Re-dispersible Tb(3+) doped LaPO(4) nanorods have been prepared using ethylene glycol (EG) as a capping agent as well as reaction medium at a relatively low temperature of 150 °C. The X-ray diffraction study reveals that all the doped samples are well crystalline with a monoclinic structure of the LaPO(4) phase. The luminescence intensity of (5)D(4)→(7)F(5) transition at 543 nm (green) is more prominent than that of (5)D(4)→(7)F(6) transition at 487 nm (blue) for all the samples. This is related to the polarizing effect from [PO(4)](3-) to the Tb(3+) site. Concentration dependent luminescence study shows that the luminescence intensity of Tb(3+) increases up to 10 at.% and decreases above this. This is due to the concentration quenching effect arising from cross relaxation among Tb(3+)-Tb(3+) ions. The results show that nanoparticles prepared in EG medium gives an enhanced luminescence compared to that prepared in water. This is attributed to the multiphonon relaxation effect from O-H groups surrounding over nanoparticles as well as the extent of increase of agglomeration among particles for samples prepared in water. Significant enhancement in the emission of Tb(3+) is also observed when Ce(3+) is used as the sensitizer in LaPO(4):Tb(3+)nanorods. The optimum concentration of Ce(3+) for maximum luminescence is found to be 7 at.% in Ce(3+) sensitized LaPO(4):Tb(3+) (5 at.%). Based on the energy transfer process from Ce(3+) to Tb(3+), the luminescence of Tb(3+) can be switched OFF and ON by performing oxidation and reduction of Ce(3+)↔Ce(4+) using KMnO(4) and ascorbic acid, respectively. The samples are re-dispersible in water, methanol and can be incorporated into polyvinyl alcohol (PVA) films. They show a dark green emission under ultraviolet radiation.

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Zinc oxide nanoparticles (ZnONP-GS) were synthesised from the precursor zinc acetate (Zn(CH3COO)2) through the green route using the milky latex from milk weed (Calotropis gigantea L. R. Br) by alkaline precipitation. Formation of the ZnONP-GS was monitored by UV-visible spectroscopy followed by characterization and confirmation by energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Both the ZnONP-GS and the commercially available ZnONP-S (Sigma-Aldrich) and cationic Zn2+ from Zn(CH3COO)2 were tested in a dose range of 0–100 mg·L−1 for their potency (i) to induce oxidative stress as measured by the generation reactive oxygen species (ROS: O2•−, H2O2 and •OH), cell death, and lipid peroxidation; (ii) to modulate the activities of antioxidant enzymes: catalase (CAT), superoxide dismutase (SOD), guaiacol peroxidase (GPX), and ascorbate peroxidase (APX); and (iii) to cause DNA damage as determined by Comet assay in Lathyrus sativus L. root bioassay system. Antioxidants such as Tiron and dimethylthiourea significantly attenuated the ZnONP-induced oxidative and DNA damage, suggesting the involvement of ROS therein. Our study demonstrated that both ZnONP-GS and ZnONP-S induced oxidative stress and DNA damage to a similar extent but were significantly less potent than Zn2+ alone.

GdVO(4) : Ln(3+) (Ln(3+) = Dy(3+), Eu(3+), Sm(3+), Tm(3+)) nanoparticles are prepared by a simple chemical route at 140 °C. The crystallite size can be tuned by varying the pH of the reaction medium. Interestingly, the crystallite size is found to increase significantly when pH increases from 6 to 12. This is related to slower nucleation of the GdVO(4) formation with increase of VO(4)(3-) present in solution. The luminescence study shows an efficient energy transfer from vanadate absorption of GdVO(4) to Ln(3+) and thereby enhanced emissions are obtained. A possible reaction mechanism at different pH values is suggested in this study. As-prepared samples are well dispersed in ethanol, methanol and water, and can be incorporated into polymer films. Luminescence and its decay lifetime studies confirm the decrease in non-radiative transition probability with the increase of heat treatment temperature. Re-dispersed particles will be useful in potential applications of life science and the film will be useful in display devices.

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