Tailoring MgO nanoparticles through precursor ratio and calcination: Structural and functional insights

Magnesium oxide (MgO) nanoparticles were synthesized by a chemical precipitation method using different precursor ratios (NaOH:Mg²⁺ = 1:1, 1:2, 1:3), followed by controlled calcination at 400 °C. The effect of precursor concentration and thermal treatment on phase formation, crystallinity, morphology, and optical behaviour was systematically investigated. XRD confirmed that the as-precipitated powders crystallised as brucite-type Mg(OH)₂, while calcination produced single-phase cubic MgO with increased crystallite size (from ∼8–11 nm to ∼12–16 nm). FTIR analysis revealed the disappearance of hydroxyl and nitrate bands after heating, validating dihydroxylation and oxide formation. SEM images showed a clear transformation from loosely stacked lamellar hydroxide platelets in unheated samples to compact granular MgO grains after calcination, with the 1:2 ratio showing relatively more uniform and well-defined morphology under the present conditions. UV–Vis spectroscopy demonstrated band gap narrowing upon heating, attributed to particle growth and defect reorganisation. This work highlights the combined influence of precursor ratio and calcination as key factors in tailoring MgO nanostructures. The findings contribute to a clearer understanding of how precursor ratio and calcination conditions influence crystallinity, optical band gap, and functional properties of MgO nanoparticles. This work provides a systematic evaluation within a conventional precipitation–calcination framework. The results demonstrate the practical relevance of controlled parameter optimization for improving material performance and highlight the potential of MgO nanoparticles as cost-effective and eco-friendly materials for environmental remediation, particularly in the photocatalytic degradation of toxic dyes. • Precipitation synthesis enabled controlled fabrication of MgO nanoparticles by tuning precursor ratios. • Calcination transformed platelet precursors into compact, crystalline cubic MgO nanoparticles. • Optimal 1:2 precursor ratio yielded highly uniform, well-defined MgO nanostructures. • Tailored MgO nanoparticles showed efficient visible-light photocatalytic degradation of Rose Bengal dye.