The low-spin end-on ferric peroxo heme intermediate has been proposed as an alternative reactive intermediate involved in the catalytic cycles of enzymes such as nitric oxide synthase and cytochrome P450. This transient heme intermediate has never been captured using synthetic heme models. We demonstrate herein our success in the solution preparation of such an end-on ferric peroxo intermediate derived from a heme model, which features both a group hanging over the porphyrin macrocycle and a covalently appended axial imidazole ligand, through one-electron reduction of its ferric superoxo precursor. The obtained ferric peroxo intermediate was further transformed into the corresponding ferric hydroperoxo species upon protonation. This heme model compound provides a convenient system for sequential preparation of the important and biologically relevant superoxo/peroxo/hydroperoxo heme intermediates through an oxygenation/one-electron reduction/protonation process similar to the mechanisms used by enzyme systems.

Atomic-scale defects/disorded states induced by sulfur sublimation are responsible for reduced lattice thermal conductivity of thermoelectric colusite.

Natural organic matter (NOM) is a heterogeneous mixture of organic compounds that is omnipresent in natural waters. To date, the understanding of the adsorption of NOM components by carbon nanotubes (CNTs) is limited because of the limited number of comprehensive studies in the literature examining the adsorption of NOM by CNTs. In this study, 11 standard NOM samples from various sources were characterized, and their adsorption behaviors on four different CNTs were examined side-by-side using total organic carbon, fluorescence, UV-visible spectroscopy, and high-performance size-exclusion chromatography (HPSEC) analysis. Adsorption was influenced by the chemical properties of the NOM, including aromaticity, degree of oxidation, and carboxylic acidity. Fluorescence excitation-emission matrix (EEM) analysis showed preferential adsorption of decomposed and terrestrial-derived NOM compared to freshly produced and microbial-derived NOM. HPSEC analysis revealed preferential adsorption of fractions in the molecular weight range of 0.5-2 kDa for humic acids but in the molecular weight range of 1-3 kDa for all fulvic acids and reverse-osmosis isolates. However, the smallest characterized fraction (MW < 0.4 kDa) in all samples did not adsorb on the CNTs.

No abstract