(2007). Quantitative analysis of the reactivity of formate species seen by DRIFTS over a Au/Ce(La)O2 water-gas shift catalyst: First unambiguous evidence of the minority role of formates as reaction intermediates. Journal of Catalysis, 247(2)(2), 277-287. DOI: 10.1016DOI: 10. /j.jcat.2007 Published in: Journal of Catalysis Queen's University Belfast -Research Portal: Link to publication record in Queen's University Belfast Research Portal General rights Copyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. AbstractThe reactivity of the species formed at the surface of a Au/Ce(La)O 2 catalyst during the water-gas shift (WGS) reaction were investigated by operando diffuse reflectance Fourier transform spectroscopy (DRIFTS) at the chemical steady state during isotopic transient kinetic analyses (SSITKA). The exchanges of the reaction product CO 2 and of formate and carbonate surface species were followed during an isotopic exchange of the reactant CO using a DRIFTS cell as a single reactor. The DRIFTS cell was a modified commercial cell that yielded identical reaction rates to that measured over a quartz plug-flow reactor. The DRIFTS signal was used to quantify the relative concentrations of the surface species and CO 2 . The analysis of the formate exchange curves between 428 and 493 K showed that at least two levels of reactivity were present. "Slow formates" displayed an exchange rate constant 10-to 20-fold slower than that of the reaction product CO 2 . "Fast formates" were exchanged on a time scale similar to that of CO 2 . Multiple nonreactive readsorption of CO 2 took place, accounting for the kinetics of the exchange of CO 2 (g) and making it impossible to determine the number of active sites through the SSITKA technique. The concentration (in mol g −1 ) of formates on the catalyst was determined through a calibration curve and allowed calculation of the specific rate of formate decomposition. The rate of CO 2 formation was more than an order of magnitude higher than the rate of decomposition of formates (slow + fast species), indicating that all of the formates detected by DRIFTS could not be the main reaction intermediates in the production of CO 2 . This work stresses the importance of full quantitative analyses (measuring both rate constants and adsorbate concentrations) when investigating the role of adsorbates as potential reaction intermediates, and illustrates how even reactive species seen by DRIFTS may be unimportant in the overall reaction scheme.

The association of cellular toxicity with the physiochemical properties of graphene‐based materials is largely unexplored. A fundamental understanding of this relationship is essential to engineer graphene‐based nanomaterials for biomedical applications. Here, an in vitro toxicological assessment of graphene oxide (GO) and reduced graphene oxide (RGO) and in correlation with their physiochemical properties is reported. GO is found to be more toxic than RGO of same size. GO and RGO induce significant increases in both intercellular reactive oxygen species (ROS) levels and messenger RNA (mRNA) levels of heme oxygenase 1 (HO1) and thioredoxin reductase (TrxR). Moreover, a significant amount of DNA damage is observed in GO treated cells, but not in RGO treated cells. Such observations support the hypothesis that oxidative stress mediates the cellular toxicity of GO. Interestingly, oxidative stress induced cytotoxicity reduces with a decreasing extent of oxygen functional group density on the RGO surface. It is concluded that although size of the GO sheet plays a role, the functional group density on the GO sheet is one of the key components in mediating cellular cytotoxicity. By controlling the GO reduction and maintaining the solubility, it is possible to minimize the toxicity of GO and unravel its wide range of biomedical applications.

Atomistic simulations reveal that the chemical reactivity of ceria nanorods is increased when tensioned and reduced when compressed promising strain-tunable reactivity; the reactivity is determined by calculating the energy required to oxidize CO to CO2 by extracting oxygen from the surface of the nanorod. Visual reactivity “fingerprints”, where surface oxygens are colored according to calculated chemical reactivity, are presented for ceria nanomaterials including: nanoparticles, nanorods, and mesoporous architectures. The images reveal directly how the nanoarchitecture (size, shape, channel curvature, morphology) and microstructure (dislocations, grain-boundaries) influences chemical reactivity. We show the generality of the approach, and its relevance to a variety of important processes and applications, by using the method to help understand: TiO2 nanoparticles (photocatalysis), mesoporous ZnS (semiconductor band gap engineering), MgO (catalysis), CeO2/YSZ interfaces (strained thin films; solid oxide fuel cells/nanoionics), and Li-MnO2 (lithiation induced strain; energy storage).

The effect of anatase, rutile, and amorphous TiO 2 nanoparticles on the combustion of solid rocket propellant was investigated. Each additive increased the burning rate of propellant strands by 30%. Typical fast-burning propellants are unstable due to oversensitivity to pressure variations, but the anatase additive yielded propellants with high yet stable burning rates over a broad pressure range. Anatase nanoparticles also catalyzed the high-temperature decomposition of ammonium perchlorate, a key component of solid propellant.