Optical excitations in carbon nanoscrolls

The optical properties of carbon nanoscrolls in the presence of uniform electric fields are investigated by using gradient approximation. Absorption spectra exhibit rich prominent peaks structures, which is caused by one-dimensional sub-bands. The numbers, spectral intensities, and energies of the absorption peaks are strongly dependent on the geometry and the electric field strength. There exists an optical selection rule originating from the two equivalent sublattices in graphene. The two-fold degeneracy of the absorption peaks can be lifted by the inter-wall interactions or the electric field. The variations of the absorption peak energies with the geometry and field strength are also explored. These theoretical predictions can be validated by optical absorption measurements.     

Studies on the interaction of salvianolic acid B with human hemoglobin by multi-spectroscopic techniques

The interaction between salvianolic acid B (Sal B) and human hemoglobin (HHb) under physiological conditions was investigated by UV-vis absorption, fluorescence, synchronous fluorescence and circular dichroism spectroscopic techniques. The experimental results indicate that the quenching mechanism of fluorescence of HHb by Sal B is a static quenching procedure, the binding reaction is spontaneous, and the hydrophobic interactions play a major role in binding of Sal B to HHb. Based on F?rster's theory of non-radiative energy transfer, the binding distance between Sal B and the inner tryptophan residues of HHb was determined to be 2.64 nm. The synchronous fluorescence experiment revealed that Sal B can not lead to the microenvironmental changes around the Tyr and Trp residues of HHb, and the binding site of Sal B on HHb is located at α(1)β(2) interface of HHb. Furthermore, the CD spectroscopy indicated the secondary structure of HHb is not changed in the presence of Sal B.     

Preparation of silver nanoparticles on cellulose nanocrystals and the application in electrochemical detection of DNA hybridization

Synthesis of Ag nanopaticles was carried out with carboxylated cellulose nanocrystals as the scaffolds by reducing metallic cations using NaBH₄. Ag particles with a size less than 10 nm were readily prepared and dispersed well. The carboxyl and hydroxyl groups of carboxylated cellulose nanocrystals supplied a coordination effect to adsorb metallic cations and Ag nanoparticles, which prevent the aggregation of nanoparticles. The carboxylated cellulose nanocrystals carrying Ag nanoparticles were used as labels for electrical detection of DNA hybridization.     

Fabrication of superhydrophobic silica film by removing polystyrene spheres

A superhydrophobic silica film has been fabricated by a facile method, which combines the co-sedimentation of dual-sized polystyrene (PS) spheres and the infiltration of a silica sol. The scanning electron microscopy (SEM) observations indicate that the as-prepared silica surface has a hierarchical micro/nano-structure. The micrometer-sized hollow silica particle with nanometer-sized holes on its surface was created by removing the organic polymer at high temperature. After chemically modified by a layer of dodecafluoroheptyl-methyl-dimethoxysilane (DFMS), the silica film has a water contact angle up to 156.4°, showing excellent superhydrophobic property. The present method may enhance widespread application of superhydrophobic film because of its simplicity and cheapness.     

表面效应对纳米线电极屈曲失稳的影响

纳米线电极在充/放电过程中引起电极的屈曲失稳行为可能会对结构造成力学损伤.本文针对纳米线电极结构,建立了包含锂扩散、应力、浓度影响弹性模量的多场耦合理论模型.基于构建的模型,研究了表面效应对纳米线电极屈曲失稳的影响.结果表明表面效应能够提高纳米线电极的抗屈曲性,延迟纳米线电极的临界屈曲时间.同时,表面效应的影响表现出半径尺寸和长细比的依赖性,即随着电极半径尺寸的增大而减小,而随着电极长细比的增大而增大.此外,模型还显示,在有表面效应的条件下,相对于弹性硬化属性的纳米线电极,具有弹性软化属性的电极因为具有更好的抗失稳性而更适宜作为电极材料.研究结果为纳米线电极的力学可靠性设计提供了一定的帮助.     

Anion recognition based on phenolic hydroxyl group in competitive media

Two novel artificial receptors, one containing phenolic hydroxyl group and diamide (1), the other only containing diamide (2), were designed and synthesized. The binding ability evaluated by UV–vis and fluorescence titration experiments in dry DMSO revealed that compound 1 could selectively recognize AcO^?. In particular, the binding ability can also be detected in the DMSO/H₂O solution by UV–vis. The interference experiment result showed that the binding ability was not influenced by the existence of other anions. In contrast, there were no detectable interaction between receptor 2 and anions. The further insights to the nature of interaction between receptor 1 and AcO^? were investigated by ¹H NMR titration experiments and theoretical investigation, which demonstrated receptor 1 complexed AcO^? through the synergistic hydrogen bonding interaction of OH and NH.     

Surfactant adsorption onto interfaces: measuring the surface excess in time

We propose a direct method to measure the equilibrium and dynamic surface properties of surfactant solutions with very low critical micellar concentrations (CMC) using a pendant drop tensiometer. We studied solutions of the nonionic surfactant hexaethylene glycol monododecyl ether (C(12)E(6)) and of the ionic surfactant hexadecyl trimethyl ammonium bromide (CTAB) with concentrated sodium bromide (NaBr). The variation of the surface tension as a function of surface concentration is obtained easily without the need for complex models and compares well with the result obtained using the Gibbs adsorption equation. The time-dependent surface concentration of each surfactant was also measured, and the adsorption process was found to be diffusion-controlled. The diffusion coefficients of the two surfactants can be extracted from the data and were found in very good agreement with literature values, further validating the method.     

Aromatic‐Amide‐Derived Olefins as a Springboard: Isomerization‐Initiated Palladium‐Catalyzed Hydrogenation of Olefins and Reductive Decarbonylation of Acyl Chlorides with Hydrosilane

A highly efficient catalytic protocol for the isomerization of substituted amide‐derived olefins is presented that successfully uses a hydride palladium catalyst system generated from [PdCl₂(PPh₃)₂] and HSi(OEt)₃. The Z to E isomerization was carried out smoothly and resulted in geometrically pure substituted olefins. Apart from the cis–trans isomerization of double bonds, the selective reduction of terminal olefins and activated alkenes was performed with excellent functional group tolerance in the presence of an amide‐derived olefin ligand, and the products were obtained in high isolated yields (up to >99 %). Furthermore, the palladium/hydrosilane system was able to promote the reductive decarbonylation of benzoyl chloride when a (Z)‐olefin with an aromatic amide moiety was used as a ligand.     

A General and Efficient CuBr2‐Catalyzed N‐Arylation of Secondary Acyclic Amides

A general and efficient Cu(II)‐catalyzed cross‐coupling method is reported for the preparation of acyclic tertiary amides. Generally moderate to excellent yields and functional group tolerance were obtained with secondary acyclic amides and aryl halides as substrates in toluene.     

Effect of composite supports on the methanation activity of Co-Mo-based sulphur-resistant catalysts

The effects of composite supports of CeO2-Al2O3,MgO-Al2O3,TiO2-Al2O3 or ZrO2-Al2O3 on the methanation activity of supported Co-Mo-based sulphur-resistant catalysts were investigated.The catalysts were further characterized by nitrogen adsorption measurement,X-ray diffraction and X-ray photoelectron spectroscopy.The catalyst of 5%CoO-15%MoO3 supported on CeO2-Al2O3,MgO-Al2O3,TiO2-Al2O3 or ZrO2-Al2O3 composite oxides,respectively,showed different catalytic performances of syngas methanation in the presence of hydrogen sulphide as compared with that of the 5%CoO-15%MoO3/Al2O3 catalyst.The Co-Mo/CeO2-Al2O3 catalyst shows the highest methanation activity among the tested catalysts.The enhanced methanation activity may be attributed to the improvement of the dispersion of active metal species and the inhibition of the formation of S6+.