced with (CH3COO)2Zn during the synthesis of the bimetallic MOF material used in the sensor. Specifically:

[0072] A method for fabricating a transistor sensor based on bimetallic MOF material, the specific steps of which are as follows:

[0073] (1) Zn(NO3)2·6H2O, Ce(NO3)3·6H2O and hexadecyltrimethylammonium bromide are uniformly mixed in methanol solution and stirred for 10 min to obtain mixed solution A, which is set aside. The mass-volume ratio of Zn(NO3)2·6H2O, Ce(NO3)3·6H2O, hexadecyltrimethylammonium bromide and methanol solution is 10 g: 1 g: 0.1 g: 30 mL. At the same time, 2-methylimidazole is dissolved in methanol solution and stirred thoroughly for 10 min to obtain mixed solution B. The mass-volume ratio of 2-methylimidazole and methanol solution is 1 g: 24.35 mL. Mixed solution A is added to mixed solution B at a volume ratio of 1:1 and allowed to react fully at room temperature for 6 h to obtain mixed solution.

[0074] (2) Centrifuge the mixed solution obtained in step (1) at 8000 rpm for 3 min, take the precipitate after centrifugation and wash it with methanol 5 times. Finally, dry the precipitate under vacuum at 80℃ for 10 h to obtain Ce@ZIF8 powder.

[0075] (3) Place Ce@ZIF8 in a tube furnace and fill it with nitrogen for 30 min. Under the protection of nitrogen atmosphere, the heating rate is 5℃ / min. After heating to 900℃ and holding for 3 h, the cooling rate is 5℃ / min. After cooling to room temperature, Ce@ZIF8 / C powder is obtained.

[0076] (4) The silicon-based carrier was cleaned three times in the ultrasonic process with acetone, ethanol and ultrapure water in sequence. It was dried with high-purity nitrogen and cut into 1×1.2cm as the substrate of the sensor. The substrate was fixed on the photomask and 10nm of Cr and 100nm of Au were deposited on the surface of the substrate in sequence. The CVD monolayer graphene was cut into appropriate size and flatly covered the area between the source and drain. The transferred device was annealed for a period of time and then immersed in acetone at 55°C until the PMMA on the surface of the CVD monolayer graphene was completely removed. The sensor was encapsulated with waterproof glue and silver paste.

[0077] (5) Dissolve chitosan powder in 1 w / v acetic acid solution and stir thoroughly until the solution is completely clear to obtain acetic acid chitosan solution. The mass-volume ratio of chitosan powder to acetic acid solution is 1 mg: 10 mL. Finally, dissolve Ce@ZIF8 / C powder prepared in step (3) in acetic acid chitosan solution and sonicate to obtain electrode modification solution.

[0078] (6) Polish the glassy carbon electrode to a mirror finish, then sonicate to remove surface impurities, dry the glassy carbon electrode surface, add a modification solution, and then dry to obtain the Ce@ZIF8 / C modified SGGT sensor.

[0079] To evaluate the Ce@ZIF8 / C prepared in Example 1, the morphology of the prepared material was characterized using scanning electron microscopy. Figure 2 It can be clearly seen that Ce@ZIF8 / C retains the unique rhombic dodecahedral structure of the parent ZIF8 even after high-temperature pyrolysis, with an average particle size of approximately 250 nm. Furthermore, X-ray energy dispersive spectroscopy (EDS) analysis of the Ce@ZIF8 / C prepared in Example 1 shows that C, N, and Ce elements are uniformly distributed within its structure. The surfactant cetyltrimethylammonium bromide added during synthesis effectively controls its morphology and size, indicating that cetyltrimethylammonium bromide can act as a protective agent, reducing the growth rate of ZIF8 crystals. The adsorption isotherm results of Example 1 are shown below. Figure 3 As shown in Table 1, Ce@ZIF8 / C exhibits a relatively large number of mesoporous structures, corresponding to the hysteresis loops in the adsorption-desorption isotherms. The total pore volumes of Ce@ZIF8 and Ce@ZIF8 / C are 0.0906 cm³, respectively. 3 ·g and 0.3463cm 3 The latter increased by nearly four times compared to the former. Mesopores can expose more active sites and promote mass transfer, which will be beneficial to improving electrocatalytic performance. The electrochemical impedance differences of the Ce@ZIF8 / C materials prepared in Example 1 and those prepared in Comparative Examples 1-3 were determined by electrochemical impedance spectroscopy (EIS). Figure 4 As can be seen, compared with Comparative Examples 1-3, the material with added hexadecyltrimethylammonium bromide (hexadecyltrimethylammonium bromide) in Example 1 has the smallest Rct value compared with other materials. This indicates that the introduction of hexadecyltrimethylammonium bromide while using Zn(NO3)2·6H2O as a zinc MOF material is beneficial to enhancing electrochemical performance.

[0080] Table 1 shows the specific parameters of the adsorption isotherm curves of the Ce@ZIF8 / C powder prepared in Example 1.

[0081]

[0082] The working principle of the fabricated sensor is as follows: Figure 5 As shown, when the graphene channel and gate electrode (GCE) are simultaneously placed in an electrolyte solution, an electrical double layer (EDL) is formed at the gate electrode / electrolyte and electrolyte / graphene channel interfaces when a voltage is applied. The solid line in the figure represents the potential distribution without the addition of BPA to the system, at a gate voltage (V). G Under the influence of BPA, a voltage value is formed at the interface between the gate electrode and the electrolyte. This voltage value then forms a corresponding voltage value between the electrolyte interface and the graphene channel. This phenomenon is called potential drop. When BPA is added to the system, the potential drop at the gate electrode and the graphene channel is shown by the dashed line. BPA molecules undergo an electro-oxidation-reduction reaction on the surface of the gate electrode, releasing two electrons and two H atoms. + A Faraday current is generated at the gate electrode / electrolyte interface, which causes a change in potential at the two EDLs. The amount of this voltage change is the effective gate voltage change (Δ). This generates a channel current response. Considering that the Ce@ZIF8 / C functionalized SGGT sensor would be subject to interference in practical applications for detecting BPA in aqueous solutions, some ions present in water and 1,4-benzenediol (HQ), which has a structure similar to BPA, were selected as interfering agents for selective testing. Figure 6 The sensor prepared in Example 1 reacts to 100 nM BPA, 1 μM glucose (Glu), and 10 μM Na. + 10μM Mg 2+ 10μM, 10μM SO4 2- And the Δ produced by 100 nM 1,4-benzenediol .Depend on Figure 6 It can be seen that the sensor prepared in Example 1 is effective against 100 nM BPA (Δ) The highest response was obtained from the interference (13.02±0.50mV), while the responses from other interfering substances were relatively low: 1.60±0.12mV for 100nMHQ, 0.68±0.04mV for 1μM Glu, and 0.60±0.04mV for 10μM Na. + The value was 0.33 ± 0.01 mV, and the value was 10 μM Mg. 2+ The concentrations were 1.72 ± 0.29 mV and 10 μM SO4. 2- The values ​​were 1.72 ± 0.29 mV and 10 μM CO3. 2- The value is 0.67 ± 0.02 mV. Therefore, it can be concluded that the Ce@ZIF8 / C functionalized SGGT sensor has a selective response to BPA.

[0083] To evaluate the effectiveness of the Ce@ZIF8 / C functionalized SGGT sensor in detecting BPA, the sensors prepared in Example 1 and Comparative Example 1 were used to perform electrochemical detection of BPA. The SGGT sensor was immersed in a small beaker containing 10 mL of 1×PBS buffer (pH=7.4), and the transfer characteristic curves (I) were measured. Ds -V G ) and channel current versus time response curve (I Ds -t).

[0084] The results are as follows Figure 7 As shown, Figures (a) and (b) are the transfer characteristic curves (V) measured in 1×PBS solution for Comparative Example 1 and Example 1, respectively. G -I Ds The transfer characteristic curves of Comparative Example 1 and Example 1 both exhibit excellent bipolar properties of the graphene material in the channel. Furthermore, Figure 7 (a) and (b) also include the time-current response curves of Comparative Example 1 and Example 1, respectively, for the continuous addition of a certain concentration of BPA. For the sensor prepared in Comparative Example 1, the detection limit is 300 nM; while the detection limit of the sensor prepared in Example 1 is 10 nM. The above results verify that the functionalization of Ce@ZIF8 / C can significantly improve the detection performance of the SGGT sensor for BPA.

[0085] To more intuitively compare the sensitivity of the sensors prepared in Comparative Example 1 and Example 1 in detecting BPA, we fabricated ΔT values ​​for the sensors prepared in Comparative Example 1 and Example 1. The relationship between BPA concentration and logarithm is shown in the graph. Figure 8 As shown in the figure. It can be seen from the figure that within a certain range, △ The linear relationship with the logarithm of BPA concentration is linear, and the linear range of the sensor prepared in Example 1 is larger than that of the sensor prepared in Comparative Example 1. Specifically, the Δ... The slope of the logarithmic relationship with BPA concentration is 6.78 mV / decade. The sensor prepared in Example 1 has a ΔV... The slope of the logarithmic relationship with BPA concentration is 19.2 mV / decade, which fully demonstrates that the modification of the gate electrode by Ce@ZIF8 / C is beneficial to improving the detection sensitivity of the sensor.

[0086] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for fabricating a bimetallic MOF material functionalized transistor sensor for bisphenol A detection, the specific fabrication steps of which are as follows: (1) Mix Zn(NO3)2·6H2O, Ce(NO3)3·6H2O and hexadecyltrimethylammonium bromide uniformly in methanol solution and stir for 10-15 min to obtain mixed solution A, which is set aside. At the same time, dissolve 2-methylimidazolium in methanol solution and stir thoroughly for 10-15 min to obtain mixed solution B. Add mixed solution A to mixed solution B and allow it to react fully at room temperature for 6-10 h to obtain mixed solution. (2) Centrifuge the mixed solution obtained in step (1) at 5000-12000 rpm for 3-15 min, take the precipitate after centrifugation and wash it with methanol 5-8 times, and finally vacuum dry the precipitate to obtain Ce@ZIF8 powder. (3) Place Ce@ZIF8 powder in a tube furnace, fill with nitrogen for 10-60 min, and heat to 600-900℃ under nitrogen atmosphere protection for 2-5 h, then cool down and wait until room temperature to obtain Ce@ZIF8 / C powder. (4) Clean the silicon-based carrier and cut it into a substrate for the sensor. Fix the substrate on the photomask and deposit 10 nm of Cr and 100 nm of Au on the substrate surface. Cut the CVD monolayer graphene into an appropriate size and cover it flat in the area between the source and drain. Anneal the transferred device for a period of time and then immerse it in acetone at 50-70°C until the PMMA on the surface of the CVD monolayer graphene is completely removed. Encapsulate the sensor with waterproof glue and silver paste. (5) Dissolve chitosan powder in acetic acid solution and stir thoroughly until the solution is completely clear to obtain acetic acid chitosan solution. Finally, dissolve Ce@ZIF8 / C powder prepared in step (3) in acetic acid chitosan solution and sonicate to obtain electrode modification solution. (6) Polish the glassy carbon electrode to a mirror finish, then sonicate to remove surface impurities, dry the glassy carbon electrode surface, add a modification solution, and then dry again to obtain a Ce@ZIF8 / C modified gate solution graphene transistor sensor.

2. The method for fabricating a bimetallic MOF material functionalized transistor sensor for bisphenol A detection according to claim 1, characterized in that: In step (1), the mass-volume ratio of Zn(NO3)2·6H2O, Ce(NO3)3·6H2O, hexadecyltrimethylammonium bromide and methanol solution is (1-30g):1g:(0.01-0.3g):(20-100mL).

3. The method for fabricating a bimetallic MOF material functionalized transistor sensor for bisphenol A detection according to claim 1, characterized in that: In step (1), the mass-to-volume ratio of 2-methylimidazole to methanol solution is 1 g: (10-30 mL).

4. The method for fabricating a bimetallic MOF material functionalized transistor sensor for bisphenol A detection according to claim 1, characterized in that: In step (2), the vacuum drying conditions are 40-100℃ for 8-12 hours.

5. The method for fabricating a bimetallic MOF material functionalized transistor sensor for bisphenol A detection according to claim 1, characterized in that: In step (3), the heating rate is 3-5℃ / min and the cooling rate is 5-20℃ / min.

6. The method for fabricating a bimetallic MOF material functionalized transistor sensor for bisphenol A detection according to claim 1, characterized in that: The specific steps for cleaning the silicon-based carrier in step (4) are as follows: the silicon-based carrier is cleaned three times in ultrasound with acetone, ethanol and ultrapure water in sequence, and then dried with high-purity nitrogen gas for later use.

7. The method for fabricating a bimetallic MOF material functionalized transistor sensor for bisphenol A detection according to claim 1, characterized in that: In step (5), the mass-to-volume ratio of chitosan powder to acetic acid solution is 1 mg: (3-20 mL).

8. The application of the transistor sensor prepared by the method for preparing a bimetallic MOF material functionalized transistor sensor for bisphenol A detection according to any one of claims 1-7 in the detection of bisphenol A.

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