Optimization of an ultra-sensitive Ag core-Au shell nanoparticle/Si Surface-enhanced Raman scattering (SERS) sensor

Abstract

Well-controlled Ag core/Au shell nanoparticles (NPs) of various shell thicknesses were synthesized in water using a laser ablation process via a low energy 1060 nm Nd-YAG laser with fluence of approximately 14 J/cm2 and a 1 Hz pulse repetition. Ag core NPs with a mean diameter of 42 nm were prepared by circa 300 pulses of a fixed energy fluence of 14 J/cm2, while Au NPs ranging from 10 to 45nm shell thickness were achieved by delivering pulses of 250 to 400nm to the Au plate. Ag core/Au shell NPs surface-enhanced Ramen scattering (SERS) sensors were synthesized by depositing the resulting bimetallic NPs onto silicon substrates using a drop casting process. The composition of the synthesised SERS sensors was confirmed using field emission scanning electron microscopy FE-SEM, HRTEM, Ultraviolet-visible spectroscopy UV-vis, XRD diffractometer, and Raman microscopy. These results showed that the performance of the novel SERS substrate had a significant effect on NPs shell thickness. The shell thickness was improved by a factor of 4.8x1011 to 1.2 x1014 for 250 to 400 nm, respectively, due to the hotspot dynamics of the core/shell NPs