Structural, optical, and luminescence properties of Ni2+-doped ZnO–CdS nanocomposite: synthesis and investigations for green light emission

Photon-carrier-spin coupling in a one-dimensional Ni(II)-doped ZnTe nanostructure

Transition metal (TM) ion doping in II-VI semiconductors can produce exciton magnetic polarons (EMPs) and localized EMPs containing longitudinal optical (LO) phonon coupling, which will be discussed in this paper. TM ion doping in II-VI semiconductors for a dilute magnetic semiconductor show emission via magnetic polarons (MPs) together with hot carrier effects that need to be understood via its optical properties. The high excitation power that is responsible for hot carrier effects suppresses the charge trapping effect in low exciton binding energy (8.12 meV) semiconductors, even at room temperature (RT). The large polaron radius exhibits strong interaction between the carrier and MP, resulting in anharmonicity effects, in which the side-band energy overtone to LO phonons. The photon-like polaritons exhibit polarized spin interactions with LO phonons that show strong spin-phonon polaritons at RT. The temperature-dependent photoluminescence spectra of Ni-doped ZnTe show free excitons (FX) and FXs interacting with 2LO phonon-spin interactions, corresponding to3T1(3F) →1T1(1G) and EMP peaks with ferromagnetically coupled Ni ions at3T1(3F) →1E(1G). In addition, other d-d transitions of single Ni ions (600-900 nm) appear at the low-energy side. RT energy shifts of 14-38 meV are observed due to localized states with density-of-states tails extending far into the bandgap-related spin-induced localization at the valence band. These results show spin-spin magnetic coupling and spin-phonon interactions at RT that open up a more realistic new horizon of optically controlled dilute magnetic semiconductor applications.

Enhanced Photocatalytic Activity of ZnO–CdS Composite Nanostructures towards the Degradation of Rhodamine B under Solar Light

A simple chemical precipitation route was utilized for the synthesis of ZnO nanoparticles (NPs), CdS NPs and ZnO–CdS nanocomposites (NCs). The synthesized nanostructures were examined for the crystal structure, morphology, optical properties and photodegradation activity of rhodamine B (RhB) dye. The ZnO–CdS NCs showed a mixed phase of hexagonal wurtzite structure for both ZnO NPs and CdS NPs. Pure ZnO NPs and CdS NPs possessed bandgaps of 3.2617 and 2.5261 eV, respectively. On the other hand, the composite nanostructures displayed a more narrow bandgap of 2.9796 eV than pure ZnO NPs. When compared to bare ZnO NPs, the PL intensity of near-band-edge emission at 381 nm was practically suppressed, suggesting a lower rate of photogenerated electron–hole (e−/h+) pairs recombination, resulting in enhanced photocatalytic activity. Under solar light, the composite nanostructures displayed a photodegradation efficiency of 98.16% towards of RhB dye. After four trials, the structural stability of ZnO–CdS NCs was verified.