Comparative and Optimized Chemical Synthesis of AgNPs for Improved Surface Reactivity and Potential Biosensing Applications

Silver nanoparticles are metallic particles with very small dimensions and excellent optical, electrical and biological properties. Lately, they have shown promising results in biosensing applications. In the material's fabrication, the synthesis parameters remain the main aspect to be considered once a certain application is targeted. Therefore, this work presents the synthesis of silver nanoparticles using a chemical reduction based on various volumes of reducing and stabilizing agents. The multiple synthesis methods proposed were tested and optimized in order to achieve the best results for further biosensing applications. In this regard, sodium borohydride (NaBH₄) was used as reducing agent in volumes of 400 μL and 1 mL, while trisodium citrate (TSC) was proposed in much smaller volumes of 10, 20, and 50 μL. The optical and morphological analysis obtained from UV-VIS and TEM microscopy confirmed the formation of nanoparticles in case of all synthesis. The average diameters of silver nanoparticles were in the range between 21 and 27 nm, with high homogeneity for the samples with 20 and 50 μL of TSC. FT-IR analysis confirmed the TSC functionalization on the AgNPs' surface. SERS analysis and the bulk sensitivity method also showed good surface results, leading to the assumption that both reducing and stabilizing agents can influence the final properties of the material. LSPR biosensing of para-aminothiophenol was tested, and was proven to have detection capabilities at concentrations as low as 10^-7 M. Overall, the results proved that the synthesis method with a smaller amount of reducing agent and a moderate quantity of stabilizing agent has superior properties for biosensing applications.