Department of Chemistry

Phone: (202) 994-6121 Fax: (202) 994-5873gwchem@gwu.eduE-mail:

Washington, DC 20052800 22nd street, NW | SEH 4000

Website: http://chemistry.columbian.gwu.edu

Indika Arachchige Department of Chemistry College of Humanities & Sciences Virginia Commonwealth University

Friday, September 30, 2016 SEH B1220 2:00 - 3:00 p.m. Refreshments will be served at 1:45 p.m.

“Synthesis and Structure-Property Elucidation of Group IV Semiconductor Nanocrystals and Metal Nanoparticle Superstructures”

Department of Chemistry Seminar

The effect of synthetic parameters on the primary particle size, morphology, composition, fundamental band structure, and optoelectronic properties will be discussed.

(b) Sol-gel Assembly of Metal Nanoparticles into Porous Superstructures The ability to assemble nanoparticles (NPs) into functional superstructures is an important challenge that needs to be addressed for the genera-tion of NP-based devices. Sol-gel method represents a facile yet powerful strategy for the assembly of metal oxides, chalcogenides, and metal-semiconductor hybrid NP systems into three-dimensionally connected porous nanostructures. In contrast to traditional oxides, where gels are produced by hydrolysis and condensation of molecular precursors, the gelation in non-oxide systems is achieved by condensation of preformed, colloidal NPs. Herein, the application of later strategy for the assembly of noble metal NPs into high surface area, uniquely porous, highly conducting nanostructures will be presented. The effect of synthetic parameters on the primary particle size, morphology, electrical conductivity, optical transparency and opacity, surface area and porosity will be discussed in the light of application in chemical sensing and

This presentation will include two projects, which we have been working over the past few years on the design and synthesis of nanocrystalline Group IV alloy semiconductors and the use of sol-gel chemistry for the assembly of metal nanoparticles into porous nanostructures.

(a) Nanocrystalline Group IV Alloy Semiconductors Group IV semiconductors have gained noteworthy interest in optoelectronic applications due to high natural abundance, low cost of elemental components, and lack of toxicity. A number of synthetic methods for colloi-dal Si and Ge nanocrystals (NCs) have been reported and new methods continue to appear. However, these methods generally lack the wider tunability of NC sizes and absorption/emission energies resulting in minimal exploration of photophysical properties. To address this issue, we have recently studied the incorpo-ration of elemental Sn into colloidal Ge NCs, to produce GexSn1-x alloy NCs that exhibit composition dependent absorption/emission properties and direct band structure. This talk will present the physical characterization of GexSn1-x alloys using steady-state and ultrafast absorption and emission spectroscopy.

BIODr. Arachchige obtained his B.S. in Chemistry from University of Kelaniya, Sri Lanka. He obtained his Ph.D. in Inorganic Chemistry from Wayne State University in 2007. After graduation, he joined the Department of Chemistry at Northwestern University as a Postdoctoral Fellow (2007-2009) and the Center for Integrated Nanotechnologies at Los Alamos National Laboratory as a Research Associate (2009-2011). He joined Virginia Commonwealth University faculty in August 2011. The focus of his laboratory is the synthetic inorganic chemistry, nanotechnology, and materials science. The research is highly interdisciplinary, with the aim to develop a fundamental understanding of how structure, particle size, shape, atomic composition and material physical properties are related in order to advance technologies such as information storage, sensors, energy conversion, and catalysis. He is specifically interested in developing synthetic methods to form novel nanoparticle systems with new or improved physical properties than those we presently know how to make and on developing methods for linking nanoparticles together to into solid state architectures for advanced technological applications.