Up-scalable synthesis of size-controlled NiSe nanoparticles using single step technique

Abstract

Pure NiSe nanoparticles were successfully produced using an adapted thermal treatment technique and an alternate nitrogen flow. Throughout a range of calcination temperatures of 500 °C-800 °C, a number of techniques were utilised in order to examine the optical, structural and magnetic characteristics of the attained NiSe nanoparticles. Ultraviolet-visible absorption spectrophotometry was employed to ascertain the optical characteristics. These evidenced a reduction in the NiSe nanoparticle conduction band with elevated calcination temperatures, i.e. from 3.58 eV to 3.37 eV at 500 °C and 800 °C, respectively. This was attributed to a higher degree of attraction between the conduction electrons and the metallic ions with rising particle dimensions, equating to a larger atom population comprising the metal nanoparticles. This means that the findings can be applied to a wide range of energy applications. The lack of impurities within the produced NiSe nanoparticles was verified utilising Fourier-transform infrared spectroscopy and energy dispersive X-ray analysis. At calcination temperatures of ≥ 500 °C, powder X-ray diffraction demonstrated that the specimen, amorphous at room temperature, had undergone conversion into hexagonal crystalline nanostructures. Transmission electron microscopy confirmed the evolution of size NiSe nanoparticles; mean particle dimensions increased from 21 nm to 54 nm at calcination temperatures of 500 °C and 800 °C, respectively. Electron spin resonance spectroscopy, used to identify the magnetic properties, supported the presence of unpaired electrons.