CURRENT FELLOWS
January 1, 2006-December 31, 2007
Kimberly Heck
Chemical Engineering
Faculty Advisor: Dr. Michael Wong
Faculty Co-Advisor: Dr. Naomi Halas
Area of Study:
Trichloroethylene (TCE) is one of the most ubiquitous pollutants of groundwater; exposure to TCE has been linked to liver damage, birth defects, and cancer in humans. Some remediation methods of TCE contamination, such as zero-valent iron and bioremediation treatments, are slow to convert the TCE and often leave byproducts (such as vinyl chloride) more harmful than TCE. Recently, it was discovered that a palladium-gold nanoparticle catalyst could not only completely convert TCE to innocuous ethane, but offer a 200 fold improvement versus the commercially available palladium on alumina catalyst. The enhancement of rate is as yet unclear; while a reaction mechanism has been proposed, it has yet to be proven.
Surface Enhanced Raman Spectroscopy (SERS), first discovered in the 1980’s, is a powerful and unique spectroscopic method to probe the structure of molecules adsorbed to metal nanoparticle surfaces. While TCE has a moderate Raman cross-section, imaging over gold nanoparticles shows little enhancement. Recently, gold nanoshells have been found to offer a substantial SERS enhancement over gold nanoparticles. It is hoped that the reaction mechanism may be delineated by identifying the modes of binding and reaction of TCE and the reaction intermediates over a Pd-Au nanoshell catalyst using SERS. Such understanding of the catalytic active site could possibly allow one to tailor a catalytic material to improve selectivity or rate of reaction.
This work is supported by NSF IGERT Grant DGE-0504425
Britt Lassiter
Physics and Astronomy
Faculty Advisor: Dr. Naomi Halas
Faculty Co-Advisor: Dr. Jason Hafner
Area of Study:
My research involves the study of plasmonic properties of single metallic nanoparticles by using dark-field spectroscopy. This method uses a dark-field microscope coupled with a spectrometer/detector to observe the spectrum of the light that is scattered by a nanoparticle.
The method allows for the study of individual particles, which eliminates problems that are associated with the more common practice of measuring ensembles of particles. For example, an ensemble of nanoparticles will contain a distribution of particles with slightly different shapes and sizes, leading to the observance of broad, indistinct spectral features. Single particle spectroscopy allows one to observe the sharp spectral features of an individual particle with a definite shape and size. This capability leads to more precise studies of how a particle’s shape, size, and symmetry affect its plasmon resonances. Examples of the particles I am studying include metallic nanoshells with both concentric and non-concentric dielectric cores, heterodimers (two nanoshells of different size in close proximity of each other), and homodimers (two nanoshells of the same size in close proximity of each other).
This work is supported by NSF IGERT Grant DGE-0504425
Kathryn Mayer
Physics and Astronomy
Faculty Advisor: Dr. Jason Hafner
Faculty Co-Advisor: Dr. James McNew
Area of Study:
In biology, there is a need for membrane-based techniques to study lipid-soluble proteins such as SNAREs, as these proteins are not well suited to traditional assay methods. I will be developing a new application of localized surface plasmon resonance (LSPR) sensing for membrane-based systems. I plan to create special substrates decorated with gold nanorods, upon which model biomembranes will be deposited. Then, I will be able to monitor the extinction spectra from the nanorods to detect shifts in LSPR wavelength upon protein binding events. I plan to study the SNARE protein system, which is implicated in membrane fusion. The goal is twofold: to extend the applications of the optical properties of metal nanoparticles, and to learn new, biologically relevant information about membranes.
This work is supported by NSF IGERT Grant DGE-0504425
Arthur Nieuwoudt
Electrical and Computer Engineering
Faculty Advisor: Dr. Massoud
Faculty Co-Advisor: Dr. Peter Nordlander
Area of Study:
For future high performance computing systems, design, modeling, and fabrication of integrated circuits will ultimately require a revolutionary paradigm shift that embraces Nanotechnology. By exploiting advances in Nanophotonics, fundamental limitations in sub-wavelength lithography, device scaling and interconnect delay, noise and power issues can be successfully overcome. In order to leverage the full potential of nanophotonic structures in future applications, accurate and efficient modeling and automated design techniques must be developed. Understanding the physical properties of nanostructures before fabrication is a crucial step in their utilization in real-world applications. The presence of irregular boundary geometries, complex boundary conditions and nonlinear relations introduced due to changes in material properties are important challenges faced when modeling complex nanostructures in inhomogeneous materials. Numerical methods can provide tractable solutions for modeling complex nanophotonic structures. Given the complexity of future nanophotonic applications, where the interactions between thousands of nanoparticles will need to be captured, the efficiency of modeling techniques is also crucial. In order to successfully model nanophotonic structures for future applications including nanoscale integrated circuits, we will investigate techniques to integrate a group of powerful electromagnetic simulation methods with complementary strengths: the Boundary Element Method (BEM), the Finite Difference Time Domain (FDTD), and the Finite Element Method (FEM). These techniques can then be used to develop integrated computational modeling platform for nanophotonic structures, which can be synergistically utilized to analyze and improve the performance of interconnections and components for applications in future nanoscale integrated circuits. By leveraging accurate and efficient automated design techniques, the computational modeling and automated synthesis of nanophotonic structures will enable many future nanoscale applications.
This work is supported by NSF IGERT Grant DGE-0504425
CURRENT FELLOWS
SEPTEMBER 1, 2006-AUGUST 31, 2008
Kenneth Jamison
Bioengineering
Faculty Advisor: Dr. Michael Diehl
Faculty Co-Advisor: Dr. Peter Saggau, Baylor College of Medicine
Area of study:
Motor proteins convert chemical energy into mechanical motion while transporting cargo along polymer tracks in cells. These motors routinely work in groups to perform their many tasks. However, the nature of their collective activities remain unknown, despite studies that link poorly functioning motor transport processes to diseases such as Alzheimer’s. The focus of this research is to investigate the behavior of motor proteins when they are arranged into complex multi-component architectures. These efforts will be directed towards advancing our knowledge of how interacting motor proteins coordinate their inherently random stepping processes in order to reliably transport cargo within the cell. To reach this objective, a series of biosynthetic tools will be developed to fabricate model systems of coupled motors that can be used to systematically probe modes of collective motor transport. To investigate the dynamics of these assemblies we will utilize a custom instrument that combines single-molecule fluorescence detection schemes with optical trapping capabilities. The structure-function relationships of coupled motor proteins that we discover through advanced optical techniques and synthetic modalities will progress the understanding of essential processes in cell biology while providing new insight into mechanisms of transport related diseases.
This work is supported by NSF IGERT Grant DGE-0504425
Daniel Ward
Physics and Astronomy
Advisor: Dr. Douglas Natelson
Co-Advisor: Dr. Bruce Johnson
Area of study:
I am researching the application of nanobowties with electromigrated nanometer size gaps as a tool for single molecule detection. My research focuses on the use of nanobowties as substrates for surface-enhanced Raman spectroscopy (SERS). SERS is a powerful nanophotonics technique that can be used to detect single molecules. Nanobowties consist of two metallic triangular halves that face each other tip to tip. A small gap between the tips acts a SERS hotspot. The gap between the tips is made via electromigration which allows the controlled growth of gaps on the order of a few nanometers. By controlling the gap size via electromigration the plasmon resonance can be tuned allowing the electromagnetic SERS enhancement can be controlled as well. Nanobowties are an interesting SERS substrate because they can also be used for molecular electronics. By combining SERS and electrical transport measurements I hope to better understand and control the SERS mechanism.
This work is supported by NSF IGERT Grant DGE-0504425
Britain Willingham
Physics and Astronomy
Advisor: Dr. Peter Nordlander
Co-advisor: Dr. Stephen Link
Area of Study:
Metallic nanorods, i.e. solid prolate spheroidal particles, exhibit plasmon modes that can be polarized both along the longitudinal and transverse axes. By changing the aspect ratio of the nanorod, the plasmon resonances can be tuned from the near-infrared (NIR) to UV wavelengths. This unique tunability of metallic nanorods makes this nanoparticle interesting as a substrate for surface enhanced spectroscopies. Using the plasmon hybridization method, I investigate the plasmonic properties of nanorod dimers as a function of interparticle separation and relative orientations of the nanorods.
This work is supported by NSF IGERT Grant DGE-0504425
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