Tuning the emission bands of nanophosphors through the refractive index of the medium

Photoluminescence spectra of nanophosphors including the yellow phosphor YAG:Ce as well as the green and red phosphors based on CdSe nanoparticles have been studied in the media of oxide gels and polymers of different refractive indices. The oxide gels employed are of silica, zirconia and their solid solutions with the refractive index, n, varying between 1.46 and 2. Different polymers afforded the variation of refractive index in the range 1.35-1.58. The wavelength corresponding to emission maxima of the phosphors are found to shift to lower wavelengths with increase in the refractive index of the medium. The shifts in the various media are found to be proportional to the refractive index term, n2 − 1/2n2 + 1. The sensitivity of the emission maxima of the nanophosphors to the medium refractive index may be useful for practical applications such as solid-state lighting.