The synthesis of binary (ZnO)_0.4 (CdO)_0.6 nanoparticles was achieved using a novel thermal treatment method. The structural, morphological, elemental composition and optical behaviour of these nanoparticles were determined using various techniques. X-ray diffraction of the sample at a calcination temperature above 500 °C showed the presence of both hexagonal and face-centred cubic crystalline structures. With increasing calcination temperature, the dispersion of the nanoparticles was improved, and the mean particle size determined by TEM micrographs suggested a corresponding increasing trend. Increased particle size led to a rise in the photoluminescent intensity as demonstrated by photoluminescence spectra, and multiple energy band gaps which lessen with increasing calcination temperature. The resulting (ZnO)_0.4 (CdO)_0.6 nanoparticles are likely to have widespread uses within numerous semiconductor applications.