Poly(vinyl alcohol)/GO-MMT nanocomposites: Preparation,structure and properties

A facile, efficient and environment friendly method is established to prepare poly(vinyl alcohol)(PVA) based graphene oxide-montmorillonite(GO-MMT) nanocomposites in aqueous media. GO-MMT nanohybrid is obtained by the combination of GO and MMT in water without any reducing or stabilizing agents. The formation of GO-MMT nanohybrid is due to the hydrogen bonding and crosslinking effects. The sodium ions within MMT sheets act as crosslinkers between GO sheets and MMT platelets. The resultant nanocomposites are characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA) and mechanical testing. Compared to that of pure PVA, PVA nanocomposites show enhanced thermal stabilities and mechanical properties, which results from strong interfacial adhesion of the nanoadditives in PVA matrix. The further increase in the tensile strength and modulus results from strong interaction between PVA chains and layered GO-MMT as well as good mechanical properties of GO-MMT hybrid, compared to PVA/GO and PVA/MMT nanocompsoites.     

性能优异的Rh改性的Pd/Al2O3密偶催化剂

采用等体积浸渍法制备了Pd/Al2O3和Rh-Pd/Al2O3密偶催化剂,运用H2程序升温还原、CO化学吸附和X射线光电子能谱等手段对催化剂进行了表征,并考察了催化剂对丙烷总包反应和单反应的转化活性.总包反应结果表明, Rh的添加使起燃温度和完全转化温度分别降低了23和18oC.单反应结果证明,添加Rh能提高各单反应丙烷的转化活性,尤其是有NO参与的反应.表征结果证明,掺杂Rh不仅可以抑制活性组分PdOx的烧结,提高PdOx的分散度,而且可以改变其电子状态.     

Franck–Condon simulation of photoelectron spectroscopy of HOO: Including Duschinsky effects

Geometry optimization and harmonic vibrational frequency calculations were performed on the and states of HOO and state of HOO⁻. The electron affinity and the term energy () of HOO were calculated at various theory levels. Franck–Condon analyses and spectral simulations were carried out on the and photodetachment processes. The spectral simulations of vibrational structures based on the computed Franck–Condon factors are in excellent agreement with the observed spectra. In addition, the equilibrium geometrical parameters of the state of HOO⁻ and state of HOO were obtained in the spectral simulations.     

Preparation, characterization and biocompatibility of poly(ethylene glycol)-poly(n-butyl cyanoacrylate) nanocapsules with oil core via miniemulsion polymerization

A new type of nanocapsules with an oil core, coated by poly(ethylene glycol) (PEG) was designed. The loading efficiency and the biocompatibility of the polymeric nanocapsules were evaluated when it was used as a carrier for hydrophobic agent paclitaxel. The nanocapsules were synthesized through miniemulsion polymerization of butylcyanoacrylate (BCA) with PEG as initiator. The particle size and zeta potential of nanocapsules were influenced by the PEG content in the polymerization system. Fourier transform infrared (FTIR) spectra and ¹H NMR demonstrated the chemical coupling between PEG and poly(butylcyanoacrylate) (PBCA). Thermal characteristics of the copolymer were investigated by differential scanning calorimetry (DSC). The encapsulation efficiency increased concurrently with the increase of the PEG content in the system. The hemolytic assay and the cytotoxicity measurement showed that the PEG coating could significantly reduce the hemolytic potential and cytotoxicity of the nanocapsules. The results showed that the PEG-PBCA nanocapsules could be an effective carrier for hydrophobic agents.     

Synthesis, crystal structure, and optical properties of a novel rare-earth complex Nd(C2F5COO)3 · Phen

A novel neodymium pentafluoropropionate binuclear complex, Nd(C₂F₅COO)₃ · Phen (Phen: 1,10-phenanthroline), was synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, FT-IR spectra, UV–Vis–NIR absorption, and PL spectra. Single-crystal data show that the complex bears centrosymmetric dinuclear structure with a planar ligand configuration. Four carboxylato groups act as η²-chelate-μ²-carboxylato-k¹O:k¹O′-bridge-ligands, the other two occupy the terminal position as monodentate ligands. At the same time, the C–O distances appear averaged which indicate the three atoms of carboxylato forming electron-conjugate system. Hydrogen bond and π–π-stacking link the binuclear to two-dimensional sheet. Optical spectra exhibit the complex possesses typical Nd(III) ion absorption and photoluminescence emission.     

Ab initio calculations of the structural and elastic properties of CoSi2

Under GGA, the geometry, energy, electronic structure, and elastic properties of the CoSi₂ have been investigated by using ab initio plane-wave ultrasoft pseudopotential method. The calculated equilibrium lattice parameter a and elastic stiffness constants c ₁₁, c ₁₂, and c ₄₄ are in better agreement with the experimental values than those obtained by both the VAMP and FLAPW with LDA. For engineering and technological applications, the isotropic elastic properties, including the shear modulus G, the bulk modulus B, Young’s modulus E, and Poisson’s ratio , are also calculated for polycrystalline CoSi₂ with Voigt, Reuss, and Hill approximations. The lower Poisson’s ratio of 0.327 means an increase in the volume is associated with the uniaxial tensile deformation and the higher ratio of bulk modulus to shear modulus B/G of 2.56 indicates the ductility of CoSi₂ which is in accordance with the metallic property of CoSi₂ obtained by the density of states.     

Synthesis and characterization of a novel double-tailed cationic surfactant

A novel double-tailed cationic surfactant, N,N′-didodecylacetamidinium bicarbonate, was prepared by reacting dimethylacetamide dimethyl acetal with dodecylamine, followed by reacting with dry ice. MSD, FTIR, ¹H NMR, ¹³C NMR, 2D-NMR were used to confirm its structure. The surfactant reduced the surface tension of pure water to 24.7 mN m⁻¹ and its critical micelle concentration was 8.75 × 10⁻⁵ M. Formation of vesicle was also observed.     

Effect of pendant group on the second-order optical nonlinearity of sol–gel films

A series of organically modified sol–gel films with various acceptor groups were prepared and characterized. All the chromophores exhibit much larger microscopic optical nonlinearity compared with the classical chromophore DR1 in solvatochromic measurement. Using in situ second harmonic generation (SHG) technique, the optimal poling temperatures (T _opt) for sol–gel films were obtained. The second harmonic coefficients (d ₃₃) of hybrid films at the wavelength of 1,064 nm were in the range of 50.1–70.3 pm/V after corona poling under their T _opt. The NLO stabilities of these poled films were also investigated by tracing the d ₃₃ value as a function of temperature and time. One of the hybrid films, which was prepared from chromophore 2,4-dinitro-4′-(N,N-dihydroxyethyl) aminoazobenzene exhibited a combination of large optical nonlinearity and high NLO stability. Furthermore, the effects of molecular structure on the NLO property and thermal stability of the hybrid films were also discussed.     

微波技术在Suzuki反应中的应用

与传统的加热方式相比,微波加热具有加热速度快、热效率高、节约能源、洁净、操作简单等优点,已成为重要的有机合成工具之一。钯催化的Suzuki反应提供了一种合成各种联芳烃的温和方法,具有较高的选择性。本文综述了近年来微波技术在Suzuki反应中的应用研究进展,涉及到各种不同的反应体系,重点讨论了KF/Al2O3负载钯和聚合物负载钯等非均相催化体系,对于均相反应则着重讨论无过渡金属和超低含量钯催化的Suzuki反应体系,还讨论了连续流动的微波反应器及Suzuki反应在有机合成中的应用。     

量子点标记链霉亲和素及其生物活性检测

选用无机盐为前驱体,在水相中合成CdTe量子点,并用此量子点标记链霉亲和素,通过SephadexG-100层析分离纯化量子点标记的链霉亲和素,采用磁颗粒标记的链霉亲和素与量子点标记的链霉亲和素竞争结合辣根过氧化酶标记的生物素,即酶联免疫竞争抑制分析法检测链霉亲和素标记量子点后的生物活性,计算约70.3%的链霉亲和素标记到量子点上,且具有生物活性。每毫克量子点大约可偶联0.14 mg的链霉亲和素。采用荧光光谱研究量子点标记前后的荧光变化,标记后量子点的最大发射波长蓝移了8 nm,而发射光谱的半峰宽基本不变,说明量子点与链霉亲和素结合后粒子没有团聚,分散性好。