Core shell heterojunction interface in green synthesized Sm3+ ions doped ZnO nano-particles to promote the charge separation for efficient photocatalytic applications

Abstract

In this work, we report core-shell heterojunction of Sm3+ ions doped ZnO nanoparticles (NPs) by green synthesis technique and their photocatalytic activity for rapid degradation of methyl green dye molecules under UV light irradiation. High-resolution X-ray diffraction and high-resolution transmission electron microscope characterization techniques were employed to investigate structural and morphological studies. It is found that, the crystallite size of NPs is decreased with increasing Sm3+ ions concentration in NPs since Sm3+ ions are inhibiting the further growth of NPs. In addition, Sm3+: ZnO NPs catalyst shows irregular core shell heterojunction ensuing in the augmentation of a charge partition. Following that, the elemental compositional studies of Sm3+: ZnO NPs were estimated by energy dispersive spectroscopy. XPS imaging is also done in this work to get chemical mapping and the results suggested that the peaks are related to the Sm3+ ions in the ZnO lattice, which confirms the appropriate incorporation of Sm3+ into the ZnO. The optical energy band gap of NPs was estimated using diffuse reflectance spectroscopy. Excitation spectrum of Sm3+: ZnO NPs tinted the typical f-f transitions of Sm3+ ions. Photoluminescence emission shows the e− /h+ pair recombination rate reduced with increasing wt% of dopant Sm3+ ions in NPs. 10 wt% Sm3+: ZnO NPs showed the optimum photodegradation efficiency towards methyl green dye under the irradiation of UV light for 50 min. The dye degradation rate of Sm3+: ZnO NPs was 91% which is 26% higher than that of pristine ZnO NPs. Furthermore, the catalyst retains its original efficiency after fifth cycle.