CH3NH3PbI3 from non-iodide lead salts for perovskite solar cells via the formation of PbI2.

We report the formation of CH3NH3PbI3 from more soluble, non-iodide lead salts like Pb(SCN)2 and Pb(NO3)2. When exposed to CH3NH3I vapours, the colourless lead salts turned yellow before the formation of the black perovskite. Investigation of this yellow intermediate suggests that anion exchange (converting lead salts to PbI2) precedes the perovskite formation. PCEs of 7.6% and 8.4% were achieved for the devices formed from Pb(SCN)2 and Pb(NO3)2, respectively.

The effect of heteroatom conformation on optoelectronic properties of cyclopentadithiophene derivatives.

Cyclopentadithiophene (CPDT) derivatives with different heteroatom conformations have been synthesized. The optical, electrochemical and charge transport properties of these molecules are reported. The CPDT-anti-ketone not only exhibits the lowest optical and electronic bandgaps, but also exhibits reasonable hole mobility, 3 × 10(-3) cm(2) (V s)(-1). Changing the carbonyl conformation to the syn position or incorporating the imine functionality results in a blue-shift in the lower energy band of the absorption spectrum indicative of the increased bandgaps.

Structural basis for the allosteric inhibitory mechanism of human kidney-type glutaminase (KGA) and its regulation by Raf-Mek-Erk signaling in cancer cell metabolism.

Besides thriving on altered glucose metabolism, cancer cells undergo glutaminolysis to meet their energy demands. As the first enzyme in catalyzing glutaminolysis, human kidney-type glutaminase isoform (KGA) is becoming an attractive target for small molecules such as BPTES [bis-2-(5 phenylacetamido-1, 2, 4-thiadiazol-2-yl) ethyl sulfide], although the regulatory mechanism of KGA remains unknown. On the basis of crystal structures, we reveal that BPTES binds to an allosteric pocket at the dimer interface of KGA, triggering a dramatic conformational change of the key loop (Glu312-Pro329) near the catalytic site and rendering it inactive. The binding mode of BPTES on the hydrophobic pocket explains its specificity to KGA. Interestingly, KGA activity in cells is stimulated by EGF, and KGA associates with all three kinase components of the Raf-1/Mek2/Erk signaling module. However, the enhanced activity is abrogated by kinase-dead, dominant negative mutants of Raf-1 (Raf-1-K375M) and Mek2 (Mek2-K101A), protein phosphatase PP2A, and Mek-inhibitor U0126, indicative of phosphorylation-dependent regulation. Furthermore, treating cells that coexpressed Mek2-K101A and KGA with suboptimal level of BPTES leads to synergistic inhibition on cell proliferation. Consequently, mutating the crucial hydrophobic residues at this key loop abrogates KGA activity and cell proliferation, despite the binding of constitutive active Mek2-S222/226D. These studies therefore offer insights into (i) allosteric inhibition of KGA by BPTES, revealing the dynamic nature of KGA's active and inhibitory sites, and (ii) cross-talk and regulation of KGA activities by EGF-mediated Raf-Mek-Erk signaling. These findings will help in the design of better inhibitors and strategies for the treatment of cancers addicted with glutamine metabolism.

Synthesis and properties of thienopyrrole based heteroacenes--indolodibenzothienopyrrole and dicarbazolodithienopyrrole.

We report the syntheses and properties of thienopyrrole based unsymmetrical and extended heteroacenes, which are isoelectronic with heptacene (30π) and nonacene (38π), respectively. Optical and electrochemical properties of these seven and nine rings fused systems are studied. The optoelectronic properties of the syn and anti-isomers of the unsymmetrical heteroacenes are also compared. The influence of the position of the heteroatoms in the fused corona, upon the optical and electrochemical properties, is rationalized based on the contributions from the benzenoid vs. quinonoid-type structures of these molecules.

Differential regulation of intracellular factors mediating cell cycle, DNA repair and inflammation following exposure to silver nanoparticles in human cells.

BACKGROUND: Investigating the cellular and molecular signatures in eukaryotic cells following exposure to nanoparticles will further our understanding on the mechanisms mediating nanoparticle induced effects. This study illustrates the molecular effects of silver nanoparticles (Ag-np) in normal human lung cells, IMR-90 and human brain cancer cells, U251 with emphasis on gene expression, induction of inflammatory mediators and the interaction of Ag-np with cytosolic proteins. RESULTS: We report that silver nanoparticles are capable of adsorbing cytosolic proteins on their surface that may influence the function of intracellular factors. Gene and protein expression profiles of Ag-np exposed cells revealed up regulation of many DNA damage response genes such as Gadd 45 in both the cell types and ATR in cancer cells. Moreover, down regulation of genes necessary for cell cycle progression (cyclin B and cyclin E) and DNA damage response/repair (XRCC1 and 3, FEN1, RAD51C, RPA1) was observed in both the cell lines. Double strand DNA damage was observed in a dose dependant manner as evidenced in γH2AX foci assay. There was a down regulation of p53 and PCNA in treated cells. Cancer cells in particular showed a concentration dependant increase in phosphorylated p53 accompanied by the cleavage of caspase 3 and PARP. Our results demonstrate the involvement of NFκB and MAP kinase pathway in response to Ag-np exposure. Up regulation of pro-inflammatory cytokines such as interleukins (IL-8, IL-6), macrophage colony stimulating factor, macrophage inflammatory protein in fibroblasts following Ag-np exposure were also observed. CONCLUSION: In summary, Ag-np can modulate gene expression and protein functions in IMR-90 cells and U251 cells, leading to defective DNA repair, proliferation arrest and inflammatory response. The observed changes could also be due to its capability to adsorb cytosolic proteins on its surface.

Novel on-site sample preparation approach with a portable agitator using functional polymer-coated multi-fibers for the microextraction of organophosphorus pesticides in seawater.

A novel on-site sample preparation approach for the organophosphorus pesticides (OPPs) using functional polymer-coated fibers with a portable agitation device has been developed and demonstrated. In this approach, a handheld battery-operated electric toothbrush was used to provide agitation of the sample solution at the sampling site to facilitate extraction. A functional conjugated polymer (2-(9,9-bis(6-bromo-2-ethylhexyl)9-H-fluoren-2-yl)benzene-1,4-diamine) was coated on commercial Technora fibers (each strand consisted of 1000 filaments, each of diameter ca. 9.23µm) which were then used for extraction. After extraction, the fibers were brought back to the laboratory in an icebox. The analytes were subsequently desorbed by organic solvent and the extract was analysed by gas chromatography-mass spectrometry. Six OPPs, triethylphosphorothiolate, thionazin, sulfotep, phorate, disulfoton and parathion were used as model compounds. Experimental parameters such as extraction time, desorption time, types of polymer fibers and fiber coatings as well the nature of desorption solvent were optimized in the laboratory prior to its on-site application of the procedure. Using optimum extraction conditions calibration curves were linear with correlation coefficient of 0.9748-0.9998 over the concentration range of 0.1-10µgl(-1). The method detection limits (at a signal-to-noise ratio of 3) were in the range of 0.3-30.3ngl(-1), which were lower than what could be achieved with solid-phase extraction performed at the laboratory. The proposed method was evaluated for the on-site extraction of OPPs in seawater samples.

Low band gap thiophene-perylene diimide systems with tunable charge transport properties.

Perylenediimide-pentathiophene systems with varied architecture of thiophene units were synthesized. The photophysical, electrochemical, and charge transport behavior of the synthesized compounds were studied. Both molecules showed a low band gap of ∼1.4 eV. Surprisingly, the molecule with pentathiophene attached via ß-position to the PDI unit upon annealing showed a predominant hole mobility of 1 × 10(-4) cm(2) V(-1) s(-1) whereas the compound with branched pentathiophene attached via ß-position showed an electron mobility of 9.8 × 10(-7) cm(2) V(-1) s(-1). This suggests that charge transport properties can be tuned by simply varying the architecture of pentathiophene units.

Synthesis and characterization of unsymmetric indolodithienopyrrole and extended diindolodithienopyrrole.

Indole-fused dithieno[3,2-b:2',3'-d]pyrrole-based unsymmetrical and extended heteroacenes were synthesized and characterized. Solid-state structures were examined using single-crystal X-ray diffraction to understand their packing behavior. The optical and electrochemical properties of these new heteroacenes are also described in detail.

Thiadiazole fused indolo[2,3-a]carbazole based oligomers and polymer.

Indolo[2,3-a]carbazole-based heteroacenes containing thiadiazole units were synthesized. Compounds showed a sandwich herringbone packing in solid state with improved stability. The change in photophysical and electrochemical properties upon incorporation of an acceptor moiety (benzothiadazole) in a fused ring system was studied. The unsubstituted compound was electropolymerized to yield a stable polymer.

Synthesis and properties of symmetric and unsymmetric dibenzothienopyrroles.

Symmetrical and unsymmetrical heteroacenes containing thiophene and pyrrole rings were synthesized. The unsymmetrical heteroacene was synthesized in two steps involving an unexpected palladium catalyzed amination of alkyl or aryl amines with benzo[b]thiophene followed by a copper catalyzed coupling. The symmetrical heteroacene was obtained by a palladium catalyzed amination reaction and also by a copper catalyzed amidation reaction. The crystal structure, photophysical and electrochemical properties of symmetrical and unsymmetrical heteroacenes are described.