Jianfeng Li,Shuang Yi,Kaiqiang Wang,Yanfei Liu,Jinjin Li
Black phosphorus (BP) is a promising material for electronic and optoelectronic applications. However, it is still challenging to obtain geometrically well-defined BP with desirable thickness. The method involving rapid BP surface reaction via alkene-catalyzed oxidation and easy removal of reactants by a mechanical effect was proposed to achieve the precise layer-by-layer thinning and real-time thickness monitoring of BP for nanopatterning with high spatial resolution based on mechanical scanning probe nanolithography. The enhanced electron affinity of oxygen with the assistance of a carbon–carbon double bond (C═C) in the alkene was demonstrated by density functional theory calculations, shortening the BP surface oxidation period by 99%, which provides access for the rapid thinning. The few-layer BP nanoflake with nested structure and arbitrary thickness on various substrates and the nanopatterned heterojunctions (BP/graphene and BP/hexagonal boron nitride) can be precisely fabricated by the adjustment of scanning number under a small load. This thinning technology was efficient and universal, which could be used to fabricate a BP field-effect transistor with a thinned channel to enhance the capability for current modulation, showing great potential applications for designing high-performance nanodevices.
Wang Xiong,Kang Wenqian,Li Guangquan,Zhang Pingsheng,Jia Huiqing,Gao Dujuan
The preparation of organic/inorganic hybrid materials has been proven to be an effective method to overcome the drawbacks of organic or inorganic materials. In this paper, porous organic polymer/montmorillonite (POP/MMT) hybrid materials by in situ intercalative radical polymerization were synthesized for metallocene catalyst support, and the prepared POP/MMT hybrid supports obtained excellent particle flowability with tunnable bulk density (0.20–0.40 cm 3 /g) and specific surface area (SSA) (100–350 m 2 /g) suitable for polyolefin catalysts. N 2 sorption porosity, TGA, IR, XRD, SEM characterization were conducted to evaluate the POP/MMT hybrid supports, and the results showed that the MMT sheets could be well-dispersed in the POP matrix through in situ intercalative polymerization when 80% DVB was used, and when DVB/HEMA with 3:1 molar ratio was added, the prepared POP/MMT hybrid support POP-7 (331 m 2 /g) gained excellent particle flowability and single peak of particle size distribution. Ethylene polymerization results exhibited that the POP/MMT supported metallocene catalysts could obtain better polymerization performance than MMT and silica gel-supported catalysts. The hybrid support POP-4 based metallocene catalyst achieved the highest polymerization activity of 8019 kg PE/mol Zr.bar.h and productivity of 1136 g PE/g cat.h with the produced PE bulk density of 0.27 g/ml. POP-4 supported metallocene catalyst obtained increased productivity of 2300 g PE/g cat.h and bulk density of 0.32 g/ml in higher ethylene partial pressure of 6 bar, and gained stable polymerization kinetics in 80 °C with no obvious decay. Furthermore, the pore structure played a significant effect on the molecular weight and molecular weight distribution by nanoconfined polymerization, and larger molecular chains could be produced on the POP/MMT supported catalysts with smaller nanopore size. Graphical abstract
Xiong Wang,Renwei Xu,Bochao Zhu,Yanfeng Li,Yanping Ma
Functional porous organic polymers (POPs) {poly(2-hydroxyethylmethylacrylate-co-divinylbenzene) [P(HEMA-co-DVB)]} with different pore structures and morphology were prepared via a dispersion polymerization strategy. The effect of different solvent types, different ethanol/H2O volume ratios in the mixture solvent, and the (HEMA)/DVB molar ratio on the specific surface area and porosity was investigated. Non-local density functional theory (NLDFT) simulation based on nitrogen sorption porosimetry and scanning electron microscopy (SEM) were used to study the pore structure and morphology of the prepared P(HEMA-co-DVB) particles. The results showed a trend that P(HEMA-co-DVB) particles with a higher specific surface area and a lower average pore diameter were obtained in ethanol/deionized water mixture solvents with better thermodynamic compatibility; however, when different types of solvents were used, a higher average pore diameter (14.5 nm) and total pore volume (0.923 cm3 g−1) were achieved in a good thermodynamically compatible solvent–ethyl acetate. The HEMA functional comonomer could also be a good pore-adjuster that provides a feasible route to prepare functionalized PDVB particles with controllable pore structure and particle morphology. In the ethylene homopolymerization evaluation of supported metallocene catalysts, these nanoporous polymer supports reveal better catalytic activity compared with silica used as the metallocene support, exhibiting great potential for future applications in the polyolefin catalysis industry.
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