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Graphene substrates are known to have randomly located functional groups on their surface, particularly at their edges, including carboxylate, carbonyl, epoxy, and alcohol functionalities. However, the detailed interactions of these graphene functionalities with metal oxide nanoclusters are unexplored. This work examined the interaction of titania nanostructures with both graphene and functionalized graphene nanoribbons (GNRs) using density functional theory (DFT) calculations. The interactions of TiO 2 (anatase, rutile, and molecular) with graphene were found to favor the physisorption of rutile titania. The interactions of TiO 2 with GNRs were found to considerably improve the strength of the nanostructure binding to the substrate with rutile and anatase showing similar chemisorption. Charge density maps showed the importance of the electron distribution in the interaction between titania and graphene with chemisorption sites. Valuable information on the strength of the binding energies was determined by studying the electronic structure using partial density of states (PDOS) of the TiO 2 /graphene systems at specific adsorption sites. These results show the potential for controlled and oriented growth mechanisms that have applications in next generation photovoltaic and photocatalytic devices.

The focus of this research is to determine the conditions under which passivity of Cu is (with the possibility of pitting) or is not possible, in anticipated bentonite pore water compositions expected to contact a Cu-coated container in a deep geological repository. Cyclic voltammetry has been used to deduce the active/passive maps that define the environmental conditions (in terms of, pH, and temperature) under which the Cu surface could be active or passive. A range of temperatures (up to 80°C), pH values (neutral to alkaline), and electrolyte compositions have been investigated. Such a database of maps shows that active/passive conditions change with the pH, temperature, and the type and concentration of anions. These maps will provide a basis for container corrosion models, as well as guidelines regarding the water compositions used when compacting the bentonite, the repository saturation time, and the optimum container spacing. ARTICLE HISTORY

Tremendous interest exists towards synthesizing nanoassemblies for dye-sensitized solar cells (DSSCs) using earth-abundant and -friendly materials with green synthetic approaches. In this work, high surface area TiO(2) nanowire arrays were grown on the surface of functionalized graphene sheets (FGSs) containing -COOH functionalities acting as a template by using a sol-gel method in the green solvent, supercritical carbon dioxide (scCO(2)). The effect of scCO(2) pressure (1500, 3000 and 5000 psi), temperature (40, 60 and 80 °C), acetic acid/titanium isopropoxide monomer ratios (HAc/TIP = 2, 4 and 6), functionalized graphene sheets (FGSs)/TIP weight ratios (1:20, 1:40 and 1:60 w/w) and solvents (EtOH, hexane) were investigated. Increasing the HAc/TIPweight ratio from 4 to 6 in scCO(2) resulted in increasing the TiO(2) nanowire diameter from 10 to 40 nm. Raman and high resolution XPS showed the interaction of TiO(2) with the -COOH groups on the surface of the graphene sheets, indicating that graphene acted as a template for polycondensation growth. UV-vis diffuse reflectance and photoluminescence spectroscopy showed a reduction in titania's bandgap and also a significant reduction in electron-hole recombination compared to bare TiO(2) nanowires. Photocurrent measurements showed that the TiO(2)nanowire/graphene composites prepared in scCO(2) gave a 5× enhancement in photoefficiency compared to bare TiO(2) nanowires.

In this work, Fe-doped TiO(2) nanoparticles ranging from a 0.2 to 1 weight % were grown from the surface of graphene sheet templates containing -COOH functionalities using sol-gel chemistry in a green solvent, a mixture of water/ethanol. The assemblies were characterized by a variety of analytical techniques, with the coordination mechanism examined theoretically using the density functional theory (DFT). Scanning electron microscopy and transmission electron microscopy images showed excellent decoration of the Fe-doped TiO(2) nanoparticles on the surface of the graphene sheets >5 nm in diameter. The surface area and optical properties of the Fe-doped photocatalysts were measured by BET, UV and PL spectrometry and compared to non-graphene and pure TiO(2) analogs, showing a plateau at 0.6% Fe. Interactions between graphene and Fe-doped anatase TiO(2) were also studied theoretically using the Vienna ab initio Simulation Package based on DFT. Our first-principles theoretical investigations validated the experimental findings, showing the strength in the physical and chemical adsorption between the graphene and Fe-doped TiO(2). The resulting assemblies were tested for photodegradation under visible light using 17β-estradiol (E2) as a model compound, with all investigated catalysts showing significant enhancements in photocatalytic activity in the degradation of E2.