A range of simple aromatic amines were used to modify Pt microcylinders with insulating electrosynthesised polymers generated amperometrically in the presence or absence of a typical globular protein, bovine serum albumin (BSA), at neutral pH. Sensitivity to a typical interference species, ascorbic acid (AA), and the most common electrochemical signal molecule for oxidase enzymes, H 2 O 2 , was used to compare the suitability of the resulting polymer-protein modified electrodes for biosensor applications. Pt modified with poly(aminobenzene), PANI, gave the lowest sensitivity to AA ( ~3000 times lower than bare Pt); incorporation of BSA into the polymer during synthesis had a detrimental effect on its AA-rejecting capability. The H 2 O 2 sensitivity of the PANI-based electrodes was poor ( ~7 times lower) compared to bare Pt. The behaviour of poly(1,2-diaminobenzene), PoPD, was different in many respects: its AA-blocking ability was enhanced 3-fold by the presence of BSA and its H 2 O 2 sensitivity was similar to bare Pt. EQCM data recorded in PBS indicated that PANI films electrosynthesised at pH 7.4 were two orders of magnitude thicker than for PoPD. These differences may be due, at least in part, to the 'ladder' structure with phenazine rings proposed for PoPD, since they were not duplicated by other mono-substituted derivatives of aniline, such as 2-methylaniline or 1,3-diaminobenzene.

Abstract:Reports that globular proteins could enhance the interference blocking ability of the PPD (poly(o-phenylenediamine) layer used as a permselective barrier in biosensor design, prompted this study where a variety of modifying agents were incorporated into PPD during its electrosynthesis on Pt-Ir electrodes. Trapped molecules, including fibrous proteins and β-cyclodextrin, altered the polymer/modifier composite selectivity by affecting the sensitivity to both H 2 O 2 (signal molecule in many enzyme-based biosensors) and the archetypal interference species, ascorbic acid. A comparison of electrochemical properties of Pt and a Pt-Ir alloy suggests that the benefits of the latter, more rigid, metal can be exploited in PPD-based biosensor design without significant loss of backward compatibility with studies involving pure Pt.

Results from a new series of experiments on turbulent flows in a rotating circular container are presented. Electromagnetic forcing is applied to induce flow in a layer of fluid of constant depth. Continuously forced and decaying flows are investigated. Optical altimetry is used to measure the gradient of the surface elevation field and to obtain the velocity and vorticity fields with high temporal and spatial resolution. Spectral analysis of the flows demonstrates the formation of dual cascade with energy and enstrophy intervals although the corresponding spectral fluxes of energy and enstrophy are not uniform in these intervals. The energy interval is characterized by the slope of ∼−5/3 in terms of wavenumber and is limited in extent by the finite radius of deformation effect. In the enstrophy range, the slope is steeper than −3 due to the presence of long-lived coherent vortices. The spatial patterns of fluxes to large or small scales in the flow indicate that inverse energy transfer and direct enstrophy transfer occur mainly in elongated vorticity patches. Cyclone/anticyclone asymmetry in favor of anticyclones is observed in our flows. Dominance of anticyclones is most clear during the decay phase of turbulence. The anticyclones remain circular, while cyclonic vorticity is stretched into elongated patches. Measurements show that skewness of vorticity distribution increases with increasing Froude number of the flow.

No abstract

No abstract

Direct experimental evidence of anion hydrogen bonding was examined for fluoride and other anions. The centre wavenumber of the polarized Raman band assigned to the symmetric hydrogen bond stretching mode agreed very well with ab initio calculations for all anions but fluoride, whose theoretical wavenumber was significantly higher than the spectroscopic value. Calculations were repeated at a higher level of theory but the difference persisted. The heavy water isotope shifts and the potential energy surface for the hydrogen bond stretching motion were similar for fluoride and the other hydrates, suggesting that the difference could be due to interactions with other molecules. It was postulated that water cluster formation about the fluoride ion contributes to the difference in wavenumbers.

No abstract

No abstract