Highly enhanced photocatalytic activity of Au nanorod-CdS nanorod heterocomposites

This paper signifies the importance of different shapes of Au and CdS-nanoparticles for fabricating Au-CdS heterocomposites {prepared by mixing or impregnation of Au-nanosphere (9.1 nm), Au-nanorod (20 nm x 8.6 nm; L x W), CdS-nanosphere (10-12 nm) and CdS-nanorod (126 nm x 5.5 nm)} onto the photoluminescence and photocatalytic study. Second derivative absorption spectra's exhibit precise onset at 441 nm (CdS-nanosphere) and 469.5 nm (CdS-nanorod) that are significantly red-shifted to 509 nm (Au-nanosphere-CdS-nanosphere), 485 nm (Au-nanosphere-CdS-nanorod), 520 nm (Au-nanorod-CdS-nanosphere) and 485.5 nm (Au-nanorod-CdS-nanorod) depending upon interfacial contact-area. XRD patterns reveal the hexagonal phase of pure and Au-CdS nanocomposites. Photoluminescence of CdS nanorods has been effectively inhibited by modifying its surface with Au-nanoparticles (0.002-0.04 wt%). Relaxation lifetime of photoexcited charge-carriers found to be improved ca. 12.5 mu s for Au-nanosphere-CdS-nanorod and 34 mu s for Au-nanorod-CdS-nanorod due to effective charge transfer kinetics at the interface, in contrast to prompt charge-recombination (2.7 mu s) in CdS. Under UV light (10.4 mW/cm(2)) irradiation, Au-nanorod-CdS-nanorod exhibits the best photocatalytic activity for the oxidation of salicylic acid (86%, k = 9 x 10(-3) min(-1)) and reduction of p-nitrophenol to p-aminophenol (53%) as a function of improved stability and better current-voltage (I-V) characteristics suitable for rapid charge transfer process during photoreaction. (c) 2013 Elsevier B.V. All rights reserved.