Helical Self-Assembly of Optically Active Phthalocyanine Derivatives: Effect of Zn?O Coordination Bond on Morphology and Handedness of Nanostructures

Two optically active phthalocyanine derivatives with eight peripheral chiral (S)-4′-(2-methylbutoxy)biphenyl moieties on the β-position of the phthalocyanine ring are synthesized. The circular dichroism (CD) spectra show signals in the Q absorption region for both compounds 1 and 2 in chloroform solution, indicating the effective chiral-information transfer from the peripheral chiral (S)-4′-(2-methylbutoxy)biphenyl side chains to the phthalocyanine chromophore at the molecular level. Their self-assembling properties are further investigated by using electronic absorption and Fourier transform infrared spectroscopy, transmission electronic microscopy, scanning electronic microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Experimental results reveal the effect of the metal-coordination bond on molecular packing models in these nanostructures, which in turn results in the self-assembled nanostructures with different morphologies, from nanosheets for 1 to helical nanofibers for 2 . In addition, good semiconducting properties of the nanostructures fabricated from phthalocyanine derivatives 1 and 2 are revealed by current–voltage measurements.     

变角度纤维复合材料圆柱壳的轴压屈曲

变角度纤维复合材料的纤维方向角可沿铺层面内连续变化,因此相应结构的性能具有更高的设计灵活性和更大的优化空间．本文假设纤维方向角沿圆柱壳的轴向呈正弦函数变化,对变角度纤维复合材料圆柱壳在两端简支边界条件下的轴压屈曲问题进行研究．基于Donnell经典壳体理论,推导变角度纤维复合材料圆柱壳的前屈曲控制方程并运用伽辽金法进行求解,然后采用瑞利里兹法求解屈曲问题．通过和现有文献及有限元数值结果的对比,验证了本文模型的收敛性和正确性,通过数值算例分析了纤维起始角和终止角的变化对圆柱壳的屈曲临界荷载的影响．本文的研究结果可为变角度纤维复合材料圆柱壳的分析和设计提供一定的参考．     

Microscopic probing of the size dependence in hydrophobic solvation

We report small angle x-ray scattering data demonstrating the direct experimental microscopic observation of the small-to-large crossover behavior of hydrophobic effects in hydrophobic solvation. By increasing the side chain length of amphiphilic tetraalkyl-ammonium (C(n)H(2n+1))(4)N(+) (R(4)N(+)) cations in aqueous solution we observe diffraction peaks indicating association between cations at a solute size between 4.4 and 5 A?, which show temperature dependence dominated by hydrophobic attraction. Using O K-edge x-ray absorption we show that small solutes affect hydrogen bonding in water similar to a temperature decrease, while large solutes affect water similar to a temperature increase. Molecular dynamics simulations support, and provide further insight into, the origin of the experimental observations.     

Electrochemical copolymerization of 9,10-dihydrophenanthrene and 3-methylthiophene and characterization of their copolymer with tunable fluorescence properties

Electrochemical copolymerization of 9,10-dihydrophenanthrene and 3-methylthiophene was successfully achieved in boron trifluoride diethyl etherate by direct anodic oxidation of the monomer mixtures. The structure and properties of the copolymers were investigated with ultraviolet–visible, Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance, fluorescence spectra, and thermal analysis. The novel copolymers had the advantages of both poly(9,10-dihydrophenanthrene) and poly(3-methylthiophene), such as good electrochemical behavior, good mechanical properties, and high electrical conductivity. Fluorescence spectroscopy studies revealed that the copolymers had good fluorescence properties, and the emitting properties of the copolymer could be parameters by changing the feed ratio of the monomer mixtures during the electrochemical polymerization.     

Synthesis of xanthones through the palladium-catalyzed carbonylation/C–H activation sequence

A series of xanthones with the dibenzo-γ-pyrone framework were synthesized through the palladium-catalyzed carbonylation/C–H activation sequence from the ortho diazonium salts of diaryl ethers in moderate to excellent yields. After screening the reaction condition, the optimal condition was 5 mol % tetrakis (triphenylphosphine) palladium (0) as the catalyst, potassium carbonate as the base, and toluene as the solvent in the presence of catalytic amount of tetrabutyl ammonium bromide under carbon monoxide atmosphere.     

Determination of glyphosate in foodstuff by one novel chemiluminescence-molecular imprinting sensor

A novel chemiluminescence (CL) sensor for the determination of glyphosate (GLY) was made up based on molecularly imprinted polymer (MIP). The molecularly imprinted microspheres (MIMs) with a small dimension which possess extremely high surface-to-volume ratio were synthesized using precipitation polymerization with GLY as template. And then the MIMs were modified on glass sheets, which were placed at the bottom of wells of microplate as the recognizer. Subsequently, a highly selective and high throughput chemiluminescence (CL)-molecular imprinting (MI) sensor for detection of GLY was achieved. Influencing factors were investigated and optimized in detail. The method can perform 96 independent measurements sequentially in 10 min and the limit of detection (LOD) for GLY was 0.046 μg mL(-1). The relative standard deviation (RSD) for 11 parallel measurements of GLY was 4.68%. The results show that CL-MI sensor can become a useful analytical technology for quick molecular recognition.     

Wide-angle X-ray diffraction and molecular dynamics study of medium-range order in ambient and hot water

We have developed wide-angle X-ray diffraction measurements with high energy-resolution and accuracy to study water structure at three different temperatures (7, 25 and 66 °C) under normal pressure. Using a spherically curved Ge crystal an energy resolution better than 15 eV has been achieved which eliminates influence from Compton scattering. The high quality of the data allows for a reliable Fourier transform of the experimental data resolving shell structure out to ~12 ?, i.e. 5 hydration shells. Large-scale molecular dynamics (MD) simulations using the TIP4P/2005 force-field reproduce excellently the experimental shell-structure in the range 4-12 ? although less agreement is seen for the first peak in the intermolecular pair-correlation function (PCF). The Shiratani-Sasai Local Structure Index [J. Chem. Phys. 104, 7671 (1996)] identifies a tetrahedral minority giving the intermediate-range oscillations in the O-O PCF and a disordered majority providing a more featureless background in this range. The current study supports the proposal that the structure of liquid water, even at high temperatures, can be described in terms of a two-state fluctuation model involving local structures related to the high-density and low-density forms of liquid water postulated in the liquid-liquid phase transition hypothesis.     

X-ray Raman scattering provides evidence for interfacial acetonitrile-water dipole interactions in aqueous solutions

Aqueous solutions of acetonitrile (MeCN) have been studied with oxygen K-edge x-ray Raman scattering (XRS) which is found to be sensitive to the interaction between water and MeCN. The changes in the XRS spectra can be attributed to water directly interacting with MeCN and are reproduced by density functional theory calculations on small clusters of water and MeCN. The dominant structural arrangement features dipole interaction instead of H-bonds between the two species as revealed by the XRS spectra combined with spectrum calculations. Small-angle x-ray scattering shows the largest heterogeneity for a MeCN to water ratio of 0.4 in agreement with earlier small-angle neutron scattering data.     

The structure of water in the hydration shell of cations from x-ray Raman and small angle x-ray scattering measurements

X-ray Raman scattering (XRS) spectroscopy and small angle x-ray scattering (SAXS) are used to study water in aqueous solutions of NaCl, MgCl(2), and AlCl(3) with the particular aim to provide information about the structure of the hydration shells of the cations. The XRS spectra show that Na(+) weakens the hydrogen bonds of water molecules in its vicinity, similar to the effect of increased temperature and pressure. Mg(2+) and Al(3+), on the other hand, cause the formation of short and strong hydrogen bonds between the surrounding water molecules. The SAXS data show that Mg(2+) and Al(3+) form tightly bound hydration shells that give a large density contrast in the scattering data. From the form factors extracted from the SAXS data, we found that Mg(2+) and Al(3+) have, respectively, an equivalent of one and one and a half stable hydration shells that appear as a density contrast. In addition, we estimated that the density of water in the hydration shells of Mg(2+) and Al(3+) is, respectively, ～61% and ～71% higher than in bulk water.     

Novel microwave-assisted solvothermal synthesis of NaYF4:Yb,Er upconversion nanoparticles and their application in cancer cell imaging

This work reports the novel microwave-assisted solvothermal synthesis and structural, topographic, spectroscopic characterization of NaYF(4):Yb,Er upconversion nanoparticles (UCNPs) as well as their application in the labeling of HeLa cells. The nanoparticles were prepared in ethylene glycol, with rare earth acetates as precursor and NH(4)F and NaCl as the fluorine and sodium sources. X-ray diffraction, transmission electron microscopy, and luminescence spectroscopy were applied to characterize the nanoparticles. Experimental results showed that the microwave-assisted solvothermal method is an effective approach to create highly crystalline, strongly luminescent UCNPs at a lower temperature (160 °C) and within a significantly shortened reaction time (only 1 h) compared to the traditional methods. The effect of fluorine source on the optical properties of UCNPs was investigated by using NH(4)F, NH(4)HF(2), NaF, and 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF(4)) as different fluorine sources; NH(4)F proved to be the best one, making the luminescent intensity increase at least 2 orders of magnitude. The UCNPs with four different colors (green, yellow, orange, and cyan) were successfully obtained. After being modified with amino groups and coupled with CEA-8 antibody, the obtained nanoparticles were successfully applied in the specific fluorescent immunolabeling and imaging of HeLa cells to further verify their function as a marker in immunolabeling.