Tuning the band gap and optical characteristics of NiO nanoparticles via tin (Sn) doping: a combined experimental and DFT investigation.

contextThe structural and electronic modifications induced by tin (Sn) doping in cubic nickel oxide (NiO) were investigated through a combined computational and experimental approach. Sn incorporation into the NiO lattice is of significant interest for tailoring its optoelectronic properties toward enhanced energy conversion and photocatalytic applications. Experimentally synthesized NiO nanoparticles confirmed the theoretical predictions, showing that increasing Sn concentration (0-12.5%) leads to lattice distortion and bandgap narrowing. The observed bandgap reduction, from 2.89 eV (pure NiO) to 2.56 eV (12.5% Sn-NiO), was attributed to a Fermi level shift and the introduction of defect states, demonstrating that Sn doping effectively tunes the electronic structure of NiO.

methodsTheoretical investigations were conducted using spin-polarized density functional theory with Hubbard correction (DFT + U) within the Quantum ESPRESSO (v7.2) framework to elucidate the electronic properties. The cubic NiO (a = 4.22 Å) was modeled with a 2 × 2 × 2 supercell using the Perdew-Burke-Ernzerhof (PBE) functional under generalized gradient approximation (GGA) and ultrasoft pseudopotentials from PSLibrary 1.0.0. Convergence tests yielded cutoffs of 50 Ry (wavefunction) and 400 Ry (charge density) with a 7 × 7 × 7 Monkhorst-Pack grid. A Hubbard U of 6.0 eV was applied to Ni 3d orbitals to correct correlation effects. Sn doping (3.125-12.5%) was introduced by substituting Ni atoms, and all structures were optimized using the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm. Electronic band structures and density of states (DOS) were calculated along high-symmetry paths to analyze the doping-induced modifications in NiO's electronic properties.