Sensitive and Stable Detection of Pesticide Residues Using Flexible 3D Nanocellulose-Based SERS Substrates

Surface-enhanced Raman spectroscopy (SERS) has gained attention as a sensitive technique for the detection of pesticide residues. However, constructing homogeneous, stable, and large-volume "hot spots" is a challenge. In this study, D-T-CNFs@Ag SERS substrates were fabricated by decorating a flexible dialdehyde TEMPO-oxidized cellulose nanofibril (D-T-CNF) film with silver nanoparticles (AgNPs). Carboxylate groups and aldehyde groups on cellulose nanofibrils were used as the growth sites for AgNPs and the main reducing agents for forming three-dimensional "hot spots", respectively. D-T-CNFs provided protection and immobilization for the AgNPs, allowing SERS substrates to withstand intense ultrasonic treatment, and had a shelf life of over 60 days. In addition, thiram and thiabendazole could be detected at a concentration as low as 10^-9 M. The D-T-CNFs@Ag SERS substrate could be used to test thiram on the surface of apples, with a limit of detection (LOD) of 0.047 ng/cm², realizing the integration of collection and detection.