RSC Advances

Kang, Baotao; Liu, Hongguang; Jang, Du-Jeon; Lee, Jin Yong

doi: 10.1039/c4ra00974fpmid: N/A

In this paper, first-principles calculations were performed regarding the electric field effect on the ground state proton transfer (GSPT) in the H-bonded p-hydroxybenzylideneimidazolidinone (HBDI) network that represents the active site of the green fluorescent protein (GFP). Potential energy surfaces (PESs) in the absence or presence of electric fields were obtained using DFT calculations with the functional CAM-B3LYP. Surprisingly, it was found that the magnitude of the equilibrium constant (K) under the electric fields can be closely fitted to a linear relationship. The concerted and asynchronous proton transfer mechanism in field free conditions can be altered by the electric field. Moreover, the electric field parallel to the x axis (Fx) has the strongest effect on the absorption energy of both the neutral and anionic HBDI complexes. Our results demonstrate that the electric field can be used for the rational design of GFP mutants with desirable properties.

Sheppard, D. A.; Corgnale, C.; Hardy, B.; Motyka, T.; Zidan, R.; Paskevicius, M.; Buckley, C. E.

doi: 10.1039/c4ra01682cpmid: N/A

A simplified techno-economic model has been used as a screening tool to explore the factors that have the largest impact on the costs of using metal hydrides for concentrating solar thermal storage. The installed costs of a number of paired metal hydride concentrating solar thermal storage systems were assessed. These comprised of magnesium-based (MgH2, Mg2FeH6, NaMgH3, NaMgH2F) high-temperature metal hydrides (HTMH) for solar thermal storage and Ti1.2Mn1.8H3.0 as the low-temperature metal hydride (LTMH) for hydrogen storage. A factored method approach was used for a 200 MWel power plant operating at a plant capacity factor (PCF) of 50% with 7 hours of thermal storage capacity at full-load. In addition, the hydrogen desorption properties of NaMgH2F have been measured for the first time. It has a practical hydrogen capacity of 2.5 wt% (2.95 wt% theoretical) and desorbs hydrogen in a single-step process above 478 °C and in a two-step process below 478 °C. In both cases the final decomposition products are NaMgF3, Na and Mg. Only the single-step desorption is suitable for concentrating solar thermal storage applications and has an enthalpy of 96.8 kJ mol−1 H2 at the midpoint of the hydrogen desorption plateau. The techno-economic model showed that the cost of the LTMH, Ti1.2Mn1.8H3.0, is the most significant component of the system and that its cost can be reduced by increasing the operating temperature and enthalpy of hydrogen absorption in the HTMH that, in turn, reduces the quantity of hydrogen required in the system for an equivalent electrical output. The result is that, despite the fact that the theoretical thermal storage capacity of NaMgH2F (1416 kJ kg−1) is substantially lower than the theoretical values for MgH2 (2814 kJ kg−1), Mg2FeH6 (2090 kJ kg−1) and NaMgH3 (1721 kJ kg−1), its higher enthalpy and operating temperature leads to the lowest installed cost of the systems considered. A further decrease in cost could be achieved by utilizing metal hydrides with yet higher enthalpies and operating temperatures or by finding a lower cost option for the LTMH.

Wan, Wen; Gao, Wei; Ma, Guobin; Ma, Lei; Wang, Fan; Wang, Jing; Jiang, Haizhen; Zhu, Shizheng; Hao, Jian

doi: 10.1039/c4ra03362kpmid: N/A

A class of chiral bifunctional N-prolyl sulfinamide and its TFA salts were prepared and proven to be effective for catalyzing the aldol reaction under solvent-free conditions. In general, the corresponding aldol adducts were obtained with high to excellent yields, and satisfactory diastereo-selectivities and enantioselectivities. A matching effect between chiral proline and sulfinamide moieties was observed in the catalysts. The enantioswitching of both enantiomers in the asymmetric aldol synthesis is found to be dominated by the prolyl moiety.

Copolovici, Dana; Isaia, Francesco; Breunig, Hans J.; Raţ, Ciprian I.; Silvestru, Cristian

doi: 10.1039/c4ra03482apmid: N/A

The chiral compound (2-Me2NCH2C6H4)PhSbCl (1) was obtained from (2-Me2NCH2C6H4)Li and PhSbCl2 in 1 : 1 molar ratio, while (2-Me2NCH2C6H4)Mes2Sb (2) was prepared from (2-Me2NCH2C6H4)SbCl2 and MesMgBr in 1 : 2 molar ratio. The compounds 1 and 2 were used to obtain the Pd(ii)/stibine complexes: [Me2NHCH2C6H5]+[PdCl3{SbCl(Ph)(C6H4CH2NMe2-2)-Sb}]− (3) and [PdCl2{SbMes2(C6H4CH2NMe2-2)-N,Sb}] (4). All the compounds were characterized by multinuclear NMR spectroscopy in solution, elemental analysis, mass spectrometry and single-crystal X-ray diffraction studies. In compounds 1–3 the coordination geometry around the antimony atom is pseudo-trigonal bipyramidal, while in compound 4 a tetrahedral geometry around the antimony atom is observed. Theoretical calculations at the DFT level on compounds 1–4 were used in order to gain insight into the nature of the coordinative bonds.

Hu, Jing; Wu, Shujie; Liu, Heng; Ding, Hong; Li, Zhifang; Guan, Jingqi; Kan, Qiubin

doi: 10.1039/c4ra03945apmid: N/A

A series of micro-mesoporous molecular sieves TNU-9-x (TNU-9 Taejon National University no. 9) were prepared by a hydrothermal reaction method for non-oxidative aromatization of methane. The physical properties of the synthesized samples were characterized by XRD, SEM, TEM, BET, NH3-TPD and FT-IR spectroscopy. Characterization results suggested that the micro-mesoporous molecular sieves TNU-9-x exhibited similar geometrical shapes, but different pore properties with conventional microporous molecular sieve TNU-9. Catalytic tests indicated that Mo–TNU-9-20 showed excellent catalytic performance with a 14.9% conversion of methane and a 9.9% yield of aromatics. In addition, the catalytic stability of Mo–TNU-9-20 was better than the conventional microporous material Mo–TNU-9. The improved catalytic behaviour might be attributed to the generation of a secondary mesoporous system within the hierarchical pore materials.

Pal, Sanchari; Chatterjee, Nabanita; Bharadwaj, Parimal K.

doi: 10.1039/c4ra02054epmid: N/A

Transition metal ions, especially the first-row ones are ubiquitous in nature and they perform many biological functions. However, high accumulation of these ions can be quite detrimental to health. Their spatial distribution with high fidelity inside as well as outside cells is, therefore, of paramount importance. In addition to biological sensing, fluorescence enhancement by transition metal ions can be potentially useful in other areas of science. However, most of the transition metal ions are paramagnetic and they very effectively quench fluorescence. Surmounting this problem of fluorescence quenching, a number of systems have been reported which are the topic of the present review.

Chaitanya, Kadali; Ju, Xue-Hai; Heron, B. Mark

doi: 10.1039/c4ra02473gpmid: N/A

The density functional theory and time-dependent density functional theory calculations of the electronic structures and electronic absorption spectra of a series of zinc porphyrin based sensitizers were reported. The sensitizers comprise of either 10H-phenothiazin-3-yl or bis(4-(hexyloxy)phenyl)amino and acene bridged carboxylic acid as electron donating and accepting units, respectively. The dye–(TiO2)36 anatase nanoparticle systems were also simulated to show the electronic structure on the interface. The calculated results show that a strong electron-donating capacity of the donor group attached at the meso-position opposite to the anchoring group of the dye will increase the molecular extinction coefficient, excited state lifetime, light harvesting efficiency and decrease the reorganization energy as compared to the structurally similar reference dye YD2-o-C8. The calculated short circuit current density and level alignment quality clearly indicate that the zinc-porphyrin dyes substituted with 10H-phenothiazin-3-yl donor and either 4-ethynylbenzoic acid or 4-ethynyl-1-naphthoic acid offer potential for use in DSSCs due to their large values when compared to the reference dye. The results obtained in this study will certainly provide a useful reference to the future design of tetra-substituted zinc porphyrins for dye sensitized solar cell applications.

Beard, J. D.; Aleksandrov, S.; Walker, C. H.; Wolverson, D.; Mitchels, J. M.; Gordeev, S. N.

doi: 10.1039/c4ra02841dpmid: N/A

Diamond-like carbon (DLC) films are widely used as protective coatings in a variety of technical macro- and micro-applications. However, most of the widely-used coating methods are not suitable for nanoscale applications. In this work, the method of magnetically enhanced plasma deposition (MEPCVD) was employed for the coating of AFM probes and free-standing nanostructures with 3–20 nm thick DLC films. The carbon bonding structure, mechanical and tribological properties of the films as well as the anisotropy of the coatings and its effect on the shape of nanoscale features were investigated and it is shown that the method employed produces very smooth coatings (roughness below 0.2 nm) with a significantly lower than usual internal stress of 0.5–0.8 GPa. Wear tests of AFM probes at a high load (1 μN) showed that the DLC coating decreases their wear rate by two orders of magnitude. It was found that coating of free-standing nanostructures even with ultrathin DLC films may cause their deformation due to the interface stress when the coating is asymmetric.

Michel, R.; Ammar, M. R.; Véron, E.; Simon, P.; Poirier, J.

doi: 10.1039/c4ra01238kpmid: N/A

A framework is presented to define the formation and migration mechanisms of oxides in olivine during their phase transformations at high temperature. The behaviour of olivine particles has been investigated at 1400 °C at two different residence times: 4 h and 115 h. The structural and vibrational properties of the resulting materials were analysed using both X-ray diffraction (notably, in situ X-ray diffraction) and Raman spectroscopy including its mapping mode. The measurements have shown the migration of magnetite and enstatite from the inner part of olivine particles towards the surface, which results in the alteration of the solid solution and the intergranular reaction of particles. These results contribute to a better knowledge of olivine material science, in particular, in the areas of catalysis, refractories and engineering.

Jiang, Liqing; Li, Meng; Lin, Lin; Li, Yongfeng; He, Xingquan; Cui, Lili

doi: 10.1039/c4ra02208dpmid: N/A

A series of non-noble-metal catalysts for oxygen reduction reaction (ORR), based on metal 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (M-THPP, M: Fe3+, Co2+, Ni2+, Mn2+) grown on poly(sodium-p-styrenesulfonate) modified reduced graphene oxide (PSS-rGO), were fabricated using an in situ solvothermal synthesis method. The morphology of the M-THPP/PSS-rGO was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Ultraviolet-visible (UV-vis) absorption spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques were utilized to analyse the unusual interactions between the metalloporphyrins and graphene sheets. Electrochemical measurements using rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) techniques were employed to study the catalytic activity and the mechanism of the oxygen reduction reaction on the as-synthesised M-THPP/PSS-rGO catalysts in an alkaline medium. The half-wave potential for the ORR on the CoTHPP/PSS-rGO catalyst was found to be around −0.22 V vs. SCE, which was much higher than those on the other M-THPP/PSS-rGO catalysts and similar to that on Pt/C (−0.20 V vs. SCE). RDE and RRDE results show that the ORR process proceeds mainly via an almost 4-electron pathway on CoTHPP/PSS-rGO. The catalyst stability tests disclose that the CoTHPP/PSS-rGO is much more stable than the other M-THPP/PSS-rGO composites. The assembled CoTHPP/PSS-rGO catalyst possesses high activity, good long-term stability, excellent tolerance to the crossover effect of methanol and a facile 4-electron pathway for ORR, which could be used as a promising Pt-free catalyst in an alkaline direct methanol fuel cell.