Facile synthesis of cellulose nanofiber nanocomposite as a SERS substrate for detection of thiram in juice.

There has been growing interest in the use of nanocellulose-based substrate for surface-enhanced Raman spectroscopy (SERS) applications. This study aimed to use cellulose nanofibers (CNF) to develop novel CNF-based nanocomposite as a SERS substrate. CNF were cationized with ammonium ions and then interacted with citrate-stabilized gold nanoparticles (AuNPs) via electrostatic attraction to form uniform nanocomposites. The CNF-based nanostructures were loaded with AuNPs that were firmly adhered on the CNF surfaces, providing a three-dimensional plasmonic SERS platform. A Raman-active probe molecule, 4-aminothiophenol, was selected to evaluate the sensitivity and reproducibility of CNF-based SERS substrate. The intensity of SERS spectra obtained from CNF/AuNP nanocomposite was 20 times higher than that from the filter paper/AuNP substrate. The SERS intensity map demonstrates good uniformity of the CNF/AuNP substrate. CNF/AuNP nanocomposites were used in rapid detection of thiram in apple juice by SERS and a limit of detection of 52 ppb of thiram was achieved. These results demonstrate that CNF/AuNP nanocomposite can be used for rapid and sensitive detection of pesticides in food products.