Screen printed graphite macroelectrodes for the direct electron transfer of cytochrome c

We report the direct electrochemistry of cytochrome c at screen printed graphite electrodes which exhibits quasi-reversible voltammetric responses without the need for any chemical or electrochemical pre-treatment, use of mediators or nanomaterials. Through voltammetric studies and X-ray photoelectron spectroscopy (XPS) it is shown that carbonyl and carboxylic surface oxygenated species likely residing at edge plane like- sites/defects of the graphite comprising the screen printed electrodes are responsible for the favourable interaction of the cytochrome c with that of the screen printed electrochemical sensing platform.     

CVD graphene electrochemistry: biologically relevant molecules

We investigate the electrochemical properties of CVD grown graphene towards the detection of various biologically prevalent analytes including l-ascorbic acid (AA), dopamine hydrochloride (DA), β-nicotinamide adenine dinucleotide (NADH), uric acid (UA) and epinephrine (EP). We find that the observed electrochemical response of the CVD-graphene towards these select analytes does not originate from the graphene, however, from various other contributions including the presence of 'graphitic islands' on the surface of the CVD-graphene which dominate its electrochemistry. In the systems studied within, it appears at best, CVD-graphene acts akin to that of an edge plane pyrolytic graphite (EPPG) electrode constructed from highly ordered pyrolytic graphite. However, in other cases, the response of the CVD-graphene is worse than that of an EPPG electrode, which is likely due to the low O/C ratio.     

CVD graphene electrochemistry: the role of graphitic islands

Graphitic islands are shown to dominate the electrochemical response at CVD grown graphene electrodes.     

Estimates for Wieferich numbers

We define Wieferich numbers to be those odd integers w≥3 that satisfy the congruence 2 ^φ(w)≡1 (mod  w ²). It is clear that the distribution of Wieferich numbers is closely related to the distribution of Wieferich primes, and we give some quantitative forms of this statement. We establish several unconditional asymptotic results about Wieferich numbers; analogous results for the set of Wieferich primes remain out of reach. Finally, we consider several modifications of the above definition and demonstrate that our methods apply to such sets of integers as well. During the preparation of this paper, W.B. was supported in part by NSF grant DMS-0070628, F.L. was supported in part by grants SEP-CONACYT 37259-E and 37260-E, and I.S. was supported in part by ARC grant DP0211459.     

An overview of the electrochemical reduction of oxygen at carbon-based modified electrodes

We present an overview of the electrochemical reduction of oxygen in water, focussing on carbon-based and modified carbon electrodes. This process is of importance for gas sensing, in fuel cells and in the electrosynthesis of hydrogen peroxide.     

Edge plane pyrolytic graphite electrodes in electroanalysis: an overview.

The recent development, behavior and scope of edge plane pyrolytic graphite electrodes in electroanalysis are overviewed. Similarities to, and advantages, over multi-walled CNT modified electrodes are noted and the wide scope of applications, ranging through gas sensing, stripping voltammetry and biosensing, illustrated.     

Thermotropic copolyesters. III. Synthesis and characterization of liquid crystal copolyesters containing the bicyclo[2.2.2]octane ring system

A number of thermotropic copolyesters which contain the bicylo[2.2.2]octane ring system have been synthesized. Because of the stiffening effect of the bicyclo[2.2.2]octane group on the chain, the sebacoyl spacer was used to obtain meltable compositions.