Fermi level engineering of single-walled carbon nanotubes by AuCl3 doping

We investigated the modulation of optical properties of single-walled carbon nanotubes (SWCNTs) by AuCl 3 doping. The van Hove singularity transitions (E 11 (S), E 22 (S), E 11 (M)) in absorption spectroscopy disappeared gradually with an increasing doping concentration and a new peak appeared at a high doping concentration. The work function was downshifted up to 0.42 eV by a strong charge transfer from the SWCNTs to AuCl 3 by a high level of p-doping. We propose that this large work function shift forces the Fermi level of the SWCNTs to be located deep in the valence band, i.e., highly degenerate, creating empty van Hove singularity states, and hence the work function shift invokes a new asymmetric transition in the absorption spectroscopy from a deeper level to newly generated empty states.     

Polyoxometalate-Cyclodextrin-Based Cluster-Organic Supramolecular Framework for Polysulfide Conversion and Guest–Host Recognition in Lithium-sulfur Batteries

Developing polyoxometalate-cyclodextrin cluster-organic supramolecular framework (POM-CD-COSF) still remains challenging due to an extremely difficult task in rationally interconnecting two dissimilar building blocks. Here we report an unprecedented POM-CD-COSF crystalline structure produced through the self-assembly process of a Krebs-type POM, [Zn₂(WO₂)₂(SbW₉O₃₃)₂]¹⁰⁻, and two β-CD units. The as-prepared POM-CD-COSF-based battery separator can be applied as a lightweight barrier (approximately 0.3 mg cm⁻²) to mitigate the polysulfide shuttle effect in lithium-sulfur batteries. The designed Li−S batteries equipped with the POM-CD-COSF modified separator exhibit remarkable electrochemical performance, attributed to fast Li⁺ diffusion through the supramolecular channel of β-CD, efficient polysulfide-capture ability by the dynamic host–guest interaction of β-CD, and improved sulfur redox kinetics by the bidirectional catalysis of POM cluster. This research provides a broad perspective for the development of multifunctional supramolecular POM frameworks and their applications in Li−S batteries.     

Excellent flame retardancy and air stability through surface coordination of few-layer black phosphorus with TiL4 in epoxy resin

Black phosphorus (BP) has been attractive for many research groups as its promising properties. However, the poor air stability of BP has limited its practical applications. To simultaneously address this problem and improve the flame retardancy of BP in epoxy resin (EP), a surface coordination strategy was proposed. Herein, a titanium ligand (denoted as TiL₄) was designed to coordinate BP nanosheets, which can occupy the lone pair electrons of BP. The Ti–P coordination contributed to the improvement of ambient stability of BP. The serious degradation was observed from pure BP owing to the oxidation. Whereas, the surface coordination can impede the ambient degradation rate of BP by 74.07%. With the addition of 1.5 wt% TiL₄@BP, the char yield of EP nanocomposites was increased by 20.55% due to the catalytic charring effect of TiL₄@BP. The incorporation of 1.5 wt% TiL₄@BP can reduce the peak of heat release rate and total heat release values of EP by 29.41% and 23.32%. The EP/TiL₄@BP 1.5 also can pass the UL-94 V-0 rating, and its value of limiting oxygen index was enhanced by 13.60%. The improvement in the flame retardancy of BP in EP can be largely ascribed to synergistic catalytic charring effects between BP and TiL₄. The condense and compact char layer can act as a physical barrier to restrict the exchange of pyrolytic products and the transfer of heat. In addition, the free radical quenching effect of BP nanosheets also accounted for the excellent flame retardant performance of EP. This work proposed a reference for synchronically obtaining the improvement for the air stability and flame retardant performance of BP.     

Charge Separation in Metal-Organic Framework Enables Heterogeneous Thiol Catalysis

Photoinduced metal–organic framework (MOF) enabled heterogeneous thiol catalysis has been achieved for the first time. MOF Zr-TPDCS-1 , consisting of Zr₆-clusters and TPDCS linkers (TPDCS=3,3′′,5,5′′-tetramercapto[1,1′:4′,1′′-terphenyl]-4,4′′-dicarboxylate), effectively catalyzed the borylation, silylation, phosphorylation, and thiolation of organic molecules. Upon irradiation, the fast electron transfer from TPDCS to Zr₆-cluster is believed to facilitate the formation of the thiyl radical, a hydrogen atom transfer catalyst, which competently abstracts the hydrogen from borane, silane, phosphine, or thiol for generating the corresponding element radical to engender the chemical transformations. The elaborate control experiments evidenced the generation of thiyl radicals in MOF and illustrated a radical reaction pathway. The gram-scale reaction worked well, and the product was conveniently separated via centrifugation and vacuum with a turnover number (TON) of ≈3880, highlighting the practical application potential of heterogeneous thiyl-radical catalysis.     

Theoretical investigation on the passivation layer with linearly graded bandgap for the amorphous/crystalline silicon heterojunction solar cell

Passivation layer with linearly graded bandgap (LGB) was proposed to improve the performance of amorphous/crystalline silicon heterojunction (SHJ) solar cell by eliminating the large abrupt energy band uncontinuity at the a‐Si:H/c‐Si interface. Theoretical investigation on the a‐Si:H(p)/the LGB passivation layer(i)/c‐Si(n)/a‐Si:H(i)/a‐Si:H(n⁺) solar cell via AFORS‐HET simulation show that such LGB passivation layer could improve the solar cell efficiency (η) by enhancing the fill factor (FF) greatly, especially when the a‐Si:H(p) emitter was not efficiently doped and the passivation layer was relatively thick. But gap defects in the LGB passivation layer could make the improvement discounted due to the open‐circuit voltage (V_OC) decrease induced by recombination. To overcome this, it was quite effective to keep the gap defects away from the middle of the bandgap by widening the minimum bandgap of the LGB passivation layer to be a little larger than that of the c‐Si base. The underlying mechanisms were analysed in detail. How to achieve the LGB passivation layer experimentally was also discussed. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Improving the conversion efficiency of an organic distributed feedback laser by varying solvents of the laser gain layer

Control experiments were performed to improve the slope conversion efficiency of the organic distributed feedback laser by varying the dissolution solvents of the laser gain layer, a conjugated polymer poly(2-methoxy-5-(2?-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) in this work. The distributed feedback configuration of the laser was prepared by holographic photopolymerisation of the polymer/liquid crystal (HPDLC) mixture. Experimental results showed that the tetrahydrofuran (THF) solvent cast laser gain layer had a lower lasing threshold (0.28 μJ/pulse) and a higher slope conversion efficiency (7.8%) than that of the xylene solvent cast laser gain layer (0.5 μJ/pulse, 4.9%). Thin film waveguide characterisation demonstrated that the THF-cast film possessed a smaller waveguide loss (5.3 cm^?1) and larger net gain (17.1 cm^?1) than the xylene-cast film (8.3 cm^?1, 15.7 cm^?1). Absorbance and photoluminescence spectra indicated that the THF-cast film showed brighter luminescence at 620 nm and larger absorbance at 532 nm, indicating that the interchain interactions of the MEH-PPV is different, which plays the vital role in improving the optical performance of our organic DFB lasers.     

Enzymatic Pretreatment Coupled with the Addition of <Emphasis Type="Italic">p</Emphasis>-Hydroxyanisole Increased Levulinic Acid Production from Steam-Exploded Rice Straw Short Fiber

Levulinic acid production, directly from lignocellulosic biomass, resulted in low yields due to the poor substrate accessibility and occurrence of side reactions. The effects of reaction conditions, enzymatic pretreatment, and inhibitor addition on the conversion of steam-exploded rice straw (SERS) short fiber to levulinic acid catalyzed by solid superacid were investigated systematically. The results indicated that the optimal reaction conditions were temperature, time, and solid superacid concentration combinations of 200 °C, 15 min, and 7.5 %. Enzymatic pretreatment improved the substrate accessibility to solid superacid catalyst, and p-hydroxyanisole inhibitor reduced the side reactions during reaction processes, which helped to increase levulinic acid yield. The levulinic acid yield reached 25.2 % under the optimal conditions, which was 61.5 % higher than that without enzymatic pretreatment and inhibitor addition. Therefore, enzymatic pretreatment coupled with the addition of p-hydroxyanisole increased levulinic acid production effectively, which contributed to the value-added utilization of lignocellulosic biomass.     

Evaluation of magnetic matrix solid‐phase dispersion for the determination of polychlorinated biphenyls in water samples by gas chromatography with electron capture detection

A vortex‐assisted magnetic matrix solid‐phase dispersion method was proposed for the determination of polychlorinated biphenyls in different matrix water samples by gas chromatography with electron capture detection. Magnetic bamboo charcoal (MBC) was synthesized for the adsorption of polychlorinated biphenyls in water samples. Complete separation of the liquid phase and the solid magnetic bamboo charcoal was easily achieved by using a permanent magnet. Under the optimized conditions, good linearity in the range of 0.006–5.0 μg/L was obtained with regression coefficients (r) higher than 0.9986. Based on a signal‐to‐noise ratio of 3, limits of detection were found to be 0.001–0.003 μg/L. Relative standard deviations ranged from 2.92 to 6.56%. Relative recoveries were 96.6–111.2% for the spiked wastewater sample and 90.7–104.7% for the spiked lake water sample. All results showed that the proposed method was simple, sensitive, and reliable for the determination of polychlorinated biphenyls in water samples.     

A lipid coating on cotton fibers with enhanced adsorption capability for fabric functionalization

Cellulose - Cotton is often modified to minimize its disadvantages during textile processing. However, most finishing methods suffer from difficulties in finding finishing reagents and chemical...