January 20, 2012
Prof. Amala Dass,
University of Mississippi
Gold Nanomolecules: Gold Nanoparticles of Molecular Definition
Abstract:
Nanoscience is a new area of science that has generated excitement worldwide. Nanomaterials are being developed to address some of the world's biggest challenges, including: clean, affordable energy; stronger, lighter, more durable materials; medical devices and drugs to detect and treat diseases; sensors to detect harmful chemical or biological agents; lighting that uses a fraction of the energy; low-cost filters to provide clean drinking water.
Nanomolecules, or molecular gold nanoparticles (<2nm) have a precise number of gold atoms and thiolate ligands; are superstable (air, moisture) and can be scaled up in large quantities. Recent results from our laboratory on the synthesis and characterization (mass spectrometry, optical, electrochemical) of Au25(SR)18, Au38(SR)24, Au68(SR)34, Au102(SR)44, Au144(SR)60 and Au~300(SR)~80; and their Ag alloy counterparts will be discussed.
References: JACS 2011 19259, JACS 2009 11666, JACS 2009 13604, JACS 2010 16783, JACS 2011 20258
Webpage: http://nanomolecules.yolasite.com/
January 27, 2012
Faculty Search Candidate: in room 2306 at 701 W. Grace Street; Begins at 2:00pm
Dr. Deepak K. Singh
Abstract:
The energetic interplay in magnetic crystal, resulting from the crystalline arrangement of the magnetic lattice in metallic environment, dictates the fundamental properties of a broad range of magnetic materials. Notable examples are the unconventional superconductors of magnetic origin, where the occurrence of superconductivity co-exists with a novel but dynamic phase of matter, quantum critical phase, at low temperature. The quantum critical phase is manifested by the dynamic nature of spin fluctuations at low temperature. Thorough understanding of the underlying mechanism of the quantum critical phase is not only necessary for a meaningful theoretical formulation of this phenomenon but to create even higher temperature superconductors. The quantum critical phenomenon is equally relevant in understanding the dynamic properties of many important materials, such as graphene.
In this pursuit, I have adopted dual approaches that consist of macroscopic investigations of candidate compounds in the bulk form of stoichiometric composition, and the nanofabrication methods to create artificial magnetic crystals. In this talk, I will show that the nano-engineered artificial magnetic crystal can be used as the prototype system to explore the broad range of magnetic phenomena without any limitations, including the energetic interplay leading to quantum critical phase of matter. In the first part of my talk, I will discuss the energetic interplay in magnetic crystal, followed by the details of macroscopic investigation of quantum critical phase in archetypal heavy electron superconductor CeCu2Ge2.1 In the second part, I will explain the artificial creation of magnetic crystal in nanostructured arrays.2 I will also briefly discuss the future application of the artificial magnetic crystal in developing magneto-electronic metamaterials.
1 D. K. Singh et al., Scientific Reports (Nature) 1, 117 (2011)
2 D. K. Singh and M. T. Tuominen, Phys. Rev. B 83, 014408 (2011)
January 27, 2012
Regular Colloquium in room 2310 at 701 W. Grace Street; Begins at 4:00pm
Prof. S. P. Tewari,
Advanced Centre of Research in High Energy Materials (ACRHEM ) and School of Physics
University of Hyderabad, Gachibowli, Hyderabad 500 046
Density Functional Study of Energetic Materials
Abstract:
In first part of my talk I would like to discuss about our recent ab-initio investigations on energetic hydrogen rich ammonia borane and its metal derivative Calcium amido borane. We focused mainly on the electronic structure and vibrational properties of these materials. The calculated structural parameters of NH3BH3 and Ca(NH2BH3)2 are found to be in good agreement with the experimental values. From the band structure calculations, the compounds are found to be insulators with band gaps of 6.0 eV and 3.27 eV for NH3BH3 and Ca(NH2BH3)2, respectively. From the total and partial density of states it is clear that the hybridized states of BH3 group are dominating at the Fermi level in NH3BH3 whereas in the case of Ca(NH2BH3)2, the states of NH2 group are dominating. The study of Mulliken bond population and the charge density distributions reveals that, the Ca-N bonds are ionic and the N-H & B-H bonds are covalent in nature. The calculated phonon density of states and vibrational frequencies of Ca(NH2BH3)2 and NH3BH3 reveals that in both the cases the heavier mass atoms Ca, N, B are involved in the low frequency vibrations whereas the higher frequency vibrations are solely from H atoms. It is also observed that the vibrational frequencies of B-H bonds are soft in Ca(NH2BH3)2 when compared to NH3BH3 and thereby concluded that Ca(NH2BH3)2 is a potential hydrogen storage material for fuel cell applications when compared to NH3BH3.
In the second part of my talk I will discuss about energetic metal azides under pressure. Inorganic metal azides are well known for their explosive properties such as detonation or deflagration. As chemically pure sources of nitrogen, alkali metal azides under high pressure have the ability to form polymeric nitrogen, an ultimate green high energy density material with energy density three times greater than those of energetic materials known today. In this present work we try to address the high-pressure behavior of LiN3 by means of density functional calculations. We found that LiN3 is structurally stable up to the studied pressure range of 60 GPa. At ambient conditions the material is insulator with a gap of 3.32eV (LiN3) and as pressure increases the band gap decreases and show semiconducting nature at high pressures. Moreover the calculated vibrational frequencies clearly show that as pressure increases the azide ion modes become hardened indicating the crystal stability of the azide. Our theoretical study proved that above 60 GPa LiN3 has the ability to form polymeric nitrogen because of the decrease in inter azide ion distance and possible overlapping of N atomic orbitals.
References:
[1] Bheema Lingam Ch, Ramesh Babu K, Tewari Surya P, Vaitheeswaran G., J. Comp Chem , 2012 Inpress.
[2] Bheema Lingam Ch, Ramesh Babu K, Tewari Surya P, Vaitheeswaran G. J Comp Chem 2011; 32; 1734-1742.
[3] Bheema Lingam Ch, Ramesh Babu K, Tewari Surya P, Vaitheeswaran G., S. Lebegue, J. Phys. Chem C, 2011,
115, 18795.
[4] Bheema Lingam Ch, Ramesh Babu K, Tewari Surya P, Vaitheeswaran G., Phys. Stat Solidi: Rapid Rese. Lett,
2011, 5, 10.
[5] Ramesh Babu K, Bheema Lingam Ch, Tewari Surya P, Vaitheeswaran G., J. Phys. Chem. A, 2011, 115, 4521.
February 3, 2012
No Colloquium
February 6, 2012 (Monday)
Faculty Search Candidate: in room 2306 at 701 W. Grace Street; Begins at 2:00pm
Dr. Edward Flagg
Quantum Optics and Quantum Dots
Abstract:
Quantum optics deals with photons and their interactions with matter on an individual level, rather than as classical fields. One common way to explore quantum optics is the investigation of quantum emitters: things that behave like a two-level quantum system and only emit or absorb one photon at a time; for example atoms, ions, and quantum dots. Quantum dots are potential traps that confine electrons and/or holes, and though they are made of hundreds of thousands of atoms, the confinement causes them to emit light at discrete wavelengths similarly to a single atom. Both the photons emitted by quantum dots and the charges trapped within them may be of great use in the field of quantum information science. I will describe some experiments on quantum dots involving resonance fluorescence, decoherence effects, cavity quantum electrodynamics, and investigation of the photons' indistinguishability.
February 10, 2012 (Friday)
Faculty Search Candidate: in room 2310 at 701 W. Grace Street; Begins at 4:00pm
Dr. Yevgeniy Kalinin
Self-assembly of microcontainers for three-dimensional control over cellular microenvironments
Abstract:
Self-assembly allows fabrication of devices which are challenging to produce using conventional, planar fabrication techniques. This talk will focus on how self-assembly can be used to create three-dimensional micro- and nanocontainers with nanoscale porosity. Several applications of these microcontainers in biophysics will be highlighted. For example, that these microcontainers can be used as three-dimensional chemical sources which can guide self-organization of motile cells in complex three-dimensional geometries such as bacteria organized in a helical curve. Alternatively living cells can be cultured inside these containers. In this case, the nanopores can be used to separate molecules that can diffuse in and out of the containers based on the molecules' size. This allows the containers to immunoisolate contents and makes them suitable candidates for bioartificial organ creation. Other applications of microcontainers, such as studies of bacterial behavior in complex geometries will also be mentioned. I will conclude the presentation by discussing future applications such as the use of self-assembly to create functional bio-mimetic micropumps and design of microscale chemical sources which can be mounted on individual cells.
February 17, 2012
Faculty Search Candidate: in room 2310 at 701 W. Grace Street; Begins at 4:00pm
Dr. Jason Reed
California NanoSystems Institute (CNSI) at UCLA
Los Angeles, California, USA
Instantaneous Mass Profiling of Live Cells via Live Cell Interferometry
Abstract:
Over the past several years, Dr. Reed's group has developed optical interference microscopy as a novel method for the study of the mechanics and dynamics of single live cells and groups of cells. Interference microscopy is extremely well suited to capture motion on the micro- and even nano-scale, with a temporal dynamic range and field of view that far exceeds scanning probe techniques. Dr. Reed will describe the development and application of live cell interferometry (LCI) for rapid, real-time quantification of single-cell mass changes in human embryonic stem cells and populations of cells exposed to changing external and internal environments. LCI is a conceptual advance in providing a mechanism to assess whole populations of cells, one cell at a time, for identifying, tracking/monitoring, and measuring cellular responses, such as to therapeutic drugs. He will also discuss the use of high speed atomic force microscopy to directly recognize individual biomolecules in complex mixtures, and a potential application of this technology in reducing the time, cost and technical complexity of small sample transcriptional profiling.
February 24, 2012
TBA
March 2, 2012
March APS Meeting
March 9, 2012
Michael Fine,
Department of Biology, VCU
TBA
March 16, 2012
Spring Break
March 23, 2012
T. A. Cropp, Department of Chemistry, VCU
TBA
March 30, 2012
Vamsi Yadavalli
Chemical Engineering, VCU
TBA
E. William Colglazier
State Department, Washington DC
TBA
April 13, 2012
TBA
April 20, 2012
Stuart Wolf
, Inst. for Nanoscale and Quantum
Scien. and Tech. Advan. Res., Univ. of Virginia
TBA
April 27, 2012
TBA
May 4, 2012
TBA
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