Thermal plasma-inspired synthesis of ZnO1-xMnx dilute magnetic semiconductors for enhanced visible light photocatalysis

We report a simple, time-consuming and scalable synthesis of ZnO1-xMnx nanocrystals (Mn-ZnO NCs) using a thermal plasma chemical method. The diffusion of the Mn2+ into the host ZnO lattice causes pronounced change in the structure, morphology, spectroscopy and magnetic properties of ZnO. The Mn-doping in ZnO lattice introduces defects by changing the lattice constant values, vibration mode shift at a particular position, decrease in the band gap energy from 3.23 to 3.08 eV, with more than 90% photoluminescence quenching proficiency which has not only makes it as the efficient photocatalyst in methylene blue dye degradation but also confirms change in the shape and the magnitude of the electron spin resonance spectra, suggesting revelation of the dilute magnetic semiconducting properties in ZnO. The onset of the sharp resonance peak at 0.6% Mn-doping level followed a sharp fall in the intensity when Mn-concentration >= 0.8% has thoroughly been investigated and explored. Moreover, a tunable optical absorption change of Mn-ZnO NCs at various Mn-contents corroborats a proficient visible light photocatalytic performance which has been optimized, exquisitely, on controlling the shape and Mn-doping concentration level. Our results offer a basic understanding of synergetic effect taking place in enhancing the photocatalytic performance, which otherwise could cause by a defect-mediated ferromagnetic coupling and optimal Mn-doping concentration.