Studies of structural, optical, and electrical properties associated with defects in sodium-doped copper oxide (CuO/Na) nanostructures
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In the present paper, we report a detailed study on the sodium (Na) doping-induced modifications in the copper oxide (CuO) nanostructure and its properties. A facile and sustainable sol–gel synthesis approach was employed for the preparation of high-quality pristine CuO- and Na-doped CuO nanostructures(1.0, 3.0, 5.0 and 7.0 mol% doping levels, CuO/Na) with controlled shape and composition. Due to the remarkable difference in the ionic radii of Cu2+ (0.73 Å) and Na+ (1.02 Å), Na+ substitution in place of Cu2+ generates strain/distortions in CuO lattice. The XRD analysis reveal the structural alteration from monoclinic to cubic symmetry with increase in doping level and also reveal the phase purity up to 3% doping level, and beyond this (i.e., for 5 and 7% doping level) small amount of impurity phase corresponding to Na2O was observed. The FTIR results further confirmed the presence of the Na–Cu–O stretching vibrations at higher Na-doped samples. Morphology of the samples indicates that the Na-doped CuO nanostructures exhibit less agglomeration compared to pristine CuO nanoparticles. The presence of Na in CuO lattice were found to greatly enhances optical and electrical properties owing to the formation of defects like copper vacancies and oxygen vacancies at the grain boundaries of the nanoparticles with increased doping of Na.
Hafsa Siddiqui and Mohammad Ramzan Parra deeply acknowledge the UGC, New Delhi, and HRDG-CSIR for the financial support given in the form of UGC-MANF videno. F1-17.1/2011-12/MANF-MUS-MAD-4694 and CSIR-SRF Ack. No. 163320/2K14/1, respectively. Authors would like to acknowledge the Director-UGC-DAE-CSR, Indore Centre for performing XRD, Raman, FTIRand UV–Vis–NIR measurements. The authors are grateful to the USIF, Aligarh Muslim University, for providing the TEM facility.
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Conflict of interest
The authors declare that they have no conflict of interests. Also all authors are entirely responsible for the content and writing of the paper.
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