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Biocatalysts are an attractive alternative to conventional noble metal catalysts for fuel cell cathodes. In principle, they combine the possibility of more efficient operation (lower intrinsic overpotential) with the benefits of renewability and low temperature operation. In this paper we discuss some fundamental biochemistry and electrochemistry of one cathode system that has attracted some interest in the biofuel cell community, laccase as catalyst with 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) as mediator. We focus on one laccase preparation from Trametes versicolor , and demonstrate that steady state electrocatalytic oxygen reduction currents can be modeled using the measured intrinsic properties of the enzyme ( k cat , K M ) and mediator ( D M ). We then discuss some of the implications of this modeling for practical electrode design.

Single-walled carbon nanotubes are efficiently cut to precise submicrometer lengths and very narrow length distributions. Chemical functional groups are placed selectively only at the ends without the nanotube walls being modified or damaged. The new methodology includes lithography to place protective photoresist patterns over the nanotubes and reactive ion etching to remove the unprotected nanostructure. This approach enables critical dimensional and chemical control for integrated nanodevice manufacturing based on chemical self-assembly under ambient conditions.

We present a novel process methodology for the controlled cutting of nanotubes and other nanostructures to well-controlled lengths and sizes. The continuing increase in complexity of electronic devices, coupled with decreasing size of individual elements, are placing more stringent demands on the resolution and accuracy of fabrication patterns. The ability to fabricate on a nanometer scale guarantees a continuation in miniaturization of functional devices. Particularly interesting is the application of nanotubes' chemical and electronic properties which vary with their dimensions and structure. One realization of this process includes the use of photolithography or electron beam lithography to place protective resist patterns over the nanostructures to be cut. Those sections which are not covered by the resist pattern are removed by reactive ion etching. This is a scaleable process which permits the simultaneous cutting of many nanostructures and ensembles of nanostructures. The lengths, shapes or length distributions can be predicted from theory and thus specified for a given application requirement. Nanostructures which can be cut in this process include nanotubes, nanofibers and nanoplanes. Large scale production of nanostructures with uniform length or specific size-distribution can be used in electronic applications such as field-emission transistors, optoelectronic elements, single electron devices and sensors.

The magnetic properties of small diameter semiconducting single-walled carbon nanotubes have been recently predicted to depend sensitively on structural details that can be ignored for larger diame...

A theory of ion-clustering is presented for Nation resins. An expression for the cluster diameter is derived; it correctly describes the experimental variations in cluster diameter with cation form, equivalent weight, and water content of the polymers. The theory further suggests that short channels connecting adjacent clusters are thermodynamically stable in support of the cluster-network model proposed by one of us earlier. The percolative aspects of ion transport and an ionic insulator-to-conductor transition in Nation resins are discussed.

Influence sur les proprietes physiques de l'evolution morphologique, (de la structure lamellaire a la structure fibrillaire). Application a un melange 25% carboxylate, 75% sulfonate d'ionomeres perfluores