Zinc oxide (ZnO) nanostructures were grown on glass substrates using hydrothermal technique followed by a sputter deposited ZnO seed layer. The influence of hexamethylenetetramine (HMTA) concentrations on the growth of ZnO nanostructures and their room temperature sensing performance were investigated. Further, the non-mutually exclusive dual role of HMTA on the growth of ZnO nanostructures were evaluated by morphological studies. Various morphologies such as nanoprisms, nanoparticles decorated nanoprisms and nanodisks were observed concerning various molar concentrations of zinc acetate and HMTA. Protonation of HMTA acted as a capping agent, which offered a unique impact on the anisotropic growth of ZnO along the c-axis direction. Nanoparticles decorated nanoprisms showed good selectivity towards acetaldehyde vapor amidst ethanol, ammonia, and acetone, which was well supported by bond dissociation energy. The presence of increased number of junction types, densities, and networked structure showed a prospect towards better sensing performance. (C) 2018 Elsevier B.V. All rights reserved.