(369e) Gold Nanorod@TiO2 Yolk-Shell Nanostructures for Visible-Light-Driven Photocatalytic Oxidation of Benzyl Alcohol

Selective oxidation of alcohols to corresponding carbonyl compounds such as aldehydes and ketones is an essential process for the synthesis of various chemicals as intermediates for pharmaceutical and fragrance industries.^[1] Recently, photocatalytic oxidation has been widely explored to meet the request of green chemistry. Among different semicondutor photocatalysts, titanium dioxide (TiO₂) is a benchmark catalyst for its effectiveness, nontoxicity, low cost, and chemical stability.^[2] However, because of the large band gap, TiO₂ shows high activity only in the UV region, which accounts for less than 5% of the total energy of the solar spectrum.^[3] Thus, efforts have been devoted to synthesize TiO₂-based photocatalysts responsive to visible light, during which the Sensitizing by plasmonic metals has been proved to be a promising method. ^[4]

In this work, three kinds of gold nanorod@TiO₂ yolk-shell (GNR@TiO₂-YSs) catalysts with different aspect ratios (2.4, 4.2 and 5.4) are synthesized by an improved silica template method, which are denoted as GNR@TiO₂-2.4-YSs, GNR@TiO₂-4.2-YSs and GNR@TiO₂-5.4-YSs, respectively. For comparison purpose, gold nanoparticles@TiO₂ yolk-shell (GNP@TiO₂-YS) catalysts and pure TiO₂hollow spheres (HSs) were also synthesized by the similar method.

With a hollow TiO₂ shell and a unique tunable cylindrical gold core, the GNR@TiO₂-YS exhibits a high surface area and a wide absorption range from ultraviolet to near infrared region. The remarkable photochemical activity is obtained when such catalyst applied to the oxidation of benzyl alcohol. A mechanism is put forward and verified to describe the reaction process, which elucidates the advantages of such a structure when the catalysts are utilized to selectively photocatalytic oxidation.

References

1. A. Tanaka, K. Hashimoto and H. Kominami (2012), “Preparation of Au/CeO₂exhibiting strong surface plasmon resonance effective for selective or chemoselective oxidation of alcohols to aldehydes or ketones in aqueous suspensions under irradiation by green light” , Chem. Soc. Rev., J. Am. Chem. Soc. 2012, 134, 14526.

2. G. Xiang, D. Wu and J. He, X. Wang (2011), “Acquired pH-responsive and reversible enrichment of organic dyes by peroxide modified ultrathin TiO₂nanosheets”, Chem. Commun. 2011, 47, 11456.

3. J. Lee, S. Mubeen, X. Ji, G. D. Stucky and M. Moskovits (2012), “Plasmonic photoanodes for solar water splitting with visible light”, Nano Lett. 2012, 12, 5014.

4. S. T. Kochuveedu, Y. H. Jang and D. H. Kim (2013), “A study on the mechanism for the interaction of light with noble metal-metal oxide semiconductor nanostructures for various photophysical applications”, Chem. Soc. Rev. 2013, 42, 8467.