Low-cost, high-performance plasmonic nanocomposites for hazardous chemical detection using surface enhanced Raman scattering

Nanoplasmonic paper holds considerable promise as an effective surface-enhanced Raman scattering (SERS) substrate for sensitive detection of small molecules. In this study, we report the development of a low cost, flexible, high-performance SERS substrate based on cellulose nanofiber/gold nanoparticle (CNF/AuNP) nanocomposites via vacuum-assisted filtration. The CNF-based matrix enables direct AuNP deposition by filtration due to its nanoscale surface roughness. In addition, the filtration process allows for precise control of the spatial distribution of AuNPs, including the number density and size ratio, which are strongly associated with interparticle plasmon coupling effects. In our experiments, the CNF-AuNP nanocomposite showed excellent SERS activity with a highly sensitive rhodamine 6 G detection limit of 10 pM and a competitive enhancement factor of 4.5 × 109. It is important to note that the control of both density number and size ratio of AuNPs contribute to enhancement of SERS. Furthermore, we demonstrated that CNF-AuNP nanocomposite-based SERS can efficiently detect two representative pesticides, thiram and tricyclazole, at trace concentrations. The limits of detection (LOD) for thiram and tricyclazole were found to be as low as 1 pM (0.3 ppt) and 10 pM (2.4 ppt), respectively, which is 100- to 1000-fold more sensitive than previously reported SERS methods. Additionally, using a CNF-AuNP nanocomposite-based swab provided sensitive detection of pesticide residues on real-world surfaces (apple peel and plant leaf), offering great potential for label-free and on-site detection of hazardous molecules.