Pyrazine-fused isoindigo: a new building block for polymer solar cells with high open circuit voltage.

Pyrazine-fused isoindigo (PzIIG) was designed and synthesized as a novel electron acceptor to construct two D-A conjugated polymers, PzIIG-BDT2TC8 and PzIIG-BTT2TC10. Both the polymers were successfully applied in polymer solar cells, and the PzIIG-BDT2TC8 based solar cell device exhibited a PCE of 5.26% with a high Voc over 1.0 V.

Conformation-controlled electron transport in single-molecule junctions containing oligo(phenylene ethynylene) derivatives.

Understanding the relationships between the molecular structure and electronic transport characteristics of single-molecule junctions is of fundamental and technological importance for future molecular electronics. Herein, we report a combined experimental and theoretical study on the single-molecule conductance of a series of oligo(phenylene ethynylene) (OPE) molecular wires, which consist of two phenyl-ethynyl-phenyl π units with different dihedral angles. The molecular conductance was studied by scanning tunneling microscopy (STM)-based break-junction techniques under different conditions, including variable temperature and bias potential, which suggested that a coherent tunneling mechanism takes place in the OPE molecular wires with a length of 2.5 nm. The conductance of OPE molecular junctions are strongly affected by the coupling strength between the two π systems, which can be tuned by controlling their intramolecular conformation. A cos(2)θ dependence was revealed between the molecular conductance and dihedral angles between the two conjugated units. Theoretical investigations on the basis of density functional theory and nonequilibrium Green's functions (NEGF) gave consistent results with the experimental observations and provided insights into the conformation-dominated molecular conductance.

A facile phosphine-free method for synthesizing PbSe nanocrystals with strong optical limiting effects.

PbSe semiconductor nanocrystals (NCs) have attracted ever-growing interest owing to both their fundamental physics and potential applications in a diverse range of fields such as optoelectronic devices and nonlinear optics. The current fabrication strategy for colloidal PbSe NCs, however, frequently involves acutely toxic reagents and tedious reaction procedures, and is plagued by products with poorly controlled size and morphology. Herein, we report a facile, low-cost, and phosphine-free method for synthesizing PbSe NCs, which provides highly uniform NCs with tunable mid-IR absorption, and they are promising for bio-related applications. These high quality NCs were obtained by the reaction of elemental Se and PbCl2 in oleylamine as both the ligand and reaction medium. The high flexibility and reproducibility of the method reported in this study allows us to synthesize monodispersed PbSe NCs with well-controlled size and morphology. In addition, these products show strong optical limiting effects, and thus hold potential for developing nonlinear optical devices.

Dimethyl 2,5-bis-(5-hexyl-thio-phen-2-yl)benzene-1,4-dioate.

In the title compound, C(30)H(38)O(4)S(2), the centroid of the benzene ring lies on a center of inversion. The thio-phene ring is aligned at 49.8 (1)° with respect to the benzene ring. The alkyl chain adopts an extended zigzag conformation.

A core-shell strategy for constructing a single-molecule junction.

Understanding the effects of intermolecular interactions on the charge-transport properties of metal/molecule/metal junctions is an important step towards using individual molecules as building blocks for electronic devices. This work reports a systematic electron-transport investigation on a series of "core-shell"-structured oligo(phenylene ethynylene) (Gn-OPE) molecular wires. By using dendrimers of different generations as insulating "shells", the intermolecular π-π interactions between the OPE "cores" can be precisely controlled in single-component monolayers. Three techniques are used to evaluate the electron-transport properties of the Au/Gn-OPE/Au molecular junctions, including crossed-wire junction, scanning tunneling spectroscopy (STS), and scanning tunneling microscope (STM) break-junction techniques. The STM break-junction measurement reveals that the electron-transport pathways are strongly affected by the size of the side groups. When the side groups are small, electron transport could occur through three pathways, including through single-molecule junctions, double-molecule junctions, and molecular bridges between adjacent molecules formed by aromatic π-π coupling. The dendrimer shells effectively prohibit the π-π coupling effect, but at the same time, very large dendrimer side groups may hinder the formation of Au-S bonds. A first-generation dendrimer acts as an optimal shell that only allows electron transport through the single-molecule junction pathway, and forbids the other undesired pathways. It is demonstrated that the dendrimer-based core-shell strategy allows the single-molecule conductance to be probed in a homogenous monolayer without the influence of intermolecular π-π interactions.

High spatial resolution label-free detection of antigen-antibody binding on patterned surface by imaging ellipsometry.

High spatial resolution and large area thickness mapping of label-free protein microarray has been achieved using imaging ellipsometry (IE) under optimized conditions. The protein patterns with feature size down to 8×8 µm(2) was readily imaged, and the binding between the surface immobilized antigen and the antibody was monitored. Quantitative thickness analysis of antibody-antigen binding on the 32×32 µm(2) micron spots was successfully performed, and we have obtained a limit of detection as low as 1.2 pg/spot. This work demonstrates that appropriately optimized IE could be used as a highly sensitive and high through-put label-free technique for studying surface antigen-antibody recognition in sub-40 µm scale.

Improving the anti-tumor effect of genistein with a biocompatible superparamagnetic drug delivery system.

The practical application of genistein as a low toxicity chemotherapeutic drug is hindered by many of its in vivo properties. To overcome these obstacles, a new multifunctional drug delivery system is developed, which is based on covalently attaching genistein onto Fe3O4 nanoparticles coated by cross-linked carboxymethylated chitosan (CMCH). The structure of the Fe3O4-CMCH-genistein nano-conjugate was confirmed by transmission electron micrographs (TEM), X-ray diffraction (XRD) and Fourier-transfer infrared (FT-IR) spectroscopy. The nano-conjugate shows good water solubility and superparamagnetic properties with a saturation magnetization of 55.1 emu/g. The effects of free genistein and FeO4-CMCH-genistein nano-conjugate on the proliferation and apoptosis of gastric cancer cell line SGC-7901 were investigated by MTT assay and flow cytometry (FACS). MTT results indicate that the Fe3O4-CMCH-genistein nano-conjugate exhibits a significantly enhanced inhibition effect to the SGC-7901 cancer cells than the free genistein. FACS data suggests that the inhibition on cell proliferation of the nano-conjugate is related with an induced apoptosis process. This drug delivery system is promising for future multifunctional chemotherapeutic application that combines drug release and magnetic hyperthermia therapy.

2-(Naphthalen-2-yl)azulene.

In the title compound, C(20)H(14), a naphthalene ring system is linked at the 2-position to the 2-C atom of the five-membered ring of an azulene unit. The compound crystallizes with two reasonably similar mol-ecules in the asymmetric unit. Neither mol-ecule is perfectly planar: the r.m.s. deviations from the best fit planes through all non-H atoms are 0.092 and 0.091 Šfor the two mol-ecules. The dihedral angle between the mol-ecular planes is 49.60 (4)°. The naphthalene and azulene ring systems are inclined at dihedral angles of 6.54 (12) and 5.68 (12)° in the two mol-ecules. The crystal structure exhibits two sets of parallel layers, a typical edge-to-face herringbone packing arrangement. The structure is stabilized by an extensive series of weak C-H⋯π inter-actions.