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We report that long-range proton diffusion (> 0.3 mm) is generated in monolithic ultraporous manganese oxide nanoarchitectures upon exposure to gas-phase water. The sol--gel-derived ambigel nanoarchitectures, with bicontinuous networks of covalently bonded nanoscale solid and through-connected mesopores, exhibit conductometric sensitivity to humidity as established by impedance spectroscopy. The spectra contain a Warburg feature from which the concentration and diffusion length of the protonic charge carriers are determined. Water adsorbs conformally onto the architecture's continuous solid network in equilibrium with atmospheric humidity to create a continuous water sheath that acts as a 3-D proton wire. As a result, monolithic manganese oxide ambigels exhibit an equilibrium conductometric response to humidity that is 14 times greater than that of previous reports for electrolytic manganese oxide. A packed bed of 1-10-[micro]m ambigel particulates in physical contact with one another, each with the same nanoscale morphology as the monolithic nanoarchitecture, also support long-range proton diffusion; however, the sensitivity to humidity is four times lower than the monolithic form due to restricted proton transport between adjacent particulates. Films composed of 0.3-12-[micro]m ambigel particulates supported on interdigitated array electrodes with 20-[micro]m electrode spacing express finite-diffusion behavior due to the short distance between the contact electrodes and have a conductometric sensitivity to humidity comparable to electrolytic Mn[O.sub.2] and 17 times lower than the monolithic ambigel. These results suggest that controlling the nature of the porous and solid phases in a nanoarchitecture provides a mechanism to limit interference from condensed water in conductometric gas-phase sensors. In addition, continuous monolithic architectures should improve electrochemical performance in devices where efficient long-range transport of protons or other ions is critical.

An iron tetraphenylporphyrin, with four appended, oligomeric (MW = 550), poly(ethylene glycol) chains ([Fe(T550PP)C1]), is an electroactive, room-temperature melt, and undergoes axial coordination with volatile bases, such as pyridines, when they are partitioned at a gas/melt interface into a film of the porphyrin. The Fe(III/II) reaction of the axially coordinated porphyrin can be used amperometrically as a means of detecting the pyridine vapor, as shown in plug flow experiments with open tubular columns. The mechanism of the ECGC detector response is analyzed. This detection scheme is minimally responsive or nonresponsive to gaseous analytes that do not coordinate to the Fe(III) state of the porphyrin. The detector's selective response to pyridine is linear over a 500-fold range but is not yet very sensitive in comparison to the (nonselective) flame ionization detector. The ECGC detector has utility in detecting weak ligand interactions with the porphyrin (i.e., alcohols), and its response also detects slow dissociation rates of the Fe(II) complex formed in the detection reaction.

An electrochemical time-of-flight technique is employed in the investigation of charge transport dynamics in a cobalt bipyridine redox polyether hybrid. Measurements of the apparent diffusion coefficient, DAPP, provide insight into electron self-exchange reactions in the undiluted molten metal complex. Results from time-of-flight measurements are compared to those from potential step chronoamperometry and cyclic voltammetry; good agreement is observed. Peak shapes are compared with simulations from a previous report; disparities noted are ascribed to differences in the potential pulse profile employed.