An Ag-SrTiO3 composite SERS substrate, its preparation method and application

Abstract

The application belongs to the technical field of SERS detection, and relates to an Ag-SrTiO3 composite SERS substrate and a preparation method and application thereof. Ag nanoparticles with uniform distribution and same size are prepared by a sodium citrate reduction method; SrTiO3 material is prepared by a high-temperature solid-phase method; and finally, a new SERS substrate Ag-SrTiO3 is prepared by a physical stirring method. The application constructs a new SERS substrate of Ag nanoparticles and cubic SrTiO3 material, which is different from a conventional SERS substrate of single Ag nanoparticles, and can detect stronger intrinsic Raman signals of probe molecules. Because the preparation of the SERS substrate needs to be combined with the cubic SrTiO3 material, charge transfer can occur at the interface where the SERS substrate contacts the probe molecules, and thus the intrinsic Raman signals of the probe molecules can be enhanced, and the SERS substrate can be better used for detecting and analyzing chemical substances.

Description

Technical Field

[0001] This invention belongs to the field of SERS detection technology, specifically relating to an Ag-SrTiO3 composite SERS substrate, its preparation method, and its application. Background Technology

[0002] p-Mercaptobenzoic acid (4-MBA), an important organosulfur compound, has wide applications in organic synthesis and materials science; however, its environmental behavior and potential hazards have also attracted widespread attention. Studies have shown that p-Mercaptobenzoic acid, once introduced into the environment, can negatively impact aquatic and soil ecosystems. Its high chemical stability and slow degradation can lead to persistent pollution and potential toxicity to higher organisms through bioaccumulation. Therefore, developing efficient and sensitive detection methods is crucial for assessing its environmental impact. Accurate detection of p-Mercaptobenzoic acid not only helps monitor its distribution and migration patterns in the environment but also provides a scientific basis for pollution control and ecological risk assessment, thereby reducing its potential threats to the environment and biological health. Furthermore, optimization of detection technologies can further promote the standardized management of p-Mercaptobenzoic acid in industrial applications, contributing to the achievement of green chemistry and sustainable development goals.

[0003] SERS, a highly sensitive, selective, and non-destructive analytical technique derived from metal surfaces, generates a large scattering cross-section, achieving several orders of magnitude enhancement, and is applied in various fields such as surface science, catalysis, and chemistry. Most importantly, it has made breakthroughs in the detection of trace pollutants. The plasmon resonance effect of Ag NPs generates a strong local electromagnetic field, exhibiting electromagnetic field enhancement, and has been proven by many researchers to be the most common metal substrate for SERS. SrTiO3, a typical perovskite material, is simple to synthesize. When 4-MBA molecules adsorb onto the SrTiO3 surface, the energy level matching between SrTiO3 and 4-MBA molecules leads to charge transfer, thereby enhancing the Raman signal. Furthermore, SrTiO3 has high structural stability and is not easily decomposed under high temperatures or strong laser irradiation, which is important for the practical application of SERS substrates. Therefore, it is an ideal material for SERS substrates. Combining Ag NPs and SrTiO3 can create a SERS substrate with both electromagnetic and chemical enhancement, which can be efficiently applied to the detection of 4-MBA molecules with high sensitivity and stability. There are no reports on the use of Ag NPs and SrTiO3 composites as SERS substrates for the detection of 4-MBA molecules. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention designs and synthesizes an Ag-SrTiO3 composite SERS substrate. Charge transfer can occur at the interface between this SERS substrate and probe molecules, thereby enhancing the intrinsic Raman signal of the probe molecules and enabling better detection and analysis of chemical substances.

[0005] The technical solution adopted in this invention is as follows:

[0006] An Ag-SrTiO3 composite SERS substrate, the preparation method of which includes the following steps:

[0007] 1) Dissolve sodium citrate powder in water, add silver nitrate, and obtain Ag nanoparticles by chemical reduction.

[0008] 2) SrTiO3 and SrCl2·6H2O were ground until uniformly dispersed, prepared by flux treatment, calcined in a muffle furnace, filtered, and then dried in an oven to obtain high-purity cubic SrTiO3.

[0009] 3) After sonicating the SrTiO3 solution in the Ag nanoparticle solution, stir thoroughly.

[0010] 4) The composite substrate obtained in step 3) is dried in an oven to obtain the Ag-SrTiO3 composite SERS substrate.

[0011] Furthermore, the above-mentioned Ag-SrTiO3 composite SERS substrate is characterized in that, in step 1), the chemical reduction method is carried out at a speed of 1100 rpm, a temperature of 100-130℃, and stirring for 0.8 h.

[0012] Furthermore, the above-mentioned Ag-SrTiO3 composite SERS substrate is characterized in that, in step 2), the mass ratio of strontium titanate to strontium chloride hexahydrate is 1:14.5, and the grinding time is 3 min.

[0013] Furthermore, the Ag-SrTiO3 composite SERS substrate described above is characterized in that, in step 2), the flux treatment method involves calcination in a crucible muffle furnace at a temperature of 1100°C for 10 hours.

[0014] Furthermore, the Ag-SrTiO3 composite SERS substrate described above is characterized in that, in step 3), the ultrasonic time is 20-40 min and the stirring time is 1.5-3 h.

[0015] Furthermore, the Ag-SrTiO3 composite SERS substrate described above is characterized in that, in step 4), the drying temperature is 50-70℃ and the drying time is 1.5-4h.

[0016] Application of the Ag-SrTiO3 composite SERS substrate described in any of the above-mentioned methods in the detection of 4-MBA molecules in water.

[0017] Furthermore, the above application is carried out as follows: under 532nm laser irradiation, the Ag-SrTiO3 composite SERS substrate is immersed in 4-MBA solution, which enhances the Raman signal of 4-MBA molecules and facilitates the detection of 4-MBA molecules in water.

[0018] This invention utilizes a constructed Ag-SrTiO3 composite SERS substrate to enhance the Raman spectrum of 4-MBA molecules, facilitating their detection in water. The beneficial effects of this method can be attributed to three aspects:

[0019] 1. The Ag-SrTiO3 composite structure disperses Ag nanoparticles through SrTiO3 support, inhibits agglomeration and forms uniform nano gaps, significantly increasing the density of electromagnetic hot spots.

[0020] 2. The introduction of SrTiO3 accelerates the propagation rate of electrons and holes, thereby enhancing the Raman spectrum of 4-MBA molecules.

[0021] 3. The polar surface of SrTiO3 fixes the upright adsorption of 4-MBA molecules and optimizes the electronic coupling path, thus synergistically improving the chemical enhancement efficiency. Attached Figure Description

[0022] Figure 1 This is the XRD pattern of the cubic SrTiO3 and Ag-SrTiO composite substrate in Example 1.

[0023] Figure 2 These are the Raman spectra of 4-MBA molecules under 532nm laser light in Example 1, and the SERS spectra of 4-MBA molecules adsorbed on Ag nanoparticles and Ag-SrTiO3 composite substrates, respectively.

[0024] Figure 3 The SERS spectrum is the result of 10 random Raman detections of 4-MBA molecules on an Ag-SrTiO3 composite substrate irradiated with a 532nm laser in Example 1.

[0025] Figure 4 This is the SERS spectrum of different concentrations of 4-MBA molecules adsorbed on the Ag-SrTiO3 composite substrate under 532nm laser light in Example 1. Detailed Implementation

[0026] To better understand the technical solution of the present invention, specific embodiments are provided for further detailed description, but the solution is not limited thereto.

[0027] Example 1: An Ag-SrTiO3 composite SERS substrate

[0028] The preparation method is as follows:

[0029] 1) Dissolve 2g of sodium citrate powder in a clean beaker containing 100mL of deionized water. After standing for a period of time, put the solution into a 100mL volumetric flask to obtain a 2% sodium citrate solution.

[0030] 2) Add 2 mL of sodium citrate solution and 0.036 g of silver nitrate to a round-bottom flask containing 100 mL of deionized water, and heat at 130 °C and stir for 0.8 h at a speed of 1100 rpm. Collect the resulting Ag nanoparticle solution in a volumetric flask.

[0031] 3) Weigh 14.5g of SrCl2·6H2O and 1g of SrTiO3 and place them in a mortar. Grind them for 10 minutes to make them evenly mixed. Then place them in an Al2O3 crucible and calcine them in a muffle furnace at 1100℃ for 10 hours. Filter them and then dry them in an oven at 60℃ for 12 hours to obtain SrTiO3 for later use.

[0032] 4) The Ag nanoparticle solution prepared in step 2) and the SrTiO3 prepared in step 3) are mixed and subjected to ultrasonication for 20-40 min and stirring for 1.5-3 h respectively. Then, they are placed in an oven and dried at a temperature of 50-70℃ for 1.5-4 h to obtain the Ag-SrTiO3 composite SERS substrate.

[0033] 5) Immerse the prepared Ag-SrTiO3 composite SERS substrate in 4-MBA solution for 2 hours, and air dry at room temperature for later use.

[0034] XRD was performed on the SrTiO3 and Ag-SrTiO3 prepared in steps 3) and 4), respectively. The test results are as follows: Figure 1 As shown in the figure, the successful preparation of the Ag-SrTiO3 composite SERS substrate can be seen.

[0035] The Ag-SrTiO3 composite SERS substrate prepared in Example 1 was used for experiments based on SERS technology with 4-MBA as the probe molecule. The testing procedure was as follows: a 532nm wavelength laser was used as the excitation source, and 4-MBA was used as the probe molecule for testing on the Ag-SrTiO3 composite SERS substrate based on SERS technology. Figure 2 , Figure 3 , Figure 4As shown, the Ag-SrTiO3 composite SERS substrate prepared in Example 1 can enhance the Raman signal of 4-MBA molecules, facilitating their detection in water. Furthermore, 10 random Raman tests were performed on the Ag-SrTiO3 composite substrate to detect 4-MBA molecules, revealing uniform Raman signal peaks and no significant changes in Raman intensity, indicating that the Ag-SrTiO3 composite SERS substrate possesses good uniformity and reproducibility. In addition, the prepared Ag-SrTiO3 composite SERS substrate can detect different concentrations of 4-MBA molecules, and it maintains high sensitivity even at extremely low concentrations, demonstrating the excellent enhancement effect of this Ag-SrTiO3 composite SERS substrate.

Claims

1. An application of an Ag-SrTiO3 composite SERS substrate in the detection of 4-MBA molecules in water, characterized in that, Immersing the Ag-SrTiO3 composite SERS substrate in a 4-MBA solution under 532nm laser irradiation enhanced the Raman signal of 4-MBA molecules, making it easier to detect 4-MBA molecules in water. The preparation method of Ag-SrTiO3 composite SERS substrate includes the following steps: 1) Dissolve sodium citrate powder in water, add silver nitrate, and obtain Ag nanoparticles by chemical reduction. 2) SrTiO3 and SrCl2·6H2O were ground to uniform dispersion at a mass ratio of 1:14.5, and prepared by flux treatment. The mixture was calcined in a muffle furnace at 1100 °C for 10 h, filtered, and then dried in an oven to obtain high-purity cubic phase SrTiO3. 3) After sonicating the high-purity cubic SrTiO3 in the Ag nanoparticle solution, stir thoroughly. 4) The composite substrate obtained in step 3) is dried in an oven to obtain the Ag-SrTiO3 composite SERS substrate.

2. The application of the Ag-SrTiO3 composite SERS substrate according to claim 1 in the detection of 4-MBA molecules in water, characterized in that, In step 1), the chemical reduction method is to maintain a speed of 1100 rpm, a temperature of 100-130℃, and stir for 0.8 h.

3. The application of the Ag-SrTiO3 composite SERS substrate according to claim 1 in the detection of 4-MBA molecules in water, characterized in that, In step 2), the grinding time is 3 minutes.

4. The application of the Ag-SrTiO3 composite SERS substrate according to claim 1 in the detection of 4-MBA molecules in water, characterized in that, In step 3), the ultrasonic time is 20-40 min and the stirring time is 1.5-3 h.

5. The application of the Ag-SrTiO3 composite SERS substrate according to claim 1 in the detection of 4-MBA molecules in water, characterized in that, In step 4), the drying temperature is 50-70 ℃ and the drying time is 1.5-4 h.

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