Photocatalytic systems working under visible and infrared light are of vital importance for efficient utilization of sunlight. Apart from doping of light elements and metal ions to semiconductor particles, combination of metal nanoparticles with semiconductor ones is one of promising systems for this purpose. Gold nanorods are advantageous since they show a broad and large absorption band from visible (l ≥ 520 nm) to near-infrared (l ~1000 nm) regime. Meanwhile, silver nanoparticles exhibit stronger absorption band in contrast to gold ones, although the band is located at shorter wavelengths (l ~400 nm).
Herein gold nanorods of different aspect ratios were employed as core and coated with either directly with titania shell or with an intermediate silver layer and outermost titania shell. The titania layer was formed by utilizing specific interaction between the titanium alkoxide and quaternary ammonium head groups of cationic surfactant (CTAB) bilayers on the gold or gold / silver nanorod surfaces.
The titania-coated gold nanorods showed a significant photocatalytic activity for oxidation of 2-propanol under visible light (l ≥ 420 nm). Intriguingly, they exhibited the photocatalytic activity also under NIR light (l ≥ 720 nm). Meanwhile, a thin silver interlayer was found to enhance the photocatalytic activity. The thickness of titania shell also influence the photocatalytic activity; about 10 nm of the shell thickness was found to be optimal.
Reference
1. Y. Horiguchi, T. Kanda, K. Torigoe, H. Sakai and M. Abe, Langmuir, 2014, 30, 922-928.
ktorigoe@rs.noda.tus.ac.jp
