Plasmon-assisted nanophase engineering of titanium dioxide for improved performances in single-particle based sensing and photocatalysis

Plasmonic Au Nanoparticle of a Au/TiO2-C3N4 Heterojunction Boosts up Photooxidation of Benzyl Alcohol Using LED Light

Plasmonic Au nanoparticles (NPs) employing localized surface plasmon resonance excitation have exhibited superior visible light absorption for many organic transformations. In this work, we prepared a ternary composite catalyst comprising plasmonic Au NPs and a 2D/2D TiO₂-C₃N₄ heterojunction via a photoreduction method of chloroauric acid in the presence of TiO₂-C₃N₄. The introduction of plasmonic nanogold particles embedded onto the TiO₂ surface of the TiO₂-C₃N₄ heterojunction can significantly improve the photocatalytic performance during photooxidation of benzyl alcohol to benzaldehyde under mild conditions (1 bar air, white LED irradiation at ambient temperature). The productivity over Au/TiO₂-C₃N₄ (0.25 mmol_reacted BA g_cat.^-1 h^-1) is found to be ∼5.6, 8.3, and 8.2-fold of these over the Au/TiO₂, TiO₂-C₃N₄, and C₃N₄-Au-TiO₂ heterojunctions, respectively. Trapping experiments and electron spin resonance (ESR) spectroscopy confirm that the superoxide (^·O₂^-) and hydroxyl radicals (^·OH) act as the reactive oxygen species during photooxidation. Furthermore, the experimental results combined with density functional theory calculations reveal that the chemisorbed benzyl alcohol population, surface oxygen vacancies, and lifetime of photoexcited electrons and holes are largely improved by plasmonic Au NPs. This study on nanogold composites provides some hints for developing new efficient and practical photocatalysts.

Material design, development, and trend for surface-enhanced Raman scattering substrates

Surface-enhanced Raman scattering (SERS) is a powerful and non-invasive spectroscopic technique that can provide rich and specific chemical fingerprint information for various target molecules through effective SERS substrates. In view of the strong dependence of the SERS signals on the properties of the SERS substrates, design, exploration, and construction of novel SERS-active nanomaterials with low cost and excellent performance as the SERS substrates have always been the foundation and the top priority for the development and application of the SERS technology. This review specifically focuses on the extensive progress made in the SERS-active nanomaterials and their enhancement mechanism since the first discovery of SERS on the nanostructured plasmonic metal substrates. The design principles, unique functions, and influencing factors on the SERS signals of different types of SERS-active nanomaterials are highlighted, and insight into their future challenge and development trends is also suggested. It is highly expected that this review could benefit a complete understanding of the research status of the SERS-active nanomaterials and arouse the research enthusiasm for them, leading to further development and wider application of the SERS technology.