The invention relates to a silver /
graphene-coated
silicon dioxide composite upconversion
nanocrystal and a preparation method thereof. The
nanocrystal structure of the obtained silver /
graphene@SiO2-NaLuF4:Yb,Gd,Er composite
fluorescent nanoparticles is as follows: silver-on-
graphene is used as an inner core and coated with
silicon dioxide, and the upconversion
nanocrystal is grafted onto the
silicon dioxide surface. The
metal reinforced
fluorescence effect of the
noble metal silver is utilized to enhance the luminescent intensity of the upconversion nanocrystal. The silver is supported on the graphene to well prevent the
silver particles from aggregation, and the silver nanoparticles, which are dispersed and fixed to the graphene, generate
field effect superposition due to
short distance, so that the mutual polarity and surface
plasma resonance are mutually reinforced. Since the graphene is an excellent
electron acceptor and conductor, after the charges of the silver nanoparticles transfer to the graphene, the
electron density becomes lower, the effective
dielectric constant increases, and thus, the surface
plasma resonance of the nano silver is enhanced, so that the
metal reinforced
fluorescence effect of the nano silver becomes higher. The method enhances the upconversion luminescent intensity of the rare-earth upconversion nanocrystal by about 50 times.