Fe-induced morphological transformation of 1-D CuO nanochains to porous nanofibers with enhanced optical, magnetic and ferroelectric properties

Abstract

The present work reports the synthesis of self-assembled 1-D polycrystalline Fe doped CuO nanostructures (Cu_1−xFe_xO, x = 0.02 (SP2), 0.05 (SP5), 0.10 (SP10)) using a wet chemical approach. The surface analysis of these nanostructures by X-ray photoelectron spectroscopy indicated Fe to be present as Fe³⁺. The doping of Fe (2 to 10%) causes exchange of Cu in CuO and creates point defects – oxygen vacancies, which are manifested by the change in morphologies of doped nanostructures from nanochains to nanofibers, a reduction in the size of CuO NPs from 19 to 5 nm, the red shifted optical absorption and fluorescence bands associated with an increase in the fluorescence lifetime(s) and blue shifted Raman spectra. The field dependent magnetization (M–H) measurements at room temperature show that for SP10 the magnetization value increases by a factor of about 3 as compared to that of the undoped sample and the superparamagnetic behavior increases with increasing Fe-content. Whereas, at 5 K it exhibits ferromagnetic behavior with increasing values of coercivity (1564 Oe) and retentivity (0.19 emu g⁻¹) and exchange bias effect decreasing with increased doping of Fe. The room temperature polarization versus electric field measurements at 200 Hz show weak ferroelectric behavior for all samples and increases with increasing Fe content in the sample. Dielectric constant and dielectric loss show decreasing values with increasing frequency. A correlation between the observed changes in morphology with optical, magnetic and ferroelectric properties upon doping of Fe has been analyzed.