En Ma

Lanthanide-doped LiLuF(4) upconversion nanoprobes for the detection of disease biomarkers.

Lanthanide-doped upconversion nanoparticles (UCNPs) have shown great promise in bioapplications. Exploring new host materials to realize efficient upconversion luminescence (UCL) output is a goal of general concern. Herein, we develop a unique strategy for the synthesis of novel LiLuF4 :Ln(3+) core/shell UCNPs with typically high absolute upconversion quantum yields of 5.0 % and 7.6 % for Er(3+) and Tm(3+) , respectively. Based on our customized UCL biodetection system, we demonstrate for the first time the application of LiLuF4 :Ln(3+) core/shell UCNPs as sensitive UCL bioprobes for the detection of an important disease marker β subunit of human chorionic gonadotropin (β-hCG) with a detection limit of 3.8 ng mL(-1) , which is comparable to the β-hCG level in the serum of normal humans. Furthermore, we use these UCNPs in proof-of-concept computed tomography imaging and UCL imaging of cancer cells, thus revealing the great potential of LiLuF4 :Ln(3+) UCNPs as efficient nano-bioprobes in disease diagnosis.

Radiative-trapping and fluorescence-concentration quenching effects of Yb:YAl 3 (BO 3 ) 4 crystals

The effects of radiative-trapping and fluorescence-concentration quenching on the emission spectra and fluorescence lifetimes of Yb3+-doped YAl3(BO3)4 crystals with a series of Yb3+ concentrations were studied. The shift of barycenters in emission spectra, Δλ, was proposed as an appraisement of the radiative-trapping effect on the spectra, and an empirical relation between Δλ and Yb3+ concentration in the Yb:YAl3(BO3)4 crystals was deduced. The model of excitation random walk was used to analyze the effects of radiative trapping and concentration quenching on the fluorescence lifetimes. The relation between fluorescence lifetime and Yb3+ concentration was obtained.

Spectroscopic and stimulated emission characteristics of Nd3+ in transparent glass ceramic embedding β-YF3 nanocrystals

A transparent SiO2–Al2O3–LiF–YF3 glass ceramic doped with Nd3+ was fabricated by melt quenching and subsequent heating. X-ray diffraction and transmission electron microscope results demonstrated that orthorhombic β-YF3 nanocrystals with a mean size of 23nm were homogeneously precipitated among the glass matrix. Confirmed by the energy dispersive x-ray spectroscopy measurements, the crystal-like absorption and emission of Nd3+ indicated the partition of Nd3+ into YF3 nanocrystals in the glass ceramic. Detailed characterizations of the Stark components of the I9∕24, I11∕24, and I13∕24 manifolds were performed using the low temperature fluorescence spectra for F3∕24→I9∕24, F3∕24→I11∕24, and F3∕24→I13∕24 transitions of Nd3+ in the glass ceramic. The stimulated emission cross sections of the F3∕24→I11∕24 intermanifold transition and the F3∕24(R1)→I11∕24(Y1) inter-Stark transition were determined to be 7.24×10−20 and 11.55×10−20cm2, respectively, being preferable to those of Nd3+-doped laser glasses and glass ...

Spectroscopic properties of Pr3+ ions in biaxial LaB3O6 crystal

LaB3O6 single crystal doped with Pr3+ ions has been grown by the Czochralski method. The angular relationship between the principal axes of the optical indicatrix and the crystallographic axes in the crystal was determined. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curves of the crystal were measured at room temperature. The modified Judd-Ofelt theories, extended to the anisotropic crystal, have been applied to analyze the spectra. The spectroscopic parameters, including the Judd-Ofelt intensity parameters Ωt,q(t=2,4,6), spontaneous emission probabilities, fluorescence branching ratios, radiative lifetimes, fluorescence quantum efficiencies, and stimulated emission cross sections were calculated and analyzed. The promising luminescent and upper laser level of the Pr3+:LaB3O6 crystal is determined.