Carbon K-edge XANES spectromicroscopy of natural graphite

Roles of surface chemistry and structural defects of activated carbons in the oxidative desulfurization of benzothiophenes

“…As before, the virgin C K-NEXAFS spectrum features broad transitions at 285 eV (assigned to C@C p ⁄ sites in graphitic structures) and 292.4 eV (assigned to CAC r ⁄ bonds indicative of long-range order) [91]. In addition, the weak 288.5 eV peak is likely due to the presence of carboxylic acid species or other bearing oxygen species such as CAO or C@O [91][92][93][94][95]. As expected, treatment with acetonitrile had minimal effect on the NEXAFS spectra; this test was performed as a control because acetonitrile was used in the following tests to remove residual weakly adsorbed volatile compounds from the carbon prior to NEAXAFS measurement.…”

Organic matter heterogeneities in 2.72Ga stromatolites: Alteration versus preservation by sulfur incorporation

“…Regarding the oxygen-bearing carbon functional groups, two origins are possible. First, they may result from secondary oxidation of organic matter, possibly during sample storage and/or preparation (Salmon et al, 2000;Brandes et al, 2008). Alternatively, these functional groups may not be artefacts but preserved chemical features of the Tumbiana organic matter: carboxyls, ketones and phenols have similarly been observed in carbonaceous fossils that experienced high-grade metamorphism and have been interpreted as remnants of primary chemical features based on a close similarity of the chemistry of the fossils with that of modern analogs (Bernard et al, 2007).…”

“…This lightly metamorphosed organic matter may thus have preserved heteroatoms as organic sulfur as well as aliphatic carbon and oxygen-bearing groups, although the latter might represent a secondary oxidation artefact (Salmon et al, 2000;Brandes et al, 2008). Heteroatoms are generally poorly preserved through metamorphism (Rouxhet et al, 1980;Lis et al, 2005).…”

Flux of Dissolved and Particulate Low-Temperature Pyrogenic Carbon from Two High-Latitude Rivers across the Spring Freshet Hydrograph

“…At the highest range of the temperature continuum (>500 • C), PyC is characterized by increasing graphene-like structures in highly condensed turbostratic aromatics, marked by the increase in condensation levels of molecular markers such as BPCAs (Keiluweit et al, 2010;Schneider et al, 2011). This PyC-derived turbostratic carbon is relatively unordered (Nguyen et al, 2010) and is therefore structurally different than graphite found in natural environments, which is derived from high temperature and pressure conditions (such as within metamorphic rock) and is likely more ordered and highly crystalline (Brandes et al, 2008). High-temperature PyC can also be formed from the condensation of gas-phase intermediates (i.e., soot carbon; Schmidt and Noack, 2000;Hammes et al, 2007).…”