Sequential use of regio- and stereoselective lipases for the efficient kinetic resolution of racemic 1-(5-phenylfuran-2-yl)ethane-1,2-diols

Possible routes for the enzymatic transformation of various substituted 1-(5-phenylfuran-2-yl)ethane-1,2-diols and their mono- and diacetylated counterparts were studied. Combining the regioselectivity of LPS mediated acylation of the starting racemic diols, the stereoselectivity of LAK shown in the enantiomer selective transformation of the previously formed racemic primary acetates and the LPS mediated mild hydrolysis-alcoholysis of the resolution products, an efficient preparative scale procedure for the synthesis of various highly enantiomerically enriched (R)- and (S)-phenylfuran-2-yl-ethane-1,2-diols has been developed.     

Preparation and characterization of zein/chitosan complex for encapsulation of α-tocopherol, and its in vitro controlled release study

Chitosan (CS) nanoparticles coated with zein has been newly demonstrated as a promising encapsulation and delivery system for hydrophilic nutrient with enhanced bioactivities in our previous study. In this study, a hydrophobic nutrient, α-tocopherol (TOC), was successfully encapsulated into zein/CS complex. The fabrication parameters, including zein concentration, zein/CS weight ratio, and TOC loading percentage, were systematically investigated. The physicochemical and structural analysis showed that the electrostatic interactions and hydrogen bonds were major forces responsible for complex formation. The scanning electron microscopy study revealed the spherical nature with smooth surface of complex. TOC encapsulation was also evidenced by differential scanning calorimetry. The particle size and zeta potential of the complex varied from 200 to 800 nm and +22.8 to +40.9 mV, respectively. The kinetic release profile of the TOC showed burst effect followed by slow release. Compared with zein nanoparticles, zein/CS complex provided better protection of TOC release against gastrointestinal conditions, due to CS coatings. Zein/CS complex is believed to be a promising delivery system for supplementation or treatment of hydrophobic nutrients or drugs.     

Multifunctional switching of a photo- and electro-chemiluminescent iridium-dithienylethene complex

Optical or electrochemical excitation of an Ir(iii) cyclometalated complex bearing photochromic and acid-sensitive dithienylethene ligands generates phosphorescence emission that can be switched on/off by light and chemical stimulation.     

Heats of formation of MHxCly (M = Si, P, As, Sb) compounds and main group fluorides from high level electronic structure calculations

Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for the MH(x)Cl(y) compounds (M = Si, P, As, and Sb) and for a number of trivalent, tetravalent, and pentavalent fluorides (SbF(3), BiF(3), GeF(4), SnF(4), PbF(4), AsF(5), SbF(5)) from coupled cluster theory (CCSD(T)) calculations using correlation consistent basis sets and extrapolation to the complete basis set limit. Small-core, relativistic effective core potentials were used for the heavier elements (Ge, As, Sn, Sb, Pb, and Bi), including correlation of the outer core electrons. Additional scalar relativistic (for the lighter elements) and atomic spin-orbit corrections are included in order to achieve near chemical accuracy of ±1.5 kcal/mol. Vibrational zero point energies were computed from scaled harmonic frequencies at the second order M?ller-Plesset perturbation theory (MP2) level where possible. Agreement between theory and the available experimental data is excellent. We present a revised heat of formation of the antimony atom in the gas phase. The calculated values will be of use in predicting the behavior of chemical vapor deposition systems.     

Umpolung reactions in an ionic liquid catalyzed by electrogenerated N-heterocyclic carbenes. Synthesis of saturated esters from activated α,β-unsaturated aldehydes

The umpolung reaction of α,β-unsaturated aldehydes to saturated esters has been carried out in an ionic liquid by organocatalysis of electrogenerated NHC. The roles of solvent, precatalyst and proton donor of the ionic liquid have been verified and good to high yields of esters have been obtained using a "green" and mild methodology.     

Differential resin-dentin bonds created after caries removal with polymer burs

The objective of this article was to investigate the effect of carbide and polymer burs caries removal methods on the bond strength of different adhesives to dentin. Resin restorations were performed in sound and caries-affected dentin, after using polymer or carbide burs and bonding with four different adhesive (Single bond, SB; Clearfil SE bond, SEB; FL-Bond II, FLB; and Fuji II-LC, FUJI). Microtensile bond strength (MTBS) was measured. Data were analyzed with ANOVA and Student-Newman-Keuls tests. Debonded surfaces were observed by scanning electron microscopy. Bonded interfaces were examined using light microscopy (Masson's trichrome staining). In sound dentin, MTBS was similar for SEB and SB, and higher than that of FLB and FUJI. Bond strength to carbide bur prepared dentin was similar for SB, SEB, and FLB; FUJI presented the lowest. SB applied on polymer bur excavated dentin presented similar values to those of the carbide bur group; MTBS attained by SEB, FLB, and FUJI decreased when bonding to dentin treated with polymer burs; FUJI yielded pretesting failures in all specimens. Polymer burs created a thick smear layer that was not infiltrated by tested self-etching agents. The bonding effectiveness of self-etching and glass-ionomer-like adhesives to dentin decreased when polymer burs were used.     

Sub-100 fs charge transfer in a novel donor-acceptor-donor triad organized in a smectic film

Ultrafast transient absorption spectroscopy is performed on a novel donor-acceptor-donor triad made of two identical bisthiophene derivatives as electron donors and a central perylenediimide moiety as electron acceptor. The triad is extended at both ends by covalently bound siloxane chains that confer self-organisation into thin smectic films at ambient temperature. When diluted in chloroform, selective excitation of the donor moiety leads to resonance energy transfer within 130 fs to the acceptor moiety, followed by the formation of a charge transfer (CT) state in ~3 ps. The CT state recombines entirely on a 55 ps time scale. In the liquid crystal films, excitonic intermolecular coupling leads to significant changes in the dynamics. Most remarkably, ultrafast intra- and intermolecular CT state formation occurs in about 60 fs, i.e. on a time scale comparable to electronic coherence times. While the intra-molecular CT states recombine on the same time scale as in solution or even faster, inter-molecular CT states live for about 1 ns. Last, triplet states of the perylenediimide moiety dominate the differential absorption after ~1 ns. We anticipate that the fast recombination of intra-molecular CT states and the triplet state formation may severely limit the photo-current in these materials.     

Aerosol-derived Ni(1-x)Zn(x) electrocatalysts for direct hydrazine fuel cells

This article reports the synthesis and performance of unsupported Ni(1-x)Zn(x) electrocatalysts for the oxidation of hydrazine in alkaline media. Characterization of these catalysts was achieved using XRD, SEM, and TEM to confirm phase compositions, crystal structures, and morphologies. High performance was observed for the α-Ni(0.87)Zn(0.13) and β(1)-Ni(0.50)Zn(0.50) electrocatalysts with an onset potential of -0.15 V (vs. RHE) and a mass activity of 4000-3800 A g(cat)(-1) at 0.4 V (vs. RHE), respectively. Additionally, in situ IRRAS studies were conducted to understand the mechanism of oxidation. These results demonstrate the feasibility of Ni(1-x)Zn(x) catalysts for direct hydrazine anionic fuel cells.     

TOF-SIMS investigation of degradation pathways occurring in a variety of organic photovoltaic devices - the ISOS-3 inter-laboratory collaboration

The present work is the fourth (and final) contribution to an inter-laboratory collaboration that was planned at the 3rd International Summit on Organic Photovoltaic Stability (ISOS-3). The collaboration involved six laboratories capable of producing seven distinct sets of OPV devices that were degraded under well-defined conditions in accordance with the ISOS-3 protocols. The degradation experiments lasted up to 1830 hours and involved more than 300 cells on more than 100 devices. The devices were analyzed and characterized at different points of their lifetimes by a large number of non-destructive and destructive techniques in order to identify specific degradation mechanisms responsible for the deterioration of the photovoltaic response. Work presented herein involves time-of-flight secondary ion mass spectrometry (TOF-SIMS) in order to study chemical degradation in-plane as well as in-depth in the organic solar cells. Various degradation mechanisms were investigated and correlated with cell performance. For example, photo-oxidation of the active material was quantitatively studied as a function of cell performance. The large variety of cell architectures used (some with and some without encapsulation) enabled valuable comparisons and important conclusions to be drawn on degradation behaviour. This comprehensive investigation of OPV stability has significantly advanced the understanding of degradation behaviour in OPV devices, which is an important step towards large scale application of organic solar cells.