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

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).