Fe(III) induced structural, optical, magnetic and electrical behavior of hydrothermally synthesized polyvinyl pyrrolidone capped CdS nanoparticles

We report facile hydrothermal synthesis of polyvinyl pyrrolidone capped pristine and iron (Fe) containing cadmium sulfide (CdS) nanoparticles. The X-ray diffraction pattern of pristine CdS indicated the formation of wurtzite type hexagonal phase with space group P6₃mc and lattice parameter a = 4.21 and c = 6.76Å average crystallite size being ~ 12nm. The increase in Fecontent revealed cell volume contraction and decrease in crystallite size, due to resulted positive pressure on the lattice caused by smaller size and higher oxidation state of Fe³⁺than Cd²⁺ion. The bandgapwas found to decrease as 2.84, 2.75 and 2.55eV (for the Fe content of 0, 2 and 4 at%, respectively) due to Fe³⁺ induced 3d³ defect levels below the lowest unoccupied molecular orbitals of CdS. Photoluminescence spectra revealed redshift and decease in emission intensity with increase in Fe content. Fourier transform infrared spectra, transmission electron micrographs together with thermal analysis exhibited that pristine and Fe doped CdS nanoparticles were capped with polyvinyl pyrrolidone. Magnetic studies revealed weak ferromagnetic order in pristine CdS, which, was found to increase with increase in Fe induced t_2g defect levels. The electrical conductivity was found to increase with increase in Fe content.