Comparison of plasmonic sensing between polymer- and silica-coated gold nanorods.

Gold nanorods (AuNRs), rod-like gold nanoparticles, show strong plasmon bands in the near-infrared region, based on the longitudinal oscillation mode of surface plasmons. In this research, we have coated AuNRs with silica or poly (sodium 4-styrenesulfonate) (PSS) in order to evaluate the effects of surface modifications as a sensing probe material of AuNR. Multilayered assemblies of the PSS-coated AuNRs have been successfully fabricated on the glass substrate by electrostatic layer-by-layer adsorption, and their plasmonic band profiles have been analyzed as a function of refractive index. The profiles showed satisfactory linear responses with the refractive indices. The effect of the thickness of silica layer on the shift of plasmon band with refractive index of the surrounding media has been investigated, along with, the effect of silica coating on the thermal stability of AuNR. The thermal stability of the silica-coated AuNR has also been investigated. The two types of the above-described coating approaches have been compared.