Coupled sorptive and oxidative antimony(III) removal by iron-modified biochar: Mechanisms of electron-donating capacity and reactive Fe species.

Sorption and oxidation are two potential pathways for the decontamination of trivalent antimony (Sb(III))-bearing water, using iron (Fe)-modified biochar (FeBC). Here we investigated the sorption and oxidation behavior of FeBC for Sb(III) in aqueous solutions. Results revealed that Sb(III) removal by FeBC was significantly improved showing the maximum Sb(III) sorption (64.0 mg g-1). Density functional theory (DFT) calculations indicated that magnetite (Fe3O4) in FeBC offered a sorption energy of -0.22 eV, which is 5 times that of non-modified biochar. With the addition of peroxymonosulfate (PMS), the sorption of Sb(III) on FeBC was 7 times higher than that on BC, indicating the sorption capacity of FeBC for Sb(III) could be substantially increased by adding oxidizing agents. Electrochemical analysis showed that Fe modification imparted FeBC higher electron-donating capacity than that of BC (0.045 v. s. 0.023 mmol e- (g biochar)-1), which might be the reason for the strong Sb(III) oxidation (63.6%) on the surface of FeBC. This study provides new information that is key for the development of effective biochar-based composite materials for the removal of Sb(III) from drinking water and wastewater. The findings from this study have important implications for protecting human health and agriculture.

Oxygen mediated oxidative couplings of flavones in alkaline water.

Catalyzed oxidative C-C bond coupling reactions play an important role in the chemical synthesis of complex natural products of medicinal importance. However, the poor functional group tolerance renders them unfit for the synthesis of naturally occurring polyphenolic flavones. We find that molecular oxygen in alkaline water acts as a hydrogen atom acceptor and oxidant in catalyst-free (without added catalyst) oxidative coupling of luteolin and other flavones. By this facile method, we achieve the synthesis of a small collection of flavone dimers and trimers including naturally occurring dicranolomin, philonotisflavone, dehydrohegoflavone, distichumtriluteolin, and cyclodistichumtriluteolin. Mechanistic studies using both experimental and computational chemistry uncover the underlying reasons for optimal pH, oxygen availability, and counter-cations that define the success of the reaction. We expect our reaction opens up a green and sustainable way to synthesize flavonoid dimers and oligomers using the readily available monomeric flavonoids isolated from biomass and exploiting their use for health care products and treatment of diseases.

Confinement of carbon dots localizing to the ultrathin layered double hydroxides toward simultaneous triple-mode bioimaging and photothermal therapy.

It is a great challenge to develop multifunctional nanocarriers for cancer diagnosis and therapy. Herein, versatile CDs/ICG-uLDHs nanovehicles for triple-modal fluorescence/photoacoustic/two-photon bioimaging and effective photothermal therapy were prepared via a facile self-assembly of red emission carbon dots (CDs), indocyanine green (ICG) with the ultrathin layered double hydroxides (uLDHs). Due to the J-aggregates of ICG constructed in the self-assembly process, CDs/ICG-uLDHs was able to stabilize the photothermal agent ICG and enhanced its photothermal efficiency. Furthermore, the unique confinement effect of uLDHs has extended the fluorescence lifetime of CDs in favor of bioimaging. Considering the excellent in vitro and in vivo phototherapeutics and multimodal imaging effects, this work provides a promising platform for the construction of multifunctional theranostic nanocarrier system for the cancer treatment.

Hydrogen bonding effect between active site and protein environment on catalysis performance in H2-producing [NiFe] hydrogenases.

The interaction between the active site and the surrounding protein environment plays a fundamental role in the hydrogen evolution reaction (HER) in [NiFe] hydrogenases. Our density functional theory (DFT) findings demonstrate that the reaction Gibbs free energy required for the rate determining step decreases by 7.1 kcal mol-1 when the surrounding protein environment is taken into account, which is chiefly due to free energy decreases for the two H+/e- addition steps (the so-called Ni-SIa to I1, and Ni-C to Ni-R), being the largest thermodynamic impediments of the whole reaction. The variety of hydrogen bonds (H-bonds) between the amino acids and the active site is hypothesised to be the main reason for such stability: H-bonds not only work as electrostatic attractive forces that influence the charge redistribution, but more importantly, they act as an electron 'pull' taking electrons from the active site towards the amino acids. Moreover, the electron 'pull' effect through H-bonds via the S- in cysteine residues shows a larger influence on the energy profile than that via the CN- ligands on Fe.

An Aluminum-Sulfur Battery with a Fast Kinetic Response.

The electrochemical performance of the aluminum-sulfur (Al-S) battery has very poor reversibility and a low charge/discharge current density owing to slow kinetic processes determined by an inevitable dissociation reaction from Al2 Cl7- to free Al3+ . Al2 Cl6 Br- was used instead of Al2 Cl7- as the dissociation reaction reagent. A 15-fold faster reaction rate of Al2 Cl6 Br- dissociation than that of Al2 Cl7- was confirmed by density function theory calculations and the Arrhenius equation. This accelerated dissociation reaction was experimentally verified by the increase of exchange current density during Al electro-deposition. Using Al2 Cl6 Br- instead of Al2 Cl7- , a kinetically accelerated Al-S battery has a sulfur utilization of more than 80 %, with at least four times the sulfur content and five times the current density than that of previous work.

An NIR-sensitive layered supramolecular nanovehicle for combined dual-modal imaging and synergistic therapy.

A supramolecular nanovehicle, denoted as ICG-DOX/Gd-LDH, was synthesized by the co-intercalation of indocyanine green (ICG) and doxorubicin hydrochloride (DOX) into a gallery of Gd3+-doped-layered double hydroxide (Gd-LDH) such that to achieve a chemo-photothermal synergistic therapeutic agent. The unique structure of Gd-LDH can not only stabilize the photothermal agent ICG to enhance the photothermal efficiency, but also hamper the recombination between electron and holes, leading to the generation of more reactive oxygen species (ROS) under irradiation in the NIR range. Together with the loading capacity of DOX, ICG-DOX/Gd-LDH exhibited excellent combinatorial effects on tumor growth inhibition in both in vitro studies on HeLa cell line and in vivo tests over tumor-bearing mouse models. Moreover, it showed ideal ability for long-term tracing of the carrier distribution via either MRI or fluorescence imaging. Thus, this study indicates that Gd-LDH is a promising platform for the construction of multifunctional formulations, especially theranostic nano-systems for cancer treatment.

Why is a proton transformed into a hydride by [NiFe] hydrogenases? An intrinsic reactivity analysis based on conceptual DFT.

The hydrogen evolution reaction (HER) catalysed by [NiFe] hydrogenases entails a series of chemical events involving great mechanistic interest. In an attempt to understand and delve into the question about 'Why does nature work in that way?', an in-depth intrinsic reactivity analysis based on conceptual DFT has been carried out focusing on the so-called to step, i.e. our work tries to answer how and why the proton attached to the reactive sulphur atom from one of the exo-cyclic cysteine residues is transformed into a bridging hydride to be shared between the Ni/Fe metals in the active site of [NiFe] hydrogenases, which involves not only H migration, but also a change of the charge state on Ni from Ni(i) to Ni(iii). Our DFT results suggest that the transformation is motivated by spontaneous rearrangements of the electron density, and stabilisation comes from the decrease of both electronic activity and electrophilicity index from Ni.

An intensified π-hole in beryllium-doped boron nitride meshes: its determinant role in CO2 conversion into hydrocarbon fuels.

DFT investigations on beryllium-doped boron nitride meshes or sheets (BNs) predict the existence of a very reactive kind of novel material capable of spontaneously reducing the first hydrogenation step in the CO2 conversion mechanism. This impressive behaviour appears as a result of the very deep π-hole generated by the beryllium moieties, and also determines its selectivity towards the production of CH4.