Novel Cu0.96V0.02M0.02O (M = Mn, Fe, Co, Ni) nanocompositions: Remarkable optical and room temperature superparamagnetic properties

Multifunctional CuO semiconductor is a promising material for the full development of electronic, spintronics, terahertz and biomedical devices. In this study, new CuO compositions with strong room temperature super paramagnetic, terahertz optical conductivity and terahertz dielectric constant properties were realized. Pure CuO, Cu0.96V0.02Mn0.02O, Cu0.96V0.02Fe0.02O, Cu0.96V0.02Co0.02O and Cu0.96V0.02Ni0.02O nanopowders were synthesized by sol-gel method. The XRD confirmed the synthesis of single phase of monoclinic CuO structure. Based on the reduction on unit cell volume, the incorporation of V3+/4+, Mn2+, Fe3+, Co2+ and Ni2+ ions into CuO lattice have been verified. The dopants lead to formation of fine spherical nanoparticles with homogenous distribution and similar size. The TEM image of Cu0.96V0.02Fe0.02O reveals the formation of uniform sphericalnanoparticles possesses define surface edges with average size of 29 nm. The FTIR vibrational absorption modes of the synthesized CuO nanocompositions ruled out the presence of impurities or the existence of Cu2O phase. Optically, both (V, Mn) and (V, Co) codoping induced a red shift in the band gap energy of CuO (1.39 eV) on contrast to (V, Fe) and (V, Ni) with obvious blue shift. CuO codoped with different transition elements has been studied by terahertz time-domain spectroscopy (THz-TDS) in the range from 0.3 to 3 THz. The higher atomic weight elements show higher values of dielectric constant and optical conductivity. Cu0.96V0.02Fe0.02O exhibited an excellent intrinsic superparamagnetic curve with semi-saturation magnetization of ~0.39 emu/g, coercivity and retentivity values close to zero.