功能化石墨烯改性聚乙烯热力学特性的分子动力学模拟

聚乙烯绝缘材料在我国高压电缆中有着广泛的应用,为了提高其耐热稳定性和力学性能,利用石墨烯对聚乙烯进行掺杂改性,并基于分子动力学模拟的研究方法分别建立了低密度聚乙烯（LDPE）、石墨烯和3种官能团接枝石墨烯掺杂聚乙烯的复合模型。研究表明,相比石墨烯直接掺杂聚乙烯,羧基（-COOH）、氨基(-NH2)和羟基(-OH)接枝石墨烯能够更加有效地提高聚乙烯的玻璃化温度（分别提高了16k、7k、5k）、减弱聚乙烯分子链的移动和降低聚乙烯的热膨胀系数、均方位移(MSD),从而使得聚乙烯复合体系的热学性能得到了有效增强;此外发现石墨烯的掺杂能够提高复合模型的力学模量,其中官能团接枝石墨烯改进效果更明显,室温下弹性模量和剪切模量的提升幅度由不接枝的33.98%、36.18%,提升到了44%和42.89%（羧基功能化体系）。研究结果可为聚乙烯绝缘材料的热老化抑制和力学性能的改善提供有益的参考。     

High-Density Polyethylene with In-Chain Photolyzable and Hydrolyzable Groups Enabling Recycling and Degradation

Polyethylenes endowed with low densities of in-chain hydrolyzable and photocleavable groups can improve their circularity and potentially reduce their environmental persistency. We show with model polymers derived from acyclic diene metathesis polymerization that the simultaneous presence of both groups has no adverse effect on the polyethylene crystal structure and thermal properties. Post-polymerization Baeyer–Villiger oxidation of keto-polyethylenes from non-alternating catalytic ethylene-CO chain growth copolymerization yield high molecular weight in-chain keto-ester polyethylenes (M_n≈50.000 g mol⁻¹). Oxidation can proceed without chain scission and consequently the desirable materials properties of HDPE are retained. At the same time we demonstrate the suitability of the in-chain ester groups for chemical recycling by methanolysis, and show that photolytic degradation by extended exposure to simulated sunlight occurs via the keto groups.     

Convenient Michael addition/β-elimination approach to the synthesis of 4-benzyl- and 4-aryl-selenyl coumarins using diselenides as selenium sources

A concise and efficient, two-step approach toward 4-organoselenyl coumarin derivatives from the easily available 4-hydroxycoumarins, is reported. The synthesis was based on conventional tosylation followed by a tandem selena-Michael addition/β-elimination reaction of an aryl-/benzyl-selenolate anion on the corresponding 4-tosyloxycoumarins. The selenolate anions were conveniently generated in situ by exposure of the corresponding diselenides to NaBH₄. Selected compounds demonstrated to exhibit antioxidant properties in mice cortex and hippocampus.     

Construction of supported lipid membrane modified piezoelectric biosensor for sensitive assay of cholera toxin based on surface-agglutination of ganglioside-bearing liposomes

A novel piezoelelctric biosensor has been developed for cholera toxin (CT) detection based on the analyte-mediated surface-agglutination of ganglioside (GM1)-functionalized liposomes. To achieve a CT-specific agglutination at the surface, the gold electrode is modified by a GM1-functionalized supported lipid membrane via spontaneous spread of the liposomes on a self-assembled monolayer of a long-chain alkanethiol. In the presence of CT, the GM1-incorporated liposomes in assay medium will rapidly specifically agglutinate at the electrode surface through the binding of CT to GM1 on the electrode surface and the liposome interface. This results in an enormous mass loading on the piezoelelctric crystal as well as a significant increase of density and viscosity at the interface, thereby generating a decrease in frequency of the piezoelelctric crystal. The combination of mass loading with interfacial change in the surface-agglutination reaction allows the developed piezoelelctric biosensor to show substantial signal amplification in response to the analyte CT. The detection limit can be achieved as low as 25 ng mL⁻¹ CT. This is the first demonstration on CT detection based on specific surface-agglutination of GM1-modified liposomes. The supported lipid layer based sensing interface can be prepared readily and renewably, making the developed technique especially useful for simple, reusable and sensitive determination of proteins.     

卟啉修饰碳纳米管研究进展

碳纳米管作为一类新型纳米材料具有许多独特的物理、化学性质,卟啉在可见光区具有广泛吸收.并可作为构筑分子体系的光捕捉单元.卟啉修饰的碳纳米管有望在生命、信息、材料科学等许多相关学科得到应用.本文综述了卟啉修饰碳纳米管的方法、影响因素,展望了其在光电领域的应用前景.     

Pore-functionalized polymer membranes for preconcentration of heavy metal ions

Functionalized membranes containing carboxylate, phosphate and sulfonate groups were prepared by UV-initiator induced graft polymerization of the functional monomer (acrylic acid, ethylene glycol methacrylate phosphate (EGMP) and 2-acrylamido-2-methyl-1-propane sulfonic acid) with a crosslinker (methylenebisacrylamide) in the pores of poly(propylene) host membranes. The functionalized membranes thus obtained were characterized by gravimetry, FTIR spectroscopy, radiotracers and scanning electron microscopy for the degree of grafting and water uptake, presence of functional groups, ion-exchange capacity, and physical structure of the membranes, respectively. The uptakes of Cs⁺, Ag⁺, Sr²⁺, Cd²⁺, Hg²⁺, Zn²⁺, Eu³⁺, Am³⁺, Hf⁴⁺ and Pu⁴⁺ ions in the functionalized membranes were studied as a function of acidity of the equilibrating aqueous solution. Among the functionalized membranes prepared in the present work, the EGMP-grafted membrane (with phosphate groups) showed acid concentration dependent selectivity towards multivalent metal ions like Eu³⁺, Am³⁺, Hf⁴⁺ and Pu⁴⁺. The solvent extraction studies of EGMP monomer in methyl isobutyl ketone (MIBK) solvent indicated that divalent and trivalent metal ions form complexes with EGMP in 1:2 proportion, but the distribution coefficients of trivalent metal ions were significantly higher that for the divalent ions. The uptakes of Eu³⁺ ions in monomeric EGMP (dissolved in MIBK) and polymeric EGMP (in the forms of crosslinked gel and membrane) were studied as a function of concentration of H⁺ ions in the equilibrating solution. This study indicated that polymeric EGMP has better binding ability towards Eu³⁺ as compared to monomeric EGMP. The variation of distribution coefficients of Eu³⁺/Am³⁺ in gel and membrane as a function of H⁺ ion concentration in the equilibrating aqueous solution indicated that ionic species held in the membrane and gel were not same. These results indicated that proximity of functional groups (phosphate) plays an important role in metal ion binding with polymeric EGMP.     

Synthesis of covalently linked linear porphyrin triad and tetrad containing different porphyrin sub-units

Covalently linked diarylethyne bridged unsymmetrical porphyrin triad containing ZnN₄, N₄, and N₂S₂ porphyrin sub-units and porphyrin tetrad containing ZnN₄, N₄, N₃S, and N₂S₂ porphyrin sub-units were synthesized over sequence of Pd(0) mediated coupling reactions. The triad and tetrad are freely soluble in all common organic solvents and characterized by ES-MS, NMR, absorption, fluorescence, and electrochemical techniques. The ¹H NMR, absorption, and electrochemical studies indicated a weak interaction between the porphyrin sub-units of porphyrin triad and porphyrin tetrad. The steady state and time-resolved fluorescence studies supported an energy transfer from one end of porphyrin array to the other end. This kind of porphyrin arrays containing different porphyrin sub-units will be useful for molecular electronics applications.     

Dispersion enhancing effect of sonochemically functionalized graphene oxide for catalysing antioxidant efficacy of curcumin

The non-hazardous sonochemical approach has been developed for the functionalization of graphene oxide (GrO) with 5-Aminoindazole (5-AIND). The formation of f-(5-AIND) GrO is confirmed with ¹³C solid state NMR, HRXPS, XRD, Raman, TGA, DSC, FTIR etc. The >80% cell viabilities on MCF-7 and Vero cell lines have confirmed the high cytocompatibility of f-(5-AIND) GrO. Additionally, the morphological impact on Vero cell line has evidently confirmed the biocompatibility of f-(5-AIND) GrO. As compared to GrO, the f-(5-AIND) GrO has demonstrated an enhanced antioxidant efficacy of 69.4–72%, evaluated with 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical assay. With a similar objective (0.01–0.05) mL peanut oil based curcumin micro and nanoemulsions have been prepared using ethanol and glycerol as co-solvent and co-surfactant respectively. The prepared emulsions are subsequently characterised with respect to morphological and physicochemical parameters via density, surface tension, viscosity, friccohesity measurement and DLS analysis. Henceforth, with an expectation to achieve higher dispersion, an ethanolic dispersion of f-(5-AIND) GrO has been mixed with curcumin carrying emulsions in 1:1. Notably, the radical scavenging activities (RSA) of the combined formulations are significantly enhanced to an extent of 26.6%.     

Unexpected Formation of Cyclic Hydroxamic Acids from O-(2-Aminobenzoyl) Hydroxylamine

Cyclic hydroxamic acids 3 and 4 are the unexpected products in the reaction of 0-(2-aminobenzoyl) hydroxylamine 1 and orthoesters, acid chlorides, ethyl chloroformate.     

Functionalized cellulose-preyssler heteropolyacid bio-composite: An engineered and green matrix for selective,fast and in–situ preparation of Pd nanostructures: synthesis,characterization and application

A new and green engineered biocomposite was synthesized by sol–gel method, using different loadings of the Preyssler heterpolyacid (8, 15, 25, 40 and 50 wt%) on the functionalized microcrystaline cellulose surface. For the first time, this two-component polymeric biocomposite used for in-situ catalytic synthesis of Pd nanoparticles with the aim of producing tricomponent nanobiocomposites. Preyssler loading on the functionalized surface, controled the size and shape of Pd nanoparticles, time, and pH of their formation. All biocomposites and nanobiocomposites were characterised by FTIR, XRD, BET, TGA, SEM, EDS and TEM. The SEM analysis for two component polymeric biocomposites confirmed the presence of the Preyssler on the surface of functionalized cellulose. The formation of Pd nanoparticles on the surface, was observed by color changing (yellow to deep brown) and confirmed by UV–visible spectroscopy. The Pd nanoparticles formation was fast (2–4 min) for 8 wt% in pH = 2–3 at 80 °C. TEM analysis illustrated the spherical Pd nanoparticles with a size of 5–20 nm, at the lowest loading of Preyssler, and rod shapes with a size of 30–40 nm at the highest loading. The obtained nanobiocomposite exhibited high catalytic activity for the decolourisation of tartrazine, as a model of dyes pollutant in the industry with high degradation efficiency. The catalytic reactions were extended with other azo dyes including methyl orange and rodamine B.