A method for detecting mercury ions

Abstract

The application discloses a mercury ion detection method. The detection method mainly comprises preparation of mercapto carbon dots, preparation of a graphene transistor sensor, modification of the graphene transistor sensor by the mercapto carbon dots, and detection of mercury ions by the sensor, etc. In the application, the mercapto carbon dots are modified to the gate of the graphene transistor sensor by cysteamine, the specific chelation between the mercapto functional groups in the mercapto carbon dots and mercury ions is utilized, a stable mercury ion-mercapto functional group-carbon dot structure is formed on the gate surface, the original double electric layer structure of the sensor is changed, the graphene channel current is changed, and the purpose of detecting mercury ions is achieved. By constructing the graphene transistor sensor detection platform functionalized by the mercapto carbon dots, specific label-free detection of mercury ions is realized, trace detection of mercury ions is realized, and the minimum detection limit reaches 10 ‑17 M, linear detection range 10 ‑16 M-10 ‑8 M, and the detection time is within 1 min, and the operating voltage is lower than 1 V. Compared with the prior art (fluorescence, colorimetric technology, etc.), the detection method provided by the application is simple in operation, low in cost, sensitive in detection, high in accuracy, and can realize detection of mercury ions in actual environmental water samples. Meanwhile, the application has great application prospect in food safety detection and biological health detection.

Description

Technical Field

[0001] This invention relates to the field of heavy metal ion detection technology, and specifically to a method for detecting mercury ions. Background Technology

[0002] Heavy metal pollution has been a global challenge for decades. Even at very low concentrations, dissolved heavy metal ions in water are highly toxic to organisms. Among various types of heavy metal ions, water-soluble mercury ions are generally considered one of the most toxic due to their cumulative properties in ecosystems. Mercury ions can cause kidney / liver disease, osteomalacia, neurological disorders (such as menthol, pulmonary edema, cyanosis, and nephrotic syndrome), immune damage, and other extremely harmful adverse effects on human health. According to the U.S. Environmental Protection Agency (EPA), the maximum permissible level for inorganic mercury in drinking water is 10 nM. Related studies have shown that mercury levels accumulate at the ends of the food chain; therefore, even if environmental mercury ions are within safe concentration ranges, they can accumulate through the food chain and lead to serious health consequences. Therefore, highly sensitive and rapid detection of low concentrations of mercury ions in biological and environmental systems is crucial.

[0003] Currently, various detection methods have been developed for mercury ions. Traditional methods include colorimetry, fluorescence, atomic absorption spectroscopy, inductively coupled plasma optical emission spectroscopy, and electrochemical detection. Among these, colorimetry and fluorescence detection methods are simple, easy to operate, and offer the advantage of rapid detection, but their detection limits are relatively high. While atomic absorption spectroscopy, inductively coupled plasma optical emission spectroscopy, and electrochemical detection methods can achieve the detection of low concentrations of mercury ions, these methods often require specialized personnel, expensive equipment, and long detection cycles. Therefore, there is an urgent need to develop a mercury ion detection method that simultaneously possesses a low detection limit, high sensitivity, and a short detection cycle.

[0004] To address the aforementioned issues, liquid-gate graphene transistor ion sensors have been developed. In detection, the prepared liquid-gate graphene transistor ion sensor is directly immersed in the analyte solution for ion concentration detection; this is a label-free detection method. The detection principle involves modifying the gate surface of the liquid-gate graphene transistor with a specific probe. When the analyte in the solution binds to the probe on the gate surface, it alters the electrical double-layer interface characteristics between the transistor and the sample solution, thereby changing the current in the graphene channel. By detecting this current change, trace amounts of the analyte in the solution can be detected. Currently, graphene transistor ion sensors have successfully achieved rapid, low-limit, and high-sensitivity detection of ions, DNA fragments, glucose, etc. However, low-limit, rapid, and high-sensitivity detection of mercury ions has not yet been achieved. Summary of the Invention

[0005] This invention primarily provides a method for detecting mercury ions. For the first time in the field of mercury ion detection, it integrates the advantages of thiol-based carbon dots and graphene transistors, resulting in a highly sensitive method for detecting mercury ions using a thiol-based carbon dot-functionalized graphene transistor sensor. This sensor offers multiple advantages in mercury ion detection: (1) High sensitivity and fast response time, with detection time controlled within 1 minute; (2) Low detection limit, reaching as low as 10 -17 M; (3) Wide detection range, applicable to 10 -16 ~10 -8 M; (4) It has a good linear detection range.

[0006] This invention provides a method for detecting mercury ions, specifically including the preparation of thiol carbon dots (SCDs), the fabrication of graphene transistors, and the combination of thiol carbon dots with a graphene transistor sensor. Specifically, thiol carbon dots are modified onto the gate surface of the graphene transistor to construct a liquid-gate graphene transistor mercury ion sensor detection platform with a carbon dot functionalized gate. Compared to existing technologies (fluorescence, colorimetric techniques, etc.), the method for detecting mercury ions provided by this invention operates at a voltage below 1V and achieves beneficial effects such as low detection limit, high sensitivity, short detection time, wide linear range, and suitability for detecting mercury ions in practical environmental water samples.

[0007] (1) Preparation of mercapto carbon dots.

[0008] Citric acid and 2,3-dimercaptosuccinic acid were dissolved in a certain amount of deionized water in a certain proportion, and mercapto carbon dots were synthesized by hydrothermal method under suitable temperature and time conditions.

[0009] (2) Fabrication of graphene transistors.

[0010] The graphene transistor comprises a substrate, a gate, a source, a drain, and a graphene channel. The transistor is fabricated using a thermal evaporation deposition method with a JSD-300 evaporation deposition system. A graphene channel exists between the source and drain of the transistor. A monolayer of graphene is then flatly attached to the source and drain channel of the transistor to obtain a graphene transistor sensor.

[0011] The gate, source, and drain electrodes were fabricated by depositing gold (~120 nm) / Cr (~13 nm) onto a substrate using a JSD-300 evaporation deposition system. Monolayer graphene (synthesized on copper foil using chemical vapor deposition) was then transferred to the source and drain electrodes (0.2 × 6 mm) using a PMMA wet transfer method. 2The channel region between the two sides. The PMMA layer was removed using acetone, and the device was then rinsed in deionized water and allowed to air dry. (3) Fabrication of a sensor with a thiol carbon dot modified gate.

[0012] Under low temperature and dark conditions, cysteine ​​is modified onto the gate surface to form a stable Au-S bond between its thiol groups and gold. After activation treatment with N-hydroxysuccinimide (EDC) / 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (NHS), thiol carbon dots are covalently linked to cysteine ​​onto the gate surface to construct a liquid gate graphene transistor mercury ion sensor with a thiol carbon dot modified gate.

[0013] The activator to carbon dot solution volume ratio was 1:1. 10 μL of the SCDs / EDC / NHS mixed solution was added dropwise to the electrode surface. Finally, the electrode was washed three times with PBS buffer to remove unfixed carbon dots.

[0014] In the above preparation method, in step (1), the mass ratio of citric acid to 2,3-dimercaptosuccinic acid is 10 / 5 to 10 / 8, with the optimal ratio being 10 / 7, and the amount of deionized water is based on adding 20 to 30 mL of deionized water to 1 g of citric acid.

[0015] In the above preparation method, in step (1), the hydrothermal time of the carbon point is 4 to 6 h, with 5 h being optimal, and the temperature is 170 to 200 ℃, with 180 ℃ being optimal.

[0016] In the above preparation method, in step (2), the transistor substrate used is preferably electronic-grade glass.

[0017] In the above preparation method, in step (2), the substrate is cleaned and dried before use. Cleaning is preferably ultrasonic cleaning, specifically using acetone, isopropanol, and ethanol sequentially for 15–30 min, most preferably 20 min. Drying is preferably oven drying.

[0018] In the above preparation method, in step (2), the thermal evaporation coating is preferably carried out under vacuum conditions; the vacuum degree is preferably 8×10⁻⁶. -4 Pa or less, more preferably 4×10 Pa -4 Pa.

[0019] In the above preparation method, in step (2), the gate, source and drain are composed of a chromium layer and a gold layer, and the chromium layer is located between the substrate and the gold layer.

[0020] In the above preparation method, in step (2), the evaporation temperature of the chromium layer is preferably 170-200 ℃, more preferably 175-190 ℃; the evaporation temperature of the gold layer is preferably 100-120 ℃, more preferably 105-110 ℃.

[0021] In the above preparation method, in step (2), the thickness of gold evaporation is 40-100 nm, and the thickness of chromium evaporation is about 5-13 nm.

[0022] In the above preparation method, in step (2), the width of the graphene channel of the transistor is 0.2 to 0.3 mm, and the length of the graphene channel is 4 to 8 mm.

[0023] In the above preparation method, in step (2), the width of the monolayer graphene is 0.5 to 2 mm and the length of the graphene is 5 to 9 mm.

[0024] In the above preparation method, in step (2), the graphene is transferred by using a wet transfer method to transfer the monolayer graphene to the channel between the source and drain.

[0025] In the above preparation method, after the graphene transfer is completed in step (2), the transferred product needs to be annealed at a temperature of 100-120 ℃, preferably 110 ℃.

[0026] In the above preparation method, in step (3), the solvent of the cysteamine solution is a mixture of deionized water and anhydrous ethanol (volume ratio of 1 / 1 to 4 / 1, preferably 3 / 1), and the concentration of the cysteamine solution is 3 to 7 mg / mL, preferably 5 mg / mL.

[0027] In the above preparation method, in step (3), the modification temperature of cysteine ​​is 0-8°C, the modification time is 10-13 h in the dark, preferably 12 h.

[0028] In the above preparation method, in step (3), the modification time of the gate by the activator and carbon dot mixed solution is 3 to 5 h, preferably 4 h; the modification temperature is 20 to 30 ℃, preferably 25 ℃.

[0029] In the above preparation method, in step (3), the concentration of the thiol carbon dots on the modified gate surface is preferably 20 to 40 mg / mL, more preferably 30 mg / mL.

[0030] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following beneficial effects: 1) This invention functionalizes the gate of a liquid-gate graphene transistor sensor by modifying the gate surface with thiol-based carbon dots. This not only enables specific detection of mercury ions, but also allows for the detection of mercury ions at a concentration of 10... -16 M~10 -8 M exhibits a good linear relationship.

[0031] 2) This invention introduces the advantages of graphene transistors into the detection of mercury ions, which greatly shortens the detection time, which can be controlled within 1 minute.

[0032] 3) Compared with traditional mercury ion detection methods, this invention introduces a liquid-gate graphene transistor detection method for mercury ion detection. The graphene transistor sensor can be directly immersed in the liquid to detect mercury ion concentration. This is a label-free detection method that is simple and convenient. Simultaneously, this method enables high-sensitivity detection of samples, significantly reducing the detection limit of mercury ions to as low as 10⁻⁶. -17 M.

[0033] In summary, compared with existing technologies, the above-described technical solutions conceived in this invention can achieve beneficial effects such as low detection limit, high sensitivity, short detection time, wide linear range, and detection of actual environmental water samples in mercury ion detection. Attached Figure Description

[0034] Figure 1 This is the ultraviolet fluorescence spectrum of thiol carbon dots under ultraviolet light excitation at a wavelength of 325 nm. Figure 2 This is the infrared spectrum of thiol carbon dots; Figure 3 This is a schematic diagram of a graphene transistor ion sensor. Figure 4 This is a schematic diagram of the three-electrode structure in a graphene transistor ion sensor; Figure 5 This is a schematic diagram illustrating the fabrication and detection process of a liquid gate graphene transistor ion sensor with a thiol-modified gate. Figure 6 This is a practical assembly schematic diagram of a mercury ion sensor with a liquid gate graphene transistor and a gate modified with thiol carbon dots. Figure 7 The graphene transistor with a thiol-modified gate and a thiol-carbon dot-modified gate is a mercury ion sensor that detects mercury ions of different concentrations. Figure 8 The output characteristic curves of the mercury ion sensor with a thiol-modified carbon dot gate liquid-gate graphene transistor when detecting mercury ions of different concentrations are compared with the corresponding standard curves (10). -16 M~10 -8 M); Figure 9 The output characteristic curves of the mercury ion sensor with a thiol-modified carbon dot gate liquid-gate graphene transistor when detecting different mercury ion concentrations are shown (10). -17 M~10 -9 M, minimum detection limit 10 -17 M); Figure 10 These are the output characteristic curves showing the changes in graphene channel current for different metal ions; Figure 11 This is an output characteristic curve of actual lake water sample testing; Figure 12 This is an output characteristic curve of actual river water sample testing; Figure 13 This is a comparison of the detected mercury ion content in actual lake water samples and actual river water samples with the actual added content. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It is to be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0036] Example 1 (1) Preparation of mercapto carbon dots The mass ratio of citric acid to 2,3-dimercaptosuccinic acid was chosen to be 10:7, the solution was deionized water, and the synthesis method was hydrothermal synthesis.

[0037] In this invention, 0.95 g to 1.1 g of citric acid, preferably 1 g, and 0.66 g to 0.72 g of 2,3-dimercaptosuccinic acid, preferably 0.68 g, were dissolved separately, mixed, and stirred evenly with a magnetic stirrer. The mixture was then placed in a 50 mL polytetrafluoroethylene liner and heated in a hydrothermal oven at 170 ℃ to 200 ℃, preferably 180 ℃, for 4 to 6 h, preferably 5 h. After natural cooling, a yellow carbon dot solution was obtained. The resulting solution was centrifuged (8000 rpm to 14000 rpm, preferably 12000 rpm), filtered through a 2 nm filter membrane, and finally dialyzed through a dialysis membrane (dialysis molecular weight cutoff 12000 to 15000 Da, preferably 14000 Da) for 72 h to obtain the desired pale yellow carbon dot solution. The obtained carbon dot solution was diluted 2-3 times, with 2 times being optimal, to a final concentration of 20-40 mg / mL. Fluorescence selective detection revealed a significant fluorescence quenching effect on mercury ions. Figure 1 As shown.

[0038] The infrared spectrum of thiol carbon dots is as follows Figure 2As shown, the carbon dot exhibits distinct thiol and carboxyl peaks. The carboxyl group can react with the amino group of cysteine ​​to form a stable amide bond; therefore, cysteine ​​can be used to modify the carbon dot onto the gate surface of a graphene transistor.

[0039] (2) Fabrication of graphene transistors.

[0040] Transistor fabrication. Chromium and gold are sequentially deposited onto a substrate in an evaporation coating system using a JSD-300 evaporation coating system. The substrate can be electronic-grade glass, silicon wafer, or polyester resin, preferably electronic-grade glass (GL-10173-1.1) with a size of 10 × 10 mm. 2 ~14×14 mm 2 More preferably 12×12 mm 2 The specific parameters of the thermal evaporation coating method are not specifically limited; the parameters are determined based on the thickness of the resulting electrode. In this embodiment of the invention, the thermal evaporation coating is preferably performed under vacuum conditions; the vacuum degree is preferably 8 × 10⁻⁶. -4 Pa or less, more preferably 4×10 Pa -4 Pa. In this embodiment of the invention, the electrode consists of a chromium layer and a gold layer, wherein the chromium layer is located between the substrate and the gold layer, the thickness of the chromium layer is 5–13 nm, and the thickness of the gold layer is 40–100 nm. The evaporation temperature of the chromium layer is preferably 170–200 °C, more preferably 175–190 °C; the evaporation temperature of the gold layer is preferably 100–120 °C, more preferably 105–110 °C. A graphene channel is located between the source and drain electrodes, the width of the channel is 0.2–0.3 mm, and the length of the channel is 4–8 mm.

[0041] Fabrication of graphene transistors. A polymethyl methacrylate film (400–600 nm, preferably 500 nm) is spin-coated onto a pre-prepared monolayer graphene (preferably copper-based CVD monolayer graphene, sourced from commercially available products well-known to those skilled in the art, or prepared according to methods well-known to those skilled in the art). Before attaching the graphene, the graphene is immersed in a ferric chloride solution for 2–4 hours to remove surface copper; the preferred time is 3 hours, depending on the graphene's transparency. The monolayer graphene is then laid flat on the graphene channels and annealed to obtain the graphene transistor. In this embodiment, the annealing temperature is preferably 100–130 °C, more preferably 110 °C; the annealing time is preferably 20–40 min, more preferably 30 min. Annealing removes moisture from the sample surface and allows for a tighter bond between the graphene and the substrate. The single-layer graphene has a width of 0.5–2 mm and a length of 5–9 mm, preferably 1.5 × 6 mm. 2Then, the prepared graphene transistor needs to be soaked in acetone at 70 °C for 3 hours to dissolve any residual material on the graphene. After cleaning and drying at room temperature, the graphene transistor can produce a stable IV curve, and the Dirac point is stable between 0.3 and 0.5 V.

[0042] (3) Fabrication of graphene transistor sensors modified with thiol carbon dots.

[0043] 20 μL of cysteamine solution (3–7 mg / mL, preferably 5 mg / mL) was drop-coated onto the gate of a graphene transistor. The mixture was then placed in the dark at 4 °C for 10–14 h, preferably 12 h, to modify the gate surface with cysteamine, forming a stable chemical bond between the thiol groups and gold. Next, a 1:1 mixture of EDC (0.2 mM, pH = 5.5 PBS) and NHS (0.5 mM, pH = 5.5 PBS) was mixed with a carbon dot solution (30 mg / mL), and 20 μL of this mixture was drop-coated onto the gate surface. The mixture was then kept at 25 °C for 4 h to covalently modify the gate surface with thiol-modified carbon dots, thus constructing a graphene transistor mercury ion sensor with a thiol-modified gate. The specific operation process is as follows: Figure 5 As shown.

[0044] Example 2 Application of thiol-modified graphene transistor sensors for detecting mercury ions.

[0045] A mercury ion detection platform was constructed using a graphene transistor sensor with a gate modified by prepared thiol carbon dots. The specific model is as follows: Figure 6 As shown. The source, drain, and gate electrodes of the graphene transistor are connected to two combined Keithley data source tables (Keithley2400), with the gate voltage... V G Source-drain voltage V D It is controlled by a LabVIEW program on the computer. For example... Figure 3 As shown, the detection principle is that the gate electrode and the graphene channel are connected by an electrolyte, forming a "double capacitor" structure. The voltage applied between the gate electrode and the graphene channel is constant. When the thiol carbon dots fixed on the gate electrode undergo a specific chelation with mercury ions, the characteristics of the double layer interface change, which in turn causes a change in the current in the graphene channel. By detecting the change in the current in the channel, the value of trace mercury ions in the solution can be quantitatively detected.

[0046] Transfer characteristic curve test: The source-drain voltage was set to a constant value ( V D=0.1 V), when the gate voltage changes continuously from 0.1 V to 1.1 V, the channel current I between the source and drain is measured. D The change was then investigated, and the concentration of mercury ions in the solution was altered (from 10...). -14 M, 10 -12 M, 10 -10 M, 10 -8 M, 10 -6 M, 10 -4 M is measured sequentially to obtain the transfer characteristic curve, such as Figure 7 As shown. According to Figure 3 The schematic diagram of a liquid-gate graphene transistor mercury ion sensor with a thiol-modified gate shows that changes in the interface alter the surface potential of the device, thus shifting the characteristic curve. According to... Figure 7 It can be seen that the current changes as the concentration of mercury ions increases.

[0047] Transfer characteristic curve test: both source-drain voltage and gate voltage were set to a constant value. V D = 0.1 V and V G = 0.2 V), continuously measure the relationship between channel current and time. Add a series of mercury ion standard solutions of varying concentrations to the sensor detection area. After the gate thiol carbon dots specifically chelate with mercury ions, record the current intensity. I D During the change, once the channel current stabilizes, the mercury ion concentration is increased, sequentially decreasing the standard mercury ion concentration from 10... -16 M, 10 -14 M, 10 -12 M, 10 -10 M, 10 -8 M changes sequentially; the difference in current intensity between the state with and without mercury ions is taken as the current intensity of mercury ion concentration and corresponding to the concentration of mercury ions in the standard solution, forming the current intensity change value |Δ I D | -Log(Hg 2+ The concentration standard curve yielded the following test results: Figure 8 As shown; according to Figure 8 It can be seen that changes in mercury ion concentration cause significant changes in current. The magnitude of the current change reflects the magnitude of the concentration change, and the sensor's current changes instantly after the mercury ion concentration is changed, demonstrating very high sensitivity. Furthermore, the standard curve shows that at 10... -16 M~10 -8 Within the range of M, the channel current change of the sensor shows a good linear relationship with the mercury ion concentration.

[0048] Output characteristic test: Source-drain voltage and gate voltage were both set to a constant value. V D =0.1 V and V G =0.2 V), tests were conducted on mercury ion solutions of different concentrations, such as Figure 9 As shown, the graphene transistor ion sensor provided by this invention can detect trace amounts of mercury ions in solution, with a detection limit as low as 10. -17 M.

[0049] Selective output characteristic test curve plotting: both source-drain voltage and gate voltage are set to a constant value. V D =0.1 V and V G = 0.2 V), the relationship between channel current and time was continuously measured for different metal ions at the same concentration. During this period, after the channel current stabilized, 10 μL of different metal ions at the same concentration were added dropwise. Multiple measurements revealed that this mercapto-based carbon dot liquid-gate graphene transistor mercury ion sensor showed a very significant response to mercury ions, but a less obvious response to other metal ions; such as Figure 10 As shown. According to Figure 10 It can be clearly observed at 10 -7 At concentration M, the sensor exhibits a very significant response to mercury ions, with the response to mercury ions being more than 6 times that of other ions.

[0050] Example 3 Application of thiol-modified graphene transistor sensors for mercury ion detection in actual environmental water samples from lakes and rivers.

[0051] Lake water and river water were used as actual water samples. The samples were filtered, dialyzed, and acidified to remove large particles and other interfering substances. Based on the standard curve from Example 2, the mercury ion content in the actual samples was tested. After dilution, certain concentrations of mercury ions (0.1 nM, 1 nM, 10 nM) were added to the actual water samples, and the samples were then tested. The characteristic curves are shown below. Figure 11 As shown. Figure 12 The table compares the mercury ion content detected in actual water samples from Shahu Lake and the Yangtze River with the actual added content. Data analysis shows that the sensor's detection error for mercury ion content in actual water samples is within 4%, meeting the detection requirements. This proves that the sensor can detect mercury ion content in actual environmental water samples.

[0052] The present invention provides a method for detecting mercury ions that significantly improves the sensitivity of mercury ion detection, shortens the detection time (controlling the detection time to within 1 minute), and lowers the detection limit (the detection limit reaches as low as 10).-17 M), and has a wide applicable detection range, within 10 -16 M~10 -8 The method exhibits good linearity within the M range. In particular, the method provided by this invention demonstrates excellent performance in actual environmental water sample testing. Therefore, this invention is of great significance in mercury ion detection, especially in actual environmental water sample testing, food safety testing, and biological health testing, providing a new research direction.

[0053] In summary, this invention provides a highly sensitive method for the detection of mercury ions. For mercury ion detection, this method achieves beneficial effects such as low detection limit, high sensitivity, short detection time, wide linear range, and suitability for detecting actual water samples.

Claims

1. A method for detecting mercury ions, characterized by the following: 1) Synthesis of thiol carbon dots: Citric acid and 2,3-dimercaptosuccinic acid are dissolved in a certain amount of deionized water in a certain proportion, and thiol carbon dots are synthesized by hydrothermal method under suitable temperature and time conditions; 2) Fabrication of graphene transistors: The graphene transistor consists of a substrate, a gate, a source, a drain, and a graphene channel. A graphene channel exists between the source and drain of the transistor. A single layer of graphene is flatly attached to the source and drain channel of the transistor to obtain a graphene transistor; 3) Thiol groups Carbon dot-modified graphene transistor: Cysteine ​​is modified onto the gate surface to form a stable structure with the gold gate; then, thiol carbon dots and cysteine ​​are covalently linked to the gate surface of the sensor to construct a thiol carbon dot-functionalized graphene transistor sensor; 4) Detection steps: First, the thiol carbon dot-modified graphene transistor sensor is combined with a polydimethylsiloxane container, and each electrode is connected to a data source table. A series of mercury ion standard solutions of various concentrations are sequentially added to the sensor detection area. After the thiol carbon dots specifically chelate with mercury ions, the current intensity is recorded. The change in current intensity is determined by taking the difference between the current intensity before and after the addition of mercury ions as the current intensity for mercury ion concentration and corresponding it to the concentration of mercury ions in the standard solution, thus establishing a current intensity change value. With mercury ion concentration Log[Hg 2+ The standard curve between [ ] is obtained; secondly, the sample to be tested is added to the detection area, and the above steps are repeated to obtain its current intensity. After comparison with the standard curve, the mercury ion concentration of the sample to be tested is obtained; 5) The detection performance of this sensor for mercury ions: the lowest detection limit is 10 -17 M; Linear detection range 10 -16 M-10 -8 M; Detection time is completed within 1 minute; Operating voltage is below 1 V; The carbon dots are prepared from citric acid, 2,3-dimercaptosuccinic acid, and deionized water, wherein the mass ratio of citric acid to 2,3-dimercaptosuccinic acid is 10:5-8; the mass-to-volume ratio of citric acid to water is 1 g:20-30 mL, and the hydrothermal temperature is 170-200 ℃; The graphene transistor has a graphene channel width of 0.2-0.3 mm and a graphene channel length of 4-8 mm; The graphene channel is a single layer of graphene; The gate, source, and drain independently include chromium and gold layers, with the chromium layer located between the substrate and the gold layer; The thickness of the chromium layer is 6-12 nm, and the thickness of the gold layer is 40-90 nm; The concentration of cysteine ​​modified onto the gate surface is 3-7 mg / mL, the modification temperature is 0-8 ℃, the modification time is 10-13 h, and the modification environment is darkness; The concentration of the carbon dots is 20-40 mg / mL, modification temperature 20-30 ℃, modification time 3-5 h.

2. The method for detecting mercury ions according to claim 1, characterized in that, The detection mechanism of this method is as follows: Thiol carbon dots are modified onto the gate of a graphene transistor to construct a graphene transistor sensor with thiol carbon dots functionalized. The specific chelation between the thiol functional groups in the thiol carbon dots and mercury ions is utilized to form a stable mercury ion-thiol functional group-carbon dot complex structure on the gate surface, thereby changing the original double-layer structure of the sensor and causing a change in the graphene channel current, thus achieving the purpose of detecting mercury ions.

Images