Date: Wednesday 30th of November 2016, 16:30.
Location: MC0025 (Media, Humanities & Technology Building).

‘Excited State Dynamics in Colloidal Quantum dots’

by Dr. Kevin Critchley,
School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK.

Abstract:

Semiconductor nanoparticles have unique properties, which have been intensely studied for many promising technological applications over the last few decades.  For example unique properties of semiconductor nanoparticles are ideally suited for back lighting displays and for fluorescence imaging.  Advanced fluorescence imaging will provide a high-resolution means of detecting diseased cells; tracking nano-encapsulated drugs; and studying intracellular mechanisms.  These semiconductor nanoparticles are commonly known as quantum dots – derived from the fact that decreasing the size of the nanoparticles introduces quantum confinement of the charge carriers leading to an increased band-gap.  By tuning the size of the semiconductor one can therefore tune the emission wavelength.   To date, the most studied semiconductor nanoparticles are cadmium-based (CdTe, CdSe, and CdS). These cadmium based quantum dots have excellent optical properties, stability, and monodisperisty.  However, increasing global restrictions and lack of biocompatibility of cadmium has lead to questions about the future of quantum dots for many applications.  It is therefore essential that we investigate alternative quantum dot materials.   We have focused our attention on the development of copper indium sulphide quantum dots, which have an ideal bulk band gap, lower toxicity, small size and ability to control surface functionality.  The properties of these recently developed quantum dots are discussed and I will be presenting recent results from atomic resolution electron energy loss spectroscopic mapping.  In the final part of my presentation I will discuss some of our most recent work, where we place an electron acceptor on the surface of the quantum dot.