Screen-printed electrode modified by nano composite material and preparation method and application of screen-printed electrode

Abstract

The invention discloses a nano composite material modified screen-printed electrode and a preparation method and application thereof, and relates to the technical field of electrochemistry, and the preparation method of the nano composite material modified screen-printed electrode comprises the following steps: preparing a reduced graphene oxide and single-walled carbon nanotube modified screen-printed electrode; and then electrochemically depositing the gold nanoparticles through a chronoamperometry. The screen-printed electrode modified by the nano composite material is used for a nitrite detection sensor, can realize ultra-low detection limit, has high anti-interference capability, and provides an efficient and stable sensing platform for development of portable nitrite detection equipment.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, and in particular to a screen-printed electrode modified with nanocomposite materials, its preparation method, and its application. Background Technology

[0002] With the advancement of technology, humanity has become acutely aware of the importance of trace detection of pollutants that harm the ecological environment and human health. It is noteworthy that excessive intake of nitrites may lead to cancer; therefore, the detection of nitrites, which are widely used in the food and agricultural industries, is particularly crucial. Regulations stipulate that the maximum concentration of nitrites in water is 3 mg / L. -1To protect human health, developing suitable methods for detecting trace amounts of nitrite is an important research topic. In recent years, a series of analytical methods have been developed, such as spectrophotometry, chromatography, molecular absorption spectroscopy, chemiluminescence, Raman spectroscopy, and fluorescence spectroscopy for nitrite analysis. Electrochemical sensors have also attracted widespread attention in the field of analytical detection due to their advantages such as rapid response, high sensitivity, low cost, and portability. Electrochemical sensors include enzyme-based and non-enzyme-based sensors. Enzyme-based electrochemical sensors are highly dependent on the external environment, which limits their practical application. Compared with enzyme-based sensors, non-enzyme sensors are less affected by the external environment; therefore, it is essential to develop stable, low-detection-limit, and highly specific non-enzyme electrochemical sensors. The further development and widespread application of non-enzymatic electrochemical sensors in nitrite detection face several key challenges, specifically in the following aspects: First, there is the problem of insufficient electrode catalytic activity. Currently widely used traditional electrode materials, such as platinum, gold, and glassy carbon, exhibit slow kinetics in the electrochemical oxidation reaction of nitrite, resulting in generally low sensor sensitivity and high detection limits (typically greater than 1 μM). Furthermore, byproducts generated during oxidation are easily adsorbed onto the electrode surface, causing catalyst poisoning and blockage of active sites, severely affecting the long-term stability and lifespan of the electrode. Second, there is the problem of limited nanomaterial modification strategies. To improve electrode performance, existing research mostly focuses on modifying electrodes with nanomaterials (such as graphene oxide or carbon nanotubes). Although these materials can improve electron transport characteristics or provide some active sites to a certain extent, using a single type of nanomaterial still suffers from low electron conduction efficiency and limited catalytic activity, restricting further improvement in the overall sensor performance and making it difficult to achieve ultra-low detection limits for nitrite. Furthermore, there is a deficiency in anti-interference capability. For example, in actual samples (such as food, body fluids, and environmental water samples), there are often various electroactive substances (such as ascorbic acid, polyphenols, uric acid, etc.), which are prone to competitive oxidation reactions at similar potentials, causing signal overlap and severely interfering with the accurate determination of the target analyte nitrite, resulting in a significant decrease in sensor selectivity. This bottleneck problem greatly limits the practical application of this technology in complex matrices.

[0003] Therefore, there is an urgent need to develop an electrode that can sensitively detect nitrite in complex matrices, and has a low detection limit and strong stability. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a screen-printed electrode modified with nanocomposite materials, its preparation method, and its application.

[0005] This invention provides a method for preparing a screen-printed electrode modified with nanocomposite materials, comprising the following steps:

[0006] S1: Mix the reduced graphene oxide solution (rGO) with the single-walled carbon nanotube solution (SWCNT) and sonicate to obtain a mixed solution;

[0007] S2: The mixed solution is coated onto the surface of a screen-printed electrode (SPE electrode), and after drying, a screen-printed electrode modified with reduced graphene oxide and single-walled carbon nanotubes is obtained.

[0008] S3: The electrode is placed in a chloroauric acid solution and modified by electrochemical deposition using a chronoamperometry method. The electrode is then rinsed with water and dried to obtain the electrode.

[0009] Glassy carbon electrodes (GCE electrodes) require a three-electrode system (working electrode, counter electrode, and reference electrode) and an electrolytic cell, which is insufficient for rapid on-site detection. This invention employs a special SPE electrode, which not only offers advantages such as low cost, portability, and mass production capability, but also, through a printing process, integrates the working electrode, counter electrode, and reference electrode onto the same substrate, significantly simplifying the detection process. Furthermore, SPE can be modified with nanomaterials (such as gold nanoparticles and carbon nanotubes) to significantly improve the detection sensitivity and anti-interference ability for nitrates. Simultaneously, the disposable nature of SPE avoids the surface contamination problems of traditional electrodes, ensuring the stability and reproducibility of detection results. The inventors have also discovered that SPE exhibits superior electrochemical performance compared to GCE, namely faster electron transfer rates and better electrochemical reversibility. Modification with rGO, SWCNTs, and AuNPs demonstrates significant advantages in the electrochemical detection of nitrites.

[0010] Furthermore, this invention also enhances electron transport efficiency and signal amplification by modifying the electrode with specific nanomaterials. The invention constructs a screen-printed electrode modified with a composite nanomaterial of reduced graphene oxide (rGO), single-walled carbon nanotubes (SWCNTs), and gold nanoparticles (AuNPs), forming numerous specific adsorption sites for nitrite. This significantly improves selectivity and enhances the electrode's resistance to interference in complex matrices. rGO's high specific surface area enhances nitrite adsorption, while SWCNTs accelerate electron transport. The inventors discovered that selecting SWCNTs in a sodium nitrite electrochemical sensor maximizes their high conductivity, large specific surface area, abundant active sites, and excellent mass transfer capabilities. When co-modified with rGO and AuNPs, it significantly improves current response and sensitivity. AuNPs catalyze the two-electron oxidation reaction, synergistically reducing oxidation overpotential, preventing electrode poisoning, enhancing catalytic activity, and inhibiting byproduct accumulation. Constructing a gold-carbon synergistic catalytic interface further enhances electron transport efficiency. The synergistic effect of multiple composite nanomaterials pushes the detection limit down to 0.01 μM. Meanwhile, this invention modifies the screen-printed electrode by using a specific method to reduce graphene oxide and single-walled carbon nanotubes, and also uses a specific chronoamperometry method to deposit gold nanomaterials. This forms a synergistic catalytic mechanism between N-doped defect sites and Au(111) crystal planes, while improving the bonding force between the modified layer and the substrate, ensuring long-term reliability. It avoids the defects of simple physical mixing that cause nanomaterials to easily agglomerate or fall off during electrochemical cycling, resulting in motor performance degradation. Through structural regulation, a distributed porous structure is formed, avoiding the disordered distribution of nano-components that restricts the exposure of active sites.

[0011] Furthermore, the chronoamperometry method involves placing the electrode in a chloroauric acid solution and applying a constant voltage of +(0.15-0.3)V for 100-175s. The inventors discovered that when electrochemical deposition is performed using the chronoamperometry method, high-density and uniform deposition of AuNPs is achieved through constant potential control, thereby endowing the electrode with more active sites and better electronic conduction and mass transfer performance. When combined with rGO and SWCNT to modify the SPE electrode, it can synergistically improve the current response and enhance mechanical stability.

[0012] Furthermore, the chronoamperometry involves placing the electrode in a chloroauric acid solution and applying a constant voltage of +0.2V for 125-150s, preferably 150s. Thereafter, the current response gradually decreases with increasing time, indicating that electron transport kinetics are impeded, possibly due to the reduction in active surface area caused by overcrowded nanoparticles.

[0013] Furthermore, the concentration of the reduced graphene oxide solution is 1-5 mg / mL, preferably 2 mg / mL;

[0014] The concentration of the single-walled carbon nanotube solution is 0.05%-0.25wt%, preferably 0.15wt%.

[0015] Furthermore, the volume ratio of the reduced graphene oxide solution to the single-walled carbon nanotube solution is (0.25-4):1, preferably (0.6-0.7):1.

[0016] Furthermore, the SPE electrode is any one of a carbon electrode, a platinum-carbon electrode, or an alloy electrode, preferably a carbon electrode.

[0017] This invention also provides a screen-printed electrode modified with nanocomposite materials, prepared using the aforementioned method. The electrode of this invention employs a three-dimensional structure of reduced graphene / carbon nanotubes loaded with gold nanoparticles to construct a highly efficient electron transport channel, enhancing detection sensitivity. Furthermore, it features structural innovation, forming a porous conductive structure through in-situ reduction, thereby increasing the density of active sites and nitrite adsorption capacity. The electrode prepared by this invention also exhibits strong storage stability; after 15 days of storage, the sensitivity decreases by less than 4.5%, demonstrating significantly greater stability compared to traditional electrodes (which typically experience a 15–20% decrease).

[0018] The present invention also provides a nitrite sensor, comprising a screen-printed electrode modified with the nanocomposite material described above.

[0019] Furthermore, the detection limit of the nitrite sensor reaches 0.01 μM.

[0020] This invention also provides the application of the aforementioned nitrite sensor in nitrite detection, specifically using square wave voltammetry (SWV) for nitrite detection. This invention achieves an ultra-low detection limit by constructing a screen-printed electrode modified with a composite nanomaterial of reduced graphene oxide (rGO) / single-walled carbon nanotubes (SWCNTs) / gold nanoparticles (AuNPs) combined with square wave voltammetry. Furthermore, by optimizing the square wave voltammetry parameters to suppress signal interference, it is suitable for accurate detection in complex matrices. For example, in the field of food safety, it can be integrated into portable detectors to achieve rapid on-site detection of nitrite in pickled foods and drinking water, avoiding the problem of long laboratory testing cycles. In the field of environmental monitoring, it can be used for real-time monitoring of trace nitrite in wastewater and soil, assisting environmental protection departments in dynamic management and providing an efficient and stable sensing platform for the development of portable nitrite detection equipment.

[0021] In summary, compared with the prior art, the present invention achieves the following technical effects:

[0022] (1) The screen-printed electrode modified with reduced graphene oxide (rGO) / single-walled carbon nanotubes (SWCNT) / gold nanoparticles (AuNPs) composite nanomaterials provided by the present invention has an ultra-low detection limit in nitrite sensors and has high electron transport efficiency through material composite and structural design.

[0023] (2) The screen-printed electrode modified with nanocomposite material provided by the present invention has strong anti-interference ability in complex matrix;

[0024] (3) The screen-printed electrode modified with nanocomposite material provided by the present invention can ensure the stability and repeatability of long-term and repeated testing.

[0025] (4) The screen-printed electrode modified with nanocomposite material provided by the present invention adopts a low-cost, mass-producible screen-printed electrode that can replace large-scale instrument detection.

[0026] (5) The preparation process of the screen-printed electrode modification layer provided by the present invention can ensure batch consistency and large-scale production feasibility;

[0027] (6) The present invention uses a screen-printed electrode (SPE) substrate and combines it with an electrodeposition AuNPs process, which significantly reduces the cost of a single electrode compared with traditional electrodes (especially gold electrodes). Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 CV test curves of SPE / rGO-SWCNT electrodes prepared with different ratios of rGO and SWCNT;

[0030] Figure 2 The CV test curves are for screen-printed electrodes (SPE) and conventional glassy carbon electrodes (GCE).

[0031] Figure 3 SEM image of the bare SPE electrode;

[0032] Figure 4 CV test curves for SPE-SWCNT and SPE-MWCNT;

[0033] Figure 5 SEM image of the SPE / rGO-SWCNT electrode;

[0034] Figure 6 SEM image of the SPE / rGO-SWCNT / AuNPs electrode prepared in Example 6;

[0035] Figure 7 CV test curves for screen-printed electrodes made of three different materials: carbon electrode, platinum-carbon electrode, and alloy electrode.

[0036] Figure 8 The CV test curves of electrodes obtained by gold nanoparticle electrodeposition on SPE / rGO-SWCNT electrodes using different methods are shown.

[0037] Figure 9 CV test curves of SPE / rGO-SWCNT / AuNPs electrodes deposited with gold nanoparticles for different times using the chronoamperometry method.

[0038] Figure 10 CV test curves for SPE, SPE / rGO-SWCNT, and SPE / rGO-SWCNT / AuNPs electrodes;

[0039] Figure 11 EIS test curves for SPE, SPE / rGO-SWCNT, and SPE / rGO-SWCNT / AuNPs electrodes;

[0040] Figure 12 The differential pulse voltammetry (DPV) curves corresponding to the detection of 0-1000 μM sodium nitrite by the nitrite sensor prepared in Example 13 at room temperature are shown.

[0041] Figure 13 The graph shows the linear fitting curve of the peak current of the nitrite sensor prepared in Example 13.

[0042] Figure 14 The image shows the DPV response of the nitrite sensor prepared in Example 13 to interfering substances.

[0043] Figure 15 The current response diagrams are for five nitrite sensors prepared repeatedly using the method of Example 13;

[0044] Figure 16 The DPV response diagram is shown for the long-term stability test of the nitrite sensor prepared in Example 13.

[0045] Figure 17 The graph shows the detection curves of the nitrite sensor prepared in Example 13 against PBS solution and real sample pickled cucumber. Detailed Implementation

[0046] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0047] Example

[0048] The present invention will be further illustrated below with reference to specific embodiments and comparative embodiments. The following specific embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments, and are not in particular limited to the types of raw materials used in the following specific embodiments.

[0049] I. The sources of raw materials for the examples and comparative examples are as follows:

[0050] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this invention are all commercially available.

[0051] The raw materials used in the examples and comparative examples are as follows: tetrachloroauric acid trihydrate (HAuCl4·3H2O, 99.9%), sulfuric acid (H2SO4, 95%), hydrochloric acid (HCl, 37%), potassium chloride (KCl, 99%), sodium dihydrogen phosphate (NaH2PO4, 99%), potassium dihydrogen phosphate (K2HPO4, 99%), potassium ferrocyanide (K4Fe(CN)6·3H2O, 99.9%), and potassium ferrocyanide (K3Fe(CN)6·3H2O, 99.9%). H2O, 99.9%; the buffer solution was phosphate solution (PBS, 10 mM), prepared by sodium chloride (NaCl, 99%), potassium chloride (KCl, 99%), NaH2PO4 and K2HPO4 in deionized water (≥18.2 MΩ·cm); all solutions were prepared using 10 mM PBS solution; the concentration of the reduced graphene oxide dispersion was 2 mg / mL; the concentration of the carboxylated single-walled carbon nanotube aqueous solution was 0.15 wt%.

[0052] II. Performance Testing Methods

[0053] (1) Environmental scanning electron microscopy (SEM) was performed using a Thermo Fisher Scientific HITACHI SU8010 model instrument with a resolution of ≤1.0nm, an accelerating voltage of 20kV, and a cold cathode field emission electron source to characterize the morphology of the electrode modification material.

[0054] (2) The cyclic voltammetry (CV) measurement scan rate was set to 50 mV / s. -1 The potential is swept from -1.0V to +1.0V.

[0055] (3) The frequency range of the electrochemical impedance spectroscopy (EIS) is 0.1 Hz to 1000 kHz, the AC amplitude is 5 mV, and the open circuit potential is used.

[0056] (4) Electrochemical testing was performed using a PalmSens4 electrochemical workstation from RadioMetChina Ltd. The nitrite sensor was tested using a three-electrode system, with the working electrode (WE), reference electrode (RE), and counter electrode (CE) connected to the commercial software-controlled electrochemical workstation.

[0057] (5) Sensitivity test of nitrite sensor: The Ag / AgCl reference electrode was tested for 60s at 0.6V using chronoamperometry in 10mM PBS buffer solution. Electrochemical characterization was performed at room temperature using a self-made Ag / AgCl reference electrode and an SPE / rGO-SWCNT counter electrode in [0.1MKCl+5.0mM K3 / K4] redox probe.

[0058] (6) Nitrite content test method: Add 50 μL of sample solution to the prepared biosensor, select square wave voltammetry (SWV) for testing, carefully clean the sample on the electrode with ultrapure water, and then perform the next test.

[0059] Example 1

[0060] Example 1: Preparation of SPE / rGO-SWCNT electrode:

[0061] S1: Mix 40 μL of reduced graphene oxide solution with a concentration of 2 mg / mL with 60 μL of single-walled carbon nanotube solution with a concentration of 0.15 wt%, and sonicate for 30 min to obtain rGO-SWCNT mixed solution.

[0062] S2: 10 μL of rGO-SWCNT mixed solution was coated onto the surface of a screen-printed electrode (with a carbon electrode as the bare electrode), and dried at room temperature for 30 min to obtain a screen-printed electrode modified with reduced graphene oxide and single-walled carbon nanotubes.

[0063] Figure 1 CV curves of SPE / rGO-SWCNT electrodes with different ratios of rGO and SWCNT were obtained, with the measurement scan rate set to 50 mV / s. -1 The potential is swept from -1.0V to +1.0V.

[0064] Example 2

[0065] The difference between Example 2 and Example 1 is that the volume ratio of the reduced graphene oxide solution to the single-walled carbon nanotube solution is 4:1.

[0066] Example 3

[0067] The difference between Example 3 and Example 1 is that the volume ratio of the reduced graphene oxide solution to the single-walled carbon nanotube solution is 1.5:1.

[0068] Example 4

[0069] The difference between Example 4 and Example 1 is that the volume ratio of the reduced graphene oxide solution to the single-walled carbon nanotube solution is 1:1.

[0070] Example 5

[0071] The difference between Example 5 and Example 1 is that the volume ratio of the reduced graphene oxide solution to the single-walled carbon nanotube solution is 0.25:1.

[0072] Example 6

[0073] Example 6: Preparation of SPE / rGO-SWCNT / AuNPs electrode:

[0074] S1: Mix 40 μL of reduced graphene oxide solution with a concentration of 2 mg / mL with 60 μL of single-walled carbon nanotube solution with a concentration of 0.15 wt%, and sonicate for 30 min to obtain rGO-SWCNT mixed solution.

[0075] S2: 10 μL of rGO-SWCNT mixed solution was coated onto the surface of the screen-printed electrode and dried at room temperature for 30 min to obtain a screen-printed electrode modified with reduced graphene oxide and single-walled carbon nanotubes.

[0076] S3: The bare SPE / rGO-SWCNT electrode was placed in a 50 mM chloroauric acid solution (with 0.5 M HCl as the electrolyte) and modified by electrochemical deposition using a chronoamperometry method. Specifically, a constant potential of +0.2 V was applied for 150 seconds, the SPE / rGO-SWCNT electrode modified with three-dimensional gold nanostructures (3D AuNPs) was rinsed with ultrapure water, and the surface was dried with nitrogen to obtain the electrode.

[0077] Figure 2 For screen-printed electrodes (SPE) and traditional glassy carbon electrodes (GCE), a 5 mM [Fe(CN)6] content is used. 3- / 4- The curve of CV test in 0.1M KCl with redox probe, with the measurement scan rate set to 50 mV / s. -1 The potential was swept from -1.0V to +1.0V, and the results showed that the SPE electrode had the highest response current. Therefore, the SPE electrode was modified in this invention.

[0078] Figure 3 SEM image of the bare SPE electrode;

[0079] Figure 4 SPE electrodes were modified with single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), respectively, namely SPE-SWCNTs and SPE-MWCNTs containing 5 mM [Fe(CN)6]. 3- / 4- The curve of CV test in 0.1M KCl with redox probe, with the measurement scan rate set to 50 mV / s. -1 The potential was swept from -1.0V to +1.0V. The test results showed that SPE-SWCNT had a higher current response, while MWCNT, after modifying SPE, had relatively weak performance due to structural complexity and electron transport limitations. Therefore, SWCNT was used to modify the SPE electrode.

[0080] Figure 5 SEM image of the SPE / rGO-SWCNT electrode;

[0081] Figure 6 SEM images of the SPE / rGO-SWCNT / AuNPs electrode;

[0082] Figure 7 The image shows the CV test curves for three different screen-printed electrodes: carbon electrode, platinum-carbon electrode, and alloy electrode, in a solution containing 5 mM [Fe(CN)6]. 3- / 4- The redox probe was subjected to CV testing in 0.1M KCl. The test results showed that the carbon electrode had the highest corresponding current. Therefore, the carbon electrode was selected as the bare electrode for modification.

[0083] Figure 8 The CV test curves of the electrodes obtained by gold nanoparticle electrodeposition of SPE / rGO-SWCNT electrodes using different methods are shown. The results show that the electrode with gold nanoparticles electrodeposited by chronoamperometry has a higher response current, while the CV method has limited morphology and loading of AuNPs due to potential dynamic changes and competitive reactions, resulting in relatively weaker performance.

[0084] Figure 9 The CV test curves of SPE / rGO-SWCNT / AuNPs electrodes with gold nanoparticles electrodeposited for different times using the chronoamperometry method are shown in the figure. The test was carried out in potassium ferricyanide solution. The results show that the response current of the SPE / rGO-SWCNT / AuNPs electrode reaches the maximum when the deposition time is 150 s.

[0085] Figure 10 CV test curves for SPE, SPE / rGO-SWCNT, and SPE / rGO-SWCNT / AuNPs electrodes;

[0086] Figure 11EIS test curves for SPE, SPE / rGO-SWCNT, and SPE / rGO-SWCNT / AuNPs electrodes.

[0087] Example 7

[0088] The difference between Example 7 and Example 6 is that the electrochemical precipitation time by the chronoamperometry in step S3 is 25s.

[0089] Example 8

[0090] The difference between Example 8 and Example 6 is that the electrochemical precipitation time by chronoamperometry in step S3 is 50s.

[0091] Example 9

[0092] The difference between Example 9 and Example 6 is that the electrochemical precipitation time by chronoamperometry in step S3 is 75s.

[0093] Example 10

[0094] The difference between Example 10 and Example 6 is that the electrochemical precipitation time by chronoamperometry in step S3 is 100s.

[0095] Example 11

[0096] The difference between Example 11 and Example 6 is that the electrochemical precipitation time by chronoamperometry in step S3 is 125s.

[0097] Example 12

[0098] The difference between Example 8 and Example 6 is that the electrochemical precipitation time by chronoamperometry in step S3 is 175s.

[0099] Example 13

[0100] Example 13 uses the SPE / rGO-SWCNT / AuNPs electrode prepared in Example 6 to prepare a nitrite sensor, which also includes a self-made Ag / AgCl reference electrode and an SPE / rGO-SWCNT counter electrode;

[0101] Figure 12 The differential pulse voltammetry (DPV) curves corresponding to the detection of sodium nitrite from 0 to 1000 μM at room temperature using the prepared nitrite sensor are shown. The sodium nitrite concentrations for SWV testing were 1 μM, 10 μM, 100 μM, 300 μM, 500 μM, 600 μM, 800 μM, and 1000 μM, respectively. The results show that the sensor has high sensitivity and fast response speed at all concentrations.

[0102] Figure 13The graph shows the linear fitting curve of the peak current of the prepared nitrite sensor. The linear range of the sodium nitrite sensor prepared in Example 13 is 1 μM-1000 μM, and the correlation coefficient R is... 2 The value is 0.991, and the linear equation is y = 1.3526X + 386.980;

[0103] Figure 14 The image shows the DPV response of the prepared nitrite sensor to interfering substances, including 10mM potassium nitrate, 10mM sodium chloride, 10mM sodium nitrate, 20mM copper chloride, 20mM sodium sulfate, 10mM ascorbic acid, and 10mM uric acid. All interfering solutions were prepared with 10mM PBS. The control group was a solution containing only nitrite. The test results show that the sodium nitrite sensor of the present invention does not show significant current changes in response to any interfering substance. Under the condition that other interfering substances are present, it does not affect the signal strength of nitrite, indicating that it has high selectivity for sodium nitrite.

[0104] Figure 15 The current response diagrams of five sodium nitrite sensors prepared by the method of Example 13 are shown. The test results show that the RSD of the five sodium nitrite sensors of the present invention is 4.2%, indicating that the sensors prepared by the present invention have good repeatability.

[0105] Figure 16 The DPV response diagram for the long-term stability of the prepared nitrite sensor shows that, at a concentration of 1 mM, the current response was still more than 90% of that on the first day until the 15th day after testing every two days, indicating that it has long-term stability.

[0106] Figure 17 The graphs show the detection curves of the prepared nitrite sensor against PBS solution and real sample pickled cucumber. The sample was obtained by squeezing the pickled cucumber to obtain juice, which was then directly added to the sensor.

[0107] Comparative Example 1

[0108] The difference between Comparative Example 1 and Example 6 is that gold nanoparticles were deposited by cyclic voltammetry in step S3, with a scanning voltage of -1.3V to 0.8V, a scanning rate of 50mV / s, and 7 scan cycles, and the electrodeposition was carried out in a 50mM sodium chloride solution of HAuCl4.

[0109] Comparative Example 2

[0110] The difference between Comparative Example 2 and Example 13 is that a single graphene oxide material is used to modify the electrode as the working electrode.

[0111] Examples 1-13 of this invention not only specifically select the bare electrode, but also make specific choices regarding the modification materials and modification methods. The resulting screen-printed electrode modified with nanocomposite materials, when applied to a nitrite sensor, can significantly reduce the detection limit and improve the anti-interference capability of the detection process. This invention, based on an electrode modified with a composite nanomaterial of reduced graphene oxide (rGO) / single-walled carbon nanotubes (SWCNTs) / gold nanoparticles (AuNPs), combined with square wave voltammetry (SWV) for nitrite detection, can achieve an ultra-low detection limit (LOD) for nitrite while significantly improving detection sensitivity.

[0112] This invention significantly improves oxidation reaction efficiency by utilizing the high specific surface area of ​​graphene to enrich nitrite, the high conductivity of SWCNTs to promote electron transfer, and the strong electrocatalytic effect of AuNPs. Simultaneous modification of the SPE electrode with these three elements further enhances the selectivity and anti-interference capability for nitrite, enabling the nitrite sensor to perform accurate detection in complex matrices. This invention combines a screen-printed electrode modified with nanocomposite materials with square wave voltammetry. Due to the high signal-to-noise ratio of SWV, its combination with the specific electrode of this invention achieves a detection limit as low as 0.01 μM, or even as low as 0.008 μM, which is two orders of magnitude lower than existing technologies, making it suitable for ultra-trace detection (such as drinking water and food additive monitoring). The rGO / SWCNT / AuNPs composite nanomaterial of this invention can detect the oxidation potential of nitrite (+0.95 V vs. Ag / AgCl). In a mixed solution containing 10 times the concentration of interfering substances (AA, UA, glucose, etc.), the nitrite signal change is <5%, far superior to electrodes modified with single materials. The screen-printed electrode modified with nanocomposite material of the present invention is used in a nitrite detection sensor, which can achieve an ultra-low detection limit and has high anti-interference ability, providing an efficient and stable sensing platform for the development of portable nitrite detection devices.

[0113] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a screen-printed electrode modified with a nanocomposite material, characterized in that, Includes the following steps: S1: Mix the reduced graphene oxide solution with the single-walled carbon nanotube solution and sonicate to obtain a mixed solution; S2: The mixed solution is coated onto the surface of the screen-printed electrode and dried to obtain a screen-printed electrode modified with reduced graphene oxide and single-walled carbon nanotubes. S3: The electrode is placed in a chloroauric acid solution and modified by electrochemical deposition using a chronoamperometry method. The electrode is then rinsed with water and dried to obtain the electrode.

2. The preparation method according to claim 1, characterized in that, The chronoamperometry method involves placing the electrode in a chloroauric acid solution and applying a constant voltage of +(0.15-0.3)V for 100-175s.

3. The preparation method according to claim 2, characterized in that, The chronoamperometry method involves placing the electrode in a chloroauric acid solution and applying a constant voltage of +0.2V for 125-150s.

4. The preparation method according to claim 1, characterized in that, The concentration of the reduced graphene oxide solution is 1-5 mg / mL; The concentration of the single-walled carbon nanotube solution is 0.05%-0.25wt%.

5. The preparation method according to claim 4, characterized in that, The volume ratio of the reduced graphene oxide solution to the single-walled carbon nanotube solution is (0.25-4):

1.

6. The preparation method according to claim 1, characterized in that, The SPE electrode is any one of a carbon electrode, a platinum-carbon electrode, or an alloy electrode.

7. A screen-printed electrode modified with a nanocomposite material, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. A nitrite sensor, characterized in that, Including the screen-printed electrode modified with the nanocomposite material as described in claim 7.

9. The nitrite sensor according to claim 8, characterized in that, The sensor has a detection limit of 0.01 μM for nitrite.

10. The application of the nitrite sensor according to any one of claims 8-9 in the detection of nitrite, characterized in that, Nitrite was determined using the square wave voltammetry method.

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