Multifunctional Nanomaterials

2009 Research Experiences for Undergraduates

May 26-July 31

Electronic Transduction

Group:  Lederman, Myers, and Edwards (Physics), Gannett (Pharmacy), Timperman (Chem), Flynn (MRBCC), Urazhdin (Physics), Carroll (Chemistry) Wu (MAE).

Research Experiences:  Nanofabrication using e-beam lithography, imaging via SPM, electrical measurements at low temperatures of single molecule devices; electronic measurements of magnetic nanostructures, magnetic characterization of nanostructures and nanoparticles via SQUID and MOKE magnetometry, calculation of electrical conductance, growth and electrical characterization of ferroelectric films.

Molecular Electronic and Magnetic Signatures: Electronic techniques involve measuring electrical conductivity of single proteins, which give the ultimate sensitivity in protein identification.  We are currently studying cytochrome P450 activity, which can be modulated by certain drugs that bind to its active site with toxicologically detrimental consequences.  Selectivity for specific molecules can be achieved by site-directed mutagenesis of CP450.  Thus, CP450 can be ‘tuned’ for use in biometric identification.  At the heart of the CP450 protein is a Fe-based heme group.  Preliminary measurements indicate single-electron transistor behavior, where one electron tunnels into the heme-group energy levels (Figure 1).  We also have demonstrated that CP450 attached to a gold film via thiol groups can be measured using sensitive (SQUID) magnetometry when CP450 binds to drugs such as flurbiprofen and dapsone. 

In addition to the break junction work, we are measuring the electrical properties of natural nanowires, such as tropomyosin or actin filaments, which are proteins that regulate muscle contraction, and DNA.  REU participants will learn to fabricate two- and four-point contacts via electron-beam lithography and measure the electrical properties of these proteins as a function of  temperature (1.7 K – 300 K).

Electro-Mechanical Detection Mechanisms: Standard techniques such as fluorescent, radioactive, and chemiluminescent antigen-antibody binding (e.g. ELISA), time of flight mass spectroscopy, electrophoretic separation, or detection in surface properties due to antigen-antibody binding are unable to identify or quantify proteins or suffer from non-specific binding of a serum analyte to the sensor surface.  We have tested this approach to detect lung cancer marker proteins by coating microcantilevers with anti-VEGF in collaboration the WVU Mary Babb Randolph Cancer Center.  Our initial experimental work, shown in Figure 2, indicates that a factor of 10 to 100 improvement in detection sensitivity over standard techniques (ELISA) can be obtained with this method.  The REU participants will measure the microcantilever resonance frequencies of the functionalized devices using a Veeco Multimode AFM, and will be trained to quantitatively interpret the data.  They will also learn to functionalize the cantilevers with the various biomolecules that make the method specific.

Bio/Nanostructure Devices:  Interactions between solid state devices and biological markers will be investigated.  Specifically, attachment of molecules to ferroelectric insulators or quantum dots and the resulting electronic signals in an underlying semiconductor will be studied.  For example, the attachment of a polar molecule to a receptor attached to a ferroelectric (FE) material may change the polarization of the FE thin film.  We are already investigating growth of high-quality FE YMnO3 on the semiconductor GaN.  Our long term goal is to bind biomolecular substrates to the ferroelectric surface to detect and recognize specific molecules.  REU participants will learn to perform MBE growth and ferroelectric characterization (leakage and polarization measurements) of the oxide compounds. 

Spintronics and Magnetism: Spintronics is the exploitation of the spin degree of freedom.  Here we study the current-induced magnetization reversal in magnetic tunnel junction nanopillars, interface effects between antiferromagnets and ferromagnets, magnetic nanoparticles for sensor applications, and roughening of ferromagnetic ultra thin films to study nanodot and nanowire self-assembly as well as quantum confinement effects.  REU participants will learn to fabricate magnetic nanostructure, measure their magnetic and magnetotransport properties, and obtain information from these experiments regarding their fundamental properties.

WVNano
886 Chestnut Ridge Road
P.O. Box 6223
Morgantown, WV 26506-6223
Phone: 304 293 8281
Fax: 304 293 6213
Email: wvnano@mail.wvu.edu
NSF