Applied Chemistry

Biography

Biography: Matthew Sheldon

Abstract

The recent discovery of plasmonic enhancement of non-thermalized, ‘hot’ carrier phenomena in metal nanostructures has prompted significant interest in the fundamental properties and applications of these short-lived, ballistic charge carriers. We describe a new class of metal-semiconductor nanocrystal heterostructures with several ideal compositional and optical properties for probing hot carrier generation and transport. Using colloidal organometallic synthesis techniques in combination with full-wave optical modeling (FDTD method), we have designed and fabricated optimal nanocrystal samples for characterization with photoluminescence excitation (PLE) spectroscopy and dark field microcopy. By systematically mapping the potential landscape that defines the charge transfer dynamics, these optical studies provide fundamental insights into non-equilibrium charge phenomena across nanoscale electronic interfaces, crucial for identifying strategies that best optimize photocatalysis and photoelectrochemical reactions. In particular, these nanocrystals heterostructures exhibit a new mechanism of up-conversion luminescence (UCL), whereby the photo-induced transfer of hot electrical carriers from the metal region over the interfacial Schottky barrier can produce band-edge luminescence in the semiconductor, with energy greater than the incident light. This novel mechanism, which we term ‘hot carrier UCL’, could have potentially significant advantages in applications that benefit from UCL, such as biological imaging, optical energy conversion, and optoelectronic signal processing and data storage. This behavior can also inform fundamental thermodynamic issues related to energy conversion.