Monitoring the transformation of colloidal crystals by styrene vapor using atomic force microscopy

The stages of transformation of a colloidal crystalline film of latex spheres to a new periodic structure were imaged by atomic force microscopy. Colloidal crystalline films were prepared with 320 nm diameter poly(styrene-co-2-hydroxyethyl methacrylate) (PSt/HEMA) spheres. The hexagonally ordered surfaces of the colloidal crystalline films were transformed with styrene vapor at room temperature to a new morphology having holes in the surface and the same periodicity as the original films. The surfaces of colloidal crystals and the transformed films have a raspberry-like texture superposed on the 320 nm hexagonal periodicity. Both height images and phase images reveal that the latex spheres shrink and the transformation proceeds by an order-disorder-order sequence. The final structure is an interconnected colloidal array with smaller polystyrene particles dispersed in a continuous PSt/HEMA matrix.     

酚醛树脂固化过程的红外光谱分析

利用红外光谱(IR)及其变温样品池、定量分析程序对酚醛树脂固化过程中的结构变化进行了研究,它对于酚醛树脂固化过程的质量控制具有重要意义。     

Preparation and Characterization of Mixed‐Valent Nickel Oxide/Nickel Hexacyanoferrate Hybrid Films and Their Electrocatalytic Properties

Polynuclear mixed‐valent nickel oxide and nickel hexacyanoferrate hybrid film was prepared on glassy carbon electrode by multiple scan cyclic voltammetry. The film growth was monitored using electrochemical quartz crystal microbalance (EQCM). The cyclic voltammogram of the nickel hexacyanoferrate film is characterized by single redox couple whereas nickel oxide/nickel hexacyanoferrate hybrid film exhibits two redox couples. Cyclic voltammetric features suggest that the charge transfer process in both films resembles that of surface‐confined redox species. In stronger basic solution (pH ≥9), nickel hexacyanoferrate film was gradually converted into nickel oxide film during potentiodynamic cycling. The peak potential of nickel oxide redox couple moved into more negative side with increasing pH of contacting solution whereas the peak potential of nickel hexacyanoferrate redox couple remains the same. Electrocatalytic behavior of hybrid film coated electrodes toward ascorbic acid, hydrazine and hydroxylamine was investigated using cyclic voltammetry technique. Analytical application of nickel oxide/nickel hexacyanoferrate hybrid film electrode was tested in amperometry and flow injection analysis.     

水-乙醇二元体系共沸混合物的热力学研究

用全自动低温绝热量热计测定了水、乙醇以及水和乙醇组成的共沸混合物在不同温区的摩尔热容Cp,m. 建立了共沸混合物Cp,m与温度T的函数关系.结果表明,水和乙醇组成的共沸混合物在98.496 K发生玻璃态转化,在158.939 K 和270.95 K发生固-液相变.获得了其相应的相变焓和相变熵.计算了以298.15 K为基准的该共沸混合物的热力学函数和超额热力学函数.     

络合型催化剂丙烯聚合动力学研究

本工作对络合型(Solvay型)TiCl_3催化剂—(C_2H_5)_2AlCl体系丙烯聚合进行了活性中心浓度C_p、链增长速率常数k_p和链增长活化能E_p等的测定,并与常规TiCl_3·0.33AlCl_3进行了比较,C_p以动力学方法求取,数均分子量以粘度法测定经分子量分布校正,结果表明,络合型催化剂活性比常规催化剂高,不仅是由于C_p增高,在更大程度上是由于k_p提高。     

Liquid-liquid extraction of thorium(IV) and uranium(VI) with three ether-amide type tripodands

N,N,N',N',N',N'-Hexaethyl-2,2′,2'-(nitrilotrisethyleneoxy-2-benzyloxy)tris(acetamide) (L3) has been prepared and characterized by using IR, ¹H NMR and positive-ion FAB mass spectra. The extraction of Th⁴⁺ and UO₂ ²⁺ with N,N,N',N',N',N'-hexaethyl-2,2',2'- (nitrilo-trisethyleneoxy)tris(acetamide) (L1), N,N,N',N',N',N'-hexaisopropyl-2,2',2'-(nitrilotrisethyleneoxy)tris(acetamide) (L2), and L3 was studied at 20±1 °C as a function of diluent, concentration of free extractant in organic phase and concentration of picrate in aqueous phase. It was found that the extracting powers of L1 and L2 for Th⁴⁺ are almost identical. The extracting power of L2 for UO22+ was slightly higher than that of L1. The difference in terminal groups (ethyl or isopropyl) of the extractants (L1 and L2) with same backbone has a little effect on the extracting power for both Th4+ and UO22+. The extracting powers of L3 for both Th4+ and UO22+ were larger than those of L1 and L2. The extractants (L1 and L3) having the same terminal group (ethyl) with different backbones have obviously different extracting powers for Th4+ or UO22+. The extracting powers of all three extractants L1, L2, and L3 for Th4+ were larger than those for UO22+. The compositions of extracted species in organic phase were predominantly ThL(Pic)3NO3 and UO2L(Pic)NO3, respectively (L denotes L1, L2 and L3). This revised version was published online in July 2006 with corrections to the Cover Date.     

Detailed Structural Characterizations of SBA‐15 and MCM‐41 Mesoporous Silicas on a High‐Resolution Transmission Electron Microscope

Using high‐resolution transmission electronic micrograph (HR‐TEM) observation, one can clearly see the pore geometry of the MCM‐41 and SBA‐15 mesoporous silicas to determine that their pore shapes are hexagonal and round, respectively. With the perpendicular orientations of the nanochannels to the electron beam, parallel line images of the (100) and (110) repeating spacings were observed. In the SBA‐15 mesoporous silicas, there are byproducts of the granular silica and disordered mesostructures, attributed to the weak hydrogen interactions between Pluronic 123 blockcopolymer and the silica species. There are also many different and significant +π disclination defects in SBA‐15 and MCM‐41 surfactant‐silica composites. The SBA‐15 with a thicker silica wall is more stable under irradiation by high‐energy electron beams compared to MCM‐41, which has thinner wall thickness. Some carbon nanostructure impurities were found in some carbon films on the metal grids.     

Characterization and transport properties of Nafion/polyaniline composite membranes

Nafion membranes were modified by chemical polymerization of aniline using ammonium peroxodisulfate as the oxidant. The Nafion-polyaniline composite membranes were extensively characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), infrared (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and ion-exchange capacity measurements. The transport properties were also evaluated by conductivity and electrodialysis measurements. The data show that when a high oxidant concentration (1 M (NH4)2S2O8) is used, polyaniline is mostly formed at the surface of the Nafion membrane with a higher proportion of oligomers. On the contrary, when 0.1 M oxidant is used, polyaniline is mostly formed inside the ionic domains of Nafion, blocking the pathway to ion transport and thus reducing the transport of Zn2+ as well as the transport of H+. These data were also compared to the data obtained with poly(styrene sulfonate)-PANI composite membranes.     

黄烷类衍生物的合成及其生物活性研究

An efficient and feasible synthetic approach was developed for the synthesis of an array of new flavane derivafives from the substituted benzaldehyde with the reduction of chalcones and subsequent cyclization as the key steps. The purity and structure of the products were confirmed by the elemental analysis and a combination of its IR, ^1H and ^13C NMR, and mass spectra. These synthetic compounds were tested for xanthine oxidase （XO） inhibitions and antifungal actions against Candida albicans, Cryptococcus neoformans, Aspergillus sp. and Trichophyton rubrum. 7-Hydrazinocarbonylmethoxy-4＇-methoxyflavane （9） was found to be the most XO inhibitory with IC50=76.4 μmol/L, and the most potent antifungal compound was 4＇-hydrazinocarbonylmethoxyflavane （12） with minimal inhibition concentration MIC=8 μg/mL against Trichophyton rubrum.     

A DNA-mediated crosslinking strategy to enhance cellular delivery and sensor performance of protein spherical nucleic acids

Intracellular delivery of enzymes is essential for protein-based diagnostic and therapeutic applications. Protein-spherical nucleic acids (ProSNAs) defined by protein core and dense shell of oligonucleotides have been demonstrated as a promising vehicle-free enzyme delivery platform. In this work, we reported a crosslinking strategy to vastly improve both delivery efficiency and intracellular sensor performance of ProSNA. By assembling individual ProSNA with lactate oxidase (LOX) core into a nanoscale particle, termed as crosslinked SNA (X-SNA), the enzyme delivery efficiency increased up to 5–6 times higher. The LOX X-SNA was later demonstrated as a ratiometric probe for quantitative detection of lactate in living cells. More importantly, X-SNA probe showed significantly improved sensor performance with signal-to-noise ratio 4 times as high as ProSNA when detecting intracellular lactate.

By crosslinking protein spherical nucleic acid (SNA) into a supramolecular architecture X-SNA, the intracellular enzyme delivery efficiency was significantly enhanced, showing 3–4 times higher signal-to-noise ratio in detecting intracellular lactate.