Abstract

Overcoming the spatial resolution limitations in optical microscopy due to the diffraction of light has become a major challenge in modern microscopy. To overcome this limit, we demonstrate here the upconversion process in rare-earth-doped fluoride nanoparticles (RE:NPs) that may serve as novel sources for fluorescent microscopy. RE:NPs have been reported to serve as efficient biolabels for cellular and small animal imaging [1]. While almost all work devoted to RE doped nanocrystals in biological applications had investigated NaYF₄, here we performed experiments with LaF₃ and KY₃F₁₀, other possible materials to host upconversion. Specifically, (2at.%) Er³⁺, (2at.%) Yb³⁺: KY₃F₁₀, (1at.%) Tm³⁺, (6at.%) Yb³⁺: LaF₃ and (0.5at.%) Tm³⁺, (12at.%) Yb³⁺: KY₃F₁₀ 20-50 nm-sized crystals had been characterized using AFM, STEM, X-ray diffraction and dynamic light scattering techniques and investigated by luminescence spectroscopy and nonlinear optical microscopy [2]. The latter was done on NP’s dispersed in PEG and spun-coated on a glass cover slip. One of the fluorescence images produced with upconversion process in these nanoparticles is presented in Fig. 1. The increase of the photon process order and the corresponding decrease in the full width of half-maximum (FWHM) of intensity point spread function (IPSF) value can be clearly observed. As the result of the photon process order, N, increase, the instrument’s optical resolution becomes:

© 2013 IEEE