The great interest in upconversion nanoparticles exists due to their high efficiency under multiphoton excitation. However, when these particles are used in scanning microscopy, the upconversion luminescence causes a streaking effect due to the long lifetime. This article describes a method of upconversion microparticle luminescence lifetime determination with help of modified Lucy–Richardson deconvolution of laser scanning microscope (LSM) image obtained under near-IR excitation using nondescanned detectors. Determination of the upconversion luminescence intensity and the decay time of separate microparticles was done by intensity profile along the image fast scan axis approximation. We studied upconversion submicroparticles based on fluoride hosts doped with Yb3+-Er3+ and Yb3+-Tm3+ rare earth ion pairs, and the characteristic decay times were 0.1 to 1.5 ms. We also compared the results of LSM measurements with the photon counting method results; the spread of values was about 13% and was associated with the approximation error. Data obtained from live cells showed the possibility of distinguishing the position of upconversion submicroparticles inside and outside the cells by the difference of their lifetime. The proposed technique allows using the upconversion microparticles without shells as probes for the presence of OH? ions and CO2 molecules.
Single-phase BaF 2 :Ce solid solutions containing 30 -40 mol. % cerium with the simultaneous entry of potassium into the crystal lattice in an amount of 0.7 -0.8 mol. % were prepared by coprecipitation from aqueous nitrate solutions with potassium fluoride as the fluoridating agent. The cerium X-ray luminescence intensity increases in response to increasing cerium concentration contrary to the concentration quenching effect.
Effect of the pH on the Formation of NaYF 4 :Yb:Er Nanopowders by Co-Crystallization in Presence of Polyethyleneimine. -Cubic single-phase samples of the title nanopowders are obtained by addition of rare earth nitrate solutions to aqueous NaF/ polyethyleneimine mixtures at pH 10, whereas single-phase hexagonal precipitates are prepared by addition of aqueous NaF solutions to aqueous rare earth nitrate/polyethyleneimine mixtures at pH 12. -(YASYRKINA, D. S.; KUZNETSOV, S. V.; FEDOROV*, P. P.; VORONOV, V. V.; ERMAKOV, R. P.; RYABOVA, A. V.; POMINOVA, D. V.; BARANCHIKOV, A. E.; IVANOV, V. K.; OSIKO, V. V.; J. Fluorine Chem. 158 (2014) 60-64, http://dx.
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