NiO nanoparticles by thermal decomposition of complex and evaluation of the structural, morphological, and optical properties

Abstract

An efficient method for the synthesis of metal oxide nanoparticles (NPs) involves the solid-state thermal decomposition of precursor complexes. This study reports on the preparation of nanocrystalline nickel oxide (NiO) through a solid-state thermal decomposition of nickel(II) bis(N-methyl-N-paramethoxyphenyl dithiocarbamate) in a furnace. The novel Ni(II) complex was characterized using various analytical techniques. The single-crystal X-ray structure of the new nickel dithiocarbamate complex, C18H20N2NiO2S4, was determined and it showed a square-planar nickel coordination environment. The C-H⋯S intramolecular hydrogen bond in this complex contributes to the planarity of the Nickel coordination environment. The complex underwent thermal decomposition in the air at about 750 °C for varying times of 90, 120, 150, and 180 min, resulting in the production of the oxide. Subsequently, the study explored how varying calcination times influenced the structural, morphological, and optical characteristics of the formed NiO nanoparticles. Face-centered cubic (FCC) structure of NiO NPs was confirmed whose crystallite size increased with an increase in the dwelling time of calcination and has been attributed to the possible coalescence of smaller crystallites to form larger ones. The confirmation of the face-centered cubic (FCC) structure of NiO nanoparticles was established, with the crystallite size observed to increase alongside longer calcination periods. This phenomenon has been linked to the potential amalgamation of smaller crystallites into larger ones. The optical energy bandgap decreased from 4.35 to 3.40 eV with an increase in the calcination time due to the increase in crystallite size occasioned by a longer reaction time from 90 to 180 min. These NPs will be useful as photocatalysts due to their high crystallinity and the capability to absorb within the visible region of the solar spectrum.