Gayatri Keskar

Detection of phospholipid-carbon nanotube translocation using fluorescence energy transfer

Single-walled carbon nanotubes (SWNTs) and lysophospholipids readily assemble into supramolecular complexes in aqueous solutions. Upon light excitation the fluorescence of rhodamine-labeled lysophospholipids was redshifted and quenched due to the optical absorption of the SWNTs. Utilizing fluorescence energy transfer, the authors detected the translocation and disassembly of SWNT complexes in MCF breast cancer cells. These lipid-coated SWNT complexes enable drugs to be delivered at an effective dose and their subsequent release to be monitored in real time.

Single-molecule fluorescence microscopy and Raman spectroscopy studies of RNA bound carbon nanotubes

While present studies on the integration of single-walled carbon nanotubes (SWNTs) with biomolecules have centered primarily on deoxyribonucleic acid and proteins, this report is focused on the binding of SWNTs with ribonucleic acid polymer poly(rU). We present fluorescence and spectroscopic evidences for the binding of poly(rU) molecules along the contour of isolated SWNTs which suggests that the π-stacking may dominate the hydrophobic interaction between the poly(rU) bases and the π-electrons of the SWNTs.

Ultra-Sensitive Duffing Behavior of a Microcantilever

We investigate the properties of an electrostatically driven microcantilever exhibiting duffing-like behavior using harmonic detection of resonance. Its potential use as a highly sensitive sensing platform is discussed. We find high sensitivity of this duffing system near its bistability point in a gaseous environment. The response of the higher harmonics of the measured charge on the cantilever induced by an ac voltage that drives the counter electrode is investigated. In particular, we follow the duffing behavior at the higher harmonics (up to the sixth harmonic) as a function of gap distance between the cantilever and counter electrode. To our knowledge, this work represents the first experimental demonstration of sensing a pressure change using the duffing behavior.

Nanostructures of Boron, Carbon and Magnesium Diboride for High Temperature Superconductivity

Direct fabrication of MgxBy nanostructures is achieved by employing metal (Ni,Mg) incorporated MCM-41 in the Hybrid Physical-Chemical Vapor Deposition (HPCVD) reaction. Different reaction conditions are tested to optimize the fabrication process. TEM analysis shows the fabrication of MgxBy nanostructures starting at the reaction temperature of 600oC, with the yield of the nanostructures increasing with increasing reaction temperature. The as-synthesized MgxBy nanostructures have the diameters in the range of 3-5nm, which do not increase with the reaction temperature consistent with templated synthesis. EELS analysis of the template removed nanostructures confirms the existence of B and Mg with possible contamination of Si and O. NEXAFS and Raman spectroscopy analysis suggested a concentric layer-by-layer MgxBy nanowire/nanotube growth model for our as-synthesized nanostructures. Ni k-edge XAS indicates that the formation of MgNi alloy particles is important for the Vapor-Liquid-Solid (VLS) growth of MgxBy nanostructures with fine diameters, and the presence of Mg vapor not just Mg in the catalyst is crucial for the formation of Ni-Mg clusters. Physical templating by the MCM-41 pores was shown to confine the diameter of the nanostructures. DC magnetization measurements indicate possible superconductive behaviors in the as-synthesized samples.