Ag Nanoparticle-Decorated Bacterial Nanocellulose for SERS-Based Detection of the Plant Hormone Salicylic Acid

This study aims to develop an innovative surface-enhanced Raman scattering (SERS) substrate for the sensitive detection of salicylic acid (SA), a key plant hormone. Bacterial nanocellulose (BNC) serves as the supporting matrix, with silver nanoparticles (AgNPs) deposited in situ onto its surface. The effects of the BNC quantity and film-forming methods (freeze-drying and thermal-drying) on substrate properties are systematically investigated. The resulting AgNPs-BNC composites are thoroughly characterized using SEM-EDS, HRTEM, UV–vis, XRD, and XPS techniques. SERS measurements are performed with various probe molecules and SA concentrations, supported by FDTD simulations to elucidate the enhancement mechanism. Among the substrates, F-AB-2 exhibits exceptional detection sensitivity with MG, MO, CV down to 10–10 M/L, excellent signal reproducibility (RSD: 7.9%–8.8%), and outstanding storage stability (maintaining performance after 90 days). It can effectively detect exogenous SA in plants at concentrations as low as 10–7 M (1.4 μg/L). This study thus presents a highly promising SERS substrate with great potential for the rapid and accurate detection of plant hormones, contributing to advancements in sustainable agriculture and plant science research.