Surfactant-less Ag@Au decorated U-bent fiber optic probes for plasmonic sensing

This study reports a simple and tunable surfactant-less seed-mediated growth synthesis technique for Ag@Au core-shell nanoparticles coated over the U-bent fiber optic probes. The synthesis root involves the immobilization of Au seeds on the aminated probe surface (A520nm= 0.05). The core was formed by the ascorbic acid-mediated reduction of Ag around the Au seed. The shell was formed by a passive deposition of Au over the Ag core. The entire process was monitored in real-time to tune the plasmonic property. The evanescent wave absorbance peak of Ag core was at 470 nm (A470nm = 2) and Au shell at 560 nm (A560nm = 2). A high refractive index (RI) sensitivity of 27.5 ΔAbsorbance/RIU was obtained. The absence of surfactant allows easier functionalization as opposed to the conventional seed-mediated synthesis techniques with C-TAB capping and a stronger adhesion of the plasmonic nanostructures