Graphene Oxide Sheets Combine into Conductive Coatings by Direct Oxidative Electropolymerization.

New coatings are obtained when graphene oxide is further oxidized at moderate anodic potentials (≤~1.3 V vs. Ag/AgCl). Based on a variety of spectroscopic and electrochemical observations, the coatings are attributed to the direct electropolymerization of graphene oxide sheets via oxidation of the phenol edge groups on graphene. Depending on the applied potential, ether or carboxylic groups are formed. The coatings obtained via further oxidation are characterized by a lower O/C ratio due to decarboxylation and a higher content of C=C bonds. These bonds extend aromatic conjugation into the combined graphene oxide sheets and are responsible for the highly conductive nature of these coatings.

Interaction of Fe(III) tetrakis(4-N-methylpyridinium)porphyrin with sodium dodecyl sulfate at submicellar concentrations.

Interaction of water soluble Fe(III) tetrakis(4- N-methylpyridinium)porphyrin (Fe(III)TMPyP) with sodium dodecyl sulfate (SDS) in submicellar concentrations has been studied by surface tension, optical absorption, resonance light scattering (RLS), zeta-potential, and energy dispersive X-ray spectroscopy (EDS) measurements. Measurements were conducted for a fixed concentration of Fe(III)TMPyP (6 x 10 (-5) M) and SDS in various concentrations ranging between 6 x 10 (-6) and 6 x 10 (-2) M. Two macroscopic phase transitions, precipitation and redissolution, were observed as function of SDS concentration. The presence of a new surface active porphyrin-surfactant complex was detected. Furthermore, the presence of two oppositely charged Fe(III)TMPyP-SDS bulk moieties has been demonstrated. Possible structures for the different moieties are suggested, and the phase transitions are discussed.

Conductivity response of porous electrodes supported on perfluorosulfonic acid membranes to acidic gas mixtures.

Gold or platinum films deposited on a Nafion membrane were used to measure surface conductance of the membrane. Acidic gases such as HCI or SO2, introduced as mixtures with an inert gas, were found to affect the conductance of the membrane surface facing this mixture while the other side of the membrane was constantly supplied with a moist inert gas. The relative conductance (G/Go) is most affected within the 0-0.5 and 3-4.5 vol % ranges both for HCI and SO2. The effect is higher for the Pt-deposited than it is for the gold-deposited membrane: for an HCI concentration of 1.5 vol %, G/Go is 5 for Pt deposited on Nafion while it is only 1.3 for gold deposited on Nafion. This is attributed to different geometries and porosity of the Pt and Au electrodes. No conductance response was observed for CO2 which yields with water a much weaker acid than those formed by HCI and SO2.

Water gradients across bovine cornea.

Twenty-six bovine corneas, 30 micron thick, were sectioned perpendicular to the visual axis. Sections, weighing 10-20 mg, were analyzed for total water content by thermogravimetric analysis and for freezable water content by differential scanning calorimetry. The total water content as well as the free (freezable) water content increase, while the bound (nonfreezable) water content decreases in progressing from epithelium to endothelium. These results are correlated with the distribution of proteoglycans and their water sorptive and retentive capacity in bovine cornea.

Small-angle light scattering studies on xylose cataract formation in bovine lenses.

Using polarized light scattered in the I'' and I+ modes, we determined the relative contributions of density and orientation fluctuation to the opacity of bovine lenses. In both the cortex and the nucleus of bovine lenses cultured in xylose column, we found that the increase in hydration effects the optical anisotropy (birefringence) first, before the lake formation will contribute heavily to the density fluctuation.