Time: 10:00-11:00am 1st Nov., 2012
Location: Conference Room 440, the 3rd Academic Building, Yuquan Campus, Zhejiang University
Single Particle Spectroelectrochemistry:
A Probe for the Photo-Physics of Charged Nanomaterials
Dr. Han Htoon
Technical Staff Member, Center for Integrated Nanotechnologies
Los Alamos National Laboratory, Los Alamos, NM 87545, USA
Abstract：
Presence of excess charges in quantum confined nanomaterials (NMs), such as semiconductor nanocrystals, nanowires, and carbon nanotubes induces dramatic changes in their electronic structure and radiative/nonradiative recombination of carriers. As a result, the key optical properties of NMs, such as photoluminescence spectrum and quantum yield are significantly altered. These effects of charging have been shown to be universal in previously studied NMs and are expected to affect in similar way in rapidly emerging, new NMs and complex nanostructures. In spite of importance and universality of charging effects, they are poorly understood at this moment. Here we demonstrate a novel approach capable of probing these effects directly.
Research Interests:
Han Htoon’s research interests have focused on development of novel spectroscopic techniques and studies on fundamental photo-physical properties at the scale of individual nanostructures. His current activities center on probing electronic structure, carrier dynamics, multi-exciton effects, charge and energy transfer processes, plasmon-exciton coupling and carrier multiplication processes in wide range of nanoscale electronic and photonic materials including colloidal nanocrystals, quantum dots, nanowires, carbon nanotubes and coupled metal-semiconductor hybrid nanostructures. He is also actively engaged in the integration of nanowires and nanocrystals into light emitting diodes as well as photo-voltaic devices.
Han Htoon
Staff Scientist (Principle Investigator)
Center for Integrated Nanotechnologies
Los Alamos National Laboratory, USA
Bibliography:
PhD in Physics, University of Texas at Austin, 2001
Director’s Postdoctoral Fellow, Los Alamos National Lab, Dec. 2001-Nov. 2005
Technical Staff Member, Los Alamos National Lab, Nov. 2005 – present
Publication:
1) "Two types of luminescence blinking revealed by spectroelectrochemistry of single quantum dots", Nature 479, 203 (2011).
2) "Near-Unity Quantum Yields of Biexciton Emission from CdSe/CdS Nanocrystals Measured Using Single-Particle Spectroscopy", PRL 106, 187401 (2011).
3) "Highly Emissive Multiexcitons in Steady-State Photoluminescence of Individual "Giant" CdSe/CdS Core/Shell Nanocrystals", Nano Lett. 10, 2401 (2010).
4) "Anomalous Circular Polarization of Photoluminescence Spectra of Individual CdSe Nanocrystals in an Applied Magnetic Field", PRL 102, 017402 (2009).
5) "Single carbon nanotubes probed by photoluminescence excitation spectroscopy: The role of phonon-assisted transition", PRL 94, 127403 (2005).
6) "Structure of excited-state transitions of individual semiconductor nanocrystals probed by photoluminescence excitation spectroscopy", PRL 93, 187402 (2004).
7) "Low temperature emission spectra of individual single-walled carbon nanotubes: Multiplicity of subspecies within single-species nanotube ensembles", PRL 93, 027401 (2004).
8) "Effect of zero- to one-dimensional transformation on multiparticle Auger recombination in semiconductor quantum rods", PRL 91, 227401 (2003).
9) "Interplay of Rabi oscillations and quantum interference in semiconductor quantum dots", PRL 88, 87401 (2002).