Synthesis of fluoride NaYF4/Yb/Tm, NaYF4/Yb/Er micro- and nanocrystals and their characterization by uv optical microscopy method

Fluoride NaYF4/Yb/Tm and NaYF4/Yb/Er microand nanocrystals, which are in the cubic (alpha-) and hexagonal (beta-) phase, have been synthesized. The sizes, crystal structure and shape of crystals (phosphors) are characterized by methods of scanning electron microscopy and Xray diffraction, as well as by high-resolution UV optical microscopy and confocal microscopy. The photoluminescence (PL) of individual phosphors and their agglomerates in upconversion was studied using IR laser pumping light with wavelength of 980 nm. It was shown that using UV microscopy with wavelength of 365 nm and confocal microscopy with wavelength of 405 nm, it is possible to determine the size and shape of particles with diameter of 300 nm. These methods occupy an intermediate position between optical microscopy (within visible range) and electron microscopy in terms of spatial resolution and are useful while analyzing of nanophosphors with organic cladding based on oleic acid.