An AgNPs-Bi3NbTiO9 composite SERS substrate material, its preparation method, and its application in organic molecule detection.

Abstract

This invention relates to an AgNPs-Bi3NbTiO9 composite SERS substrate material, its preparation method, and its application in the detection of organic molecules, belonging to the field of surface-enhanced Raman spectroscopy and functional composite materials technology. This invention prepares a Bi3NbTiO9 support via a molten salt method and combines it with an ascorbic acid in-situ reduction strategy to uniformly load silver nanoparticles onto its surface, achieving a synergistic effect of plasma enhancement and interfacial charge transfer. The prepared material exhibits good structural stability and a high-density "hot spot" distribution, demonstrating excellent Raman enhancement performance for 4-mercaptobenzoic acid molecules. Experimental results show that this composite substrate has stronger signal enhancement and better uniformity than a single Ag substrate, achieving highly sensitive detection of target molecules at the ppm level in river water. The material preparation method described in this invention is simple, reproducible, and suitable for the rapid detection of trace organic pollutants in environmental water bodies.

Description

Technical Field

[0001] This invention belongs to the field of surface-enhanced Raman spectroscopy detection and functional composite materials technology, specifically relating to an AgNPs-Bi3NbTiO9 composite SERS substrate material, its preparation method, and its application in organic molecule detection. Background Technology

[0002] With the increasing severity of environmental pollution, rapid detection of trace organic pollutants in water bodies has become a research hotspot. 4-Mercaptobenzoic acid (4-MBA), as a typical sulfur-containing aromatic molecule, is often used as a SERS probe molecule, but it also poses certain environmental risks.

[0003] Traditional detection methods such as high-performance liquid chromatography (HPLC) and mass spectrometry (MS) offer high sensitivity, but suffer from drawbacks such as expensive equipment and complex operation. In contrast, surface-enhanced Raman scattering (SERS) technology has attracted widespread attention due to its speed, sensitivity, and strong molecular fingerprint recognition capabilities.

[0004] Currently, most common SERS substrates rely on noble metal nanostructures, but these suffer from poor stability and insufficient reproducibility. Constructing heterostructures by combining noble metals with semiconductor materials is considered an important strategy for improving SERS performance. However, existing research largely focuses on simple loading structures, and the synergistic mechanism of interfacial charge transfer and local electromagnetic enhancement remains insufficient.

[0005] Therefore, it is of great significance to develop a composite SERS substrate material that is structurally stable, has a significant reinforcing effect, and is suitable for testing complex systems. Summary of the Invention

[0006] The present invention aims to provide an AgNPs-Bi3NbTiO9 composite SERS substrate material with excellent enhancement properties and good stability, and to establish a method for detecting organic molecules in actual water bodies.

[0007] The technical solution adopted in this invention is as follows: an AgNPs-Bi3NbTiO9 composite SERS substrate material is prepared by molten salt method to prepare Bi3NbTiO9 support, and Ag nanoparticles are grown in situ on the surface of Bi3NbTiO9 support in ascorbic acid reduction system to obtain AgNPs-Bi3NbTiO9 composite SERS substrate material with enhanced Raman signal capability.

[0008] A method for preparing the above-mentioned AgNPs-Bi3NbTiO9 composite SERS substrate material is as follows: Bi3NbTiO9 powder is dispersed in deionized water, ultrasonically treated to form a uniform suspension, silver nitrate solution is added, and the mixture is stirred and mixed evenly. Then, ascorbic acid solution is added dropwise, and the reaction is continuously stirred at room temperature. During the process, the solution gradually turns light gray, indicating the formation of Ag nanoparticles. After the reaction is completed, the product is collected by centrifugation, washed several times, and dried to obtain the AgNPs-Bi3NbTiO9 composite SERS substrate material.

[0009] The preparation method of the AgNPs-Bi3NbTiO9 composite SERS substrate material is as follows: Bi2O3, TiO2, Nb2O5 are mixed with NaCl-KCl mixed salt, ground to make them fully mixed and uniform, calcined, cooled to room temperature, washed to remove molten salt, and dried to obtain Bi3NbTiO9 powder.

[0010] The above-mentioned method for preparing an AgNPs-Bi3NbTiO9 composite SERS substrate material, according to the cation molar ratio, Bi 3 + Ti 4+ :Nb 5+ The ratio is 3-3.2:1:1.

[0011] In the above-mentioned method for preparing AgNPs-Bi3NbTiO9 composite SERS substrate material, the molar ratio of NaCl to KCl in the NaCl-KCl mixed salt is 1:1.

[0012] The above-mentioned method for preparing AgNPs-Bi3NbTiO9 composite SERS substrate material involves calcination at 700-900℃ for 2-4 hours.

[0013] The above-mentioned method for preparing an AgNPs-Bi3NbTiO9 composite SERS substrate material uses a molar ratio of Bi3NbTiO9:silver nitrate = 5-6:1.

[0014] In the above-mentioned method for preparing AgNPs-Bi3NbTiO9 composite SERS substrate material, the dropping rate of ascorbic acid solution is 1 mL / min.

[0015] An AgNPs-Bi3NbTiO9 composite SERS substrate is prepared by dispersing the AgNPs-Bi3NbTiO9 composite SERS substrate material in deionized water, drop-coating the solution onto the surface of a silicon wafer, and drying to form the AgNPs-Bi3NbTiO9 composite SERS substrate.

[0016] An application of the above-mentioned AgNPs-Bi3NbTiO9 composite SERS substrate in the detection of organic molecules, wherein the organic molecule is 4-MBA.

[0017] Compared with the prior art, the present invention has the following beneficial effects.

[0018] 1. Significant Enhancement: The introduction of Ag nanoparticles allows their localized surface plasmon resonance (LSPR) effect to generate a strong localized electromagnetic field under incident light excitation, thereby significantly amplifying the Raman scattering signal of the analyte molecule. Simultaneously, the controllable size and distribution of Ag nanoparticles facilitate the formation of high-density "hot spots," further enhancing the overall signal intensity.

[0019] 2. Clear interfacial synergy: Ag nanoparticles and Bi3NbTiO9 semiconductors form a tight interfacial contact. Under illumination, Ag, as an electron-rich aggregate, can effectively capture photogenerated electrons, while Bi3NbTiO9 provides a charge transfer channel. The two work synergistically to promote charge separation and migration. This "metal-semiconductor" synergistic mechanism not only enhances the electromagnetic effect but also further improves the Raman signal sensitivity through chemical enhancement (charge transfer mechanism).

[0020] 3. High structural stability: Bi3NbTiO9 itself is a layered perovskite oxide with good chemical inertness, and it is not easily dissolved or structurally damaged in acidic or weakly alkaline aqueous solutions. Furthermore, it is not prone to photocorrosion or photodegradation under prolonged light exposure, maintaining the integrity of the material structure. In addition, its composite system can be stored for a long time at room temperature and pressure with minimal performance degradation, which is beneficial for long-term storage and repeated use in practical applications.

[0021] 4. Excellent uniformity: By rationally controlling the loading mode of Ag nanoparticles on the Bi3NbTiO9 surface, a relatively uniform dispersion state can be achieved, thus making the "hot spots" more uniformly distributed on the substrate surface. This uniform distribution effectively reduces signal fluctuations during the test, improves the consistency between different test points, and makes the Raman signal have good repeatability and comparability.

[0022] 5. Strong practical applicability: This composite material maintains good detection performance in complex aquatic environments (such as actual water samples containing multiple ions, organic matter, or suspended particles), exhibiting high selectivity and anti-interference ability for target molecules. Simultaneously, its stability and reusability reduce usage costs, making it suitable for rapid detection needs in practical samples such as environmental monitoring and food safety. Attached Figure Description

[0023] Figure 1 The XRD pattern of AgNPs-Bi3NbTiO9 material.

[0024] Figure 2 The SERS spectra of 4-MBA on Ag substrate and AgNPs-Bi3NbTiO9 substrate are shown.

[0025] Figure 3 The SERS test results are obtained from 10 randomly selected sites on the AgNPs-Bi3NbTiO9 substrate.

[0026] Figure 4 The graph shows the detection results of different concentrations of 4-MBA in the river system. Detailed Implementation

[0027] 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.

[0028] Example 1: Preparation of AgNPs-Bi3NbTiO9 material.

[0029] Grind 0.699g Bi2O3, 0.08g TiO2, and 0.133g Nb2O5 with 8g NaCl-KCl mixed salt (molar ratio 1:1) in an agate mortar for 30 minutes to ensure thorough mixing.

[0030] The resulting mixture was transferred to an alumina crucible and calcined at 800°C for 2 hours. After the reaction was complete, it was cooled to room temperature, repeatedly washed with hot deionized water to remove the molten salt, and dried to obtain Bi3NbTiO9 powder.

[0031] Weigh 50 mg of Bi3NbTiO9 powder and disperse it in 50 mL of deionized water. Sonicate the solution for 30 min to form a uniform suspension. Add 10 mL of 1 mM silver nitrate solution and mix thoroughly under magnetic stirring.

[0032] Then, 10 mL of 2 mM ascorbic acid solution (freshly prepared) was added dropwise at a rate of approximately 1 mL / min, and the reaction was continuously stirred at room temperature for 30 min. During the process, the solution gradually turned light gray, indicating the formation of Ag nanoparticles.

[0033] After the reaction was completed, the product was collected by centrifugation, washed three times with deionized water and ethanol, and dried at 60°C to obtain the AgNPs-Bi3NbTiO9 composite SERS substrate material. Figure 1 The XRD results shown indicate that Ag was successfully loaded onto the Bi3NbTiO9 surface.

[0034] Example 2: AgNPs-Bi3NbTiO9 composite SERS substrate.

[0035] 0.005g of AgNPs-Bi3NbTiO9 composite SERS substrate material was dispersed in 10mL of deionized water, dropped onto the surface of a 1cm×5cm silicon wafer, and allowed to dry naturally to form the AgNPs-Bi3NbTiO9 composite SERS substrate.

[0036] Example 3: SERS substrate performance test of AgNPs-Bi3NbTiO9 composite material.

[0037] A series of 4-MBA solutions were prepared using deionized water for substrate performance testing. The method was as follows: the substrate material was immersed in 4-MBA of various concentrations for 20 minutes, dried, and then subjected to Raman spectroscopy.

[0038] like Figure 2 As shown, compared to the pure Ag substrate (which is prepared by dropping a pre-prepared AgNPs solution onto the surface of a 1cm×5cm silicon wafer and then allowing it to dry naturally), the composite substrate exhibits a stronger enhancement effect. Figure 3 Ten sites were randomly selected from different regions on the AgNPs-Bi3NbTiO9 substrate for testing, which showed that the signal consistency at different test locations was good.

[0039] Example 4: SERS detection of 4-MBA in actual river water using AgNPs-Bi3NbTiO9 composite substrate.

[0040] Actual river water samples were taken, and after simple filtration to remove suspended impurities, 4-MBA was added to the river water to prepare river water solutions containing 5 ppm, 10 ppm, 50 ppm and 100 ppm of 4-MBA.

[0041] 10 μL of 4-MBA aqueous solution with concentrations of 5 ppm, 10 ppm, 50 ppm and 100 ppm was dropped onto the substrate surface, and Raman spectroscopy was performed after drying.

[0042] Test results are as follows Figure 4 As shown, the results indicate that the characteristic peak signal of 4-MBA can be observed in actual water samples under different concentration conditions, and the signal intensity increases with increasing concentration, with little interference from stray peaks, proving that the substrate has good practical detection capabilities.

[0043] In summary, this AgNPs-Bi3NbTiO9 composite SERS substrate has good potential for detecting 4-MBA in complex water systems.

Claims

1. An AgNPs-Bi3NbTiO9 composite SERS substrate material, characterized in that: Bi3NbTiO9 support was prepared by molten salt method, and Ag nanoparticles were grown in situ on the surface of Bi3NbTiO9 support in ascorbic acid reduction system to obtain AgNPs-Bi3NbTiO9 composite SERS substrate material with enhanced Raman signal capability.

2. A method for preparing the AgNPs-Bi3NbTiO9 composite SERS substrate material according to claim 1, characterized in that, The method is as follows: Bi3NbTiO9 powder is dispersed in deionized water, ultrasonically treated to form a uniform suspension, silver nitrate solution is added, and the mixture is stirred and mixed evenly. Then, ascorbic acid solution is added dropwise, and the reaction is continuously stirred at room temperature. During the process, the solution gradually turns light gray, indicating the formation of Ag nanoparticles. After the reaction is completed, the product is collected by centrifugation, washed several times, and dried to obtain AgNPs-Bi3NbTiO9 composite SERS substrate material.

3. The method for preparing an AgNPs-Bi3NbTiO9 composite SERS substrate material according to claim 2, characterized in that: The preparation method of Bi3NbTiO9 is as follows: Bi2O3, TiO2, Nb2O5 and NaCl-KCl mixed salt are mixed, ground to make them fully mixed and uniform, calcined, cooled to room temperature, washed to remove molten salt, and dried to obtain Bi3NbTiO9 powder.

4. The method for preparing an AgNPs-Bi3NbTiO9 composite SERS substrate material according to claim 3, characterized in that: According to the cation molar ratio, Bi 3+ Ti 4+ :Nb 5+ The ratio is 3-3.2:1:

1.

5. The method for preparing an AgNPs-Bi3NbTiO9 composite SERS substrate material according to claim 3, characterized in that: In the NaCl-KCl mixed salt, the molar ratio of NaCl to KCl is 1:

1.

6. The method for preparing an AgNPs-Bi3NbTiO9 composite SERS substrate material according to claim 3, characterized in that: The calcination is carried out at 700-900℃ for 2-4 hours.

7. The method for preparing an AgNPs-Bi3NbTiO9 composite SERS substrate material according to claim 2, characterized in that: The molar ratio of Bi3NbTiO9 to silver nitrate is 5-6:

1.

8. The method for preparing an AgNPs-Bi3NbTiO9 composite SERS substrate material according to claim 2, characterized in that: The ascorbic acid solution was added at a rate of 1 mL / min.

9. An AgNPs-Bi3NbTiO9 composite SERS substrate, characterized in that, The AgNPs-Bi3NbTiO9 composite SERS substrate material of claim 1 is dispersed in deionized water, the solution is drop-coated onto the surface of a silicon wafer, and dried to form the AgNPs-Bi3NbTiO9 composite SERS substrate.

10. The application of the AgNPs-Bi3NbTiO9 composite SERS substrate according to claim 9 in the detection of organic molecules, characterized in that, The organic molecule mentioned is 4-MBA.

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