Stabilization of Organic–Inorganic Perovskite Layers by Partial Substitution of Iodide by Bromide in Methylammonium Lead Iodide

Thin films of the methylammonium lead halides CH₃NH₃Pb(I_1?xBr_x)₃ are prepared on fluorine‐doped tin oxide substrates and exposed to humid air in the dark and under illumination. To characterize the stability of the materials, UV/Vis spectra are acquired at fixed intervals, accompanied by XRD, energy‐dispersive X‐ray spectroscopy, SEM, and confocal laser scanning microscopy. Different degradation mechanisms are observed depending on the environmental conditions. It is found that bromide can successfully suppress the transformation of the perovskite into the monohydrate, presumably owing to stronger hydrogen‐bonding interactions with the organic cation. However, under illumination in humid air, rather rapid decomposition of the perovskites was still observed, which is due to phase segregation. The use of increased bromide content in methylammonium lead halide absorbers is discussed in terms of their application in perovskite solar cells.     

表面高巯基功能化介孔材料的制备及对Hg~(2+)的吸附性能

在酸性条件下,以三嵌段非离子表面活性剂P123为模板剂,四氧基硅烷(TEOS)预水解后与3-巯基丙基三乙基硅(MPTES)共聚,合成了具有不同巯基官能团比例x[n(MPTES)/n(TEOS+MPTES)]的功能化介孔材料(SBA-SH-x),其结构和性能经FT-IR,元素分析,SEM,TEM,小角X-ray和N2吸附-脱附表征。结果表明:x10%,SBA-SH-x为六方p6mm介观结构;10%x15%,SBA-SH-x为立方Ia3d介孔结构;x20%,SBA-SH-x为无序结构。SBA-SH-x在水溶液中吸附Hg2+的研究结果表明:SBA-SH-10和SBA-SH-15对Hg~(2+)吸附性能较好。     

Synthesis of novel structurally simplified estrogen analogues

A library of 17 novel estrogen analogues 3 and 4 containing different substituents at rings A and D (steroid nomenclature) was prepared in a five- to seven-step synthesis. The key transformation is a Sonogashira-coupling of cyclic vinyl iodides of type 7 or 8 with phenylacetylenes of type 9. Reduction of the keto function in 3 led to the estradiol analogue 5.     

The reaction of SF5Br with select 1,2-dihaloethylenes

SF₅Br reacts with 1,2-haloethylenes (F, Cl, Br) in distinct ways. In the case of F- and Cl-olefins, the expected addition occurs while with 1,2-dibromoethylene a metathetical reaction yielding in a clean reaction a 1:1 mixture of SF₅CHCHBr and CHBr₂CHBr₂ is found. The mechanism for this reaction is discussed.     

Triton-B catalyzed,efficient one-pot synthesis of dithiocarbazates

A quick and efficient, one-pot synthesis of dithiocarbazates was accomplished in high yields by the reaction of various primary, secondary, and tert. alkyl halides with a variety of substituted hydrazines using the benzyl-trimethylammonium hydroxide (Triton-B)/CS₂ system. The reaction conditions are mild with simpler work-up procedures than the reported methods. Correspondence: Devdutt Chaturvedi, Medicinal and Process Chemistry Division, Central Drug Research Institute, Lucknow-226001, U.P., India.     

Electroanalytical Study of the Antioxidant and Antitumor Agent Curcumin

Curcumin (CU) shows a wide range of pharmacological properties including antioxidant, anti‐inflammatory, and antitumor effects. In order to understand the chemical basis of different activities of curcumin, we have studied the oxidation and reduction of curcumin. Based on cyclic and differential pulse voltammetric methods, using carbon paste and hanging mercury drop electrodes, in the present study we tested different parameters to optimize the conditions for the determination of curcumin and its electrochemical characteristics. Better results were obtained via differential pulse voltammetry using carbon paste electrode. Curcumin yields well‐defined differential pulse voltammetric responses with well‐defined oxidation (in the potential region of 0.3–0.6 V, vs. Ag/AgCl) and reduction (at 0.3 V) peaks using carbon paste electrode.