Zinc oxide nanoparticles provide a wide bandgap, strong excitonic emission, piezoelectricity, and excellent UV absorption, properties that intensify with nanoscale engineering. They also exhibit antimicrobial behaviour and their high surface energy makes them reactive under light and sensitive to gases. ZnO finds use in UV-blocking coatings and sunscreens, gas sensors, optoelectronic devices and heterogeneous photocatalysis for environmental treatment.