ZnO-ZnS-Ag2S ternary nanostructures were prepared by a simple and low-cost chemical precipitation method. The sample was characterised by X-ray diffraction, energy-dispersive X-ray, UV-Vis-NIR, Raman and Fourier transform infrared spectroscopy. Morphology of the sample was studied by scanning electron microscopy and it was observed that ZnO nanoplates were covered with ZnS and Ag2S nanoparticles. A high resolution transmission electron microscope was used to obtain further information about the crystalline domains of the prepared ternary nanostructure. The Kramers-Kronig method and classical dispersion theory were utilised to study the optical properties of the sample in the far-infrared region. Photocatalytic activity of the prepared samples was also attained in the gas-solid phase by using a solar lamp (simulating outdoor lighting) and monitoring NOx degradation.