Rational design of bifunctional nanoparticles
SERS monitoring of nanoparticle-catalyzed reactions requires bifunctional substrates with both SERS and catalytic activities. Unfortunately, conventional catalysts are not SERS-active. For example, small Au nanoparticles that are catalytically active are not SERS active due to the very small scattering cross-sections. In our group, we design and synthesize nanoparticle hybrids and assemblies (superstructures) using plasmonic metals together with catalytically active materials. The chemical reactions on the catalyst surface can be monitored under real reaction conditions by SERS.
Label-free monitoring of catalysis
Via in situ SERS, the different components at the catalytic interface can be detected simultaneously. We investigate not only the molecular structural changes during the reaction but also the reaction kinetics under different reaction conditions. To ensure that the reaction occurs under the required conditions, i.e. temperature, pressure, pH, and solvents, the in situ sample cells/reactors have to be designed according to the reactions. We aim at establishing a non-destructive in situ characterization platform for mechanistic study of nanoparticle-catalyzed reactions.
Hybrid plasmonic nanostructures are synthesized for plasmon-induced chemical transformations. When plasmons are excited on the metal surface, there are two fundamentally different decay channels: the radiative channel, in which the metal nanoparticle acts as a nanoantenna (scattering), and the non-radiative channel (absorption). The absorption of photons may lead to the generation of heat by electron–phonon coupling or to the generation of charge carriers by the excitation of electron–hole pairs. In the latter case, the generated high-energy electrons can be transferred from the surface of the metal to an adjacent electron acceptor, e.g. a semiconductor or a molecule.