CN111257386A - Method for electrochemical synchronous detection of zinc, cadmium, lead, copper and mercury ions - Google Patents

Abstract

The invention discloses a method for electrochemical synchronous detection of zinc, cadmium, lead, copper and mercury ions. The method can realize high-sensitivity simultaneous detection of various heavy metal ions, and the detection sensitivities of zinc, cadmium, lead, copper and mercury ions are: 0.17, 0.51, 0.68, 0.89, 0.51μAμg ^‑1 L ^‑1 cm ^‑2 , The detection limits were 0.08, 0.09, 0.05, 0.19, 0.01 μg/L, respectively, and the linear ranges were 6-7000, 4-6000, 6-5000, 4-4000, 6-5000 μg/L, respectively. It has high sensitivity, good selectivity, wide linear range, excellent reproducibility and stability, and achieves simple, inexpensive, fast and sensitive detection results.

Description

A method for electrochemical simultaneous detection of zinc, cadmium, lead, copper and mercury ions

technical field

The invention relates to the field of electrochemical sensors for detecting various heavy metals and food safety analysis, in particular to a method for synchronously detecting zinc, cadmium, lead, copper and mercury ions in agricultural products.

Background technique

Today, heavy metal pollution has become an increasingly serious problem in food safety. Due to the large-scale development and utilization of mineral resources, the widespread use of various chemical products, pesticides and fertilizers, and the unreasonable disposal of municipal waste and sludge, various heavy metals continue to accumulate through the food chain, ultimately threatening human health and life. As an important transport medium of heavy metals, food plays an important link between heavy metals and human health. Among the heavy metals monitored by most institutions in the world, zinc, cadmium, lead, copper, and mercury are the most common typical heavy metals in food. According to the World Health Organization, lead, mercury and cadmium are the most toxic heavy metals and can cause liver and kidney failure, lung damage, and brain death. Although appropriate concentrations of copper and zinc in the body are beneficial to human health, excessive intake of copper and zinc can lead to mental dementia, liver failure, iron deficiency anemia, acute poisoning and even death. Recent studies have shown that the coexistence of multiple heavy metals, especially zinc, cadmium, lead, copper, and mercury, can induce synergistic and additive toxicological effects in humans and animals. With the increasingly serious problems caused by multiple heavy metals in the environment and food, it is urgent to develop a rapid, sensitive and simple method for the simultaneous detection of multiple heavy metal ions.

At present, the main methods used to detect heavy metal ions are atomic fluorescence spectrometry, atomic absorption spectrometry, inductively coupled plasma mass spectrometry and so on. Problems and defects of the prior art: Although the above-mentioned methods have good selectivity and high sensitivity, the equipment required by these methods is expensive, the equipment is bulky, not conducive to carrying, and the preparation of samples takes a long time, The equipment is complicated to operate, requires professional detection, and cannot be used for real-time online detection of heavy metal ions. Electrochemical stripping voltammetry, due to its advantages of high sensitivity, simple operation, low cost, low detection limit, and fast response, can overcome the problems encountered by traditional techniques and is a promising application for A method for the detection of trace heavy metal ions. Among various electrochemical stripping voltammetry methods, square wave anode stripping voltammetry has higher sensitivity and is more suitable for the detection of heavy metal ions.

When square wave anodic stripping voltammetry detects heavy metal ions, the key to its performance depends on the modified electrode material. At present, the commonly used electrode materials are multi-walled carbon nanotubes, metal nano-ions, metal oxides, etc. However, the sensors prepared based on the above materials have not obtained obvious performance for detecting heavy metal zinc, cadmium, lead, copper and mercury ions. improve. In order to improve the performance and practical application ability of the sensor, it is necessary to study and design nanomaterials with good adsorption performance, high specific surface area, good catalytic performance and electrical conductivity as modified electrode materials for the detection of heavy metal ions.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the object of the present invention is to provide a kind of electrochemical sensor based on fluorinated graphene/gold nanocage composite material, preparation method, and apply it to zinc, cadmium, lead, copper, mercury in agricultural products Simultaneous detection of ions.

The present invention realizes through the following technical solutions:

Provided is a gold nano-cages/fluorinated graphene composite material, comprising nano-scale gold nano-cages and fluorinated graphene nano-sheets, wherein: the gold nano-cages have a three-dimensional cage-like hollow porous shape, and the fluorinated graphene nano-sheets are folded and layered morphology, the gold nanocages are uniformly attached to the fluorinated graphene nanosheets.

According to the above scheme, the particle size of the gold nanocages is 30-60 nm.

Provided is an electrochemical sensor based on gold nano-cages/fluorinated graphene, comprising an electrode substrate and a gold nano-cages/fluorinated graphene composite material supported on the electrode substrate.

According to the above scheme, the electrode substrate is a glassy carbon electrode.

Provided is a preparation method of an electrochemical sensor based on gold nano-cages/fluorinated graphene, comprising the following steps: pre-treating an electrode substrate; drop-coating a gold nano-cages/fluorinated graphene composite material solution onto the pre-treated electrode substrate The surface, naturally dried, and repeated for many times, obtained the electrochemical sensor based on gold nanocages/fluorinated graphene.

According to the above scheme, the electrode substrate is a glassy carbon electrode, and the pretreatment is as follows: polishing the glassy carbon electrode, and then placing the electrode in a potassium ferricyanide solution to perform a cyclic voltammetry test, so that the cyclic voltammetry The redox peak potential difference of the curve is less than 70mV. Finally, the glassy carbon electrode is ultrasonically cleaned with ultrapure water and absolute ethanol, and the glassy carbon electrode is blown dry with nitrogen.

A preparation method of gold nano-cage/fluorinated graphene composite material is provided, comprising the following steps:

(1) The preparation of gold nanocages, the precursor chloroauric acid and hexamethylenetetramine were mixed, and then polyvinylpyrrolidone protective agent, silver nitrate crystal surface regulator, and ascorbic acid reducing agent were added in sequence, stirring, and static at room temperature. Set the reaction to obtain a solution of gold nanocages;

(2) the preparation of fluorinated graphene, the graphene is placed in a tube furnace, and air is removed to remove impurities, and then F ₂ is introduced to carry out a fluorination reaction to prepare fluorinated graphene;

(3) Preparation of gold nanocages/fluorinated graphene, fluorinated graphene is dispersed in ethanol-Nafion solution, ultrasonically dispersed, and then added to the gold nanocages solution of step (1) and ultrasonicated to obtain gold nanocages/fluorinated graphite vinyl composites.

According to the above scheme, the reaction time at room temperature is 22-26h.

According to the above scheme, the molar ratio of the chloroauric acid and hexamethylenetetramine is: 1:37-1:42.

According to the above scheme, the molar ratio of the chloroauric acid and the polyvinylpyrrolidone protective agent is 1:390-1:410.

The molar ratio of the chloroauric acid and the silver nitrate crystal face regulator is: 1:0.40-1:0.50, and the molar ratio of the chloroauric acid and the ascorbic acid reducing agent is: 1:1.60-1:1.80.

According to the above scheme, described step (2) is to place graphene in the reactor, then place it in the tube furnace, pass N ₂ to remove the air and impurities in the reactor, then pass F ₂ into the Carry out fluorination reaction at 165-185 ℃ for 1-2 hours, wherein the atmosphere is F ₂ /N ₂ (1:4-1:2, v/v), finally degassing to remove unreacted gas, and cooling to obtain graphite fluoride ene.

According to the above scheme, in the preparation of the fluorinated graphene dispersion: the mass fraction of Nafion in the ethanol-Nafion solution is 0.2-0.5 wt.%, and the ultrasonic dispersion time is 15-25 min.

According to the above scheme, the volume ratio of the fluorinated graphene solution and the gold nanocage solution is 3:1-4:1, and the ultrasonic time after adding the gold nanocage is 25-35min.

Provided is a method for synchronously detecting zinc, cadmium, lead, copper, and mercury ions in agricultural products. As the working electrode, the silver/silver chloride electrode is the counter electrode, and the platinum column electrode is the auxiliary electrode. Based on the three-electrode system, square wave anodic stripping voltammetry is used to measure the solution containing zinc, cadmium, lead, copper and mercury ions. Scanning is performed, wherein: the deposition potential is: -1.15V--1.55V, and the deposition time is 120-160s. Record the square wave anode stripping voltammetric peak current change, according to the corresponding square wave anode stripping voltammetry characteristic peak-to-peak current density and zinc, cadmium, lead, copper, mercury ion concentration of each peak current density-heavy metal ion concentration linear relationship curve, respectively Calculate the content of zinc, cadmium, lead, copper and mercury ions.

According to the above scheme, the electrolyte solution is 0.05-0.15M acetate buffer with pH value of 4.0-6.0.

According to the above scheme, the scanning window is -1.3V-0.6V.

According to the above scheme, the peak-to-peak current density of the square-wave anode stripping voltammetry characteristic peak-to-peak current density and the concentration of zinc, cadmium, lead, copper, and mercury ions are obtained as follows: The amperometric method scans standard solutions with different concentrations of zinc, cadmium, lead, copper, and mercury ions, and records the current changes to obtain the corresponding characteristic anodic stripping voltammetry peaks under standard solutions with different concentrations of zinc, cadmium, lead, copper, and mercury. The peak current density-heavy metal ion concentration linear relationship curves of zinc, cadmium, lead, copper, and mercury ion concentrations and their corresponding characteristic peak-to-peak current densities were obtained by fitting respectively.

Beneficial effects of the present invention:

① The gold nano-cages/fluorinated graphene composite material provided by the present invention has excellent properties such as large specific surface area, good catalytic activity, strong adsorption capacity, etc., wherein the fluorinated graphene in the gold nano-cages/fluorinated graphene has fast electron The characteristics of transport rate, large specific surface area and easy modification, and due to the introduction of C-F bonds by fluorination, the negative charge of fluorinated graphene is enhanced, thereby enhancing the adsorption capacity for cations; the gold nanocages have good catalytic activity and The adsorption performance of heavy metal ions is good, and the gold nano-cages are evenly dispersed on the fluorinated graphene, so that the specific surface area of the composite material is large, and the electron transfer rate is good, and the gold nano-cages/fluorinated graphene composite material of the present invention is It can combine the excellent properties of the two. Based on the synergistic effect of fluorinated graphene and gold nanocages, it has excellent electrochemical properties, which is of great benefit to improve the sensitivity of heavy metal detection. It can be used for heavy metals such as zinc, cadmium, lead, copper, High sensitivity detection of mercury ions.

^②The electrochemical sensor can realize high ^- sensitivity ^synchronous detection of heavy metal zinc, cadmium, lead, copper and mercury ions. They are 0.08, 0.09, 0.05, 0.19, 0.01 μg/L, respectively, and the linear ranges are 6-7000, 4-6000, 6-5000, 4-4000, 6-5000 μg/L, respectively. Compared with other methods for detecting heavy metal zinc, cadmium, lead, copper and mercury ions, the electrochemical sensor has the advantages of wide detection linear range, high detection sensitivity, low detection limit, good selectivity, reproducibility and reproducibility and response. The advantage of fast performance.

③ The electrochemical sensor can be applied to detect heavy metal zinc, cadmium, lead, copper and mercury ions in actual agricultural products (such as peanuts, rape moss, and tea).

Description of drawings

Figure 1 is (A) XRD pattern of FGP, AuNCs/FG; (B) XPS full spectrum of FGP, AuNCs/FG; high-resolution XPS spectrum of each element in AuNCs/FG: C 1s (C), F 1s (D), Au 4f (E). The crystal structure of the composites was determined by XRD characterization. In Figure 1A, the peaks of FGP at 14.54°, 29.08° and 41.06° correspond to the (001), (002) and (100) crystal plane diffraction peaks of FGP standard card (JCPDS 30-0476). The diffraction peaks of AuNCs/FG at 38.50°, 44.67°, 65.13°, 78.35° and 85.78° are consistent with those of AuNC standard card (JCPDS 04-0784) (111), (200), (220), (311) and ( 222) The diffraction peaks of the crystal planes are consistent. The XRD characterization results showed that the AuNCs/FG composites were successfully prepared, and no other impurity peaks appeared, indicating that the prepared AuNCs/FG had high purity. The chemical composition and electronic structure of AuNCs/FG were investigated by XPS method in Figure 1B. In FGP, we find that the peak of C1s is located at 284.6 eV, the peak of O 1s is located at 532.7 eV, and the peak of F 1 is located at 688.7 eV. In AuNCs/FG, a new peak appeared at 86.2 eV for Au 4f, indicating that AuNCs were successfully loaded onto FGP. The XPS characterization results were consistent with the results of FGP and AuNCs reported in the literature. Figure 1C-E show the high-resolution XPS spectra of C1s, F1s, and Au4f, respectively. From the C1s spectrum (Fig. 1C), it can be found that the six fitted peaks are located at 292.1eV, 290.3eV, 287.9eV, 286.2eV, 285.2eV and 284.6eV, corresponding to -CF ₂ , CF, C=O, CO, The chemical groups CC and C=C. From the F1s spectrum (Fig. 1D), it is clear that there are two different bond types: CF bond (689.0 eV) and -CF2 bond (690.1 eV). The Au4f spectrum (Fig. 1E) shows two peaks at 87.2 eV and 83.7 eV, corresponding to the Au4f5/2 and Au4f7/2 orbitals, respectively.

In conclusion, XRD and XPS characterizations demonstrated that gold nanocages/fluorinated graphene (AuNCs/FG) nanocomposites were successfully fabricated.

Figure 2 shows the SEM images of (A) FGP, (B) AuNCs, (C) AuNCs/FG; (D) high-resolution SEM images of AuNCs/FG; (E) AuNCs/FG, (F) C, (G) )F, (H) Elemental mapping of Au. The morphologies of FGP, AuNCs and AuNCs/FG were investigated by field emission scanning electron microscopy (SEM). In Figure 2A, the FGP has a wrinkled, multilayered filamentary morphology. In Figure 2B, the AuNCs were found to be uniformly distributed hollow polygonal cage-like morphology with a particle size of about 50 nm. Figure 2C and Figure 2D are the low-magnification SEM images and high-magnification SEM images of the AuNCs/FG nanocomposite, respectively, and it can be clearly seen that the AuNCs are uniformly distributed on the FGP. The distribution of AuNCs/FG was investigated by elemental mapping characterization. Different colors represent C, F and Au, respectively (Fig. 2F-H). It can be seen from the figure that C, F and Au are uniformly distributed in Figure 2E, which means that AuNCs and FGPs are successfully composited, and AuNCs/FG composites are successfully prepared.

Figure 3 is a transmission electron microscope (TEM) image of (A) AuNCs, (C) AuNCs/FG; (B) AuNCs, (D) high-resolution transmission electron microscope image of AuNCs/FG. The morphologies of AuNCs and AuNCs/FG were further characterized by transmission electron microscopy and high-resolution transmission electron microscopy. The TEM characterization results were consistent with the SEM characterization results. It can be seen from Fig. 3A that the AuNCs have good homogeneity, and the corresponding high-resolution transmission electron microscope (Fig. 3B) shows that the morphology is a three-dimensional cage-like hollow porous morphology with a particle size of about 50 nm. The TEM image of the AuNCs/FG in Figure 3C showed that the FG nanosheets were in wrinkled and layered morphology, and the AuNCs were uniformly attached to the FG. The corresponding HRTEM characterization of AuNCs/FG (Fig. 3D) further showed that AuNCs were successfully loaded onto FG and the hollow porous structure of AuNCs remained intact.

Figure 4 is a comparison diagram of the square-wave anode stripping voltammetric response of four different modified electrodes to the same concentrations of Zn ²⁺ , Cd ²⁺ , Pb2+, Cu ²⁺ and Hg ²⁺ , among which graphene GP(a), fluorinated graphite Alkene FGP(b), gold nanocages AuNC(c) and AuNCs/FG(d); test conditions are: the same concentration content in 20mL 0.1M NaAc-HAc solution (pH 5.0), the deposition potential is -1.25V, the deposition The time is 140s, and the scanning potential range: -1.3V-0.6V.

As shown in Figure 4, among the four modified electrodes, GP(a), FGP(b), AuNC(c), and AuNCs/FG(d), the AuNCs/FG sensor had the highest response current density to five heavy metal ions. Compared with the other three modified electrodes, the response current densities of AuNCs/FG of Zn ²⁺ (378μA cm ^-2 ), Cd ²⁺ (1614μAcm ^-2 ), Pb ²⁺ (2012μAcm ^-2 ), Cu ²⁺ (2480μA cm -2 ) ^-2 ), and Hg ²⁺ (1969μAcm ^-2 ) max. The results showed that AuNC significantly promoted the catalytic performance of FGP/AuNC composites. The FGP/AuNC sensor has the best catalytic performance.

Figure 5 is (A) the square wave anode stripping voltammetry response of the electrochemical sensor based on FGP/AuNCs for simultaneous detection of five metal ions; simultaneous detection of Zn ²⁺ (B), Cd ²⁺ (C), Pb ²⁺ (D) Linear graphs of five ions of Cu ²⁺ (E) and Hg ²⁺ (F).

The electrochemical detection performance of AuNCs/FG sensor for Zn ²⁺ , Cd ²⁺ , Pb ²⁺ , Cu ²⁺ , Hg ²⁺ was evaluated by square wave anodic stripping voltammetry. In Figure 5A, the potentials -1.10±0.01V, -0.77±0.03V, -0.50±0.02V, -0.01±0.01V, -0.31±0.02V are attributed to Zn ²⁺ , Cd ²⁺ , Pb ²⁺ , respectively , Cu ²⁺ , Hg ²⁺ characteristic peak potential. Furthermore, the response current density increased with the increase of heavy metal ion concentration (from 1 μg/L to 8000 μg/L). The calibration curves of Zn ²⁺ (Fig. 5b), Cd ²⁺ (Fig. 5c), Pb ²⁺ (Fig. 5d), Cu ²⁺ (Fig. 5e), and Hg ²⁺ (Fig. 5f), respectively, show good linearity relationship, the abscissa x (mg/L) is the heavy metal concentration, and the corresponding ordinate y (mA cm ^-2 ) is the maximum stripping peak current density. The detection linear ranges of AuNCs/FG sensor for simultaneous electrochemical detection of five heavy metals (Zn ²⁺ , Cd ²⁺ , Pb ²⁺ , Cu ²⁺ , and Hg ²⁺ ) are 6-7000μg/L, 4-6000μg/L, respectively , 6-5000μg/L, 4-4000μg/L, and 6-5000μg/L; sensitivities were 0.17, 0.51, 0.68, 0.89, and 0.51μAμg ^-1 L ^-1 cm ^-2 ; detection limits were 0.08, 0.09, respectively , 0.05, 0.19, and 0.01 μg/L. Compared with the reported literature, the electrochemical sensor of the present invention has lower detection limit, wider linear range and better correlation.

Detailed ways

Example 1

(1) Preparation of gold nanocages, 6 mL of 0.05M hexamethylenetetramine and 6 mL of 1.25 mM chloroauric acid were mixed in a 50 mL beaker. Then, 6 mL of 0.50 M polyvinylpyrrolidone, 0.57 mg of silver nitrate and 2.35 mg of ascorbic acid were sequentially added to the mixed solution and stirred for 60 s. Finally, it was allowed to stand at room temperature for 24 hours to obtain a solution of gold nanocages.

( ₂ ) Preparation of fluorinated graphene, 200 mg of graphene was placed in a reactor, and N was introduced to remove air and impurities in the reactor. Then, F ₂ was introduced, and the fluorination reaction was carried out at 180° C. for 1 hour, wherein the atmosphere was F ₂ /N ₂ (1:3, v/v), and finally the unreacted gas was removed by degassing, and the graphite fluoride was obtained by cooling. ene.

(3) Preparation of gold nanocages/fluorinated graphene, 3 mg of fluorinated graphene was dispersed in 500 μL of ethanol-Nafion solution (wherein in the ethanol-Nafion solution, the mass fraction of Nafion was 0.5% wt.%), After ultrasonic dispersion for 20 min, 125 μL of gold nanocage was added and ultrasonicated for 30 min to obtain the gold nanocage/fluorinated graphene composite AuNCs/FG.

Preparation method of gold nanocages/fluorinated graphene modified electrode

(1) Polish the glassy carbon electrode with 0.3 and 0.05 μm alumina slurry in turn, then place the electrode in a 5 mmol/L potassium ferricyanide solution and scan at -0.2 to 0.6 V potential to oxidize The reduction peak potential difference is less than 70mV, and finally the glassy carbon electrode is ultrasonically cleaned with ultrapure water and absolute ethanol, and the glassy carbon electrode is blown dry with nitrogen;

(2) Use a pipette to take 3 μL of the gold nanocages/fluorinated graphene composite material and apply it to the surface of the polished glassy carbon electrode, and then dry it naturally. alkene-modified electrodes.

Simultaneous detection of five heavy metal ions (Zn ²⁺ , Cd ²⁺ , Pb ²⁺ , Cu ²⁺ , and Hg ²⁺ )

[1] Drawing of standard curve:

(1) Use an electrochemical workstation to measure with a three-electrode system, using the above-mentioned fluorinated graphene/gold nanocage modified electrode as the working electrode, the silver/silver chloride electrode as the counter electrode, and the platinum column electrode as the auxiliary electrode. Square-wave anodic stripping voltammetry was performed on standard solutions of 5 heavy metal ions ranging from 1 μg/L to 8000 μg/L in 0.1 mol/L acetate buffer, and the current changes were recorded (Fig. 5A). The enrichment voltage was - 1.25V, the enrichment time is set to 140s, and the scanning window is -1.3V-0.6V. According to the anodic stripping voltammetric response peak current density and the concentration of heavy metal ions, the working curve is drawn, as shown in Figure 5B. From the corresponding linear The curve (Fig. 5B) can be calculated to obtain the detection linear range of 5 heavy metals (Zn ²⁺ , Cd ²⁺ , Pb ²⁺ , Cu ²⁺ , and Hg ²⁺ ) in the simultaneous electrochemical detection of the AuNCs/FG modified electrode, which are 6– 7000μg/L, 4-6000μg/L, 6-500μg/L, 0 4-4000μg/L, and 6-5000μg/L; Sensitivity 0.17, 0.51, 0.68, 0.89, and 0.51μAμg ^-1 L ^-1 cm, respectively ^-2 ; detection limits were 0.08, 0.09, 0.05, 0.19, and 0.01 μg/L, respectively.

[2] Detection of actual sample solution:

The actual sample solution was used instead of the standard solution for quantitative detection.

(1) Sample preparation, put 0.5g of ground samples (tea leaves, rape moss, peanuts) into microwave digestion apparatus respectively, add 5mL mixed solution of nitric acid and hydrogen peroxide (v/v=1:3), seal After that, the temperature was set to 180°C for 30 minutes. It was then removed and continued to heat until nearly dry, and the remaining digestion solution was made up to 10 mL with water.

(2) Each heavy metal ion was added to the digestion solution of the actual sample according to the standard value of 2 mg/L. In order to verify the reliability of the sensor, the actual samples and their spiked samples were subjected to AuNCs/FG electrochemical sensing detection, and ICP-MS and AFS were used to compare and verify the samples of peanut, rape moss and tea. The experimental results are shown in Table 2. The relative standard deviation of the sensor detection results is 0.46%-5.26%, and the recovery rate reaches 93.50%-105.00%. In addition, the detection results of AuNCs/FG modified electrodes are in good agreement with those of ICP-MS and AFS methods. Therefore, the proposed electrochemical method can simultaneously detect Zn ²⁺ , Cd ²⁺ , Pb ²⁺ , Cu ²⁺ and Hg ²⁺ in real samples.

Table 2 AuNCs/FG electrochemical sensor spiked recovery detection comparison between actual samples and classical methods (n=3)

Nd: not detected

a: Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

b: Atomic Fluorescence Spectroscopy (AFS)

c: Relative standard deviation (%) calculated from the experimental data of 3 separate tests

Claims (10)

1. the method for zinc, cadmium, lead, copper, mercury ion in electrochemical synchronous detection, is characterized in that: described method is: with gold nano cage/fluorinated graphene modified electrode as working electrode, silver/chlorinated The silver electrode is the counter electrode, and the platinum column electrode is the auxiliary electrode. Based on the three-electrode system, the solution to be tested containing zinc, cadmium, lead, copper and mercury ions is scanned by square wave anodic stripping voltammetry, wherein: the deposition potential is : -1.15V～-1.55V, deposition time is 120～160s, record the change of square wave anode stripping voltammetric peak current, according to the corresponding square wave anode stripping voltammetry peak current and zinc, cadmium, lead, copper, mercury ion concentration The linear relationship curve of each peak current-heavy metal ion concentration was calculated, and the contents of zinc, cadmium, lead, copper and mercury ions were calculated respectively; The gold nanocage/fluorinated graphene modified electrode includes an electrode substrate and a gold nanocage/fluorinated graphene composite material supported on the electrode substrate; the gold nanocage/fluorinated graphene composite material includes nanoscale gold Nanocages and fluorinated graphene nanosheets, wherein: gold nanocages have a three-dimensional cage-like hollow porous morphology, fluorinated graphene nanosheets are folded and layered, and gold nanocages are uniformly attached to the fluorinated graphene nanosheets. 2 . The method according to claim 1 , wherein the particle size of the gold nanocages is 30-60 nm. 3 . 3. The method according to claim 1, wherein the electrode substrate is a glassy carbon electrode. 4. method according to claim 1, is characterized in that: the preparation method of described gold nano-cage/fluorinated graphene composite material, comprises the following steps: (1) The preparation of gold nanocages, the precursor chloroauric acid and hexamethylenetetramine were mixed, and then polyvinylpyrrolidone protective agent, silver nitrate crystal surface regulator, and ascorbic acid reducing agent were added in sequence, stirring, and static at room temperature. Set the reaction to obtain a solution of gold nanocages; (2) the preparation of fluorinated graphene, the graphene is placed in a tube furnace, and air is removed to remove impurities, and then F ₂ is introduced to carry out a fluorination reaction to prepare fluorinated graphene; (3) Preparation of gold nanocage/fluorinated graphene, fluorinated graphene is dispersed in ethanol-Nafion solution, and ultrasonically dispersed to obtain fluorinated graphene dispersion; then the gold nanocage of step (1) is added, and ultrasonically obtained Gold nanocages/fluorinated graphene composites. 5. method according to claim 4, is characterized in that: the reaction time of leaving standstill at room temperature is 22-26h; The mol ratio of described chloroauric acid and hexamethylenetetramine is: 1:37-1:42; The molar ratio of the chloroauric acid and the polyvinylpyrrolidone protective agent is 1:390-1:410; the molar ratio of the chloroauric acid and the silver nitrate crystal face regulator is: 1:0.40-1:0.50, the The molar ratio of chloroauric acid and ascorbic acid reducing agent is: 1:1.60-1:1.80. 6. method according to claim 4 is characterized in that: described step (2) is to place Graphene in the reactor, then be placed in the tube furnace, pass N ₂ remove the air in the reactor and impurities, then, F ₂ was introduced, and the fluorination reaction was carried out at 165-185 ° C for 1-2 hours, wherein the atmosphere was F ₂ /N ₂ (1:4-1:2, v/v), and finally degassed Unreacted gas is removed and cooled to obtain fluorinated graphene. 7. method according to claim 4 is characterized in that: in the preparation of described fluorinated graphene dispersion liquid: the mass fraction of Nafion in ethanol-Nafion solution is 0.2-0.5wt.%, and ultrasonic dispersion time is 15- 25min. 8. method according to claim 4 is characterized in that: the volume ratio of described fluorinated graphene dispersion liquid and gold nano-cage solution is 3:1-4:1, and the ultrasonic time after adding gold nano-cage is 25-35min. 9. The method according to claim 1, wherein: the electrolyte solution is 0.05-0.15M acetate buffer with a pH value of 4.0-6.0; the scanning window is -1.3V-0.6 V. 10. The method according to claim 1, characterized in that: each peak current-heavy metal ion concentration linear relationship between the square wave anode stripping voltammetry characteristic peak-to-peak current density and zinc, cadmium, lead, copper, and mercury ion concentrations The curve is obtained by scanning the standard solutions with different concentrations of zinc, cadmium, lead, copper and mercury ions by square wave anodic stripping voltammetry, and recording the current changes to obtain standard solutions with different concentrations of zinc, cadmium, lead, copper and mercury. The peak current density of each corresponding characteristic anodic stripping voltammetric peak current density under the corresponding characteristic, and the peak current density-heavy metal ion concentration linear relationship curve of zinc, cadmium, lead, copper, and mercury ion concentrations and their corresponding characteristic peak-to-peak current densities was obtained by fitting respectively.

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