In this work we present a novel metal-semiconductor heterostructure that contains triangular and prism-shaped plasmonic gold nanostructures directly synthesized and assembled onto ZnO nanostructures. Spatially-resolved (SR) high-resolution electron energy loss spectroscopy (EELS) at the local (sub-nanometer scale) level confirmed the field enhancement of the local electromagnetic fields in the surroundings of the triangular and prism-shaped Au nanostructures and in the interfacial junction between Au and ZnO. Different LED excitation sources have been systematically selected in the whole UV-vis-NIR range to evaluate the photocatalytic response of the Au-ZnO heterostructures towards the oxidation of n-hexane, selected as a model VOC present in indoor environments. The Au-ZnO exhibits visible expanded photo-response with the more energetic interband and intraband electrons and the higher LED irradiation wavelengths and it is able to outperform its ZnO plain counterpart.