Au@Ag Core-shell Nanorods Self-assembled on Polyelectrolyte Multilayers for Ultra-High Sensitivity SERS Fiber Probes

We demonstrated a chemical process in the fabrication of a SERS fiber probe with an ultrahigh sensitivity. The synthesis was carried out by preparing Au@Ag core-shell nanorods (Au@Ag-NRs) self-assembled on polyelectrolyte (PE) multilayers, for which Au@Ag-NRs were controlled by adjusting the silver layer thickness. The effect of silver layer thickness of Au@Ag-NRs on the SERS performance of the fiber probe was investigated. The SERS fiber probe shows the best performance when the silver layer thickness is controlled at 8.57 nm. Under the condition of optimizing silver layer thickness, the fiber probe exhibits ultra-high sensitivity ( i e , 10 −10 M crystalline violet, CV), good reproducibility ( i e , RSD of 3.5%) and stability. Besides, electromagnetic field distribution of the SERS fiber probe was also investigated. The strongest enhancement is found within the core of fiber, whereas a weakened electromagnetic field exists in the fiber cladding layer. The SERS fiber probe can be a good candidate in ultra-trace detection for biomedical and environmental areas.