Nanoparticles (NPs) that can be optically tracked are of interest for cell and organismal biodistribution studies. However, dyes or fluorophores crosslinked or adsorbed onto NP surfaces may detach or leach, resulting in optical artifacts. NP surfaces altered to carry dyes or fluorophores are also anticipated to affect toxicity profiles, protein interactions, and cell uptake. Zinc oxide (ZnO) NPs provide a potential solution. We have produced ZnO nanoparticles with different morphologies and defect emissions in the visible range using sol-gel chemistry. Several of the nanocomposites produced have a wide visible band emission. ZnO semiconductor nanocomposites have broad applications in many fields. They may be dispersed in polymers, functionalized for cell targeting, conjugated to drugs or proteins. We report a unique 600 nm emission peak, which is of interest for nano-bio interaction studies currently limited by autofluorescence in biologicals and the spectral overlap of common fluorescent dyes and proteins.