Functionalized Cobalt Triarylcorrole Covalently Bonded with Graphene Oxide: A Selective Catalyst for the Two- or Four-Electron Reduction of Oxygen.

A cobalt triphenylcorrole (CorCo) was covalently bonded to graphene oxide (GO), and the resulting product, represented as GO-CorCo, was characterized by UV-vis, FT-IR, and micro-Raman spectroscopy as well as by HRTEM, TGA, XRD, XPS, and AFM. The electrocatalytic activity of GO-CorCo toward the oxygen reduction reaction (ORR) was then examined in air-saturated 0.1 M KOH and 0.5 M H2SO4 solutions by cyclic voltammetry and linear sweep voltammetry using a rotating disk electrode and/or a rotating ring-disk electrode. An overall 4-electron reduction of O2 is obtained in alkaline media while under acidic conditions a 2-electron process is seen. The ORR results thus indicate that covalently bonded GO-CoCor can be used as a selective catalyst for either the 2- or 4-electron reduction of oxygen, the prevailing reaction depending upon the acidity of the solution.

Aggregation of P3HT as a preferred pathway for its chemical doping with F4-TCNQ.

The chemical doping reaction of P3HT with F4-TCNQ was studied by optical absorption spectroscopy, atomic force microscopy, and Kelvin probe force microscopy. We demonstrate that P3HT aggregation preferentially occurs before the actual charge transfer step takes place, emphasizing the impact of morphology on the chemical doping reaction of conjugated polymers at the molecular level.

The Impact of Aggregation on the p-Doping Kinetics of Poly(3-hexylthiophene).

The morphological effects of regioregular poly(3-hexylthiophene) (P3HT) on its p-doping kinetics with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) in solution are studied using optical absorption spectroscopy and stopped-flow technique. Two morphological forms, solubilized (s-P3HT) and nanowhiskers (nw-P3HT), are investigated. Both P3HT solubilized and aggregated solutions show similar characteristic near-IR absorption bands for integer charge transfer products with F4-TCNQ. Kinetic analysis on p-doping of s-P3HT with F4-TCNQ indicates that the doping reaction proceeds with a single reaction mechanism that is first order in s-P3HT. The doping kinetics of P3HT aggregate solution shows two distinctive reaction mechanisms. The slow mechanism has a reaction rate constant similar to that of solubilized P3HT solution, so it likely results from s-P3HT components that are present in the aggregate solution. The fast one is assigned to the nw-P3HT component, probably due to more efficient charge delocalization in the aggregated P3HT nanostructures. Additionally, the kinetic trends of the p-doping reactions are better fitted with the consideration of a Gaussian-like distribution of reactivities from P3HT, matching the complexity of polymeric systems originating from molecular weight and morphology variations. This study highlights the importance of considering different morphological forms of conjugated polymers on their charge-transfer reaction kinetics. The knowledge gained here should be fundamentally and practically important for future chemical doping applications in organic electronic device fabrications.

Eumelanin-inspired core derived from vanillin: a new building block for organic semiconductors.

An eumelanin-inspired core derived from the natural product, vanillin (vanilla bean extract) was utilized for the synthesis of eumelanin-inspired small molecules and polymer via Sonogashira cross coupling. The materials demonstrate that the methyl 4,7-dibromo-5,6-dimethoxy-N-methyl-1H-indole-2-carboxylate core can serve as a new building block for organic semiconductors.

Preparation and Characterization of Polyhedral Oligomeric Silsesquioxane-Containing, Titania-Thiol-Ene Composite Photocatalytic Coatings, Emphasizing the Hydrophobic-Hydrophilic Transition.

Coatings prepared from titania-thiol-ene compositions were found to be both self-cleaning, as measured by changes in water contact angle, and photocatalytic toward the degradation of an organic dye. Stable titania-thiol-ene dispersions at approximately 2 wt % solids were prepared using a combination of high-shear mixing and sonication in acetone solvent from photocatalytic titania, trisilanol isobutyl polyhedral oligomeric silsesquioxane (POSS) dispersant, and select thiol-ene monomers, i.e., trimethylolpropane tris(3-mercaptopropionate) (TMPMP), pentaerythritol allyl ether (APE), and 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TTT). The dispersed particle compositions were characterized by DLS and TEM. The synthetic methods employed yield a strongly bound particle/POSS complex, supported by IR, 29Si NMR, and TGA. The factors of spray techniques, carrier solvent volatility, and particle size and size distributions, in combination, likely all contribute to the highly textured but uniform surfaces observed via SEM and AFM. Polymer composites possessed thermal transitions (e.g., Tg) consistent with composition. In general, the presence of polymer matrix provided mechanical integrity, without significantly compromising or prohibiting other critical performance characteristics, such as film processing, photocatalytic degradation of adsorbed contaminants, and the hydrophobic-hydrophilic transition. In all cases, coatings containing photocatalytic titania were converted from superhydrophobic to superhydrophilic, as defined by changes in the water contact angle. The superhydrophilic state of samples was considered persistent, since long time durations in complete darkness were required to observe any significant hydrophobic return. In a preliminary demonstration, the photocatalytic activity of prepared coatings was confirmed through the degradation of crystal violet dye. This work demonstrates that a scalable process can be found to prepare titania-thiol-ene coatings having improved coating properties which also exhibit photocatalytic and self-cleaning attributes.