synthesis of silver nanoparticles and preparation of flexible sers detection substrate

Fabrication of Flexible Substrate for SERS Detection of R6G and Thiram

Surface-Enhanced Raman Scattering (SERS), as a type of Raman scattering, offers the advantages of high sensitivity and gentle detection conditions, and can even achieve single molecule detection1,2,3,4. Metal nanostructures, such as gold and silver, are typically used as SERS substrates to enable substance detection5,6. Electromagnetic coupling enhancement on nanostructured surfaces plays a significant role in SERS applications. Metallic nanostructures with varying sizes, shapes, interparticle distances, and compositions can aggregate to create numerous &#34;hotspots&#34; generating intense electromagnetic fields due to localized surface plasmon resonances7,8. Many studies have developed metal nanoparticles with different morphologies as SERS substrates, demonstrating their effectiveness in achieving SERS enhancement9,10.
Flexible SERS substrates find wide applications, with nanostructures capable of producing SERS effects deposited on flexible substrates to facilitate direct detection on curved surfaces. Flexible SERS substrates are employed for detecting and collecting analytes on irregular, non-planar, or curved surfaces. Common flexible SERS substrates include fibers, polymer films, and graphene oxide films11,12,13,14. Among them, polydimethylsiloxane (PDMS) is one of the most widely used polymer materials and offers advantages such as high transparency, high tensile strength, chemical stability, non-toxicity, and adhesion15,16,17. PDMS has a low Raman cross-section, making its impact on the Raman signal negligible18. Since the PDMS prepolymer is in liquid form, it can be cured by heat or light, providing a high degree of controllability and convenience. PDMS-based SERS substrates are relatively common flexible SERS substrates, having been used in previous studies to embed various metal nanoparticles for detecting different biochemical substances with exemplary performance19,20.
In the preparation of SERS substrates, the fabrication of nanogap structures is crucial. Physical deposition technology offers advantages like high scalability, uniformity, and reproducibility but typically requires good vacuum conditions and specialized equipment, limiting its practical applications21. Additionally, fabricating nanostructures at the few-nanometer scale remains challenging with conventional deposition techniques22. Consequently, nanoparticles synthesized through chemical methods can be adsorbed onto flexible transparent films through various interactions, facilitating the self-assembly of metallic structures at the nanoscale. To ensure successful adsorption, interactions can be adjusted by physically or chemically modifying the film surface to alter its surface hydrophilicity23. Silver nanoparticles, compared to gold nanoparticles, exhibit better SERS performance, but their instability, particularly their susceptibility to oxidation in air, results in a rapid decrease in the SERS Enhancement Factor (EF), affecting substrate performance24. Hence, it is essential to develop a stable particle method.
The presence of pesticide residues has garnered significant attention, creating a pressing need for robust methods capable of rapidly detecting and identifying various classes of hazardous chemicals in food in the field25,26. Flexible SERS substrates offer unique advantages in practical applications, particularly in the realm of food safety. This article introduces a method for preparing a flexible SERS substrate by bonding synthesized glucose-coated silver nanoparticles (AgNPs) onto a PDMS substrate (Figure 1). The presence of glucose protects the AgNPs, mitigating silver oxidation in the air. The substrate demonstrates excellent detection performance, capable of detecting Rhodamine 6G (R6G) as low as 10-10 M and pesticide Thiram as low as 10-8 M, with good uniformity. Moreover, the flexible substrate can be employed for detection through bonding and sampling, with numerous potential application scenarios.

Author Spotlight: Development and Application of SERS Flexible Substrates Using Synthesized AgNPs 

Fabrication of polydimethylsiloxane (PDMS)-Based Flexible Surface-Enhanced Raman Scattering (SERS) Substrate for Ultrasensitive Detection

This protocol describes preparing SERS flexible substrates, applying them to actual detection scenarios. The SERS flexible substrate offered by this protocol is environmental friendly and achieves good detection performance. The silver nanoparticles can be synthesized easily by simple vessels, and do not require complicated experimental conditions and environment.In our laboratory, we plan to focus on researching the silver nanoparticles synthesized through the vessel used in this study. We'll explore methods to enhance their SERS detection capabilities, and leverage their unique properties and characteristics to design better performing SERS detection substrates.

Watch this Scientific Journal Video about Synthesis of Silver Nanoparticles and Preparation of Flexible SERS Detection Substrate at JoVE.com

Synthesis of Silver Nanoparticles and Preparation of Flexible SERS Detection Substrate  

To prepare silver nitrate solution, measure 0.0017 grams of AR grade silver nitrate on a weighing balance. Add the weighed powder to 10 milliliters of deionized water and stir the mixture. Draw one milliliter of AR grade ammonia water using a syringe and add it to the silver nitrate solution while stirring, until the solution becomes clear.To prepare 0.2 molar glucose solution, weigh 0.36 grams of glucose powder and add it to 10 milliliters of deionized water. Stir the mixture thoroughly. Next, using a pipette gun, add 30 microliters of the silver ammonia complex into the glucose solution at 30 minute intervals.To synthesize yellow colored silver nanoparticles. To synthesize the PDMS substrate, take five grams of PDMS A solution and add B solution into it, at a ratio of one to 10. Stir the mixture thoroughly.Transfer the mixed PDMS into a square Petri dish and bake it in an 80 degree Celsius oven for two hours. Once cured, use a scalpel to cut the PDMS along the dark grid of the dish, creating small cubes. Next, move the handheld plasma processor back and forth over the PDMS piece for surface plasma treatment.For APTES modification, immerse the surface modified PDMS pieces into 10%APTES solution for 10 hours. Finally, immerse the PDMS substrate into the silver nanoparticle solution for 10 hours. ESEM images showed uniformity in synthesized nanoparticles with diameters between 20 and 50 nanometers.The Surface-Enhanced Raman Scattering signals for fabricated PDMS substrates displayed excellent detection capability, reaching a limit of 10 to the negative 10th molar for R6G with notable enhancement effect. The substrate also showed Thiram detection with clear characteristic peaks, up to 10 to the minus eighth molar. The paste and peel method on the apple surface show the detection of Thiram up to 10 to the minus seventh molar, indicating the effectiveness of the substrate for identifying pesticide residues on fruit surfaces.

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JoVE Journal

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381 次观看.  Peking University. 要制备硝酸银溶液，请在称重天平上测量 0.0017 克 AR 级硝酸银。将称量的粉末加入 10 毫升去离子水中并搅拌混合物。用注射器抽取一毫升AR级氨水，在搅拌的同时加入硝酸银溶液中，直到溶液变得清澈。要制备 0.2 摩尔葡萄糖溶液，称取 0.36 克葡萄糖粉并将其加入 10 毫升去离子水中。彻底搅拌混合物。接下来，使用移液枪，每隔 30 分钟将 30 微升银氨络合物加入葡萄糖?...