Luminescence properties of Ce-doped ZrO2 phosphors synthesized by combustion method

Zr_1−xCe_xO₂ with x = 0.005, 0.01, 0.02, and 0.03 samples were synthesized using a combustion technique. The X-ray diffraction results revealed that Ce-doped ZrO₂ nanoparticles were in a monoclinic structure up to 1 mol% Ce concentration. The increase in the Ce concentration caused more distortion in the monoclinic structure of zirconia. The samples showed a mixed phase (monoclinic + tetragonal) beyond 1 mol% Ce content. The crystallite size (D) and strain (ε) were calculated from the Williamson–Hall equation. The D decreased from 25 ± 1 to 20 ± 1 nm and ε increased from 0.03 to 0.28% with an increase in Ce concentration. Photoluminescence (PL) spectra of Zr_1−xCe_xO₂ showed emission in the blue region under an excitation wavelength of 290 nm. Zr_0.995Ce_0.005O₂ showed the highest PL intensity with an average lifetime of 0.93 μs, and the PL intensity decreased with the increase in the Ce concentration. Thermoluminescence (TL) glow curves of Zr_1−xCe_xO₂ were measured after gamma irradiation (500 Gy) with a heating rate of 5 K s⁻¹. The TL curve of Zr_0.995Ce_0.005O₂ showed two prominent peaks at 412 K (peak 1) and 600 K (peak 2). The first TL glow peak was shifted towards a higher temperature at 440 K above 1 mol% Ce concentration. Repetitive TL measurements on the same aliquot exhibited excellent repeatability. Kinetic parameters associated with the TL peaks were calculated using the curve fitting method. Peak 1 followed non-first-order kinetics. The value of the activation energy of the 440 K peak was found to be 0.95 ± 0.01 eV for Zr_0.99Ce_0.01O₂. These findings showed that Zr_1−xCe_xO₂ might be used in lighting and radiation dosimeter applications.     

Clearance of circulating desialylated thyroglobulins in the rat.

Canine and rat thyroglobulins were labeled with 125I either in vitro or in vivo, and were utilized for plasma clearance studies performed with rat. The half-life of physiologically radioiodinated asialothyroglobulins was about 6 min, while that of chemically radioiodinated asialothyroglobulin was about 12 min. No marked species difference was observed in this clearance. The label which had disappeared from the blood was recovered mainly in the liver, and this uptake was blocked by the simultaneous injection of desialylated orosomucoid but not by native orosomucoid. Radiolabeled monoiodotyrosine, diiodotyrosine, triiodothyronine and thyroxine were detected in the liver 17 min after intravenous injection of asialothyroglobulin labeled with 125I in vivo, suggesting the possible production of thyroid hormones in extrathyroidal tissues.     

Clearance of circulating desialylated thyroglobulins in the rat

Canine and rat thyroglobulins were labeled with ¹²⁵I either in vitro or in vivo, and were utilized for plasma clearance studies performed with rat. The half-life of physiologically radioiodinated asialothyroglobulins was about 6 min, while that of chemically radioiodinated asialothyroglobulin was about 12 min. No marked species difference was observed in this clearance. The label which had disappeared from the blood was recovered mainly in the liver, and this uptake was blocked by the simultaneous injection of desialylated orosomucoid but not by native orosomucoid. Radiolabeled monoiodotyrosine, diiodotyrosine, triiodothyronine and thyroxine were detected in the liver 17 min after intravenous injection of asialothyroglobulin labeled with ¹²⁵I in vivo, suggesting the possible production of thyroid hormones in extrathyroidal tissues.