Active Nanostructures at Interfaces for Photocatalytic Reactors and Low-power Consumption Sensors
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Active Nanostructures at Interfaces for Photocatalytic Reactors and Low-power Consumption Sensors James L Gole1,2, Serdar Ozdemir1 Sharka M. Prokes3 and David A. Dixon4 1 School of Physics, Georgia Institute of Technology, 837 State St, Atlanta, GA, 30332-0430. 2 School of Mechnaical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405. 3 Naval Research Laboratory, Washington, DC 20375-5000, USA. 4 Department of Chemistry, The University of Alabama, Shelby Hall, Box 870336, Tuscaloosa, Alabama 35487-0336. ABSTRACT Active nanostructures which provide unique transformations are being introduced to phase matched porous silicon (PS) nano/micropores to form a platform for low power consumption highly selective sensors and microreactors. TiO2-xNx photocatalysts have been formed in seconds at room temperature at the nanoscale via the direct nitration of anatase TiO2 nanocolloids. Tunability throughout the visible depends upon the degree of agglomeration and the ability to seed these nanoparticles with metal ions. Co metal ion seeding leads to the efficient room temperature phase transformation, of anatase to rutile TiO2, where normally much higher temperatures are required. Seeding of a properly nitridated TiO2 nanocolloid with transition metal ions (Co, Ni) allows for the enhancement of the infrared spectra of the TiO2-xNx nitridated titania surface in excess of 10-fold, providing a means to analyze for minor contaminants and intermediates. Evidence for nitrogen fixation is found in Fe treated systems. The TiO2-xNx systems act as visible light absorbing photocatalyts. These photocatalysts and additional nanostructured metal oxides can be placed on the surface of PS-based sensor and microreactor configurations to greatly improve the interface response. INTRODUCTION Nanostructured materials enable exciting opportunities and the development of new paradigms for the modification of interfaces useful for microreactor and sensing capabilities due to their uniquely confined structural and electronic properties. Decorated and decorating nanostructures undergo changes in state in order to catalyze a chemical reaction or to sense a chemical. Thus these are active nanostructures. Domains localized in nanometer sized centers can undergo confined and rate enhancing changes as a process proceeds. Within the proviso of controlling activity-reactivity, through the control of nanoscale morphologies and the use of active nanostructured materials, it can be shown that it is possible to greatly enhance sensor sensitivity and selectivity for a variety of gases as the sensors rely on active nanoparticles whose controlled and enhanced interaction can readily be measured. The development of both enhanced chemical transformation and the attainment of an enhanced sensor capability display a synergism which can further be used in the development of microreactor technologies. Active nanostructures are being introduced to phase matched porous silicon (PS) nano/micropores to form selective sensors and microreactors. Active
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