Photon upconversion emission in transparent solutions of nanocrystalline hexagonal NaGdF/sub 4/:Yb/sup 3+/, Er/sup 3+/

Photon upconversion (UC) is a nonlinear optical process in which long-wavelength (NIR) radiation is converted into short-wavelength (VIS) radiation. We have extended our synthetic and spectroscopic work towards Yb/sup 3+//Er/sup 3+/ codoped nanoparticles of NaGdF/sub 4/. The /spl beta/-NaGdF/sub 4/:Yb/sup 3+/, Er/sup 3+/ nanoparticles of roughly spherical shape and a size of about 30 nm can be transparently dissolved in DMSO. The UC emission spectra upon laser excitation of the transparent solution of /spl beta/-NaGdF/sub 4/:Yb/sup 3+/, Er/sup 3+/ nanoparticles in DMSO are observed.