Controlled growth of polyhedral and plate-like Ag nanocrystals on a nanofiber mat as a SERS substrateElectronic supplementary information (ESI) available: UV-Vis spectra of the PAN-g-PmPD nanofiber and the AgNC@PAN-g-PmPD nanofiber; XRD patterns of the AgNC@PAN-g-PmPD nanofiber mat; the photograph of the AgNC@PAN-g-PmPD nanofiber mat which was folded into a hollow cylinder and tailored into several pieces with any desired shape; SERS spectra of 10−9 M 4-MBA adsorbed on the AgNC@PAN-g-PmPD nanofi

We report chemical deposition of silver nanocrystals (AgNCs) of different sizes and morphologies, such as polyhedra and plates, on a polyacrylonitrile (PAN) nanofiber mat. High performance surface-enhanced Raman scattering (SERS) substrates are achieved. The effect of the experimental parameters, such as the temperature, concentration and pH of [Ag(NH 3 ) 2 ]OH aqueous solution, on the morphology evolution and density of AgNCs is systematically investigated. The results suggest that the optimized nanofiber mat exhibits a significant SERS performance with superior stability and reproduction, and the SERS enhancement factor (EF) can reach as high as 10 8 for 4-mercaptobenzoic acid (4-MBA). The optimized nanofiber mat also shows high SERS activity for p -aminothiophenol (4-ATP) over the whole nanofiber mat demonstrating the feasibility for detection of both analytes. The detection limit of 4-MBA and 4-ATP is as low as 10 −9 M and 10 −10 M respectively, making the nanofiber mat a promising candidate for SERS detection of chemical pollutants. A flexible 3D SERS substrate was prepared by controlled growth of Ag nanocrystals on the surface of a PAN- g -PmPD nanofiber mat.