Shape- and Size-Dependent Refractive Index Sensitivity of Gold Nanoparticles

TLDR

The study investigates how the surface plasmon peaks of gold nanoparticles of various shapes and sizes respond to changes in the refractive index of water–glycerol mixtures. The authors dispersed nanospheres, nanocubes, nanobranches, nanorods, and nanobipyramids into water–glycerol mixtures with varying volume ratios and measured the resulting plasmon peak shifts. Refractive index sensitivity and figure of merit depend on shape and size, with elongated and sharper‑apex particles showing higher sensitivities (44 nm/RIU for nanospheres to 703 nm/RIU for nanobranches) and nanobipyramids achieving the highest figures of merit, rising from 1.7 to 4.5 as the aspect ratio increases from 1.5 to 4.7.

Abstract

Gold nanoparticles of different shapes and sizes, including nanospheres, nanocubes, nanobranches, nanorods, and nanobipyramids, were dispersed into water−glycerol mixtures of varying volume ratios to investigate the response of their surface plasmon peaks to the refractive index of the surrounding medium. The refractive index sensitivities and figures of merit were found to be dependent on both the shape and the size of the Au nanoparticles. The index sensitivities generally increase as Au nanoparticles become elongated and their apexes become sharper. Au nanospheres exhibit the smallest refractive index sensitivity of 44 nm/RIU and Au nanobranches exhibit the largest index sensitivity of 703 nm/RIU. Au nanobipyramids possess the largest figures of merit, which increase from 1.7 to 4.5 as the aspect ratio is increased from 1.5 to 4.7.