The Interaction of Water with Solid Surfaces: Fundamental Aspects Revisited

Optically excited plasmonic nanoparticles can activate chemical reactions on their surfaces. The underlying physical mechanisms responsible for the chemical activity and advances in photocatalysis on plasmonic metallic nanostructures are discussed. The strong interaction of electromagnetic fields with plasmonic nanomaterials offers opportunities in various technologies that take advantage of photophysical processes amplified by this light–matter interaction. Recently, it has been shown that in addition to photophysical processes, optically excited plasmonic nanoparticles can also activate chemical transformations directly on their surfaces. This potentially offers a number of opportunities in the field of selective chemical synthesis. In this Review we summarize recent progress in the field of photochemical catalysis on plasmonic metallic nanostructures. We discuss the underlying physical mechanisms responsible for the observed chemical activity, and the issues that must be better understood to see progress in the field of plasmon-mediated photocatalysis.

http://www-nature-com-443.webvpn.bjmu.tsg211.com/articles/nmat4281.pdf

Photochemical transformations on plasmonic metal nanoparticles

Recent reports have shown that plasmonic nanostructures can be used to drive direct photocatalysis with visible photons, where nanostructures act as the light absorber and the catalytic active site. These reports have showcased direct plasmon driven photocatalysis as a route to concentrate and channel the energy of low intensity visible light into adsorbed molecules, enhancing the rates of chemical transformations, and offering pathways to control reaction selectivity. In this perspective, we will discuss the fundamental photophysics of localized surface plasmon resonance (LSPR) excitation in the context of driving chemical transformations. The various demonstrated chemical conversions executed using direct plasmonic photocatalysis will be reviewed. Experimental observations, such as the dependence of photocatalytic rate on illumination intensity and photon energy, will be related to microscopic mechanisms of photocatalysis. In addition, theoretical treatments of various mechanisms within the process of d...

Direct Photocatalysis by Plasmonic Nanostructures

The photochemistry of small molecules on well-defined metal surfaces has been the subject of intense research for more than three decades.1 This field is of interest because it rests on the superposition of two influences. On one hand, new reaction channels can become possible by electronic excitation, which are usually not accessible by thermal activation. On the other hand, compared to molecular photochemistry in the gas phase, interactions of molecules with solid substrates open unique pathways of photoexcitation and photoreaction not accessible in homogeneous reactions. This is primarily due to the fact that the bonding interactions with the substrate modify not only the ground state but also the electronically excited states of the adsorbates. In addition, the very rapid exchange of excitation energy between adsorbates and substrate, in particular on metal and semiconductor surfaces, can lead to fast quenching of excited adsorbate states by transfer of charge and/or energy from the adsorbates to the substrate. Furthermore, excitation of adsorbates by hot (excited) electrons produced by photoabsorption in the substrate plays an important role as it induces charge and energy transfer in the opposite direction, from the substrate to adsorbates. Well-defined metal surfaces covered by adsorbate layers under ultrahigh vacuum (UHV) conditions provide systems which are well characterized in all aspects, particularly regarding geometry and electronic structure. The fact that such layers usually consist of molecules which are naturally aligned on the surface2 makes surface photochemistry a powerful alternative to the stereodynamic control of chemical reactions by optically aligned molecular beams.3 Well-defined adsorbate systems thus provide unique playgrounds for surface photochemistry.

http://w0.rz-berlin.mpg.de/hjfdb/pdf/449e.pdf

Photochemistry on Metal Nanoparticles

Nanometal materials play very important roles in solar-to-chemical energy conversion due to their unique catalytic and optical characteristics They have found wide applications from semiconductor photocatalysis to rapidly growing surface plasmon-mediated heterogeneous catalysis The recent research achievements of nanometals are reviewed here, with regard to applications in semiconductor photocatalysis, plasmonic photocatalysis, and plasmonic photo-thermocatalysis As the first important topic discussed here, the latest progress in the design of nanometal cocatalysts and their applications in semiconductor photocatalysis are introduced Then, plasmonic photocatalysis and plasmonic photo-thermocatalysis are discussed A better understanding of electron-driven and temperature-driven catalytic behaviors over plasmonic nanometals is helpful to bridge the present gap between the communities of photocatalysis and conventional catalysis controlled by temperature The objective here is to provide instructive information on how to take the advantages of the unique functions of nanometals in different types of catalytic processes to improve the efficiency of solar-energy utilization for more practical artificial photosynthesis

Nanometals for Solar-to-Chemical Energy Conversion: From Semiconductor-Based Photocatalysis to Plasmon-Mediated Photocatalysis and Photo-Thermocatalysis.

X.-L. Zhou

Papers

Photochemistry at adsorbate/metal interfaces