Picraux NanoScience Research Group

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Picraux NanoScience Research Group Research Activities
	Nanostructure Synthesis and Processing We are exploring a variety of selective growth techniques to form heteroepitaxial nanostructures on Si. Seeded by gold dots ranging from 5 to 30 nm, nanowires of Si and Ge are produced via VLS (vapor-liquid-solid) growth using selective CVD methods. A rich variety of nanostructures, from nanopillars to nanowires can be grown by varying the pressure and temperature Read more ... In another approach electrochemical dealloying of bi-metallic alloy mixtures provides a novel way to form nanoporous structures. We have demonstrated the extension of this concept to metal-silicon thin films on silicon platforms for PtxSi1-x, achieving typical Pt nanoporous networks with 5 to 10 nm pore diameters and large effective surface areas. Read more … Nanostructured Functional Surfaces The objective of this work is to develop photo-switchable surface monolayers that allow nanoscale control of interfacial properties for nanomolecular devices. For example, by designing monolayers containing tethered spiropyrans we can reversibly change the wetting characteristics of a surface upon exposure to uv and visible light. Potential applications exist for reversible photoswitchable materials in the fields of micro and nanofluidic valves, pumps, preconcentrators, and separators and for use in the areas of drug delivery, sensing, and environmental monitoring. Nanosensors The most sensitive way to detect a molecule is with another molecule, as is amply demonstrated in biology, from the operation of cells to the sense of smell. Nanoscale wires, dots, and sheets are being used to provide the platform for exploiting receptor molecules in highly sensitive sensing schemes. For example, nanoscale wires are functionalized with receptor molecules with varying affinities for target species. Sensing is based on the change in current vs. voltage though these quantum structures due to the attachment of chemical species. A variety of nanoscale structures and architectures are being investigated. Read more ... Interfacial Force Microscopy The interfacial force microscope at ASU is the type invented by Jack Houston at Sandia National Laboratories. It is being used to examine the properties of molecular nanostructures on sensors surfaces.  The instrument incorporates electrostatic force feedback in a differential capacitor arrangement, providing a variable ‘spring constant’ to trace probe-surface interactions from attractive to repulsive over the whole force curve in a quantitative and reproducible manner. Mechanical, electrostatic, chemical, and other interactions can be examined in detail under controlled gaseous and liquid environments. Scanning mode allows examination of self organized structures as well as lateral force and friction responses.

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Monday, February 16, 2004