Surface plasmon resonance absorption peak control through regulation of particle size and concentration of an indium tin oxide nanoparticle solution

This study investigates the possibility of tuning the surface plasmon resonance (SPR) absorption peak frequency in the near-infrared (NIR) region by changing the size and concentration of indium tin oxide nanoparticles (ITO NPs). Dispersion solutions containing ITO NPs with dimensions of 18, 50, and 100 nm were prepared in isopropanol and deposited on a Si substrate by spin coating. The position of the SPR peak varied depending on the size of the ITO NPs and was slightly shifted according to the dispersion concentration. A significant effect of the surface roughness of the sample on the shift of the SPR peak was confirmed using atomic force microscopy measurements. Subsequently, a new SPR peak was obtained by mixing ITO NPs with different sizes. Thus, in this study, by controlling the size, concentration, and ratio of ITO NPs, the SPR absorption peak frequency was easily controlled in a wider NIR region compared with previous studies.