Isotropic shrinkage-inspired strategy for plasmonic nanoparticle-loaded hydrogel SERS sensor towards robust and sensitive detection of pesticides

Irregular shrinkage induced by traditional dehydration methods restricts the robustness and sensitivity of hydrogel surface-enhanced Raman scattering (SERS) sensors in chemical analysis, despite increased signal intensity. Herein, a novel strategy employing ethanol dehydration (ED)-mediated isotropic shrinkage of silver nanoparticles@polyacrylamide (Ag@PAM) is proposed for reliable and versatile pesticide sensing. Isotropic shrinkage draws Ag nanoparticles (AgNPs) closer together, intensifying “hotspots” distribution and analyte enrichment, achieving a 17.00-fold Raman signal increase for 4-nitrothiophenol (4-NBT). Compared to air drying (AD), ED-Ag@PAM demonstrates rapid SERS enhancement within 12 min, improved homogeneity (RSD < 10 %), and greater sensitivity to 4-NBT, with a limit of detection (LOD) as low as 2.21 × 10 –12 M (∼3.43 × 10 –13 g·mL −1 (S/N = 3)). The SERS sensor exhibits high sensitivity for thiram (a dithiocarbamate fungicide) and thiabendazole (TBZ, a systemic benzimidazole fungicide and parasite deodorizer) in liquid environments, with LODs of 5.26 × 10 –10 g·mL −1 and 3.00 × 10 –8 g·mL −1 , respectively. A satisfactory recovery rate (82.78 %–115.12 %) in fruit juices highlights robust anti-interference capabilities in complex metrices. Moreover, the SERS method was effectively applied to curved fruit surfaces for trace detection of thiram and TBZ, achieving recovery rates between 82.50 % and 115.35 %. The proposed ED-mediated sensor offers simplicity, rapid response, high sensitivity, and versatility for both liquid environments and curved surfaces, presenting promising potential for diverse on-situ analytical applications.