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Langmuir 2006, 22, 4462-4466
Nanoscale Conductivity Mapping of Hybrid Nanoarchitectures: Ultrathin Poly(o-phenylenediamine) on Mesoporous Manganese Oxide Ambigels Todd M. McEvoy† and Jeffrey W. Long* NaVal Research Laboratory, Surface Chemistry Branch, Code 6170, 4555 OVerlook AVenue SW, Washington, DC 20375-5342
Timothy J. Smith and Keith J. Stevenson* Department of Chemistry and Biochemistry, Center for Nano- and Molecular Science and Technology, Texas Materials Institute, UniVersity of Texas at Austin, Austin, Texas 78712 ReceiVed September 21, 2005. In Final Form: March 21, 2006 We use conductive-probe atomic force microscopy (CP-AFM) to characterize and image hybrid electrode structures comprising mesoporous manganese oxide (MnO2) ambigel nanoarchitectures coated with an ultrathin (200 m2 g-1) MnO2 ambigel, the resulting hybrid structures display an ∼20-fold reduction in conductivity, as determined from CP-AFM measurements. The CP-AFM imaging studies confirm that the ultrathin, insulating PPD layer conformally and homogeneously coats the conductive nanoarchitecture. CP-AFM imaging of PPD-MnO2 hybrid electrodes following electrochemical cycling in an aqueous acid electrolyte reveals that the ultrathin PPD coating serves as an effective barrier to the electrolyte, protecting the underlying MnO2 nanoarchitecture from electrochemical dissolution.
The need for high-performance electrochemical power sources has spurred the development of new electrode materials and structures, with a particular emphasis on materials with nanostructured forms.1,2 One emerging class of materials comprises electrically conductive aerogels, ambigels, and related sol-gelderived nanoarchitectures3,4 that exhibit enhanced electrochemical performance because of a combination of high specific surface area (tens to hundreds of m2g-1) and extensive, well-connected pore networks. We are developing strategies to extend the versatility and functionality of such conductive, ultraporous nanoarchitectures; one approach uses electrodeposition to form ultrathin (
