Adjustable color response during plasmon resonance by monochromatic light irradiation

A combination of plasmonic nanoparticles with a semiconductor is a feasible approach to realize multiple color exhibitions. The phenomenon is based on plasmon-driven charge separation between electrons and metal ions, but suitable only for light excitation with different wavelengths. Here, we introduce a color-adjustable method under monochromatic light irradiation. A smart strategy is proposed to construct sandwich structures of a hydrogel coating layer, thermally deposited Ag nanoparticles, and mesoporous TiO₂ matrices. The contacting mode of TiO₂ and nano-Ag at the Schottky interface is strongly dependent on the pore morphology of the oxide. Surface and interface plasmon resonances result in sample color switching from cyan to green and from brown to purple, respectively. The color response ability is further controlled by hydrogel coating, besides the exciting light wavelength. This Letter paves a bright way for colorful displays and information encryption.