Nitrite electrochemical sensor based on graphene oxide and polyurea composite material as well as preparation method and application of nitrite electrochemical sensor

Abstract

The invention discloses a nitrite electrochemical sensor based on a graphene oxide and polyurea composite material and a preparation method and application thereof, and belongs to the field of electrochemical method detection, the preparation method comprises the following steps: uniformly dispensing a graphene oxide suspension on the surface of a glassy carbon electrode, and drying to obtain a graphene oxide modified glassy carbon electrode GO / GCE; immersing the obtained graphene oxide modified glassy carbon electrode into an electrolytic tank containing a urea solution for electropolymerization, and scanning by using a CV method to prepare Purea / GO / GCE; a saturated calomel electrode is used as a reference electrode, a platinum wire electrode is used as a counter electrode, and Purea / GO / GCE is used as a working electrode, so that the nitrite electrochemical sensor of a three-electrode system is constructed. The nitrite electrochemical sensor prepared by the invention is more accurate and sensitive in nitrite detection, the linear detection range is 0.002-6.0 mmol / L, and the detection limit is 1 * 10 <-4 > mmol / L.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemical detection, in particular to a nitrite electrochemical sensor based on graphene oxide and polyurea composite material, and a preparation method and application thereof. Background Art

[0002] Nitrite is a common food preservative, additive and corrosion inhibitor, which is widely present in drinking water, food and environmental systems. The misuse and overuse of inorganic fertilizers can lead to excessive nitrite content in water and agricultural products. Excessive nitrite is not only harmful to the environment, but also to human health. Nitrite is used as an official food preservative, which can inhibit the growth of harmful bacteria such as Clostridium botulinum. In addition, nitrite has also been developed as an important color preservative. It is added to meat products in the form of sodium or potassium salts and can react with myoglobin to preserve the color and flavor of fresh meat. At the same time, nitrite can interfere with the body's oxygen transport system and interact with amines in the stomach to produce carcinogenic nitrosamines, which is particularly harmful to pregnant women and infants. The World Health Organization (WHO) has included nitrite in the list of carcinogens, and most countries have enacted laws and regulations to limit and control the use of nitrite in food and industrial production. These measures have alleviated people's concerns about the hazards of nitrite to a certain extent, but the best solution is to establish a complete nitrite monitoring and control system. In addition, according to the World Health Organization (WHO), the nitrite concentration limit in drinking water is 3 mg / L.

[0003] As people's awareness of environmental protection and food safety increases, the detection of nitrite has become an important item in environmental testing and food analysis.

[0004] In view of this, it is necessary to develop a method for detecting nitrite concentration that is highly sensitive, stable, simple and low-cost. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a nitrite electrochemical sensor based on graphene oxide and polyurea composite material, and a preparation method and application thereof. The prepared nitrite electrochemical sensor is more accurate and sensitive in detecting nitrite.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for preparing a nitrite electrochemical sensor based on a graphene oxide and polyurea composite material comprises the following steps: Step 1, evenly drop a graphene oxide suspension on the surface of a glassy carbon electrode, and then dry it to obtain a graphene oxide modified glassy carbon electrode GO / GCE; Step 2, immersing the graphene oxide modified glassy carbon electrode obtained in step 1 into an electrolytic cell containing a urea solution for electropolymerization, and scanning by CV method to prepare Purea / GO / GCE; Step 3, a nitrite electrochemical sensor with a three-electrode system was constructed using a saturated calomel electrode as a reference electrode, a platinum wire electrode as a counter electrode, and Purea / GO / GCE as a working electrode.

[0007] A further improvement of the technical solution of the present invention is that in step 1, the modification amount of the graphene oxide is 10 μL.

[0008] A further improvement of the technical solution of the present invention is that in step 2, when the electropolymerization is carried out by the CV method, the potential range is -1.1V~1.8V, the scanning rate is 0.1V / s, and the scanning is 30 circles.

[0009] A further improvement of the technical solution of the present invention is that in step 2, the concentration of the urea solution is 2.0 mmol / L.

[0010] A further improvement of the technical solution of the present invention is that the preparation method also includes the preparation of a graphene oxide suspension, specifically: 0.01 g of GO powder is weighed with an analytical balance and placed in an electrolytic cell, 10.0 mL of deionized water is added to the electrolytic cell and mixed evenly, and after ultrasonic treatment for 60 minutes, a graphene oxide suspension is obtained for use.

[0011] A further improvement of the technical solution of the present invention is that the preparation method also includes pretreatment of GCE, specifically: wiping the surface of the bare GCE clean, polishing it in a clockwise direction with 1.0 μm, 0.30 μm, and 0.050 μm alumina powders, respectively, polishing it to a mirror surface, washing it with ultrapure water until there are no obvious impurities, and then placing it in a beaker, and then adding deionized water-anhydrous ethanol-deionized water to the beaker in sequence, ultrasonicating for 5 minutes respectively, and taking it out to obtain the treated GCE.

[0012] The preparation method is used to prepare a nitrite electrochemical sensor based on a graphene oxide and polyurea composite material.

[0013] Application of the nitrite electrochemical sensor based on graphene oxide and polyurea composite material prepared by the preparation method in detecting nitrite concentration.

[0014] A further improvement of the technical solution of the present invention is that the nitrite electrochemical sensor based on graphene oxide and polyurea composite material is applied to direct real-time detection of nitrite in liquid phase.

[0015] A further improvement of the technical solution of the present invention is that: in specific application, the detection steps are: (1) The constructed nitrite electrochemical sensor was placed in a 0.1 mol / L phosphate buffer solution with a pH value of 3.0; (2) Add the water sample containing nitrite to be tested into the base solution; (3) Determination of the oxidation peak current value i of nitrite by DPV method p ; Observe and record the DPV curve p value, and then i p The value is substituted into the linear regression equation to calculate the nitrite content in the water sample to be tested; the specific parameters are set as: potential range 0.4~1.0V, amplitude 50mV, pulse width 0.2s, sampling width 0.0167, pulse period 0.5s, and standing time 2s.

[0016] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is: 1. The present invention prepares Purea / GO / GCE, wherein graphene oxide has good stability and can increase the specific surface area of ​​the electrode and improve the adsorption efficiency of the electrode when attached to the electrode; urea also has excellent conductivity, so graphene oxide and urea are co-modified on the electrode surface, and the synergistic effect of the two increases the number of active sites on the electrode and improves the electrocatalytic performance of the working electrode for nitrite.

[0017] 2. The present invention uses Purea / GO / GCE as the working electrode, adopts GO modification amount of 10 μL, electrolyte pH of 3, enrichment stirring time of 120 s, Purea modification amount of 30 cycles, and constructs a nitrite electrochemical sensor. The linear detection range of the nitrite electrochemical sensor is 0.002~6.0mmol / L, and the detection limit is 1×10 -4 mmol / L, with a wide linear range and a low detection limit.

[0018] 3. The nitrite electrochemical sensor constructed by the present invention was used to measure nitrite at the same concentration in parallel 12 times, and the relative standard deviation was 3.44%.

[0019] 4. The nitrite electrochemical sensor provided by the present invention is simple to prepare and operate, has low cost, and has good stability and selectivity, and is expected to be applied to the determination of nitrite in actual samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work. Figure 1 is a flow chart of the preparation method provided by the present invention; Figure 2 are SEM images of GCE, GO / GE, and Purea / GO / GCE in the embodiments of the present invention; Among them, a-SEM image of GCE; b- SEM image of GO / GCE; c-SEM image of Purea / GO / GCE; Figure 3 CV graphs of Purea / GO / GCE in different electrolytes in an embodiment of the present invention; Among them, a-blank 0.1mol / L PBS electrolyte; b-containing 1.00×10 -4 mol / L nitrite in 0.1 mol / L PBS electrolyte; Figure 4 CV diagrams of nitrite on different electrodes in the embodiment of the present invention; Among them, a-Purea / GCE; b-GCE; c-GO / GCE; d-Purea / GO / GCE; Figure 5 is a standard curve diagram of nitrite in an embodiment of the present invention; Figure 6 is a DPV diagram of different concentrations of nitrite in an embodiment of the present invention; Among them, the nitrite concentrations of the DPV curve from top to bottom are 0.002, 0.04, 0.1, 0.2, 0.4, 0.8, 1.0, 2.0, 4.0, and 6.0 mmol / L. DETAILED DESCRIPTION

[0021] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatus.

[0022] The present invention is further described in detail below with reference to the accompanying drawings and embodiments: like Figure 1 As shown, a method for preparing a nitrite electrochemical sensor based on a graphene oxide and polyurea composite material comprises the following steps: (1) Preparation of graphene oxide suspension: Specifically, 0.01 g of GO powder was weighed using an analytical balance and placed in an electrolytic cell. 10.0 mL of deionized water was then added to the electrolytic cell and mixed evenly. After ultrasonic treatment for 60 min, a graphene oxide suspension was obtained for use.

[0023] (2) Pretreatment of GCE: Wipe the surface of the bare GCE clean, polish it in a clockwise direction with 1.0 μm, 0.30 μm, and 0.050 μm alumina powders, respectively. After polishing to a mirror surface, wash it with ultrapure water until there are no obvious impurities. Then place it in a beaker, and then add deionized water, anhydrous ethanol, and deionized water to the beaker in sequence, and ultrasonicate for 5 min each. Take it out to obtain the treated GCE.

[0024] (3) Preparation of GO / GCE: Ensure that the surface of the pretreated GCE remains dry and clean, and use a cleaned microsyringe to transfer a certain amount of graphene oxide suspension. The graphene oxide in the graphene oxide suspension must remain suspended to prevent it from precipitating. Use the drop coating method to drop graphene oxide on the surface of GCE, ensuring that the graphene oxide completely covers the electrode surface, and wait for the water to completely evaporate to form a graphene oxide film, and then GO / GCE can be obtained.

[0025] (4) Preparation of Purea / GO / GCE: The prepared GO / GC electrode was immersed in an electrolytic cell containing 2.0 mmol / L urea solution for electropolymerization. The CV method was used for scanning in the range of -1.1 V to 1.8 V, at a scanning rate of 0.1 V / s, for 30 cycles to prepare Purea / GO / GCE. (5) A three-electrode system of nitrite electrochemical sensor was constructed using saturated calomel electrode as the reference electrode, platinum wire electrode as the counter electrode, and Purea / GO / GCE as the working electrode.

[0026] Purea / GCE was also prepared in the embodiment of the present invention. The prepared GCE was placed in an electrolytic cell containing 2.0 mmol / L urea solution for electropolymerization and scanned by CV method with a potential range of -1.1 V to 1.8 V and a scanning rate of 0.1 V / s. After 20 cycles of scanning, the preparation of Purea / GCE was completed.

[0027] Specifically, the instruments used include: JSM-7900F field emission scanning electron microscope, CHI660c electrochemical workstation, 85-2 digital display constant temperature magnetic stirrer, pHs-3C acidity meter, FA2204B electronic balance, laboratory pure water treatment system, HN6-180 ultrasonic cleaner, 1-100μL micropipette, KH-A infrared lamp, etc.

[0028] An electrochemical sensor is constructed using a three-electrode system, an electrochemical workstation, an electrolytic cell and a display to determine nitrite.

[0029] Three-electrode system: the reference electrode is a saturated calomel electrode; the counter electrode is a platinum wire electrode; the working electrode is a glassy carbon electrode (GCE) or a graphene oxide modified glassy carbon electrode (GO / GCE) or a polyurea modified glassy carbon electrode (Purea / GCE) or a polyurea / graphene oxide modified glassy carbon electrode (Purea / GO / GCE).

[0030] Note: Electrode in English is Electrode, and E is the abbreviation of electrode in English, that is, E in the present invention represents electrode.

[0031] Main reagents: urea, potassium ferrocyanide, sodium nitrite, 0.1 mol / L phosphate buffer solution (PBS) (prepared by yourself using 0.1 mol / L sodium dihydrogen phosphate and disodium hydrogen phosphate).

[0032] The application of nitrite electrochemical sensor based on graphene oxide and polyurea composite in detecting nitrite concentration.

[0033] The nitrite electrochemical sensor based on graphene oxide and polyurea composite material is applied to the direct real-time detection of nitrite in liquid phase. The detection steps are as follows: (1) The constructed nitrite electrochemical sensor was placed in a 0.1 mol / L, pH 3.0 phosphate buffer solution; (2) Add the water sample containing nitrite to be tested into the base solution; (3) Determination of the oxidation peak current value i of nitrite by DPV method p ; Observe and record the i near 0.80V on the DPV curve p value, and then i p The value is substituted into the linear regression equation to calculate the nitrite content in the water sample to be tested. The specific parameters are set as follows: potential range 0.4~1.0V, amplitude 50mV, pulse width 0.2s, sampling width 0.0167, pulse period 0.5s, and standing time 2s.

[0034] 1. Characterization of modified electrodes 1.1 SEM characterization of working electrode Scanning electron microscopy was performed on the three working electrodes: GCE, GO / GCE, and Purea / GO / GCE. Figure 2 Comparing SEM characterization images a and b, it can be seen that GO is successfully modified on GCE, and comparing SEM characterization images b and c, it can be seen that Purea is successfully electropolymerized on GO / GCE.

[0035] 1.2 Electrochemical behavior of nitrite on different electrodes Using cyclic voltammetry, Purea / GO / GCE was tested in blank PBS electrolyte (c=0.1mol / L) and 1.00×10 -4 The scanning was carried out in 0.1 mol / L PBS electrolyte (pH = 3) containing mol / L nitrite. The CV curve scanning range was 0.4~1.2V and the scanning rate was 0.1V / s. Figure 3 shown.

[0036] Depend on Figure 3 It can be seen that CV curve b has an additional oxidation peak in the potential range of 0.8V~0.9V compared with CV curve a, which is caused by the oxidation reaction of nitrite on Purea / GO / GCE.

[0037] Cyclic voltammetry was used to study the electrochemical properties of GCE, GO / GCE, Purea / GCE, and Purea / GO / GCE in nitrite-containing PBS electrolyte (c=1.00×10 -4 mol / L, pH=3) in electrocatalytic performance, CV graphs are shown in Figure 4 shown.

[0038] Depend on Figure 4 It can be seen that the oxidation peak currents of curve b, curve a, curve c, and curve d increase successively near 0.8V, among which curve d has the most obvious oxidation peak compared with other curves, which indicates that under the joint action of GO and Purea, the catalytic performance is significantly enhanced. Therefore, Purea / GO / GCE has a more significant electrocatalytic effect on nitrite than other electrodes.

[0039] 2. Sensor performance test 2.1 Standard curve and detection limit The nitrite electrochemical sensor constructed by the present invention with Purea / GO / GCE as the working electrode was used to measure the nitrite standard solutions of different concentrations by differential pulse voltammetry (DPV), and the oxidation peak current value i was recorded. p , plotting the nitrite concentration c versus i p The standard curve of the value is as follows: Figure 5 , Figure 6 shown.

[0040] Depend on Figure 5 It can be seen that when the concentration of nitrite is 0.002 to 6.0 mmol / L, the nitrite concentration c and the peak current i p The values ​​are linearly related and conform to the linear equation i p(μA) = 4.3934c (mmol / L) + 0.5139, R = 0.9980, the detection limit is 1×10 -4 mmol / L.

[0041] according to Figure 6 It can be seen that i p The value increases with the increase of nitrite concentration.

[0042] 2.2 Precision The nitrite electrochemical sensor constructed by the present invention with Purea / GO / GCE as the working electrode is effective for nitrite with a concentration of 1.00×10 -4 mol / L nitrite was measured 12 times in parallel with the same electrode, and the relative standard deviation (RSD) was 3.44%, indicating that the sensor has high precision.

[0043] 2.3 Selectivity Under the optimal experimental conditions, the DPV method was used to study the selectivity of the nitrite electrochemical sensor constructed in the present invention with Purea / GO / GCE as the working electrode. -4 mol / L nitrite solution was added with different multiples of interfering substances for determination. Within the error range of ±5%, it can be concluded that: 100 times Mg 2+ 、Na + , Cl - 、SO4 2- , Ca 2+ PO4 3- , K + 、NO2 - and 20 times the Fe 2+ There was no interference with the determination of nitrite.

[0044] 2.4 Sample testing and spike recovery experiment A simulated water sample of nitrite was prepared, and the nitrite concentration therein was determined using the nitrite electrochemical sensor constructed by the present invention with Purea / GO / GCE as the working electrode. The experimental method is as follows: the peak current value of nitrite in the water sample is determined by the electrochemical sensor constructed by the present invention, and its concentration c1 is calculated using the standard curve. A certain volume of nitrite standard solution is added to the water sample to increase its concentration by Δc, and the concentration c2 of nitrite after the addition is obtained by the same operation as above. Finally, the nitrite concentration measured before and after the addition is calculated according to the formula The spike recovery was calculated and found to be 99% to 105%. The results are shown in Table 1.

[0045] Table 1 Spike recovery experiment

[0046]

[0047] In summary, the present invention uses Purea / GO / GCE as the working electrode, GO modification amount is 10 μL, the pH of the electrolyte is 3, the enrichment stirring time is 120s, and the Purea modification amount is 30 cycles to construct a nitrite electrochemical sensor. The linear detection range of the nitrite electrochemical sensor is 0.002~6.0mmol / L, and the detection limit is 1×10 -4 mmol / L, with a wide linear range and a low detection limit. The nitrite electrochemical sensor constructed by the present invention was used to parallelly measure nitrite at the same concentration for 12 times, and the relative standard deviation was 3.44%. The nitrite electrochemical sensor is simple to prepare and operate, low in cost, and has good stability and selectivity, and is expected to be applied to the determination of nitrite in actual samples.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a nitrite electrochemical sensor based on a graphene oxide and polyurea composite material, characterized in that: The following steps are involved: Step 1, evenly drop a graphene oxide suspension on the surface of a glassy carbon electrode, and then dry it to obtain a graphene oxide modified glassy carbon electrode GO / GCE; Step 2, immersing the graphene oxide modified glassy carbon electrode obtained in step 1 into an electrolytic cell containing a urea solution for electropolymerization, and scanning by CV method to prepare Purea / GO / GCE; Step 3, a nitrite electrochemical sensor with a three-electrode system was constructed using a saturated calomel electrode as a reference electrode, a platinum wire electrode as a counter electrode, and Purea / GO / GCE as a working electrode.

2. The preparation method according to claim 1, characterized in that: In step 1, the modification amount of graphene oxide is 10 μL.

3. The preparation method according to claim 1, characterized in that: In step 2, when scanning by CV method, the potential range is -1.1V~1.8V, the scanning rate is 0.1V / s, and the scanning is 30 cycles.

4. The preparation method according to claim 1, characterized in that: In step 2, the concentration of the urea solution is 2.0 mmol / L.

5. The preparation method according to claim 1, characterized in that: The preparation method also includes the preparation of graphene oxide suspension, specifically: weighing 0.01g of GO powder using an analytical balance and placing it in an electrolytic cell, then adding 10.0mL of deionized water to the electrolytic cell and mixing evenly, and ultrasonically treating for 60 minutes to obtain a graphene oxide suspension for use.

6. The preparation method according to claim 1, characterized in that: The preparation method also includes pretreatment of GCE, specifically: wiping the surface of the bare GCE clean, polishing it in a clockwise direction with 1.0 μm, 0.30 μm, and 0.050 μm alumina powders respectively, polishing it to a mirror surface, washing it with ultrapure water until there are no obvious impurities, and then placing it in a beaker, and then adding deionized water-anhydrous ethanol-deionized water to the beaker in sequence, ultrasonicating for 5 minutes respectively, and taking it out to obtain the treated GCE.

7. A nitrite electrochemical sensor based on a composite material of graphene oxide and polyurea prepared by the preparation method according to any one of claims 1 to 6.

8. Application of a nitrite electrochemical sensor based on graphene oxide and polyurea composite material prepared by the preparation method according to any one of claims 1 to 6 in detecting nitrite concentration.

9. The use according to claim 8, characterized in that: The nitrite electrochemical sensor based on graphene oxide and polyurea composite material is applied to direct real-time detection of nitrite in liquid phase.

10. The use according to claim 9, characterized in that: In specific applications, the detection steps are: (1) The constructed nitrite electrochemical sensor was placed in a 0.1 mol / L, pH 3.0 phosphate buffer solution; (2) Add the water sample containing nitrite to be tested into the base solution; (3) Determination of the oxidation peak current value i of nitrite by DPV method p ; Observe and record the i on the DPV curve p value, and then i p The value is substituted into the linear regression equation to calculate the nitrite content in the water sample to be tested; the specific parameters are set as: potential range 0.4~1.0V, amplitude 50mV, pulse width 0.2s, sampling width 0.0167, pulse period 0.5s, and standing time 2s.

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