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Nanomaterials in One Dimension: Exploring Mesoscopic Phenomena in Template-Grown Nanowires

Seminar Group: 


Professor Thomas E. Mallouk


Evan Pugh Professor of Materials, Chemistry and Physics
Penn State University


Friday, October 19, 2012 - 4:00pm


ESB 1001


Prof. Ram Seshadri

Mesoscopic properties are those that emerge when the size of an object matches a characteristic physical length scale, such as the exciton radius in a semiconductor or the coherence length of Cooper pairs in a superconductor. Nanowires are particularly interesting in this context as quasi-1D materials.

By using anodic alumina and track-etched polymer membranes act as hard templates, we have made “striped” and core-shell nanowires with precise control over dimensions and composition. These structural features allow one to explore unusual electronic transport properties of single-crystal nanowires and their possible applications in molecular and nanoscale electronics.

The motion of nano- and microwires in fluids is also a mesoscopic phenomenon at low Reynolds number. In this application, bi- and trimetallic nanorods are catalytically self-propelled in fuel-containing solutions at speeds that are comparable to those of flagellar bacteria. Despite the difference in propulsion mechanisms, catalytic nano- and micromotors are subject to the same external forces as natural motors such as bacteria. Therefore they follow the same scaling laws and exhibit similar emergent behavior (e.g., magnetotaxis, chemotaxis, schooling, and predator-prey behavior).

Recently we have found that bimetallic nanowires also undergo autonomous motion and a range of collective behavior in fluids when excited by low power ultrasound. The acoustophoretic propulsion mechanism may be particularly useful for biomedical applications because it is salt-tolerant and does not involve toxic chemical fuels.