­Improved Luminescence and Photocatalytic Proprieties of Sm3+-doped ZnO Nanoparticles Via Modified Sol-Gel Route: An Unified Experimental and DFT+U Approach

In the current study, a modified sol-gel route was followed to produce undoped and Sm 3+ doped (1, 3 and 5 mol %) nanoparticles. The study of opto-structural properties of Sm 3+ doped NPs was carried out both experimentally and theoretically. Complete dissolution of Sm 3+ ions into the ZnO lattice was obvious from XRD analysis. Morphological evolution with doping was studied using FESEM and TEM. XPS was carried out to confirm the presence of Sm 3+ on the surface of the doped NPs. Increasing dopant quantity resulted in a red shift of the NPs along with a reduction in band gap with increasing absorption in the visible range, and a minimum of 3.18 eV of optical band gap for Zn 0.97 Sm 0.03 O was found. Photoluminescence spectroscopy revealed a drop in the recombination rate of electron-hole with increasing doping till 3 mole %, followed by an increase for Zn 0.95 Sm 0.05 O. Photogenerated electron-hole pair recombination was revealed by the orange band in the luminescence spectra. Theoretical analysis was also carried out with density function theory (DFT). This work also unfolds the fundamental understanding of the structural properties of the synthesized NPs to enhance photocatalytic activity successfully. Later, photocatalytic activity for the optimum composition i.e., 3 mole percent, was assessed experimentally.