We report a new route for the direct synthesis of gamma-alumina nanocrystals with size and shape control in the presence of oleylamine as the capping agent. Their morphology can be controlled from nanospheres to nanorods by simply tuning a proper amount of concentrated nitric acid (67%) in the synthetic mixture. The as-made nanoparticle products after calcination show gamma-alumina nano-size with unique porosity and high specific surface area and retained morphology. The XRD patterns of these calcined samples exhibit broad diffraction lines which are characteristic of nanocrystal size of gamma-alumina. This synthesis procedure has been extended to the one-pot synthesis of nano-alumina based Ag catalysts with spherical and rod-shaped nano-alumina morphologies. Selective catalytic reduction (SCR) of NO with C3H6 over these catalysts was investigated. The results were compared to those of the conventional Ag/gamma-Al(2)o(3) and gamma-nanoalumina alone. These nano-alumina based Ag catalysts exhibit excellent NO reduction activity in the presence of C3H6. Even in the presence of large oxygen concentration (15%), N-2 yields as high as 90% at quite low temperature (similar to 350 degrees C) have been achieved. The significantly high catalytic activity of this new type of nanocatalysts can also be attributed to their high surface area and good dispersion of silver species in the alumina matrix as well as the synergism and new properties that arise at the silver-nanoalumina interface. (C) 2016 Elsevier Inc. All rights reserved.