Rapid and tailorable silver nanoplate (SNP) synthesis for a promising SERS substrate in sulfathiazole detection

Abstract

Silver nanoplates (SNPs) are particularly attractive in surface-enhanced Raman scattering (SERS) activity due to their unique physicochemical properties, including localized surface plasmon resonance (LSPR) and strongly electromagnetic “hot spots” in the vicinity of their tips and edges. In this study, we report a novel, rapid, and simplified methodology for preparing SNPs using a one-pot synthesis approach with AgNO₃, NaBH₄, TSC, PVP, and an oxidation agent, H₂O₂. By adjusting precursor ratios, the LSPR peak can be easily adjusted from 400 to 800 nm, with a change in morphology from spherical, undefined structures, nano-disks, and triangular. In this study, Na₂CO₃ was added to the reaction to react with excess H₂O₂ to obtain long-term stable nanoparticles in a colloidal solution for 21 days. Crystal violet (CV) dye was used as a Raman probe to evaluate the SERS performance of SNP substrates at different diameters (35, 60, 120, 210 nm). The results showed that SERS activity was inverse to the SNP diameter. The finite-difference time domain (FDTD) was employed to compute the E-field around SNPs, indicating that E-field intensity depends on the SNPs' size, shape, and LSPR peak position. The 35 nm SNP substrates exhibited high sensitivity and good reproductivity in detecting CV dye, with a limit of detection (LOD) of 0.020 mg L⁻¹ and a limit of quantification (LOQ) of 0.060 mg L⁻¹. Additionally, SNP substrates can detect sulfathiazole (STZ) at trace-level concentrations, with LOD and LOQ of 0.031 and 0.095 mg L⁻¹, respectively. These studies on silver nanoplate substrates displayed potential for further ultra-trace analysis applications in organic compounds.