Three-dimensional Ag NPs-cellulose fiber/polyacrylamide hydrogels as a novel SERS platform for the efficient determination of thiram in fruits and juice

The preparation of sensitive, homogeneous and reproducible surface-enhanced Raman spectroscopy (SERS) platforms is imperative for rapid in situ measurements, but remains a formidable task. We constructed a high-performance, stable and homogeneous Ag NPs-TOCNF/PAAM hydrogel SERS platform using a cellulose-based hydrogel with a porous network structure composed of TEMPO-oxidized cellulose nanofibers (TOCNF) and polyacrylamide (PAAM) to attach, coordinate and protect silver nanoparticles (Ag NPs). The -COO- group in the TOCNF is coordinated to the silver atoms, resulting in a more uniform distribution of Ag NPs. The encapsulation of hydrogel effectively protects the Ag NPs from oxidation and improves the stability of the substrate. The volume shrinkage treatment of the hydrogel can adjust the structural gap of the Ag NPs, thus exhibiting high sensitivity. The SERS performance of the hydrogel was evaluated using the molecule R6G. Its enhancement factor is up to 7.56 × 10−7. In addition, SERS activity remained above 85% even after 50 days. Finally, the Ag NPs-TOCNF/PAAM hydrogel platform was used to detect thiram in fruit peels with a detection limit of 10−6 M. In conclusion, the platform shows great promise for the determination of hazardous chemicals in the field environment.