We present a one-step approach to polydopamine-modified graphene hydrogel, with dopamine serving as both reductant and surface functionalization agents. The synthetic method is based on the spontaneous polymerization of dopamine and the self-assembly of graphene nanosheets into porous hydrogel structures. Benefiting from the abundant functional groups of polydopamine and the high specific surface areas of graphene hydrogel with three-dimensional interconnected pores, the prepared material exhibits high adsorption capacities toward a wide spectrum of contaminants, including heavy metals, synthetic dyes, and aromatic pollutants. Importantly, the free-standing graphene hydrogel can be easily removed from water after adsorption process, and can be regenerated by altering the pH values of the solution for adsorbed heavy metals or using low-cost alcohols for synthetic dyes and aromatic molecules.

We report the development of a highly efficient photocatalytic system by immobilizing high-quality CdS quantum dots and dendritic Pt nanocrystals on thiol-functionalized graphene substrates. We have demonstrated that the use of QDs with compact sizes leads to a dramatically enhanced performance in comparison with their bulk counterparts. Our design allows for systematic examination of the impact of QD sizes and the loading, morphology, and surface coating of the Pt nanocrystal cocatalyst on the H2 evolution activity. It was found that the CdS-Pt binary system has a high photocatalytic efficiency of 1.37 mmol h(-1) for visible light driven H2 evolution, and there was a 30% improvement by introducing the thiolated reduced graphene oxide to form the three-component CdS-Pt-Gcys nanocomposites. The highest H2 evolution rate of 2.15 mmol h(-1) (λ ≥ 420 nm) with a QE of 50.7% was achieved by further photo-annealing of the CdS-Pt-Gcys nanocomposites prior to the photocatalytic reaction.

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The reactions of so called “tuck-in” permethyl zirconocene compounds Cp*(η5-η1-C5Me4CH2)ZrX (X = Cl (1a), C6H5 (1b), CH3 (1c)) with the highly electrophilic boranes HB(C6F5)2 and B(C6F5)3 are described. The products are zwitterionic olefin polymerization catalysts. Reactions with 1a and 1b yielded single products cleanly, but reactions with tuck-in methyl starting material 1c gave mixtures. Spectroscopic and structural studies showed that the electrophilic zirconium center in the product zwitterions was stabilized by a variety of mechanisms. In the products of reaction between 1a and 1b with HB(C6F5)2, Cp*[η5,η1-C5Me4CH2B(C6F5)2(μ-H)]ZrX (X = Cl (2a), 74%), C6H5 (2b, 62%)), the metal is chelated by a pendant hydridoborate moiety. Chloride product 2a was characterized crystallographically. In the reaction of B(C6F5)3 with 1a, the fluxional zwitterionic product Cp*[η5-C5Me4CH2B(C6F5)3]ZrCl (3a, 84%) is stabilized by a weak donor interaction between one of the ortho fluorine atoms of the −CH2B-(C6F5)3 counterion and the zirconium center (Zr−F = 2.267(5) Å). In the product of the reaction between 1b and B(C6F5)3, Cp*[η5-C5Me4CH2B(C6F5)3]ZrC6H5 (3b, 82%), a similar ortho-fluorine interaction was found in a yellow kinetic product (y-3b), which converted upon heating gently to a thermodynamic orange polymorph (o-3b) in which the zirconium center is compensated via an agostic interaction from an ortho C−H bond of the phenyl group and an interaction between the methylene group of the −CH2B-(C6F5)3 counteranion. These compounds were both characterized by X-ray crystallography. Zwitterion o-3b reacts with H2 to form the zwitterionic hydride Cp*[η5-C5Me4CH2B(C6F5)3]ZrH (4, 77%), characterized by NMR spectroscopy and X-ray crystallography to reveal a return to the ortho-fluorine mode of stabilization. Compounds 2a, 3a, o-3b, and 4 were all found to be active ethlyene polymerization catalysts; the chloride derivatives required minimal amounts of methylaluminoxane (MAO) to alkylate the zirconium center. Polymerization data are discussed in light of the structural findings for the catalysts employed.

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