Electrochemical surface enhanced Raman scattering substrate as well as preparation method and application thereof

Abstract

The invention discloses an electrochemical surface enhanced Raman scattering substrate as well as a preparation method and application thereof, and belongs to the technical field of pollutant analysis and detection.Prussian blue or analogue nanoparticles thereof are introduced into a conductive substrate, so that the conductivity and specific surface area of the substrate are improved, meanwhile, uniform coverage of silver nanoparticles is realized, and the electrochemical surface enhanced Raman scattering substrate is prepared. The Prussian blue or the analogue thereof is introduced while the conductivity of the substrate is improved, so that potential control is facilitated, target molecules can obtain better affinity on the surface of an electrode, and the stability and the sensitivity of the surface-enhanced Raman scattering substrate are enhanced. According to the invention, the Prussian blue analogue is introduced on the conductive substrate, so that the problem that silver nanoparticles cannot be uniformly deposited on the conductive substrate is solved, a remarkable surface-enhanced Raman scattering enhancement effect is displayed in an electric field, and sensitive vibration spectrum information suitable for monitoring the dynamic state of target molecules is provided.

Description

Technical Field

[0001] The present invention relates to the technical field of pollutant analysis and detection, and particularly relates to an electrochemical surface-enhanced Raman scattering substrate, a preparation method thereof, and an application thereof. Background Art

[0002] Acetamiprid (AAP) is a neonicotinoid pesticide, which is widely used in agricultural production because of its good water solubility and significant pest control effect. However, excessive use of acetamiprid may cause pollution to plants, water, soil and air, and accumulate biologically through the food chain in the ecosystem, posing a significant risk to human health. Therefore, to ensure food safety and protect public health, it is necessary to explore a detection method with high precision and high sensitivity for acetamiprid.

[0003] Traditional analytical methods for detecting acetamiprid include high performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), liquid chromatography-tandem mass spectrometry (LC-MS / MS), immunoassay, and biosensing detection methods. However, the above detection methods are challenging for on-site detection due to the high cost of instruments and high operation and maintenance requirements. In addition, immunoassay methods also have relatively low accuracy and sensitivity, which limits their wider application in food analysis. Given these limitations, there is an urgent need to develop cost-effective, easy-to-use and accurate detection methods to be reliable and stable in identifying acetamiprid contamination in food.

[0004] Surface-enhanced Raman scattering (SERS) is a highly sensitive and selective technique that can achieve rapid detection of food pollutants. However, conventional SERS detection methods require the detection substance to be in close proximity to the SERS substrate to obtain sufficient localized surface plasmon resonance (LSPR) effect. However, due to the large molecular weight of conventional detection substances and the potential repulsion between the SERS substrate and the analyte, insufficient SERS signals cannot be generated. Electrochemical surface-enhanced Raman spectroscopy (EC-SERS) combines electrochemical reactions with surface-enhanced Raman scattering detection, and prepares an efficient SERS substrate through in-situ electrochemical deposition, so as to achieve the effect of detecting target molecules at lower concentrations. EC-SERS has successfully detected trace food pollutants such as pesticides, bacteria, drugs, and caffeine.

[0005] Due to the excellent conductivity and surface plasmon resonance effect of silver nanoparticles (Ag NPs), depositing silver nanoparticles on a screen-printed electrode when preparing a SERS substrate can greatly enhance the Raman scattering signal, thereby improving the detection sensitivity. However, when using a simple noble metal material for deposition on a screen-printed electrode, due to fewer binding sites, the noble metal nanoparticles cannot be uniformly deposited on the screen-printed electrode, thus affecting the detection sensitivity and stability. Summary of the Invention

[0006] The present invention provides an electrochemical surface-enhanced Raman scattering substrate, a preparation method thereof, and an application thereof, effectively solving the technical problem in the prior art that when preparing a SERS substrate, due to fewer binding sites of a simple noble metal on a screen-printed electrode, the deposited noble metal nanoparticles cannot be uniformly deposited on the screen-printed electrode, resulting in non-uniform preparation of the SERS substrate, thereby affecting the detection sensitivity and stability. The present invention introduces a Prussian blue analogue (PBAs) into the SERS substrate, improving the conductivity and specific surface area of the substrate, enabling silver nanoparticles to be uniformly covered, overcoming the problem of depositing silver nanoparticles on a screen-printed electrode, and enhancing the stability and sensitivity of the surface-enhanced Raman scattering substrate, showing a significant surface-enhanced Raman scattering enhancement effect under an electric field, and providing sensitive vibration spectral information suitable for monitoring the dynamics of target molecules.

[0007] The first object of the present invention is to provide an electrochemical surface-enhanced Raman scattering substrate, including a conductive substrate, on which a Prussian blue analogue and a noble metal are successively arranged from bottom to top; the Prussian blue analogue is selected from Fe4[Fe(CN)6]3, Fe3[Fe(CN)6]2, Cu[Fe(CN)6], Cu2[Fe(CN)6], Cu3[Fe(CN)6]2, Co[Fe(CN)6], Co2[Fe(CN)6], Co3[Fe(CN)6]2, Ni3[Fe(CN)6]2 or Mn3[Fe(CN)6]2.

[0008] As a preferred embodiment, the noble metal is silver nanoparticles or gold nanoparticles.

[0009] The second object of the present invention is to provide a preparation method of the above-mentioned electrochemical surface-enhanced Raman scattering substrate, including the following steps:

[0010] Coat a precursor solution of a Prussian blue analogue on a conductive substrate and maintain it at a first constant potential to obtain a conductive substrate-Prussian blue substrate.

[0011] The conductive substrate - Prussian blue substrate is immersed in a solution containing noble metal ions and maintained at a second constant potential to obtain noble metal nanoparticles and in-situ deposit them on the surface of the conductive substrate - Prussian blue substrate, thereby obtaining an electrochemical surface enhanced Raman scattering substrate.

[0012] As a preferred embodiment, the Prussian blue analog is selected from Fe4[Fe(CN)6]3, Fe3[Fe(CN)6]2, Cu[Fe(CN)6], Cu2[Fe(CN)6], Cu3[Fe(CN)6]2, Co[Fe(CN)6], Co2[Fe(CN)6], Co3[Fe(CN)6]2, Ni3[Fe(CN)6]2 or Mn3[Fe(CN)6]2; on the conductive substrate - Prussian blue substrate, the coating thickness of the Prussian blue analog is 10 nm to 100 nm.

[0013] As a preferred embodiment, the precursor solution of the Prussian blue analog is prepared by dissolving metal salts of KCl, FeCl3 and K3Fe(CN)6 in ultrapure water and then adding HCl. Specifically: KCl, FeCl3 and K3Fe(CN)6 are added to 10 μL of ultrapure water such that the concentrations of KCl, FeCl3 and K3Fe(CN)6 are 0.1 M, 5 mM and 5 mM respectively, and then 32.2 μL of HCl is added to prepare the Prussian blue analog solution.

[0014] As a preferred embodiment, the noble metal nanoparticles are silver nanoparticles or gold nanoparticles, and the deposition thickness of the noble metal nanoparticles is 5 nm to 200 nm.

[0015] As a preferred embodiment, the conductive substrate is prepared from a low-resistance conductive carbon paste, and the thickness of the conductive substrate is 0.05 mm to 0.1 mm.

[0016] As a preferred embodiment, the first constant potential is -0.6 V to -0.4 V, and the holding time is 100 s to 400 s; the second constant potential is -0.6 V to -0.4 V, and the holding time is 50 s to 600 s.

[0017] The third object of the present invention is to provide an application of the above-mentioned electrochemical surface enhanced Raman scattering substrate in detecting acetamiprid.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] The present invention provides an electrochemical surface-enhanced Raman scattering substrate, which modifies a Prussian blue analogue and a noble metal on a conductive substrate, improving the sensitivity and stability of surface-enhanced Raman spectroscopy detection. The present invention introduces Prussian blue or its analogue nanoparticles into the conductive substrate, providing more anchoring sites, significantly improving the uniform deposition of noble metal nanoparticles on the conductive substrate, regulating the surface morphology, and at the same time improving the wettability of the conductive substrate surface, increasing the conductivity and specific surface area of the substrate. While increasing the conductivity of the substrate, introducing Prussian blue or its analogue is beneficial for controlling the potential and enabling target molecules to obtain better affinity on the electrode surface, thereby enhancing the stability and sensitivity of the surface-enhanced Raman scattering substrate. The present invention overcomes the problem of the inability to uniformly deposit silver nanoparticles on the conductive substrate by introducing Prussian blue analogues on the conductive substrate, and shows a significant surface-enhanced Raman scattering enhancement effect under an electric field, providing sensitive vibration spectral information suitable for monitoring the dynamics of target molecules.

[0020] The electrochemical surface-enhanced Raman scattering substrate provided by the present invention can simultaneously serve as a surface-enhanced Raman scattering substrate and an electrochemical electrode. By applying different constant voltages from -1.0 V to 0 V on the working electrode and using a Raman spectrometer to analyze the SERS signal, it is found that the best acetamiprid signal can be generated at -0.6 V. By detecting the intensity of the characteristic peak of acetamiprid at 630 cm -1 -1, the concentration detection of acetamiprid is realized. The detection limit is about 10 times lower than that of the conventional SERS detection method. The electrochemical surface-enhanced Raman spectroscopy substrate prepared by the present invention is not only superior to the traditional SERS platform in terms of sensitivity and stability, but can be easily reused by rinsing with pure water and maintain its high sensitivity. This EC-SERS method uses the direct detection of a label-free SERS substrate, providing a simple, reliable, safe and efficient strategy for the rapid and non-destructive identification of food contaminants. Description of the Drawings

[0021] Figure 1 is the SEM image of the electrochemical surface-enhanced Raman scattering substrate prepared by the present invention; among them, Figure a is the working electrode of the bare screen-printed electrode (SPE), Figure b is the screen-printed electrode-Prussian blue (SPE-PB), Figure c is the screen-printed electrode-Prussian blue-silver (SPE-PB-Ag) substrate, I, II, and III in Figure d respectively correspond to the macroscopic morphologies of the modified layers in Figure a, Figure b, and Figure c, Figure e is the TEM image of the screen-printed electrode-Prussian blue (SPE-PB), and Figure f is the TEM image of the screen-printed electrode-Prussian blue-silver (SPE-PB-Ag) substrate.

[0022] Figure 2 is the element distribution map of the screen-printed electrode-Prussian blue (SPE-PB).

[0023] Figure 3 Element distribution map of the printed electrode - Prussian blue - silver (SPE - PB - Ag) substrate.

[0024] Figure 4 Surface - enhanced Raman scattering spectra of acetamiprid at different concentrations of the present invention.

[0025] Figure 5 For the linear relationship diagram of the acetamiprid concentration in the range of 1 μM - 100 μM and the SERS intensity at 630 cm -1 .

[0026] Figure 6 Electrochemical surface - enhanced Raman scattering spectra of acetamiprid at different concentrations.

[0027] Figure 7 For the linear relationship diagram of the acetamiprid concentration in the range of 0.1 μM - 100 μM and the EC - SERS intensity at 630 cm -1 .

[0028] Figure 8 Influence diagram of applying different constant voltages (from open - circuit potential (OPC) to - 1.0 V) on the Raman spectrum of 100 μM acetamiprid.

[0029] Figure 9 Electrochemical surface - enhanced Raman scattering spectra of acetamiprid before and after applying voltage.

[0030] Figure 10 Schematic diagram of the electrochemical surface - enhanced Raman scattering detection process. Detailed implementation manners

[0031] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention will be further described below in conjunction with specific embodiments and drawings, but the embodiments cited do not limit the present invention. The following test methods and detection methods are all conventional methods unless otherwise specified; the reagents and raw materials are all commercially available unless otherwise specified.

[0032] Regarding the problems mentioned in the background technology of the present invention: First, when using the conventional SERS detection method, due to the large molecular weight of the detected substance and the reason that the SERS substrate and the substance to be detected cannot be closely close, sufficient SERS signals cannot be generated; Second, when using electrochemical - surface - enhanced Raman spectroscopy (EC - SERS) for detection, due to the uneven coverage of noble metal nanoparticles on the conductive substrate, the preparation of the SERS substrate is uneven, thus affecting the sensitivity and stability of the detection. The present invention provides an electrochemical surface - enhanced Raman scattering substrate, its preparation method and application.

[0033] The technical solution of the present invention will be described in detail below.

[0034] The present invention first provides an electrochemical surface-enhanced Raman scattering substrate, which includes a conductive substrate, and on the conductive substrate, there are Prussian blue analogs and noble metals from bottom to top in sequence.

[0035] In the above technical solution, modifying Prussian blue analogs and noble metals on the conductive substrate not only improves the conductivity and specific surface area of the substrate, but also realizes the uniform coverage of silver nanoparticles on the substrate, thereby improving the sensitivity and stability of surface-enhanced Raman spectroscopy detection. The present invention introduces Prussian blue or its analogs on the substrate, which is beneficial to controlling the potential and enabling the target molecule to obtain better affinity on the electrode surface, thereby enhancing the stability and sensitivity of the surface-enhanced Raman scattering substrate.

[0036] In order to further improve the conductivity of the electrochemical surface-enhanced Raman scattering substrate and improve the uniform coverage of silver nanoparticles, the Prussian blue analogs adopted in the present invention are selected from Fe4[Fe(CN)6]3, Fe3[Fe(CN)6]2, Cu[Fe(CN)6], Cu2[Fe(CN)6], Co[Fe(CN)6] or Co2[Fe(CN)6]. The above-provided Prussian blue analogs can all achieve the effects of improving the substrate conductivity and the uniform coverage of silver nanoparticles. In subsequent implementation cases, experiments are carried out using K3[Fe(CN)6] and the technical effects generated are elaborated.

[0037] It should be noted that the noble metal nanoparticles adopted in the present invention are silver nanoparticles or gold nanoparticles. The above noble metal nanoparticles can all achieve excellent conductivity and surface plasmon resonance effects. In subsequent embodiments of the present invention, silver nanoparticles are selected to carry out experiments and the effects are described.

[0038] The present invention also provides a preparation method of the above electrochemical surface-enhanced Raman scattering substrate, which includes the following steps:

[0039] Preparing a conductive substrate: Coating a low-resistance conductive carbon paste (purchased from Shenzhen Jieyongcheng Technology Co., Ltd., model: JC-2110) on a printing template, with a PVC (polyvinyl chloride) plastic sheet padded under the template, and drying at 30°C for 5 min in a dry place to obtain a conductive substrate with a thickness of 0.05 mm to 0.1 mm, that is, a screen-printed electrode.

[0040] Coating the precursor solution of Prussian blue analogs on the conductive substrate and maintaining it at a first constant potential of -0.4 V for 200 s to obtain a conductive substrate-Prussian blue substrate.

[0041] The conductive substrate - Prussian blue substrate is immersed in a solution containing noble metal ions and maintained at a second constant potential of -0.6 V for 200 s, obtaining noble metal nanoparticles that are uniformly and tightly deposited on the surface of the conductive substrate - Prussian blue substrate, thereby obtaining an electrochemical surface - enhanced Raman spectroscopy substrate.

[0042] To further improve the electrochemical surface - enhanced Raman scattering, the Prussian blue analog is selected from Fe4[Fe(CN)6]3, Fe3[Fe(CN)6]2, Cu[Fe(CN)6], Cu2[Fe(CN)6], Co[Fe(CN)6], or Co2[Fe(CN)6]; on the conductive substrate - Prussian blue substrate, the coating thickness of the Prussian blue analog is 10 nm to 100 nm. If the deposition amount is too small, less than 10 nm, it will lead to insufficient SERS enhancement and low detection sensitivity; if the deposition amount is too large, more than 100 nm, it will cause hindered electron transfer and reduced surface activity, thus interfering with the signal.

[0043] To illustrate the technical effect of introducing the Prussian blue analog on the electrochemical surface - enhanced Raman scattering detection of the present invention, in the subsequent examples of the present invention, the Prussian blue analog is Fe4[Fe(CN)6]3. The preparation method of the precursor solution of the above - mentioned Prussian blue analog is as follows: Add KCl, FeCl3, and K3Fe(CN)6 to 10 μL of ultrapure water, such that the concentrations of KCl, FeCl3, and K3Fe(CN)6 are 0.1 M, 5 mM, and 5 mM respectively, and then add 32.2 μL of HCl to prepare the Prussian blue analog solution.

[0044] As a preferred embodiment, the noble metal nanoparticles are silver nanoparticles or gold nanoparticles, and the deposition thickness of the noble metal nanoparticles is 5 nm to 200 nm. If the deposition amount is too small, less than 10 nm, it will lead to insufficient SERS enhancement and low detection sensitivity; if the deposition amount is too large, more than 100 nm, it will cause hindered electron transfer and reduced surface activity, thus interfering with the signal.

[0045] It should be noted that in the subsequent examples of the present invention, the noble metal nanoparticles used are silver nanoparticles, the solution of the above - mentioned noble metal ions is a solution containing noble metal ions Ag + and the solution containing noble metal ions Ag + is a 0.5 M H2SO4 solution containing 0.05 M AgNO3.

[0046] The following describes the technical effects of the present invention in combination with specific examples and comparative examples.

[0047] Example 1

[0048] An electrochemical surface-enhanced Raman scattering substrate, comprising a screen-printed electrode, on which Prussian blue Fe4[Fe(CN)6]3 and noble metal silver nanoparticles are successively arranged from bottom to top.

[0049] The preparation method of the above-mentioned electrochemical surface-enhanced Raman scattering substrate comprises the following steps:

[0050] S1, Prepare a screen-printed electrode: Coat a low-resistance conductive carbon paste (purchased from Shenzhen Jieyongcheng Technology Co., Ltd., model: JC-2110) on a printing template, with a polyvinyl chloride (PVC) plastic sheet padded under the template, and dry it at 30°C in a dry place for 5 minutes to obtain a conductive substrate with a thickness of 0.1 mm, which is the screen-printed electrode.

[0051] S2, Coat 100 μL of the precursor solution of Prussian blue Fe4[Fe(CN)6]3 on the screen-printed electrode, and maintain it at the first constant potential of -0.4 V for 200 s, with a coating thickness of 50 nm, to obtain a screen-printed electrode-Prussian blue substrate.

[0052] S3, Immerse the screen-printed electrode-Prussian blue substrate in a 0.5 M H2SO4 solution containing 0.05 M AgNO3, and maintain it at the second constant potential of -0.6 V for 200 s to obtain silver nanoparticles and deposit them uniformly and tightly on the surface of the screen-printed electrode-Prussian blue substrate. The deposition thickness of the silver nanoparticles is 20 nm, to obtain an electrochemical surface-enhanced Raman scattering substrate, denoted as SPE-PB-Ag substrate.

[0053] Example 2

[0054] An electrochemical surface-enhanced Raman scattering substrate, comprising a screen-printed electrode, on which Prussian blue Fe4[Fe(CN)6]3 and noble metal silver nanoparticles are successively arranged from bottom to top.

[0055] The preparation method of the above-mentioned electrochemical surface-enhanced Raman scattering substrate comprises the following steps:

[0056] S1, Prepare a screen-printed electrode: Coat a low-resistance conductive carbon paste (purchased from Shenzhen Jieyongcheng Technology Co., Ltd., model: JC-2110) on a printing template, with a polyvinyl chloride (PVC) plastic sheet padded under the template, and dry it at 30°C in a dry place for 5 minutes to obtain a conductive substrate with a thickness of 0.1 mm, which is the screen-printed electrode.

[0057] S2, Coat 100 μL of the precursor solution of Prussian blue Fe4[Fe(CN)6]3 on the screen-printed electrode, and maintain it at the first constant potential of -0.4 V for 200 s, with a coating thickness of 50 nm, to obtain a screen-printed electrode-Prussian blue substrate.

[0058] S3. Immerse the screen-printed electrode-PB substrate into a 0.5 M H2SO4 solution containing 0.05 M AgNO3, and maintain it at a second constant potential of -0.6 V for 200 s to obtain silver nanoparticles which are uniformly and tightly deposited on the surface of the screen-printed electrode-PB substrate. The deposition thickness of the nanoparticles is 50 nm, thereby obtaining an electrochemical surface-enhanced Raman scattering substrate, denoted as SPE-PB-Ag substrate.

[0059] Example 3

[0060] An electrochemical surface-enhanced Raman scattering substrate includes a screen-printed electrode, and on the screen-printed electrode, Prussian blue Fe4[Fe(CN)6]3 and noble metal silver nanoparticles are successively arranged from bottom to top.

[0061] The preparation method of the above-mentioned electrochemical surface-enhanced Raman scattering substrate includes the following steps:

[0062] S1. Prepare a screen-printed electrode: Coat a low-resistance conductive carbon paste (purchased from Shenzhen Jieyongcheng Technology Co., Ltd., model: JC-2110) on a printing template, with a PVC plastic sheet padded under the template, and dry it at 30 °C in a dry place for 5 min to obtain a conductive substrate with a thickness of 0.1 mm, i.e., the screen-printed electrode.

[0063] S2. Coat 100 μL of the precursor solution of Prussian blue Fe4[Fe(CN)6]3 on the screen-printed electrode, and maintain it at a first constant potential of -0.4 V for 200 s. The coating thickness is 100 nm to obtain a screen-printed electrode-PB substrate.

[0064] S3. Immerse the screen-printed electrode-PB substrate into a 0.5 M H2SO4 solution containing 0.05 M AgNO3, and maintain it at a second constant potential of -0.6 V for 200 s to obtain silver nanoparticles which are uniformly and tightly deposited on the surface of the screen-printed electrode-PB substrate. The deposition thickness of the nanoparticles is 50 nm, thereby obtaining an electrochemical surface-enhanced Raman scattering substrate, denoted as SPE-PB-Ag substrate.

[0065] Example 4

[0066] An electrochemical surface-enhanced Raman scattering substrate includes a screen-printed electrode, and on the screen-printed electrode, Prussian blue Fe4[Fe(CN)6]3 and noble metal silver nanoparticles are successively arranged from bottom to top.

[0067] The preparation method of the above-mentioned electrochemical surface-enhanced Raman scattering substrate includes the following steps:

[0068] S1. Preparation of screen-printed electrode: Coat a low-resistance conductive carbon paste (purchased from Shenzhen Jieyongcheng Technology Co., Ltd., model: JC-2110) on a printing template with a polyvinyl chloride (PVC) plastic sheet placed under the template, and dry it at 30 °C in a dry place for 5 min to obtain a conductive substrate with a thickness of 0.1 mm, i.e., the screen-printed electrode.

[0069] S2. Coat 100 μL of the precursor solution of Prussian blue Fe4[Fe(CN)6]3 on the screen-printed electrode, maintain it at the first constant potential of -0.4 V for 200 s, and the coating thickness is 100 nm to obtain a screen-printed electrode-Prussian blue substrate.

[0070] S3. Immerse the screen-printed electrode-Prussian blue substrate in a 0.5 M H2SO4 solution containing 0.05 M AgNO3, maintain it at the second constant potential of -0.6 V for 200 s, obtain silver nanoparticles and deposit them uniformly and tightly on the surface of the screen-printed electrode-Prussian blue substrate, and the deposition thickness of the nanoparticles is 100 nm to obtain an electrochemical surface-enhanced Raman scattering substrate, denoted as the SPE-PB-Ag substrate.

[0071] Example 5

[0072] An electrochemical surface-enhanced Raman scattering substrate includes a screen-printed electrode, and on the screen-printed electrode, Prussian blue Fe4[Fe(CN)6]3 and noble metal silver nanoparticles are successively arranged from bottom to top.

[0073] The preparation method of the above-mentioned electrochemical surface-enhanced Raman scattering substrate includes the following steps:

[0074] S1. Preparation of screen-printed electrode: Coat a low-resistance conductive carbon paste (purchased from Shenzhen Jieyongcheng Technology Co., Ltd., model: JC-2110) on a printing template with a polyvinyl chloride (PVC) plastic sheet placed under the template, and dry it at 30 °C in a dry place for 5 min to obtain a conductive substrate with a thickness of 0.1 mm, i.e., the screen-printed electrode.

[0075] S2. Coat 100 μL of the precursor solution of Prussian blue Fe4[Fe(CN)6]3 on the screen-printed electrode, maintain it at the first constant potential of -0.4 V for 200 s, and the coating thickness is 50 nm to obtain a screen-printed electrode-Prussian blue substrate.

[0076] S3. Immerse the screen-printed electrode-Prussian blue substrate in a 0.5 M H2SO4 solution containing 0.05 M AgNO3, maintain it at the second constant potential of -0.6 V for 200 s, obtain silver nanoparticles and deposit them uniformly and tightly on the surface of the screen-printed electrode-Prussian blue substrate, and the deposition thickness of the nanoparticles is 200 nm to obtain an electrochemical surface-enhanced Raman scattering substrate, denoted as the SPE-PB-Ag substrate.

[0077] To further illustrate the technical effects of the present invention, the present invention also provides comparative examples as follows:

[0078] Comparative Example 1

[0079] Compared with Example 1, the difference is that instead of coating the Prussian blue solution on the conductive substrate, silver nanoparticles are directly deposited.

[0080] An electrochemical surface-enhanced Raman scattering substrate includes a screen-printed electrode, and noble metal silver nanoparticles are deposited on the screen-printed electrode.

[0081] The preparation method of the above-mentioned electrochemical surface-enhanced Raman scattering substrate includes the following steps:

[0082] S1. Prepare a screen-printed electrode: Coat a low-resistance conductive carbon paste (purchased from Shenzhen Jieyongcheng Technology Co., Ltd., model: JC-2110) on a printing template, with a polyvinyl chloride (PVC) plastic sheet padded under the template, and dry it at 30 °C in a dry place for 5 min to obtain a conductive substrate with a thickness of 0.1 mm, that is, the screen-printed electrode.

[0083] S2. Immerse the screen-printed electrode in a 0.5 M H2SO4 solution containing 0.05 M AgNO3, and maintain it at a second constant potential of -0.6 V for 200 s to obtain silver nanoparticles and deposit them on the surface of the screen-printed electrode. The deposition thickness of the silver nanoparticles is 20 nm, and an electrochemical surface-enhanced Raman scattering substrate is obtained, denoted as SPE-Ag substrate.

[0084] Comparative Example 2

[0085] Compared with Example 1, the difference is that only the screen-printed electrode is used as the electrochemical surface-enhanced Raman scattering substrate, without coating the Prussian blue analog and without depositing silver nanoparticles.

[0086] An electrochemical surface-enhanced Raman scattering substrate includes a screen-printed electrode.

[0087] The preparation method of the above-mentioned electrochemical surface-enhanced Raman scattering substrate includes the following steps:

[0088] Prepare a screen-printed electrode: Coat a low-resistance conductive carbon paste (purchased from Shenzhen Jieyongcheng Technology Co., Ltd., model: JC-2110) on a printing template, with a polyvinyl chloride (PVC) plastic sheet padded under the template, and dry it at 30 °C in a dry place for 5 min to obtain a conductive substrate with a thickness of 0.1 mm, that is, the screen-printed electrode, denoted as SPE substrate.

[0089] The morphological and performance characterizations of the electrochemically surface-enhanced Raman scattering substrates prepared in the embodiments and comparative examples of the present invention are as follows.

[0090] To observe the morphologies of the bare screen-printed electrode (SPE) of Comparative Example 2, the screen-printed electrode - Prussian blue (SPE-PB) of Comparative Example 1, and the screen-printed electrode - Prussian blue - silver (SPE-PB-Ag) of the embodiment, scanning electron microscope (SEM) images were taken. As Figure 1 shown, the process was first to electrochemically deposit a Prussian blue (PB) film onto the original screen-printed electrode at a controllable potential, as shown in Figure 1 Figure a in it, forming a uniform and dense coating on the electrode surface, as shown in Figure 1 Figure b in it. Subsequently, a large number of silver nanoparticles (Ag NPs) were introduced onto the Prussian blue-modified surface, improving the flexibility and functionality of the substrate, as shown in Figure 1 Figure c in it. This modification caused a significant visual change on the electrode surface, indicating the successful modification of Prussian blue and silver nanoparticles, as shown in Figure 1 Figure d in it. Figure 1 Figures e and f in it prove the TEM images of the screen-printed electrode - Prussian blue (SPE-PB), and Figure f is the TEM image of the screen-printed electrode - Prussian blue - silver (SPE-PB-Ag) substrate.

[0091] Figure 2 The elemental distribution map of the screen-printed electrode - Prussian blue (SPE-PB) shows the presence of iron (Fe) and nitrogen (N) elements, confirming the presence of Prussian blue nanoparticles on the surface of the screen-printed electrode. After modification with silver nanoparticles, small particle structures appeared, indicating that the silver nanoparticles densely and relatively uniformly covered the surface of the working electrode, as shown in Figure 3 shown. This modification enriched the composition of the substrate and endowed it with the enhanced performance crucial for effective electrochemically surface-enhanced Raman scattering (EC-SERS) detection.

[0092] Steps for electrochemically surface-enhanced Raman scattering (EC-SERS) detection of acetamiprid (AAP)

[0093] First, prepare a 0.1 M sodium chloride (NaCl) solution with pH = 7 as the background electrolyte for the acetamiprid solution. Then, place the SPE-PB-Ag substrate prepared in the embodiment at the electrode interface and add 50 μL of the acetamiprid solution to completely immerse the three electrodes. Collect the electrochemically surface-enhanced Raman scattering spectrum after applying the potential for 50 seconds.

[0094] In electrochemical surface-enhanced Raman scattering (EC-SERS) detection, using sodium chloride solution as the background electrolyte for acetamiprid solution can provide sufficient ionic strength to ensure the smooth progress of the electrochemical reaction and maintain the conductivity of the electrochemical cell; the sodium chloride solution helps to stabilize the electrochemical environment, reduce the influence of other interfering substances, and ensure the consistency of experimental conditions; the presence of sodium chloride can optimize the charge distribution on the nanostructured surface, enhance the SERS effect, and thus improve the Raman signal of acetamiprid. Although sodium chloride itself may produce signals in the Raman spectrum, these signals are usually weak and easy to distinguish. The Raman signal of acetamiprid will be significantly enhanced on the SERS substrate, so the measured Raman spectrum mainly reflects the molecular vibration information of acetamiprid rather than the signal of sodium chloride.

[0095] To determine the optimal potential for electrochemical surface-enhanced Raman scattering, the constant potential was varied from the open circuit potential (OCP) in 0.1 V steps to -1.0 V, and the spectra of 100 μM acetamiprid were recorded. Acetamiprid solutions with different concentrations (0.1, 1, 5, 10, 30, 50, 80, 100 μM) were prepared, and electrochemical surface-enhanced Raman scattering spectra were collected at the most suitable potential. All measurements were carried out at room temperature, and the sample volume was kept at 50 μL. Each potential was tested at least three times, the total measurement time was controlled within 300 seconds, and the average value and standard deviation of the results were calculated.

[0096] By applying different constant voltages from -1.0 V to 0 V on the working electrode and analyzing the SERS signals using a Raman spectrometer, it was found that the best acetamiprid signal could be generated at -0.6 V. At the potential of -0.6 V, the EC-SERS band at 630 cm -1 was used to measure the concentration of acetamiprid and its corresponding SERS intensity. As Figure 6 shown, a standard curve for quantitative analysis of AAP was established. As Figure 7 shown, its standard curve was Y = 19.9X + 79, the correlation coefficient R 2 = 0.9950, and the low detection limit was 0.038 μM.

[0097] Meanwhile, the present invention also used the SERS band at 630 cm -1 to measure the concentration of acetamiprid and its corresponding SERS intensity at the potential of -0.6 V. As Figure 4 shown, a standard curve for quantitative analysis of AAP was established. As Figure 5 shown, its standard curve was Y = 3.4X + 58, the correlation coefficient R 2 = 0.9936, and the low detection limit was 0.366 μM.

[0098] As Figure 4 shown, as the concentration of AAP increased, at 630 cm-1 The Raman intensity of the characteristic peak gradually increases. The signal intensity of the prepared electrochemical surface-enhanced Raman scattering substrate is much higher than that of the conventional SERS detection. A good linear relationship is presented in the concentration range of AAP from 0.10 μM to 100 μM, as Figure 7 , and the regression equation is Y = 19.9X + 79, with the correlation coefficient R 2 = 0.9950. The low detection limit is 0.038 μM, which is about 10 times lower than the conventional SERS detection limit (0.366 μM).

[0099] For the application of EC-SERS detection of the SPE-PB-Ag substrate, experiments were carried out with negative samples spiked. It was detected that the sample did not contain acetamiprid. By adding acetamiprid to test Raman and detecting the Raman intensity of the actual sample added with acetamiprid, the recovery rate was determined to verify the feasibility of the method.

[0100] (1) Sample pretreatment: Thoroughly chop, mix and homogenize the tomato sample (or bean sample). Weigh 10 g of the sample, mix it with 10 mL of acetonitrile, then shake and stir. Subsequently, anhydrous magnesium sulfate, sodium chloride, trisodium citrate dihydrate and disodium citrate are added in turn, shake vigorously and centrifuge, collect the supernatant and refrigerate it at 4 °C. Acetamiprid is added to these treated samples to make its final concentration reach 0.6 μM, 6 μM and 60 μM.

[0101] (2) For electrochemical surface-enhanced Raman scattering (EC-SERS) measurement, drop a sample liquid onto the SPE-PB-Ag substrate, let it dry naturally, and then carefully add 50 μL of electrolyte for detection. After the sample is dried, repeat the dropping multiple times to enhance the Raman test result. Finally, bring the measured SERS signal of AAP into the standard curve Y = 19.9X + 79 to calculate the concentration of AAP in the sample.

[0102] It can be seen from Figure 8 that applying different electrode potentials also affects the surface-enhanced Raman scattering peak intensity of acetamiprid. As the electrode potential decreases from 0 V, the surface-enhanced Raman scattering signal increases and reaches the maximum value at -0.6 V, which is about 7 times that at the open circuit potential (OCP), as Figure 9 shown. These results confirm the feasibility of the screen-printed electrode - Prussian blue - silver substrate for electrochemical surface-enhanced Raman scattering (EC-SERS) detection. Due to the excitation of local surface plasmon resonance (LSPR), the Raman scattering of acetamiprid (AAP) molecules in the oscillating electromagnetic field is enhanced. In the potential range from -1.0 V to 0 V, the change in the surface-enhanced Raman scattering (SERS) peak intensity is synchronous. At 630 cm -1The surface-enhanced Raman scattering signal at [[]] is attributed to the C-C-C vibration of the pyridine ring, indicating that the adsorption orientation of the pyridine ring on the surface of the screen-printed electrode-prussian blue-silver (SPE-PB-Ag) is stable. Applying a potential of -0.6 V can effectively form the interaction between the molecule and the surface, and help attract more acetamiprid molecules to the "hot spots" of the screen-printed electrode-prussian blue-silver substrate, as Figure 10 shown.

[0103] In summary, the present invention introduces a prussian blue analogue onto the electrochemical surface-enhanced Raman scattering substrate, improving the conductivity of the substrate and enhancing the interaction between the screen-printed electrode-prussian blue-silver substrate and the target molecule, thereby improving the sensitivity and stability of EC-SERS detection. In addition, the electrochemical surface-enhanced Raman scattering substrate prepared by the present invention can be easily reused by rinsing with pure water and can maintain its high sensitivity.

[0104] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. An electrochemical surface-enhanced Raman scattering substrate, characterized in that, It includes a conductive substrate, on which a Prussian blue analogue and a noble metal are successively arranged from bottom to top; The Prussian blue analogue is selected from Fe4[Fe(CN)6]3, Fe3[Fe(CN)6]2, Cu[Fe(CN)6], Cu2[Fe(CN)6], Cu3[Fe(CN)6]2, Co[Fe(CN)6], Co2[Fe(CN)6], Co3[Fe(CN)6]2, Ni3[Fe(CN)6]2 or Mn3[Fe(CN)6]2.

2. The electrochemical surface-enhanced Raman scattering substrate according to claim 1, wherein The noble metal is silver nanoparticles or gold nanoparticles.

3. A method for preparing the electrochemical surface-enhanced Raman scattering substrate according to claim 1, characterized in that, It includes the following steps: Coat the precursor solution of the Prussian blue analogue on the conductive substrate and maintain it at a first constant potential to obtain a conductive substrate-Prussian blue substrate; Immerse the conductive substrate-Prussian blue substrate in a solution containing noble metal ions and maintain it at a second constant potential to obtain noble metal nanoparticles and in-situ deposit them on the surface of the conductive substrate-Prussian blue substrate to obtain an electrochemical surface-enhanced Raman scattering substrate.

4. The preparation method according to claim 3, characterized in that, The Prussian blue analogue is selected from Fe4[Fe(CN)6]3, Fe3[Fe(CN)6]2, Cu[Fe(CN)6], Cu2[Fe(CN)6], Cu3[Fe(CN)6]2, Co[Fe(CN)6], Co2[Fe(CN)6], Co3[Fe(CN)6]2, Ni3[Fe(CN)6]2 or Mn3[Fe(CN)6]2; on the conductive substrate-Prussian blue substrate, the coating thickness of the Prussian blue analogue is 10 nm to 100 nm.

5. The preparation method according to claim 3, characterized in that, The precursor solution of the Prussian blue analogue is prepared by dissolving KCl, FeCl3 and K3Fe(CN)6 as metal salts in ultrapure water and then adding HCl.

6. The preparation method according to claim 3, wherein The noble metal nanoparticles are silver nanoparticles or gold nanoparticles, and the deposition thickness of the noble metal nanoparticles is 5 nm to 200 nm.

7. The preparation method according to claim 3, characterized in that, The conductive substrate is prepared from a low-resistance conductive carbon paste, and the thickness of the conductive substrate is 0.05 mm to 0.1 mm.

8. The preparation method according to claim 3, characterized in that, The first constant potential is -0.6 V to -0.4 V, and the holding time is 100 s to 400 s; the second constant potential is -0.6 V, and the holding time is 50 s to 600 s.

9. Application of the electrochemical surface-enhanced Raman scattering substrate according to claim 1 or 2 in detecting acetamiprid.

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