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231.
    
Additives are one of the important means to improve the performance of perovskite solar cells. To explore the effects of different addition methods on the crystallinity of perovskite, in this paper, guanidine thiocyanate (GASCN) is added in three different methods, i.e., added in SnO2 precursor solution; in PbI2 precursor solution; or FAI precursor solution, respectively. The guanidine hydroiodide (GAI) and methylamine thiocyanate (MASCN) are selected as contrast additives to evaluate the role of GA+ and SCN−. Though the efficiency and stability of the perovskite solar cells with all additives are improved, the systematic study by grazing incidence wide-angle X-ray scattering (GIWAXS), quasi-in situ GIWAXS, and in situ X-ray diffraction (XRD) proved that the mechanism by the three different addition methods behaved in many different ways, which corresponded, respectively, to the surface of the SnO2 electron transport layer, dominance orientation especially vertical growth of perovskite, or low-dimensional perovskite structure. This provides a new view for optimizing the appropriate synthesis conditions in the future.  相似文献   
232.
    
Upon activation with diethylaluminium chloride (Et2AlCl), a series of phenyl‐substituted α‐diimine nickel precatalysts conducted 4‐methyl1pentene (4MP) and ethylene (E) (co)polymerizations via controlled chain‐walking to generate branched amorphous polymers with high molecular weight and narrow molecular weight distribution (Mw/Mn < 1.6). The obtained poly(4MP)s were amorphous elastomers with glass transition temperature (Tg) of ?10 ~ ?24 °C, which are higher than that of E‐4MP copolymer ( ? 63.0 °C). At room temperature (25 °C), 4MP polymerization proceeds in a living manner. The microstructures of the produced poly(4MP)s indicated the 2,1 and 1,2insertion followed by chain‐walking, the latter being predominant. The NMR analyses of the polymers showed that the obtained poly(4MP) possessed methyl, isobutyl, 2,4dimethylpentyl and 2methylhexyl groups, while the isobutyl and 2,4dimethylalkyl branches derived from 4MP were observed in the E‐4MP copolymer. The branch structures and the insertiontype of monomer were depended on the polymerization temperature, and the content of methyl branch increased with an increase in the polymerization temperature.  相似文献   
233.
    
Multisubstituted arenes such as indanes with attached all‐carbon quaternary centers are unique scaffolds in synthetic functional molecules and sophisticated natural products. A key challenge in preparing such molecules lies in the enantioselective installation of the quaternary carbon centers. Conventional methods in this direction include asymmetric substitution reactions and substrate‐controlled cyclization reactions. These reactions lead to poor stereoselectivities and/or require long and tedious synthetic steps. Disclosed here is a one‐step organic catalytic strategy for enantioselective access to this class of molecules. The reaction involves an N‐heterocyclic carbene catalyzed process for direct benzene construction, indane formation, remote‐carbon desymmetrization, and excellent chirality control. This approach will enable the concise synthesis of arene‐containing molecules, including those with complex structures and challenging chiral centers.  相似文献   
234.
    
A new cosensitization photoelectrochemical (PEC) strategy was established by using a donor–acceptor-type photoactive material, poly{4,8-bis[5-(2-ethylhexyl)thiophen-2-yl]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophene-4,6-diyl} (PTB7-Th), as a signal indicator, which was cosensitized with bis(4,4′dicarboxyl-2,2′-bipyridyl)(4,5,9,14-tetraazabenzo[b]triphenylene)ruthenium(II) ([Ru(dcbpy)2dppz]2+) embedded in the grooves of the DNA duplex and fullerene (nano-C60) immobilized on the surface of DNA nanoflowers for microRNA assay. [Ru(dcbpy)2dppz]2+ and nano-C60 could effectively enhance the photoelectric conversion efficiency (PCE) of PTB7-Th as a result of well-matched energy levels among nano-C60, [Ru(dcbpy)2dppz]2+ and PTB7-Th, leading to a clearly enhanced photocurrent signal. Meanwhile, a target recycling magnification technique based on duplex-specific nuclease was applied in this work to obtain higher detection sensitivity. The proposed biosensor demonstrated excellent analytical properties within a linear detection range of 2.5 fm to 2.5 nm and a limit of detection down to 0.83 fm . Impressively, this cosensitization PEC strategy offers an effective and convenient avenue to significantly improve the PCE of a photoactive material, resulting in a remarkably improved photocurrent signal for ultrasensitive and highly accurate detection of various targets.  相似文献   
235.
    
Conductive hydrogels with ionic compounds possess great potential for the development of soft smart devices. A dielectric scarfskin is typically required for these devices to prevent short circuiting, leading to devices with lower stretchability than the hydrogel. Henceforth, commonly used dielectric materials, such as PDMS and Ecoflex, cannot be largely stretched. Hydrogel devices with ultrastretchability are required to accommodate hostile application environments. Herein, we propose a hydrogel fiber coated with a dielectric layer that can be stretched to over 2000% of its initial length. The fiber remains conductive when stretched to ~1300%. In addition, the core/sheath hydrogel fiber can be endowed with a variety of functional properties, such as electroluminescence (EL), photoluminescence (PL), and magnetic‐responsiveness, demonstrating scalability of the resultant fiber. The present work can pave the way for numerous next‐generation soft devices, such as smart textiles and wearable electronics. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 272–280  相似文献   
236.
    
The realization of water electrolysis on the basis of highly active, cost-effective electrocatalysts is significant yet challenging for achieving sustainable hydrogen production from water. Herein, N-doped Ni3S2/N-doped MoS2 1D hetero-nanowires supported by Ni foam (N-Ni3S2/N-MoS2/NF) are readily synthesized through a chemical transformation strategy by using NiMoO4 nanowire array growth on Ni foam (NiMoO4/NF) as the starting material. With the in situ generation of Ni3S2/MoS2 heterointerfaces within nanowires and the incorporation of N anions, an extraordinary hydrophilic nature with abundant, well-exposed active sites and optimal reaction dynamics for both oxidation and reduction of water are obtained. Attributed to these properties, as-converted N-Ni3S2/N-MoS2/NF exhibits highly efficient electrocatalytic activities for both hydrogen and oxygen evolution reactions under alkaline conditions. The superior bifunctional properties of N-Ni3S2/N-MoS2/NF enable it to effectively catalyze the overall water-splitting reaction.  相似文献   
237.
    
In this work, a novel sandwich‐type electrochemical immunosensor with electroactive nickel hexacyanoferrate nanoparticles (NiHCFNPs) as matrix was constructed for α‐fetoprotein (AFP) detection in a signal‐off manner by using FeS2?AuNPs nanocomposite catalyzed insoluble precipitation to significantly inhibit the electrochemical signal. Initially, the NiHCFNPs with excellent electrochemical property was modified on the electrodeposited nano‐Au electrode to obtain a strong initial electrochemical signal. Subsequently, another nano‐Au layer was formed for immobilization of capture antibody (Ab1). In the presence of target AFP, the prepared FeS2?AuNPs‐Ab2 bioconjugate could be specifically recognized and immobilized on electrode through the sandwich‐type immunoreaction. The FeS2 with large specific surface areas were used as scaffolds to load abundant mimicking enzyme AuNPs. With the help of hydrogen peroxide (H2O2), FeS2?AuNPs with peroxidase‐like activity accelerated the 4‐chloro‐1‐naphthol (4‐CN) oxidation with generation of insoluble precipitation on electrode, which would greatly hinder the electron transfer and thus caused the decrease of electrochemical signal for quantitative determination of AFP. This approach achieved a wide dynamic linear range from 0.0001 to 100 ng mL?1 with an ultralow limit detection of 0.028 pg mL?1. Especially, the proposed AFP immunosensor can be applied to detect human serum samples with satisfactory results, indicating a potential application in clinical monitoring of tumor biomarkers.  相似文献   
238.
239.
    
Two mononuclear Pt(II) complexes, Pt(dbbpy)Cl2 (1) and [Pt(dbbpy)2](PF6)2 (2) (dbbpy?=?4,4′-ditertbutyl-2,2′-biyridine) were synthesized and characterized by single-crystal X-ray diffraction analysis, elemental analysis, 1H NMR, and ESI–MS. Their binding affinities for both double-stranded (DS) calf thymus DNA (ct-DNA) and G-quadruplex DNA (HT21 and BCL-2) were investigated. In addition to structural differences, complex 1 displayed higher binding affinity for DS ct-DNA, whereas positively charged complex 2 was selective for binding to G-quadruplex DNA over DS DNA. The time-dependent cleavage of supercoiled circular plasmid pBR322 DNA by 1 was observed using agarose gel electrophoresis, whereas complex 2 hardly cleaved DS DNA. Stabilization of G-quadruplex HT21 DNA by both complexes was assessed by PCR stop assays. Both complexes exhibited moderate activities for inhibition of topoisomerase I as well as modest antiproliferation activities toward cancer cells in CKK-8 assays.  相似文献   
240.
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