A simple post-treatment method of irradiation with a Xe lamp for 2 h has been observed to enhance the catalytic performances of a nanocatalyst on a large scale. The light treatment of mesoporous silica-coated gold nanorods having an average diameter of 17.5 nm and a typical aspect ratio of 4 with a uniform shell thickness of 20 nm improves the catalytic activity of the nanocatalyst for the reduction of 4-nitrophenol in the presence of NaBH4 extensively without deteriorating the encapsulation effect of mesoporous silica that enhances the stability and reusability of the nanocatalyst by preventing the aggregation and dissolution of gold nanorods. Irradiation increases the catalytic rate constant largely with reducing the activation energy and the induction time of the catalytic reaction substantially; surface atom restructuring induced by photothermal annealing during irradiation has rendered the metallic surface to adsorb reactants easily and to facilitate rapid electron relays from BH4- to 4-nitrophenol, lowering the kinetic barrier of the catalytic reaction considerably. (C) 2014 Elsevier B.V. All rights reserved.