In-situ growth of gold nanoparticles on electrospun flexible multilayered PVDF nanofibers for SERS sensing of molecules and bacteria

Plasmonic surface of flexible multilayered nanofibers possesses special superiority for the surface-enhanced Raman scattering (SERS) sensing of molecules and microbial cells. However, the fabrication of flexible plasmonic nanofibers with high sensitivity and reproducibility is difficult. Herein, we report a smart strategy for fabricating flexible plasmonic fibers, in which compact and homogeneous gold nanoparticles (Au NPs) are in-situ grown on the high-curvature surface of multilayered fibers of electrospun polyvinylidene fluoride (PVDF). Firstly, the surface of PVDF fibers is changed electrically, and Au seeds are deposited on the surface of PVDF fibers using electrostatic driving force. Secondly, a stable AuI4− complex is formed employing coordination between I− and AuCl4− ions, which could decrease the reduction potential of AuCl4− and restrain the self-nucleation, and then the reduction reaction of AuI4− is initiated by introducing PVDF@Au seeds to pull down the barrier of potential energy. Finally, in-situ growth of AuNPs is generated on the high-curvature surface of PVDF nanofibers, and large-scale hotspots are generated by adjacent AuNPs coupling in the three-dimensional (3D) space of multilayered fibers. Membrane of PVDF@Au nanofibers also realizes the sensitive detection of thiram molecules (low limit of detection of 0.1 nM) and good reproducibility (relative standard deviation of 10.6%). Meanwhile, due to the multilayered construction of PVDF@Au nanofibers, a valid SERS signal on 3D surface of bacteria could be generated. 3D distribution of hotspots on multilayered PVDF@Au nanofibers gives a clear advantage for SERS sensing of organic molecules and microbial cells.