White and Tunable Emission from and Rhodamine B Detection by Modified Zinc Oxide Nanowalls

Single-phased emission-tunable Mg and Ce co-doped ZnO quantum dots for white LEDs

In this study, a simple low-temperature route is presented for the synthesis of Mg and Ce co-doped ZnO quantum dots (QDs). X-ray diffraction, transmission electron microscopy, electron paramagnetic resonance, X-ray photoelectron spectroscopy, UV-vis absorption spectra, and fluorescence measurements were used to characterize the synthesized QDs. The results indicate that the oxygen vacancy concentration could be tuned via Mg and Ce ions doping, which leads to the regulation of luminescence. The visible emission was directly associated with oxygen vacancies, and a blue shift of the visible emission with increasing Ce doping concentration was due to the quantum confinement effect. Finally, we explored the application of Mg and Ce co-doped ZnO QDs by fabricating a white LED device. Notably, the white LED device presents good luminescence properties under a voltage of 3 V and a driven current of 200 mA. The Commission International de l'Eclairage chromaticity, the correlated color temperature, and the color rendering index were determined to be (x = 0.32, y = 0.30), 5733 K, and 81, respectively, which make them potential candidates as single-phased QDs for white light-emitting diodes.

Cobalt Phthalocyanine-Sensitized Graphene-ZnO Composite: An Efficient Near-Infrared-Active Photothermal Agent

Herein, a promising near-infrared-responsive photothermal agent was designed by anchoring of rice grain-shaped ZnO particles over graphene (GR) nanosheets and subsequent sensitization with cobalt phthalocyanine (CoPc). Thus, produced GR-ZnO-CoPc was able to attain the temperature of 68 °C by irradiating to 980 nm laser for 7 min, which is extremely higher than the endurance temperature of cancer cells. The linear fashioned progression in the photothermal effect of GR nanosheets was conquered by immobilization of ZnO particles and successive sensitization with CoPc. The excellence found in the photothermal effect of GR-ZnO-CoPc was verified by estimation of its photothermal conversion efficiency. The photothermal conversion efficiency assessed for GR-ZnO-CoPc was higher than those for the popular gold- and CuS-based photothermal agents. In addition, it possessed significant stability against photobleaching and structural rupture. It was found that the photothermal effect of GR-ZnO-CoPc is proportional to its concentration. However, by replacement of a 980 nm laser system with 808 nm, the photothermal effect of GR-ZnO-CoPc was reduced, which could be due to lower absorption of GR-ZnO-CoPc at 808 nm compared to 980 nm. On account of its significance and important properties, GR-ZnO-CoPc could be an interesting photothermal agent to employ in future photothermal therapy for cancer.