Performance enhancement of paper-based SERS chips by shell-isolated nanoparticle-enhanced Raman spectroscopy

Paper-based flexible surface-enhanced Raman scattering (SERS) chips have been demonstrated to have great potential for future practical applications in point-of-care testing (POCT) due to the potentials of massive fabrication, low cost, efficient sample collection and short signal acquisition time. In this work, common filter paper and Ag@SiO₂core-shell nanoparticles (NP) have been utilized to fabricate SERS chips based on shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS). The SERS performance of the chips for POCT applications was systematically investigated. We used crystal violet as the model molecule to study the influence of the size of the Ag core and the thickness of the SiO₂coating layer on the SERS activity and then the morphology optimized Ag@SiO₂core-shell NPs was employed to detect thiram. By utilizing the smartphone as a miniaturized Raman spectral analyzer, high SERS sensitivity of thiram with a detection limit of 10⁻⁹M was obtained. The study on the stability of the SERS chips shows that a SiO₂shell of 3 nm can effectively protect the as-prepared SERS chips against oxidation in ambient atmosphere without seriously weakening the SERS sensitivity. Our results indicated that the SERS chips by SHINERS had great potential of practical application, such as pesticide residues detection in POCT.