Exploring the Defects and Vacancies with Photoluminescence and XANES Studies of Gd³⁺‐Substituted ZnO Nanoparticles

Abstract

of ZnO has not yet been completely realized and explored despite two decades of rigorous research. It has a wide range of uses in photocatalysts, UV lasers, solar cells, photodiodes, sensors, optoelectronics, spintronic devices, and more. [1][2][3][4][5][6] Depending on the application, essential modifications have been made over time to increase the stability of ZnO nanostructures. High quantum confinement effect plays a significant role in the configuration of the electronic structure at the nanoscale. Also, factors such as doping, defects, and crystallinity affect various properties of the nanostructures. Doping ZnO with appropriate ions with varying sizes is great approach way to vary its properties for certain device applications. [7][8][9] According to Chaudhary et al., WO 3 -ZnO@rGO nanocomposites can be used for relevant photocatalytic applications and wastewater purification. [10] Additionally, Yousaf et al. have reported that the ZnO-NiO/rGO nanohybrid shows exceptional photocatalytic performance and is a reliable contender in the field of catalysis. [11] Transition metal (TM) and rare earth (RE)-doped metal oxides have been studied extensively under this regime. For optoelectronics and spintronic applications, ZnO doped with rare-earth ions is Undoped ZnO and Zn 1−x Gd x O nanoparticles are made using a sono-chemical co-precipitation approach. X-ray diffraction and transmission electron microscopy investigations verified the formation of a wurtzite structure with spherical geometry. All the samples are found to be nanocrystalline by transmission electron microscopy, with crystallite diameters ranging from 14 to 22 nm. The optical constants are calculated via diffuse reflectance spectroscopy. The Urbach energy and photoluminescence spectrum both showed that all doped nanoparticle samples contained defects and disorder due to vacancies. The band structure finding suggest that the forbidden gap of ZnO may change due to the conduction band shift, Burstein-Moss shift, and shrinkage effect. The near band emission in the ultraviolet region and deep level emission of the photoluminescence spectrum are both strong and decreased with increasing Gd 3+ concentration. Studies using X-ray absorption near edge spectroscopy revealed that the host nano-lattice Zn sites are substituted with Gd 3+ cations to preserve the symmetry with minor distortion. Investigations into charge transfer through the oxygen bands (Gd-O-Zn) are made using O K-edge spectra. The defect emission bands identified through Gd doping indicated that these emissions may be changed for ZnO samples, which could be advantageous for applications in phosphors and light-emitting devices.