Effects of Co and Mn doping on structural, optical and magnetic properties of hydrated vanadium pentoxide (V₂O₅⋅nH₂O) nanocrystals

Un-doped, cobalt (Co)-doped (5% and 10%) and manganese (Mn)-doped (5% and 10%) hydrated vanadium pentoxide (V₂O₅⋅nH₂O, HVO) nanocrystals have been synthesized by the chemical co-precipitation method. The synthesized materials have been characterized using X-ray diffractometer (XRD), field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectrometer (EDX), thermogravimetric analyser (TGA), Fourier transform infra-red spectrometer (FT-IR), micro-Raman spectrometer, UV–visible spectrophotometer, spectrofluorometer and vibrating sample magnetometer (VSM). The un-doped HVO nanocrystals are found to exhibit a monoclinic crystal structure. Although, the crystal structure remains the same in the Co-doped and Mn-doped HVO nanocrystals as that of the un-doped HVO nanocrystals; the lattice parameters are found to depend on the doping concentrations. The average crystallite size and band gap of the HVO nanocrystals vary in the ranges of 4–11 nm and 2.18–2.30 eV, respectively. The doped HVO nanocrystals are found to exhibit higher average crystallite size and band gap than those of the un-doped ones. Photoluminescence (PL) spectra of the HVO nanocrystals show an emission at 540 nm, which is attributed to the presence of vanadium vacancies in the nanocrystals. The un-doped, Co-doped and Mn-doped HVO nanocrystals are found to exhibit ferromagnetic behaviour at room temperature. The Mn-doped HVO nanocrystals exhibit enhanced ferromagnetic behaviour that makes them suitable for spintronics applications. (author)