Defect-engineered ZnO and Fe3O4 nanoparticles for photoluminescence-based metal-ion sensing

The development of nanoscale materials represents a significant advancement in science, enabling the controlled synthesis of functional nanoparticles with enhanced properties. In this study, zinc oxide (ZnO) and iron oxide (Fe3O4) nanoparticles were synthesized using a coprecipitation method. The structural, optical, morphological, elemental, and functional properties of the synthesized nanoparticles were characterized using Fourier transform infrared (FTIR) spectroscopy, UV-visible spectroscopy, scanning electron microscopy (SEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). FTIR analysis confirmed the formation of ZnO and Fe3O4 nanoparticles along with functional groups such as -OH, C=O, N-H, C-N, and C-H. UV-visible spectra showed characteristic absorption peaks at 195 and 243 nm, corresponding to bandgap energies of 3.3 and 2.9 eV, respectively. SEM images revealed partially aggregated nanoparticles with rodlike and spherical morphologies. XRD patterns confirmed the crystalline nature of the synthesized samples, while XPS analysis indicated the presence of Zn-O and Fe-O bonds, confirming high purity without detectable impurities. Furthermore, photoluminescence studies demonstrated that the synthesized nanoparticles exhibit excellent optical sensing performance toward Pb+ and K+ ions, highlighting their potential application in metal-ion detection.