The manufacturing of doped semiconductor Ag2O.La2O3 (Ag-La) nanoparticles (NPs) in an alkaline medium at 60–70 °C is described in this paper, utilising a straightforward wet chemical procedure. Numerous tools are used to characterise Ag-La NPs, such as ultraviolet/visible spectroscopy (UV/Vis.), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), and powder X-ray diffractometer (XRD). An X-ray diffraction analysis revealed that the Ag-doped Nps are polycrystalline in nature and crystallise in a hexagonal phase with crystallites oriented in various directions. The morphology of the particles shows layers of aggregation of different sized and shaped nanosheets. Studies on their optical properties, however, have revealed that absorption takes place in the 270–291 nm range and that the transmission value, which ranges from 30 to 64%, is influenced by the temperature during annealing. An increase in annealing temperature results in a corresponding drop in band gap energy, from 4.27 to 4.10 eV.