Reversible tuning of surface plasmon resonance of silver nanoparticles using a thermochromic matrix

Reversible tuning of surface plasmon resonance (SPR) of Ag nanoparticles by temperature was achieved using a thermochromic VO2 as matrix. The SPR wavelength (λSPR) was significantly shifted from 506nm for Ag on sapphire to 1070nm for Ag embedded in VO2 at room temperature, giving a large sensitivity factor (ΔλSPR∕Δn) of approximate 352nm per refractive index (n) unit. The λSPR of Ag in VO2 can be changed reversibly and easily by heating-cooling circles between λSPR=1070nm at 20°C and λSPR=844nm at 90°C, a tunable wavelength range of as large as 226nm only by changing the temperature. The reversible change of refractive index of thermochromic VO2 matrix upon temperature is responsible for this λSPR tuning.