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A biofuel cell incorporating a bienzymatic trehalase|glucose oxidase trehalose anode and a bilirubin oxidase dioxygen cathode using Os complexes grafted to a polymeric backbone as electron relays was designed and constructed. The specific power densities of the biofuel cell implanted in a female Blaberus discoidalis through incisions into its abdomen yielded maximum values of ca. 55 μW/cm(2) at 0.2 V that decreased by only ca. 5% after ca. 2.5 h of operation.

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Structural and electronic aspects of IrO 2 films prepared by electrodeposition on Au substrates were investigated by in situ L III -edge X-ray absorption and surface enhanced Raman spectroscopies in both acid and alkaline aqueous solutions. Linear correlations were found between the extent of oxidation of Ir 3+ in the films determined from a statistical fit of the white line, which includes contributions from each of the sites differing by a single electron, and from coulometric analysis of the voltammetric curves. Analysis of the extended X-ray absorption fine structure (EXAFS) yielded Ir-O bond lengths decreasing in the sequence 2.02, 1.97, and 1.93 Å for Ir 3+ , Ir 4+ , and Ir 5+ sites, respectively. Whereas SERS provided evidence for the presence of crystalline IrO 2 in the highly hydrated films, the lack of intense shells in the Fourier transform of the EXAFS function beyond the nearest oxygen neighbors indicates that the films do not display long-range order.

Electronic aspects of an iron porphyrin, 5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphine iron(III) chloride (FeTMPPCl) molecularly dispersed on a high area carbon black (Black Pearls 2000, BP) and then heat-treated (or thermally activated) at 800°C in a flowing inert atmosphere, were investigated in situ in 1.0 M H 3 PO 4 by Fe K-edge X-ray near-edge structure (XANES). Profound differences were observed between the ex situ (dry) XANES of electrodes incorporating FeTMPPCl/BP before and after heat treatment and, likewise, in the case of the thermally treated FeTMPPCl/BP before and after immersion of the electrodes in the electrolyte. Monotonic shifts in the absorption edge toward higher energies were observed for heattreated FeTMPPCl/BP as the potential was increased over a range of over 1 V. The overall magnitude of the shift, ca. 2.5 eV, was virtually the same as that obtained with non-heat-treated (or intact) FeTMPPCl/BP, which occurred in a much narrower potential range, ca. 0.2 V. In contrast to the behavior observed for the intact adsorbed macrocycle, its heat-treated counterpart displayed no affinity for CO, indicating that, to the level of sensitivity of this technique, iron sites in the thermally activated material are quite different from those in the N 4 environment of the intact macrocycle.

In situ Mossbauer spectra revealed changes in the electronic and structural properties of Fe sites brought about by redox processes attributed formally to Ni sites in a composite iron/nickel hydroxide. Measurements on the oxidized form, polarized in 1 M KOH at 0.5 V vs. Hg/HgO, revealed a singlet with an isomer shift of 0.22 mm/s vs. a-Fe. After reduction and polarization at 0.0 V, a doublet with an isomer shift of 0.32 mm/s and a quadrupole splitting of 0.44 mm/s was observed. The spectral changes, which accompanied the formal oxidation of Ni sites at 0.5

In situ scanning tunneling microscopy images of self-assembled monolayers (SAMs) of 4-mercaptopyridine (4-MPy) on Au(111) recorded in neat 0.1 M H2SO4 solutions provided evidence for a potential-induced phase transition over the range 0.40-0.15 V versus saturated calomel electrode. Analysis of the data was consistent with the presence of a (5 x square root(3)) and (10 x square root(3)) superstructure (phase A) at the positive end, that is, 0.40 V, for which the local coverage, theta(loc), is about 0.2 (two 4-MPy molecules per unit cell), which compresses at the negative end, that is, 0.15 V, to yield a much denser superstructure (phase B, theta(loc) ca. 0.5). This behavior is unlike that reported for the 4-MPy-Au(111) SAM prepared by identical means, in 0.1 M HClO4 (or in sulfate solutions of a much higher pH) for which only the (5 x square root(3)) superstructure was observed over the same potential range. The compression associated with the phase A to phase B transition is attributed to the formation of a hydrogen-bonded network of bisulfate coordinated in turn to the 4-MPy layer via the acidic hydrogens of the pyridinium moieties. Such conditions promote better packing of adsorbed 4-MPy species, which are aided by intermolecular pi-pi ring interactions, resulting in higher local coverages.

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