Synthesis of mesoporous Ag/ZnO nanocrystals with enhanced photocatalytic activity

Mesoporous Ag/ZnO nanocrystals have been successfully synthesized at different Ag contents (0-10 wt%) through a single-step sol-gel method in presence of triblock copolymer as a structure directing agent. The as-prepared hybrid materials were calcined at 450 degrees C in air for 4 h, subsequently, Ag nanoparticles have been photo-reduced from AgNO3 onto mesopores ZnO nanocyrstals. The XRD and Raman analysis revealed that well crystalline ZnO hexagonal wurtzite phase and face-centered cubic metallic Ag nanoparticles were formed. TEM images of mesoporous ZnO nanocrystals showed that synthesized materials composed of discrete ZnO nanoparticles agglomerated with worm-like mesoporous structure. The lattice fringes exhibit the typical distances, i.e., Ag(111) and ZnO(1 0 0) and the average Ag and ZnO nanoparticle diameters are similar to 5 and 10 nm, respectively. The photocatalytic performance of different prepared photocatalysts was evaluated by degradation of methylene blue (MB) under visible light irradiation. The results indicate that the photocatalytic efficiencies of mesoporous ZnO photocatalysts were remarkably enhanced by adding 1% Ag nanoparticles which completely degrade the target MB dye within 150 min. The photodegradation rate was found to increase linearly with increasing the Ag contents from 0 to 1% and it is faster 2.2 times than undoped ZnO. From economic point of view, 1% Ag/ZnO photocatalyst contains optimum Ag content as there is no significant increase in the photocalatytic performance at higher Ag content. (C) 2014 Elsevier B.V. All rights reserved.