We are using visible light illumination to excite non-thermal electron distributions in noble metal nanoparticles to achieve reaction selectivity that is not possible using purely thermal reaction chemistry in both materials synthesis and catalytic transformations.
Metal nanoparticles, particularly those of silver and gold, have unique optical properties that arise from a phenomenon known as localized surface plasmon resonance, which is the collective oscillation of conduction band electrons in a metal nanoparticle upon excitation with incident light. The excited “hot” electrons and resulting “hot” holes can be used as reducing and oxidizing equivalents, respectively, in chemical transformations. Direct transfer of plasmonically excited electrons to adsorbed molecules can also drive desorption or bond dissociation, thereby enabling selectivity that is unachievable using heat energy. We are harnessing this non-thermal plasmon-driven chemistry to selectively accelerate kinetically slow metal ion reduction processes and overcome key challenges in the synthesis of bimetallic nanoparticles. Our group recently reported the first use of plasmon excitation to drive the reduction of ions of a poorly plasmonic metal by a weak reducing agent, yielding a core-satellite nanoparticle architecture that was not accessible via existing methods. In addition to challenges in nanoparticle synthesis, the mechanisms of plasmon-driven catalysis on metal nanoparticles, particularly those with well-defined shapes, are just beginning to be understood. We are working to elucidate the mechanistic complexities of plasmon-mediated chemical reactions at bimetallic interfaces, including core-shell, core-satellite, and dilute bimetallic surface architectures.