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Poster Competition Winners / Abstracts - Physical Sciences

Physical Sciences 1 - 1st Place
Biocompatible Luminescent Silicon Quantum Dots for Imaging of Cancer Cells
By Ngozi Agbasionwe, University at Buffalo

Luminescent silicon quantum dots (Si QDs) have great potential for use in biological imaging and diagnostic applications. To exploit this potential, they must remain luminescent and stably dispersed in water and biological fluids over a wide range of pH and salt concentration. There have been many challenges in creating such stable water-dispersible Si QDs, including instability of photoluminescence due their fast oxidation in aqueous environments and the difficulty of attaching hydrophilic molecules to Si QD surfaces. We report the preparation of highly stable aqueous suspensions of Si QDs using phospholipids micelles, in which the optical properties of Si nanocrystals are retained. These luminescent micelle-encapsulated Si QDs were used as luminescent labels for pancreatic cancer cells. This paves the way for silicon quantum dots to be a valuable optical probe in biomedical diagnostics.

Physical Sciences 1 - 2nd Place
Analysis of Some Near-Infrared Spectra of C2Br
By Elizabeth J. Millings, Suffolk County Community College

In combustion chemistry, the C2H molecule has been studied extensively because it is an important intermediate and provides an example of the breakdown of the Born-Oppenheimer approximation. A related molecule, C2Br, supplies a different view of the Born-Oppenheimer breakdown. Previously, only computational studies have been reported regarding C2Br. Its energy states and spectra were theoretically determined, and a model equation was developed to describe its rotational energy levels. Recently, a spectrum of C2Br was accidentally detected at Brookhaven National Laboratory. In this project, the spectroscopic data were further examined in an attempt to confirm the assignments, determine the rotational constants, identify spectral lines corresponding to the two bromine isotopes, and identify the band origins. To accomplish this, a LabVIEW computer program was developed and used to calculate the energy levels and predict spectra, which were then compared to the experimental near-infrared (NIR) spectra. The error between the data and the calculations was minimized by adjusting the modeling constants and testing possible assignments. A simulated spectrum was created with each new calculation enabling a set of “best fit” values to be determined.

Physical Sciences 2 - 1st Place
Synthesis and Characterization of Copolymer-templated Periodic Mesoporous Methylenesilicas and Phenylenesilicas
By Abhishek Roka, College of Staten Island

Surfactant-templated periodic mesoporous organosilicas (PMOs) have received much attention as well-defined periodic inorganic-organic hybrids, catalyst supports, hosts for nanoobjects and media for immobilization of biomolecules. In some applications of PMOs, it would be beneficial to enlarge the pore diameter beyond 10 nm, which is a typical limiting pore size value. Recently, it was demonstrated that this goal can be achieved by performing the block-copolymer-templated synthesis of PMO with spherical pores at low temperature (5-15 °C) in the presence of aromatic hydrocarbon (trimethylbenzene) as a micelle expander, following the method reported earlier for large-pore ordered mesoporous silicas. The current project is intended to further explore the opportunities in the synthesis of large-pore PMOs with methylene and phenylene bridging groups and with large cylindrical pores using micelle swelling agents. The work in progress includes:

- Attempt of synthesis of large-pore methylene and phenylene PMOs in the presence of different hydrocarbons and under adjusted conditions, and characterization of the products.
- Optimization of block copolymer ratios, and temperature variations in order to further increase pore diameter to a maximum.

Physical Sciences 2- 2nd Place
An Electron Paramagnetic Resonance (EPR) Study of Metal-Site Dynamics in Amino Acids: Copper Hopping in Cd-Histidine Crystals
By Brenda Marmol, SUNY College at Old Westbury

To understand copper dynamic behavior in a simple biological system, EPR spectroscopy was applied to crystalline samples of a model histidine complex. Dynamics were detected by measuring the EPR spectra as a function of temperature. At low temperature (<160K) the spectra displays two copper patterns, related by a crystallographic two-fold axis. At high temperatures (>230K), the EPR spectrum shows a single copper species. EPR hyperfine component line-widths were fit at the various temperatures in order to determine dynamic characteristics. These results are interpreted using a model where copper atoms hop between two binding sites at low temperature (Tc ~190K). Below Tc, the copper is frozen in one of the two, symmetry-related sites. As Tc is exceeded, the two patterns collapse into an “averaged” spectrum. We propose that the copper is bound to only one of the symmetry related histidine molecules at temperatures lower than Tc, and at higher temperatures, the copper ion hops across the two-fold rotation axis.



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