Localized surface plasmon resonance (LSPR) and refractive index sensitivity of vacuum evaporated nanostructured gold thin films

TL;DR

This study investigates the plasmonic properties and refractive index sensitivity of vacuum evaporated nanostructured gold thin films, demonstrating their potential as sensors for organic molecules based on LSPR shifts.

Contribution

It presents the characterization of nanostructured gold thin films with unique nanoparticle shapes and their sensitivity to environmental refractive index changes, a novel application for sensing.

Findings

Presence of nanorods with non-cylindrical shapes in films thicker than 6 nm

Observation of two plasmon bands in absorption spectra

Refractive index sensitivity ranging from 250 to 305 nm/RIU

Abstract

The plasmonic properties of vacuum evaporated nanostructured gold thin films having different types of nanoparticles are presented. The films with more than 6 nm thickness show presence of nanorods having non cylindrical shape with triangular base. Two characteristics plasmon bands have been recoreded in absorption spectra. First one occurs below 500 nm and other one at higher wavelength side. Both the peaks show dependence on the dielectric property of surroundings. The higher wavelength localized surface plasmon resonance (LSPR) peak shifts to higher wavelength with an increase in the nanoparticle size, surface roughness and refractive index of the surrounding (Methylene Blue dye coating). This shows that such thin films can be used as sensor for organic molecules with a refractive index sensitivity ranging from 250 - 305 nm/RIU (Refractive Index Unit).