Ultrahigh sensitive metal-free SERS platforms by functional-groups

Surface-enhanced Raman scattering (SERS) is a powerful molecule sensing technique with excellent identification via a specific Raman fingerprint. Nanometal-based SERS platforms that utilize plasmonic resonance mechanisms have high sensitivity, but have high cost and low stability. Ceramic-based SERS platforms that utilize chemical enhancement mechanisms have low cost and high stability, but have low sensitivity. In the present work, a high-sensitivity, low-cost, and stable sensing platform based on functional-group-enhanced Raman scattering (FGERS) is proposed and investigated. Functional groups (FGs), including carboxyls, carbonyls, and epoxides, formed on graphene oxide (GO) via the coupling effects of GO and ZnO under appropriate heat treatment or ultraviolet (UV) illumination. The key factors for the formation of FGs on GO are heat or UV energy, processing time, ZnO carrier type, and atmosphere composition. The optimized composites show a maximum enhancement factor that exceeds 105, the highest enhancement reported for dipole-induced local fields. The excellent detection performance of 10−10 M allows the potential fabrication of ultrasensitive, low-cost, and reliable platforms for molecule sensing. Moreover, the FG formation mechanisms can be employed to develop other composite FGERS systems.