A local shrinkage approach for creating dynamic hot-spots on thermoresponsive nanocellulose-based SERS substrate

Surface-enhanced Raman scattering (SERS) is a highly sensitive technology to detect target analytes. The construction of dynamic "hot-spots" represents a significant approach to enhancing detection sensitivity. Herein, a hybrid plasma platform with dynamic "hot-spots" was developed for SERS recognition based on the assembly of gold nanospheres (AuNSs) on temperature-sensitive bacterial cellulose (BC) film grafted with poly(N-isopropylacrylamide) (PNIPAM). The dynamic "hot-spots" structure was regulated in-situ by local conformational contraction of the grafted thermoresponsive PNIPAM around the BC backbone without changing the overall morphology of the substrate. Moreover, the heating process was simplified by utilizing the plasma photothermal effect of AuNSs to regulate the "hot-spot" structure. The dynamic regulation measured value of the Raman signal of Rhodamine 6G (R6G) was increased by 6.5-times, and the SERS substrate exhibited extremely high sensitivity with a limit of detection (LOD) of 8.47 × 10^-9 g/L and a relative standard deviation (RSD) of 9.24 %. Meanwhile, it can accurately detect the pesticide residues of thiram on apple peel with the detection limit of 6.54 × 10^-11 g/L. This dynamic "hot-spot" modulation strategy via local structural regulation has significant potential to improve the convenience, flexibility, and sensitivity of on-site SERS detection.