Direct demonstration of environment-sensitive surface plasmon resonance band in single gold nanoparticles

We investigated single gold nanoparticles embedded in poly(vinyl alcohol) (PVA) films with different thicknesses using Rayleigh light-scattering microspectroscopy. First, gold nanoparticles with a mean radius of 40 nm were dispersed in a thin polymer film. Then, the film was covered with multiple layers of PVA to the desired thickness. As a result, we confirmed that the surface plasmon (SP) resonance band of single particles demonstrated redshift with the film thickness increase. In a thick film, the SP band peak position was well explained in terms of the size of Lite gold nanoparticles. In contrast, the spectral variance observed in a thin film did not follow the size-dependence trend. Since nanoparticles in a thin film are partially covered with PVA layers and thus are partially exposed to air, our results confirm that SP resonance strongly depends not only on a Particle's size but also on its surrounding dielectric conditions.