Tracing mechanism of optically and thermally stimulated luminescence in Lu2O3:Tb,MLu_2O_3:Tb,M (M = Hf, Zr, Ti) ceramic storage phosphors

A series of energy storage phosphors, Lu2O3:Tb,M (M = Hf, Zr, Ti), were investigated by means of photo- and thermoluminescence techniques to compare the effect of the co-dopant from the same group of periodic table of elements on charge carriers trapping capability and trap parameters. Most of the investigated processes were tracked individually for the Tb3+ in the two different metal sites offered by the Lu2O3 host – noncentrosymmetric C2 and centrosymmetric C3i. It is proved that both Tb3+ ions participate in hole trapping and electrons are immobilized in traps whose depths are defined by the co-dopant. Deepest traps, ∼1.79 eV, appear upon Ti addition, while Zr and Hf generate traps of very similar, ∼1.40–1.44 eV, depths. The stored energy may be released not only by means of thermal stimulation but also upon the impact of optical photons. Light from the 390–430 nm range of wavelengths was found the most efficient in the latter process. Also deep red radiation of 780 nm releases most of the trapped electrons in Zr/Hf co-doped ceramics but is much less effective in the case of Tb, Ti material. Consistent scheme of electronic levels engaged in charge carriers trapping and subsequent generation of thermo- and optically stimulated luminescence was constructed

Chemical Components of <i>Oxytropis pseudoglandulosa</i> Induce Apoptotic-Type Cell Death of Caco-2 Cells

Oxytropis pseudoglandulosa plant is used in traditional Mongolian medicine. However, its chemical composition and biological properties are poorly explored. In this study, the total content of polyphenols and flavonoids as well as antioxidant activity were verified in plant extract. The total phenolic and flavonoid contents were determined by spectrometric (6.62 mg GAE/g and 10.32 mg QE/g) and chromatographic (17,598 mg/kg and 17,467 mg/kg) assays. The antioxidant potential was investigated by DPPH assay and yielded IC50 at 18.76 µg/mL. Twelve phenolic compounds were identified as components of O. pseudoglandulosa extract. Kaempferol-3-O-robinosyl-7-O-rhamnoside and kaempferol-3-(p-coumaroyl)-rutinosyl-7-rhamnoside made up 80% of determined components and were found to be the major polyphenolic compounds. The biological properties of O. pseudoglandulosa extracts were determined in vitro using human epithelial adenocarcinoma Caco-2 cell line. Low concentrations of extract (0–30 µg/mL) exhibited protective effects against cell damage caused by chemically induced oxidative stress. Elevated concentrations, on the other hand, resulted in apoptotic-type cell death induction. Metabolic failure, ROS elevation and membrane permeabilization observed in cells upon incubation with extract dosages above 50 µg/mL allowed us to conclude on O. pseudoglandulosa being predominantly a necrosis inducer