Preparation method of anti-scaling electrode and application of anti-scaling electrode in residual chlorine electrochemical sensing

Abstract

The invention provides a preparation method of an anti-scaling electrode and application of the anti-scaling electrode in residual chlorine electrochemical sensing. The preparation method comprises the following steps: dispersing boron nitride powder into a phosphate buffer solution, centrifuging, and taking supernate to obtain a precursor; centrifuging the precursor again, taking lower-layer precipitate, adding water, and performing ultrasonic treatment to obtain a boron nitride nanosheet dispersion; centrifuging the graphene dispersion dispersed in the phosphate buffer solution, and taking supernate to obtain a graphene nanosheet dispersion; the graphene nanosheet dispersion and the boron nitride nanosheet dispersion are mixed, stirred and subjected to ultrasonic treatment, and a graphene-boron nitride composite film dispersion is obtained; and dispensing the graphene-boron nitride composite film dispersion on the surface of a gold electrode, drying and washing to obtain the graphene-boron nitride composite film modified gold electrode. When the designed composite membrane is used for residual chlorine electrochemical sensing, an enhanced electrochemical signal can be generated. Meanwhile, the generation of electrode scaling on the surface of the electrode can be effectively avoided, and long-term continuous electrochemical residual chlorine detection in a complex water body is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical sensing, and relates to a preparation method of an anti-scaling electrode and its application in residual chlorine electrochemical sensing, and can be specifically used for quantitatively monitoring the concentration of residual chlorine in complex water bodies. Background Technique

[0002] Chlorine has always been the most commonly used disinfectant in the world, and is commonly used in public water supply, food disinfection, wastewater treatment and control of biological fouling. However, if the concentration of residual chlorine after disinfection is not well controlled, it will not only affect the taste and smell of drinking water, but also pose a threat to aquatic animals and humans. Therefore, the emission standard of the residual chlorine concentration after chlorine-based disinfection is very strict, and the monitoring of the residual chlorine concentration is also very important.

[0003] Due to the advantages of continuous on-line monitoring and less economic cost in electrochemical detection, electrochemical residual chlorine monitoring devices are generally set at the drainage outlets of various water plants to ensure that the residual chlorine concentration in the effluent meets the standards. However, when using the electrochemical method to detect residual chlorine, the electrodes are often affected by fouling. Research shows that when the electrodes are immersed in complex water quality samples, on the one hand, due to the favorable interaction between the fouling and the electrode surface, the fouling tends to adhere to the electrode surface, which depends on the specific chemical properties of the fouling and the electrode surface, including hydrophobic, hydrophilic and electrostatic interactions, so that the natural non-specific adsorption of various organic fouling immediately occurs on the electrode surface; on the other hand, the electrode surface will generate an electric field effect on the ions in the solution, which will cause metal ions (such as calcium ions Ca 2+ etc.) to migrate towards the electrode surface, resulting in an increase in the local concentration of these ions, forming a supersaturated state and precipitating out of the solution to become solid deposits. At the same time, organic matter also undergoes redox reactions on the cathode surface to form organic fouling. The fouling layer on these electrode surfaces will hinder and slow down the transfer of charge and mass, resulting in low analysis sensitivity.

[0004] Regarding the fouling problem, on the one hand, "Anti-fouling graphene-based membranes for effective water desalination" uses graphene-based membranes to reduce fouling. However, graphene is prone to structural damage or performance degradation due to external forces or changes in environmental conditions (such as water flow impact) during actual use, affecting the long-term anti-fouling effect, resulting in an unsatisfactory anti-fouling effect, so it is not widely used. On the other hand, two-dimensional hexagonal boron nitride (2D-hBN) is an emerging two-dimensional material. "Ultrahigh resistance of hexagonal boron nitride to mineral scale formation" reports that hBN is more resistant to the formation of mineral scale than ordinary metals, polymer surfaces, and graphene, which makes hBN potentially the most anti-fouling material reported so far. This anti-fouling property is mainly attributed to the atomically smooth surface of hBN, the in-plane atomic energy corrugation caused by polar boron-nitrogen bonds, and the close match between its atomic spacing and the size of water molecules. The latter two properties result in a strong polar interaction with water, forming a dense hydration layer on the surface, strongly hindering the approach of mineral ions and crystals, thereby reducing surface heterogeneous nucleation and crystal attachment. However, the crystal structure of hBN does not allow the flow of free electrons, so it has a very high resistivity, which makes it not suitable for direct use as an electrode material in traditional electrochemical applications.

[0005] However, since 2D-hBN has a crystal structure similar to that of graphene, and graphene is a zero-bandgap semiconductor, its π-electron system is the source of its unique electronic properties. Therefore, additional electrons or holes can be introduced by doping boron nitride into graphene, thereby affecting the electronic structure of boron nitride. The doped BN-Graphene composite membrane provides anti-fouling performance while improving the conductivity and mechanical strength of the composite material, enabling it to have a long-term anti-fouling effect. Summary of the Invention

[0006] The present invention provides a method for preparing an anti-fouling electrode. The gold electrode is modified with a composite film of boron nitride (BN) and graphene (Graphene), significantly improving the anti-fouling performance of the electrode, effectively reducing the attachment of mineral fouling and organic fouling, thereby improving the stability and long-term monitoring ability of the electrode when used in complex water bodies. On the basis of this material, an anti-fouling electrochemical residual chlorine sensor with high sensitivity and anti-fouling performance is developed. The sensor can be used for highly sensitive and long-term continuous on-line detection of residual chlorine in complex water quality, and can effectively shield the interference of mineral fouling and organic fouling.

[0007] The technical solution of the present invention:

[0008] A preparation method of an anti-scaling electrode is as follows:

[0009] 1) Pretreatment: Polish and clean the bare gold electrode to obtain a clean gold electrode;

[0010] 2) Disperse BN in phosphate buffer solution (PBS), centrifuge at a speed of 4000 rpm for 30 min, and take the supernatant; centrifuge the supernatant at a speed of 8000 rpm for 50 min, take the lower precipitate, add deionized water and ultrasonicate for 30 min to obtain a BN nanosheet dispersion solution;

[0011] where the concentration of PBS is 100 mM and the pH is 5 - 9;

[0012] 3) Mix the BN nanosheet dispersion solution and the Graphene dispersion solution evenly, continuously stir with a magnetic stirrer at room temperature for 1 h, and then ultrasonicate for 30 min to obtain a BN - Graphene composite film dispersion solution;

[0013] wherein, the volume ratio of the BN nanosheet dispersion solution to the Graphene dispersion solution is 3:(4 - 8), the concentration of the BN nanosheet dispersion solution is 2.5 - 3.5 mg / L, and the concentration of the Graphene dispersion solution is 4.5 - 6.5 mg / L;

[0014] 4) Drop - coat the BN - Graphene composite film dispersion solution on the surface of the gold electrode and dry it. Immerse the prepared electrode in water to remove unbound particles and dry it to make an anti - scaling electrode BN - Graphene / AuE;

[0015] wherein, the modification amount of the BN - Graphene composite film dispersion solution is 0.45 - 1.25 μL / mm 2 ;

[0016] wherein, the drying temperature is 40 - 50 °C.

[0017] Use the anti - scaling electrode BN - Graphene / AuE for the electrochemical detection of residual chlorine:

[0018] Use an electrochemical workstation to record the electrochemical response signals of the modified electrode to different concentrations of residual chlorine in deionized water at a fixed potential, and obtain a standard curve and a linear equation based on the changes in the response signals.

[0019] Among them, the working electrode of the electrochemical sensor is BNGraphene / AuE, the counter electrode is made of platinum, and the reference electrode is made of saturated calomel.

[0020] Among them, the electrochemical measurement technique is differential pulse voltammetry, and the applied potential is 0.0 to +0.6 V;

[0021] Among them, the residual chlorine concentration is 0.1 to 100 mM.

[0022] Advantages of the present invention:

[0023] 1) In the present invention, boron nitride-doped graphene is prepared into a BN-Graphene composite film. This composite film exhibits high conductivity compared to BN and high mechanical strength compared to graphene, enabling the BN-Graphene composite film to achieve long-term continuous online monitoring of residual chlorine in sewage while possessing both electrochemical performance and anti-scaling performance;

[0024] 2) In the present invention, the BN-Graphene composite thin film is modified on the electrode surface, significantly improving the anti-scaling ability of the electrode and effectively inhibiting the attachment of mineral and organic fouling;

[0025] 3) An electrochemical residual chlorine sensor with high sensitivity and anti-scaling ability is constructed, greatly avoiding the interference of mineral fouling and organic fouling on electrochemical signals caused by long-term operation in sewage. The detection range of its residual chlorine is 0.1 to 100 mM, and the detection limit is 0.03 mM. Moreover, the modified electrode can be used for real-time monitoring of residual chlorine;

[0026] 4) The present invention has the advantages of low cost, easy operation, low detection limit, good stability, anti-scaling property, and real-time monitoring. Description of the Drawings

[0027] Figure 1 It is a scanning electron microscope image of the prepared boron nitride-graphene thin film.

[0028] Figure 2 It is a standard curve graph for monitoring the change of residual chlorine concentration using the prepared boron nitride-graphene modified electrode.

[0029] Figure 3 It is a cyclic voltammogram of a bare electrode, BN / Au, Graphene / Au, and BN-Graphene / AuE in a residual chlorine solution.

[0030] Figure 4 It is a differential pulse voltammogram of a bare electrode, BN / Au, Graphene / Au, and BN-Graphene / AuE in a residual chlorine solution.

[0031] Figure 5 It is a test comparison graph of the anti-scaling ability of the prepared BN-Graphene / AuE compared to the bare electrode Detailed Embodiments

[0032] The following further describes the specific embodiments of the present invention in conjunction with the accompanying drawings and technical solutions.

[0033] Example 1:

[0034] 1. Preparation of boron nitride nanosheets:

[0035] 1) 0.5 g of hexagonal boron nitride powder was dispersed in 100 mM PBS (pH 7) (10 mL), and then sonicated in a water bath for 30 min. The BN dispersion was centrifuged at 4000 rpm for 30 min. Subsequently, the top supernatant BN dispersion (~70%) was collected to obtain precursor 1;

[0036] 2) The supernatant was centrifuged again at 8000 rpm for 50 min to sediment the BN nanosheets. Then, the supernatant containing PBS was discarded. To redisperse the BN nanosheets, 10 mL of distilled water was added and sonicated for 30 min. This was repeated several times to remove all unwanted ions, and finally a BN nanosheet dispersion was obtained with the BN concentration maintained at 3 mg / mL;

[0037] 2. Preparation of boron nitride / graphene film dispersion:

[0038] The graphene dispersion was centrifuged at 4000 rpm for 30 minutes, and the upper supernatant (~70%) was obtained to get the graphene nanosheet dispersion with the concentration maintained at 5 mg / mL. Then, the BN and graphene dispersions were mixed in a ratio of 3:7, continuously stirred with a magnetic stirrer at room temperature for 1 h, and then sonicated for 30 min to obtain the BN-Graphene film dispersion and store it. Figure 1 For the scanning electron microscope image of the prepared boron nitride-graphene film, it shows the nanosheet structure of boron nitride-graphene;

[0039] 3. Preparation of the anti-scaling residual chlorine electrochemical sensor:

[0040] 1) Pretreatment of the Au electrode: Before modification, the Au electrode was polished using alumina powder on a polishing cloth and sonicated in a water bath with distilled water. Subsequently, the Au was electrochemically treated in 0.1M H 2 SO 4 by scanning 10 cycles between 0.5 and 1.0 V;

[0041] 2) Preparation of BN-Graphene / AuE: 6 μL of the BN-Graphene composite film dispersion was drop-coated on the Au surface and dried at 50 °C. Then, the prepared electrode was carefully immersed in water to remove unbound particles and dried to obtain BN-Graphene / AuE;

[0042] 3) Using differential pulse voltammetry of an electrochemical workstation, record the electrochemical response signals of the modified electrode to 0.1 - 100 μM residual chlorine in deionized water at a potential of +0.4 V, and obtain the standard curve and linear equation based on the changes in the response signals. The standard curve is shown in Figure 2 , and the linear equation is I / μA = -4.74×c / μM - 1.78 (R 2 = 0.993), and the detection limit is 0.03 nM;

[0043] Among them, the working electrode diameter is BN-Graphene / AuE, the counter electrode is made of platinum, and the reference electrode is made of saturated calomel paste;

[0044] Comparative Example 1:

[0045] Construction of a gold electrode modified with BN nanosheets for residual chlorine detection

[0046] 1) Disperse 0.5 g of hexagonal boron nitride powder in 100 mM PBS (pH 7) (10 mL), then perform ultrasonic treatment in a water bath for 30 min, and centrifuge the BN dispersion at 4000 rpm for 30 min. After that, collect the top supernatant BN dispersion (~70%) to obtain precursor 1;

[0047] Centrifuge the supernatant again at 8000 rpm for 50 min to sediment the BN nanosheets. Then, discard the supernatant containing PBS. To redisperse the BN nanosheets, add 10 mL of distilled water and perform ultrasonic treatment for 30 min. Repeat several times to remove all unwanted ions, and finally obtain a BN nanosheet dispersion with the BN concentration maintained at 3 mg / mL.

[0048] 2) Preparation of a BN nanosheet-modified Au electrode: Drop 6 μL of the BN nanosheet dispersion onto the Au surface and dry it at 50 °C. Then, carefully immerse the prepared BN-modified Au electrode in water to remove unbound particles and dry it to obtain BN / AuE;

[0049] 3) Using differential pulse voltammetry of an electrochemical workstation, record the electrochemical response signals of the modified electrode to residual chlorine in deionized water at a potential of 0 - +0.6 V; for comparison, also perform the electrochemical test in step 3 of Comparative Example 1 on the working electrode prepared in step 3-2 of the example.

[0050] Among them, the working electrode is BN / AuE, the counter electrode is made of platinum, and the reference electrode is made of saturated calomel paste; Comparative Example 2:

[0051] Construction of a gold electrode modified with graphene nanosheets for residual chlorine detection

[0052] 1) Centrifuge the graphene dispersion at 4000 rpm for 30 min. Take the upper supernatant (~70%) to obtain a graphene nanoplate dispersion with a concentration maintained at 5 mg / mL;

[0053] 2) Drop 6 μL of the graphene nanoplate dispersion onto the Au surface and dry it at 50 °C. Then, carefully immerse the prepared Graphene-modified Au electrode in water to remove unbound particles and dry it to obtain Graphene / AuE;

[0054] 3) Use differential pulse voltammetry of an electrochemical workstation to record the electrochemical response signal of the modified electrode to residual chlorine at a potential of 0 to +0.6 V in deionized water. As a comparison, the working electrode prepared in step 3-2 of the example is also subjected to the electrochemical test in step 3 of Comparative Example 2.

[0055] Among them, the working electrode is Graphene / AuE, the counter electrode is made of platinum, and the reference electrode is made of saturated calomel paste;

[0056] The cyclic voltammograms of the three modified electrodes for residual chlorine are shown in Figure 3 , showing an increase in the electrochemical active area of BN-Graphene / AuE. Figure 4 The differential pulse voltammograms of the three modified electrodes for residual chlorine are shown in the figure. It can be seen that a reduction peak appears at about +0.4 V for all three modified electrodes. However, the reduction peaks generated by the BN / AuE and Graphene / AuE used as comparisons are weaker than that of BN-Graphene / AuE. This improvement in performance is attributed to the doping of graphene and boron nitride, which effectively enhances the electrochemical activity during the detection of residual chlorine.

[0057] Application Example 1:

[0058] Sensor anti-fouling performance test 1

[0059] Place the bare Au, BN / AuE, Graphene / AuE, and BN-Graphene / AuE in saturated CaCO 3 solution and 10 mg / L humic acid solution respectively. Apply a constant voltage of +0.6 V to the two electrodes using an electrochemical workstation to induce fouling for 48 h, and test the DPV signals before (I 0 ) and after (I) the induced fouling, and calculate the signal inhibition rate. The signal inhibition rate = (ΔI / I 0 ) × 100%, ΔI = I 0 -I. The anti-fouling ability is reflected by the change in the DPV signal. The larger the signal inhibition rate, the more fouling occurs on its surface, indicating a worse anti-fouling effect.

[0060] As shown inFigure 5 showed that after the two electrodes were induced to form CaCO 3 scale, the electrochemical signal intensity decreased. The signal inhibition rates of bare Au, BN / AuE, Graphene / AuE, and BN-Graphene / AuE were 19.46%, 4.19%, 19.79%, and 2.65% respectively. After being induced to form humus scale, the signal inhibition rates of bare Au and BN-Graphene / AuE were 12.37%, 1.77%, 4.57%, and 1.23% respectively. The above results indicate that serious scale fouling occurred on the surfaces of bare Au, BN / AuE, and Graphene / AuE. In contrast, after the BN-Graphene / AuE was induced to form scale, the DPV signal hardly changed and the signal inhibition rate was very small. This shows that the modification of the BN-Graphene composite film enhanced the anti-scaling ability and electrochemical signal intensity of the electrode.

[0061] Application Example 2:

[0062] Sensor Anti-scaling Performance Test II

[0063] The bare Au, BN / AuE, Graphene / AuE, and BN-Graphene / AuE were respectively immersed in a 10 mg / L humus solution to cause adsorption scale on the electrode surface. After soaking for 48 h, the DPV signals before (I 0 ) and after (I) the adsorption scale were measured, and the signal inhibition rate was calculated. The signal inhibition rate = (ΔI / I 0 ) × 100%, ΔI = I 0 -I. The anti-fouling ability was reflected by the change in the DPV signal.

[0064] As Figure 5 shown, after the two electrodes were adsorbed with scale, the electrochemical signal intensity decreased. The signal inhibition rates of bare Au, BN / AuE, Graphene / AuE, and BN-Graphene / AuE were 4.75%, 1.68%, 3.56%, and 1.03% respectively. The above results indicate that after the BN-Graphene / AuE was scaled, the DPV signal hardly changed and the signal inhibition rate was very small. This result shows that the composite film can effectively reduce the attachment of scaling substances, maintain the electrochemical activity of the electrode, and thus ensure the long-term reliability and accuracy of the residual chlorine sensor.

[0065] The above describes in detail the preferred embodiments of this patent. However, this patent is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, other different forms of changes or alterations can be made. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an anti-scaling electrode, characterized in that: Here are the steps: 1) Pretreatment: polishing, grinding and cleaning the bare gold electrode to obtain a clean gold electrode; 2) Disperse BN in phosphate buffered saline (PBS), centrifuge and take the supernatant; The supernatant was centrifuged to remove the lower precipitate, deionized water was added and ultrasonicated to obtain a BN nanosheet dispersion solution; 3) mixing the BN nanosheet dispersion solution and the graphene dispersion solution uniformly, stirring continuously with a magnetic stirrer at room temperature, and then ultrasonically treating to obtain a BN-graphene composite film dispersion solution; 4) The BN-Graphene composite film dispersion solution was drop-coated on the surface of the gold electrode and dried, and the prepared electrode was immersed in water to remove unbound particles and dried to prepare the anti-scaling electrode BN-Graphene / AuE.

2. The preparation method according to claim 1, characterized in that: In step 2), the specific conditions for taking the supernatant by centrifugation are: centrifuging at a speed of 4000 rpm for 30 minutes and taking the supernatant.

3. The preparation method according to claim 1, characterized in that: In step 2), the specific conditions for centrifuging the supernatant to remove the lower precipitate are: the supernatant is centrifuged at 8000 rpm for 50 min, and the lower precipitate is removed.

4. The preparation method according to claim 1, characterized in that: In step 2), the concentration of PBS is 100 mM and the pH is 5-9.

5. The preparation method according to claim 1, characterized in that: In step 3), the volume ratio of the BN nanosheet dispersion solution to the graphene dispersion solution is 3:(4-8), the concentration of the BN nanosheet dispersion solution is 2.5-3.5 mg / L, and the concentration of the graphene dispersion solution is 4.5-6.5 mg / L.

6. The preparation method according to claim 1, characterized in that: In step 4), the modification amount of the BN-Graphene composite membrane dispersion solution is 0.45 to 1.25 μL / mm 2 .

7. The preparation method according to claim 1, characterized in that: In step 4), the drying temperature is 40-50°C.

8. Use of the anti-scaling electrode obtained by the preparation method according to any one of claims 1 to 7 for electrochemical detection of residual chlorine. The electrochemical workstation is used to record the electrochemical response signals of the anti-scaling electrode to different concentrations of residual chlorine in deionized water at a fixed potential, and the standard curve and linear equation are obtained according to the changes in the response signals; in, The working electrode is the anti-scaling electrode BNGraphene / AuE, the counter electrode is the platinum electrode, and the reference electrode is the saturated calomel electrode.

9. The use according to claim 8, characterized in that: The electrochemical measurement technique of the electrochemical workstation was differential pulse voltammetry, and the applied potential was 0.0 to +0.6 V.

10. The use according to claim 8, characterized in that: The concentration of residual chlorine is 0.1~100mM.

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