Chromium-doped magnesium oxide (Mg₁₋ₓCrₓO) nanoparticles ( x = 0–10 wt.%) were synthesized using a sol–gel method to investigate the influence of Cr incorporation on their structural, optical, dielectric, and antibacterial properties. X-ray diffraction confirmed a single-phase cubic MgO structure (Fm–3 m) with lattice expansion and crystallite-size reduction from 24.49 nm (pure MgO) to ~ 10 nm at 10 wt.% Cr. Optical measurements showed a systematic bandgap reduction from 5.25 to 2.25 eV due to Cr-induced defect states, consistent with photoluminescence (PL) results that revealed suppressed near-band-edge emission (~ 450 nm) and enhanced defect-related emission (700–800 nm) at higher Cr levels. X-ray photoelectron spectroscopy (XPS) confirmed successful doping through the emergence of Cr 2p₃/₂ peaks at ~ 577–579 eV and modifications in the O 1 s environment. Dielectric analysis (10–10⁶ Hz; 60–380 °C) indicated strong frequency- and temperature-dependent behavior, non-Debye relaxation, and activation energies of 3.970, 2.226, and 1.753 eV. Antibacterial activity improved markedly with Cr content, producing inhibition zones up to 40 mm and complete bacterial suppression in spread plate assays at low doping levels (2.5–5 wt.%). The integrated structural, optical, dielectric, and biological results demonstrate that Cr doping significantly enhances the multifunctional performance of MgO nanoparticles, supporting their potential use in antimicrobial coatings, dielectric devices, and nanobiotechnology applications.
Aity et al. (2026) studied this question.