Structural, morphological, optical, and electromechanical analysis of green-synthesized Ti-doped ZnO nanoparticles for optoelectronic applications

In this study titanium (Ti 4+ ) doped zinc oxide (ZnO) nanoparticles were synthesized via a green solution combustion method employing Calotropis gigantea as fuel. Employing various characterization techniques, the structural, morphological, elastic, and electromechanical properties were studied. The Rietveld refinement confirms the presence of hexagonal wurtzite structure with lattice strain induced by Ti 4+ substitution. The computational simulation using GULP reveals how Ti 4+ doping modifies the mechanical stiffness and dielectric response of ZnO by showing direction-dependent elastic and dielectric behaviour. The crystallite size obtained using Scherrer equation and dislocation density have shown a non-linear trend with optimal grain growth at 5% of Ti 4+ as observed in 3D map. Electron density (ED) mapping reveals evolving symmetry and strain distribution across doping levels. The analysis of surface texture highlights enhanced surface waviness and roughness with heterogeneity. The shift in vibrational modes can be seen in FTIR spectra, affirming dopant incorporation and reduced surface organics. A tunable bandgap from 3.25 to 3.50 eV have been obtained using UV–Vis absorption, showing potential for optoelectronics. These materials have application in UV-protective coatings, sensors, and photocatalytic systems. • First combined experimental and GULP approach on pure and Ti-doped ZnO nanoparticles, overcoming challenges of supercell construction, Buckingham potentials, and complex atomic optimization. • Green synthesis using Calotropis gigantea provided an eco-friendly route, yielding Ti–ZnO nanoparticles with controlled surface morphology and improved crystallite growth. • Rietveld refinement confirmed hexagonal wurtzite phase across all doping levels, while electron density mapping revealed lattice strain, symmetry changes, and charge redistribution. • GULP-based elastic and electromechanical simulations highlighted strong anisotropy in stiffness, dielectric constants, and piezoelectric coefficients, showing application potential in sensors and energy harvesters. • Crystallite size analysis using Scherrer, Williamson–Hall, and modified W–H methods showed non-linear trends, peaking at 5% Ti doping and correlating with dislocation density. • FTIR spectra verified Ti incorporation through shifted Zn–O and Ti–O vibrations, while also indicating reduced organic residues from the green fuel source. • UV–Vis absorption studies demonstrated a tunable bandgap from 2.50 to 2.85 eV, governed by Burstein–Moss effect and defect-induced shifts, relevant for optoelectronic applications. • Surface texture and morphology analyses showed increased roughness, waviness, and active edge sites with doping, leading to enhanced photocatalytic, UV-protective, and sensing behaviour.