Hot Electrons, Hot Holes, or Both? Tandem Synthesis of Imines Driven by the Plasmonic Excitation in Au/CeO(2)Nanorods

Solar-to-chemical conversion via photocatalysis is of paramount importance for a sustainable future. Thus, investigating the synergistic effects promoted by light in photocatalytic reactions is crucial. The tandem oxidative coupling of alcohols and amines is an attractive route to synthesize imines. Here, we unravel the performance and underlying reaction pathway in the visible-light-driven tandem oxidative coupling of benzyl alcohol and aniline employing Au/CeO(2)nanorods as catalysts. We propose an alternative reaction pathway for this transformation that leads to improved efficiencies relative to individual CeO(2)nanorods, in which the localized surface plasmon resonance (LSPR) excitation in Au nanoparticles (NPs) plays an important role. Our data suggests a synergism between the hot electrons and holes generated from the LSPR excitation in Au NPs. While the oxygen vacancies in CeO(2)nanorods trap the hot electrons and facilitate their transfer to adsorbed O(2)at surface vacancy sites, the hot holes in the Au NPs facilitate the alpha-H abstraction from the adsorbed benzyl alcohol, evolving into benzaldehyde, which then couples with aniline in the next step to yield the corresponding imine. Finally, cerium-coordinated superoxide species abstract hydrogen from the Au surface, regenerating the catalyst surface.Peer reviewe

Hot Electrons, Hot Holes, or Both? Tandem Synthesis of Imines Driven by the Plasmonic Excitation in Au/CeO2 Nanorods

Solar-to-chemical conversion via photocatalysis is of paramount importance for a sustainable future. Thus, investigating the synergistic effects promoted by light in photocatalytic reactions is crucial. The tandem oxidative coupling of alcohols and amines is an attractive route to synthesize imines. Here, we unravel the performance and underlying reaction pathway in the visible-light-driven tandem oxidative coupling of benzyl alcohol and aniline employing Au/CeO2 nanorods as catalysts. We propose an alternative reaction pathway for this transformation that leads to improved efficiencies relative to individual CeO2 nanorods, in which the localized surface plasmon resonance (LSPR) excitation in Au nanoparticles (NPs) plays an important role. Our data suggests a synergism between the hot electrons and holes generated from the LSPR excitation in Au NPs. While the oxygen vacancies in CeO2 nanorods trap the hot electrons and facilitate their transfer to adsorbed O2 at surface vacancy sites, the hot holes in the Au NPs facilitate the α-H abstraction from the adsorbed benzyl alcohol, evolving into benzaldehyde, which then couples with aniline in the next step to yield the corresponding imine. Finally, cerium-coordinated superoxide species abstract hydrogen from the Au surface, regenerating the catalyst surface

Controlled synthesis of noble metal nanomaterials: motivation, principles, and opportunities in nanocatalysis

ABSTRACT This review describes some principles of the controlled synthesis of metal nanoparticles, focusing on how the fundamental understanding of their synthesis in the solution-phase can be put to tailor size, shape, composition, and architecture. The maneuvering over these parameters not only enable the tuning of properties, but also the maximization and optimization of performances for various applications. Herein, we start with a brief description of metallic nanoparticles, highlighting the motivation for achieving physicochemical control in their synthesis. After that, we turn our attention to some important definitions and classifications as well as their unique properties such as surface and quantum effects. Moreover, we discuss the strategies for the controlled synthesis of metal nanomaterials based on the top-down and bottom-up approaches, focusing our discussion on their formation mechanisms in liquid-phase in terms of both thermodynamic and kinetic control. Finally, we point out the promising applications of controlled nanomaterials in the field of nanocatalysis and plasmon-enhanced catalysis, describing some of the current challenges in these fields

Uso de hidroxiapatita nanométrica em enxertos na fíbula de ratos

A apatita é um mineral que pertence ao grupo dos fosfatos e que possui diversas aplicações na linha de desenvolvimento de novos materiais. Dentre as variantes de apatitas, encontramos as hidroxiapatitas (HAP), que constituem uma porção considerável do nosso tecido ósseo. Atualmente, em práticas de enxertia, são utilizados diferentes tipos de cerâmicas para que se possa regenerar um defeito ósseo. No entanto, a utilização da hidroxiapatita nanométrica em enxertos tem sido uma alternativa interessante e plenamente satisfatória, pois este material apresenta propriedades similares às do tecido ósseo. Desta forma, este trabalho tem como objetivo estudar como a composição e a cristalinidade da hidroxiapatita podem afetar o enxerto ósseo. Para isto foram estudados três tipos de amostras, HAP comercial cristalina, HAP nanométrica e HAP carbonatada nanométrica (HAC). As amostras foram testadas em enxertos ósseos utilizando ratos machos jovens. A análise microestrutural foi realizada utilizando a técnica de difração de raios X por pó e o refinamento foi feito pelo método de Le Bail

Marrying SPR excitation and metal–support interactions: unravelling the contribution of active surface species in plasmonic catalysis

Plasmonic catalysis takes advantage of the surface plasmon resonance (SPR) excitation to drive or accelerate chemical transformations. In addition to the plasmonic component, the control over metal-support interactions in these catalysts is expected to strongly influence the performances. For example, CeO2 has been widely employed towards oxidation reactions due to its oxygen mobility and storage properties, which allow for the formation of Ce3+ sites and adsorbed oxygen species from metal-support interactions. It is anticipated that these species may be activated by the SPR excitation and contribute to the catalytic activity of the material. Thus, a clear understanding of the role played by the SPR-mediated activation of surface oxide species at the metal-support interface is needed in order to take advantage of this phenomenon. Herein, we describe and quantify the contribution from active surface oxide species at the metal-support interface (relative to O2 from air) to the activities in green SPR-mediated oxidation reactions. We employed CeO2 decorated with Au NPs (Au/CeO2) as a model plasmonic catalyst and the oxidation of p-aminothiophenol (PATP) and aniline as proof-of-concept transformations. We compared the results with SiO2 decorated with Au NPs (Au/SiO2), in which the formation of surface oxide species at the metal-support interface is not expected. We found that the SPR-mediated activation of surface oxide species at the metal-support interface in Au/CeO2 played a pivotal role in the detected activities, being even higher than the contribution coming from the activation of O2 from air