纳米晶状磷酸钙盐/Al2O3-Ti生物复合材料的制备与结构表征

0引言众所周知,钛及其合金具有优良的机械力学性能,但其生物活性不足。因此,在金属基体上涂敷一层生物活性涂层,结合金属与生物活性材料的各自优势,已成为世界各国学者研究最为活跃的生物复合材料体系之一。该体系可用于临床医学,作为人体硬组织等的修复替换材料。目前,已开发出多种在金属基体上制备生物活性涂层的工艺和方法。如:等离子沉积法[1]、离子束溅射法[2]、激光熔覆法[3]、溶胶鄄凝胶法[4]、电化学沉积与水热处理合成法[5]、电泳沉积[6]、电结晶[7]等多种方法。但现有涂层材料尚存在一些问题:(1)由于替换材料的高硬度而导致其周围硬组织坏死[8];(2)由于疲劳磨损或热膨胀不匹配引起涂层脱落[9];(3)由于异质相导致生物活性降解[10]。因此,研究新的制备工艺,开发新的生物复合材料体系就显得十分重要。考虑到Al2O3具有优异的抗磨损、耐腐蚀等性能,以及较好的生物相容性,常作为临床选用的人造硬组织承载材料[11],故在本研究工作中,我们首次采用阳极氧化与水热处理复合工艺研制酸式磷酸钙/Al2O3鄄Ti生物复合材料体系。该体系不同于由日本Ishizawa等研制的HAp/TiO2鄄Ti复合体系[12]。主要体现在两...     

Phosphated Alumina Catalysts: Surface Properties and Reactivity towards 2-PrOH Decomposition

Summary. The influence of the type of precursor, the phosphate content, as well as the source of phosphate ions on the surface texture, acidity, and catalytic activity of phosphated aluminas has been described. Phosphated alumina catalysts were prepared by impregnating two different precursors with two different sources of phosphate in different loading levels w = 3, 6, and 10% PO₄ ³⁻. The characterisation of the catalyst was performed using X-ray powder diffraction (XRD), thermal analysis (TG), and nitrogen adsorption–desorption methods at 77 K. The surface acidity of the catalysts has been studied by FT-IR spectroscopy of adsorbed pyridine at different temperatures. Moreover, the activity in the catalytic decomposition of isopropanol (2-PrOH) has been investigated at 520 K. Investigation of the surface properties shows that the addition of phosphate ions does not change the crystal phase (γ-phase) and the samples prepared from gel and phosphoric acid have the highest surface area. An FT-IR study of pyridine adsorption shows both Lewis and Br?nsted acid sites on the surface of the samples prepared from gel, while only Lewis acid sites are detected on the samples prepared from crystalline oxide. The catalytic activity by 2-PrOH conversion shows that the conversion of 2-PrOH as well as the selectivity towards propene formation increases from w = 3 to 6% followed by a decline for w = 10%. Moreover, the strongest activity was detected in case of phosphated alumina gel with w = 6% which gives 97.3% propene and 96.1% conversion of 2-PrOH.     

Development of an Optical Fiber Fluorescence Setup for in situ PAHs Detection in Porous Media. Application to Pyranine Transport in Sand Columns

Abstract

An optical method based on fluorescence spectroscopy was developed for in-situ non-destructive, real time, organic pollutant detection and quantification in soil. Optical fiber-based light-induced fluorescence probes allowing in-situ specific chemical detection were constructed. Pyranine was chosen as a model fluorescent Polycyclic Aromatic Hydrocarbon (PAH). The effect of sand particles on fluorescence measurements was established: the fluorescence intensity in water-saturated sand was eight times lower than in aqueous solutions, due to light scattering by the sand particles. To adapt the method to dynamic pollutant concentration measurements in soil, two different designs of light diffusers were constructed and compared. A light distributor with a quartz window was chosen for its higher sensitivity and reproducibility. The probes were introduced into two different columns: short ones used to study the effect of the measurement location in the column and longer ones to study pyranine transport. It was shown that, in columns, the measurement location plays an important role; measurements near the walls, in particular, were different from those performed more towards the center of the column in a given section. As a consequence, one should avoid measurements near the circumference. Preliminary results were successfully compared to a chemical transport model and revealed that the methodology is a powerful tool to measure in-situ concentration changes; on the other hand, fluorescent measurements can be used efficiently to determine transport parameters and give results comparable with those obtained with classical breakthrough curve fittings.     

Ruthenium-tin sol-gel catalysts: effect of the preparation and tin precursor influence

The influence of the synthesis route and the chemical nature of tin precursors on the catalytic properties of supported sol-gel Ru-Sn/SiO₂ catalysts were studied. It was demonstrated that introduction of tin afforded better selectivities than a monometallic sol-gel catalyst in the liquid-phase hydrogenation of cinnamaldehyde; however, the chemical nature of the tin precursor did not influence the catalyst performance. Sol-gel catalyst properties depended significantly upon the preparation method used and on the activation temperature. The selectivity to unsaturated alcohol increased with conversion, which is indicative of the in-situ creation of active sites selective in the carbonyl bond hydrogenation.     

[3 + 3] Cycloaddition of aza-oxyallyl cations with 1,4-dithiane-2,5-diols for the construction of 3-thiomorpholinones

Abstract

Base-mediated [3?+?3] cycloaddition reaction of in-situ formed aza-oxyallyl cations and 1,4-dithiane-2,5-diols has been achieved under mild reaction conditions. This strategy provides direct and efficient access to prepare desired thiomorpholin-3-one derivatives in moderate-to-high yields. The approach features broad substrates scope and short reaction time. Moreover, the resulting products can be readily converted into other useful heterocyclic compounds including 2H-1,4-thiazin-3(4H)-ones and thiomorpholine-3,5-diones.     

Kinetic resolution of both 1-phenylethanol enantiomers produced by hydrolysis of 1-phenylethyl acetate with <Emphasis Type="Italic">Candida antarctica</Emphasis> lipase B in different solvent systems

The enzymatic resolution of (R, S)-1-phenylethanol produced by hydrolysis of (R, S)-1-phenylethyl acetate catalyzed by immobilized Candida antarctica lipase B (CALB) was successfully carried out in different solvent systems. A systematic screening and optimization of the reaction parameters such as enzyme amount, the nature and the content of organic solvent, pressure and temperature in supercritical carbon dioxide (SC-CO₂) and phosphate buffer, with respect to the conversion rate, were performed. CALB exhibits high enantioselectivity in both tert-butanol with 0.025 mol/l phosphate buffer (pH 7.5) and SC-CO₂ with 0.025 mol/l phosphate buffer (pH 7.5) systems. The conversion rate was 41.2% higher in SC-CO₂ with 0.025 mol/l phosphate buffer (pH 7.5) then in tert-butanol with 0.025 mol/l phosphate buffer (pH 7.5) and the reaction time decreased from 8 h to 90 min.     

Polymer-polymer rectifying heterojunction based on poly(3,4-dicyanothiophene) and MEH-PPV

Thin, homogeneous films of a high electron affinity (n-dopable) polymer, poly(3,4-dicyanothiophene) (PDCTh), were prepared by in-situ thermal polymerization of 2,5-diiodo-3,4-dicyanothiophene on substrates. As a result of the presence of two cyano substituents on the thiophene backbone, PDCTh is an electronegative polymer, with the LUMO at ca. 3.6 eV and the HOMO at ca. 6.7 eV. We demonstrate the fabrication of polymer-polymer rectifying heterojunctions using PDCTh and poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) polymer layers on ITO-glass. Rectification ratios in the current voltage characteristics of these devices exceed 10.³ This device exhibits a photovoltaic effect with a dc sensitivity at -3 V reverse bias of 4 × 10^-4 A/W or quantum yield of 0.1% electrons/photon. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 3115–3120, 1998     

Substrate-Independent Stable and Adherent Reactive Surface Coatings and their Conversion with Amines

Summary: To create stable, adherent and reactive surface coatings, a hybrid polymer composed of poly(methylsilsesquioxane) (PMSSQ) and poly(pentafluorophenyl acrylate) PFPA with a M_n of 32000 g/mol was prepared by a RAFT polymerization procedure. These hybrid polymer has been used for coating experiments. The PFPA part enabled a variable functionalization of the coating afterwards. The stability on various substrates (e.g. glass, PMMA, steel) was tested in an ISO tape test. These reactive surface coatings were modified using different amines, such as amino-terminated PEG, dodecyl amine and N-isopropyl amine. The conversion was analyzed by FT-IR and contact angle measurements.     

Colorimetric and electrochemical detection of ligase through ligation reaction-induced streptavidin assembly

We propose a concept for ligase detection by conversion of aggregation-based homogeneous analysis into surface-tethered electrochemical assay through streptavidin（SA）-biotin interaction. Sortase A（Srt A）served as the model analyte and two biotinylated peptides（bio-LPETGG and GGGK-bio） were used as the substrates. Srt A-catalyzed ligation of the peptide substrates led to the generation of bio-LPETGGGKbio. The ligation product（bio-LPETGGGK-bio） induced the aggregation and color change of SA-modifi...     

Deracemization By Simultaneous Bio‐oxidative Kinetic Resolution and Stereoinversion

Deracemization, that is, the transformation of a racemate into a single product enantiomer with theoretically 100 % conversion and 100 % ee, is an appealing but also challenging option for asymmetric synthesis. Herein a novel chemo‐enzymatic deracemization concept by a cascade is described: the pathway involves two enantioselective oxidation steps and one non‐stereoselective reduction step, enabling stereoinversion and a simultaneous kinetic resolution. The concept was exemplified for the transformation of rac‐benzylisoquinolines to optically pure (S)‐berbines. The racemic substrates were transformed to optically pure products (ee>97 %) with up to 98 % conversion and up to 88 % yield of isolated product.     

Colorimetric and electrochemical phosphodiesterase inhibition assays for yessotoxin detection: development and comparison with LC-MS/MS

This work describes the development and applicability of two functional assays for the detection of yessotoxin (YTX), a polycyclic ether marine toxin produced by dinoflagellates. The assays are based on the interaction between this toxin and the phosphodiesterase (PDE) enzyme and the subsequent measurement of the enzyme activity by colorimetric and electrochemical methods. Firstly, several enzyme substrates were tested in order to select those able to be detected by colorimetry or electrochemistry after enzymatic hydrolysis. The substrates that provided the highest absorbance values and density currents were p-nitrophenyl phenylphosphonate and α-naphthyl phosphate, respectively. After optimisation of the experimental parameters, limits of detection of 0.8 and 0.6 μM were attained by colorimetry and electrochemistry, respectively. An inhibitory effect of YTX on the PDE activity was observed. The assays have been applied to the analysis of YTX production by Protoceratium reticulatum cultures, and results were compared with liquid chromatography–tandem mass spectrometry analysis.     

高岭土原位无溶剂法合成小粒径ZSM-5分子筛

结合原位水热法和无溶剂法的优点,在不添加有机模板剂和溶剂的基础上,以高岭土为原料通过晶种诱导绿色高效地合成出ZSM-5分子筛。运用X射线衍射、N2吸附-脱附、扫描电镜、透射电镜和NH3程序升温脱附(TPD-NH3)等技术对ZSM-5分子筛进行表征。表征结果与原位水热法合成的ZSM-5分子筛相比,原位无溶剂法合成ZSM-5分子筛的结晶度较高、晶体粒径较小、酸强度略高、孔结构相似。     

In-situ atomic force microscopy investigation of aerosols exposed to different humidities

In-situ atomic force microscopy (AFM) studies were performed on aerosol samples showing the potential of a topochemical approach for gaining information on chemical and physical aerosol properties. The behavior of single sub-micron particles has been investigated with respect to changing humidity in the surrounding atmosphere. Volume calculations allowed monitoring of these changes on a quantitative basis. As expected these in-situ experiments showed the restructuring of particles with highly agglomerated chain-like structures induced by condensation and evaporation on a nanometer scale. The particle volumes decreased as the branched chain-like structure changed into a more regular clump-like structure. The degree of restructuring was clearly depending on the chemical surface properties as could be proven for soot-like test aerosol particles. The collapse of the chain-like structure on a nanometer scale was found to be significantly more pronounced for soot particles previously exposed to ozone. Furthermore, in-situ studies were performed on ammonium sulfate test aerosol. Though a distinct deliquescence point typical for salts could not be detected, neither in the topography nor in the phase image, ammonium sulfate test aerosol particles seemed to partially dissolve in humid atmosphere and hence to decrease in volume. Thus, the volume decrease induced by purging with humid nitrogen and subsequent drying which was also observed for a considerable fraction of urban aerosol, could be interpreted in terms of composition and surface properties considering the geometrical structure (i.e. state of agglomeration) of the particles. Received: 14 January 1999 / Revised: 1 March 1999 / Accepted: 4 March 1999     

Lateral Deprotometallation-Trapping Reactions on Methylated Pyridines,Quinolines and Quinoxalines Using Lithium Diethylamide

The functionalization of methylated azines and diazines has aroused the interest of chemists given the structural diversity that it affords. Hindered lithium dialkylamides have been used to deprotometallate these substrates chemoselectively. In contrast, it can be observed that, despite some promising work, lithium diethylamide has been used very little for this purpose. Our objective here is on the one hand to make an inventory of what reagents have been used to deprotometallate methylpyridines, -quinolines and -quinoxalines, and on the other hand to describe the results obtained by seeking to functionalize a series of substrates with lithium diethylamide (picolines, 2,4-lutidine, methylquinolines and 2-methylquinoxaline). Our efforts to take advantage of the use of an in-situ trap (a zinc chloride chelate) in these reactions are also described.     

Antibacterial glass films prepared on metal surfaces by sol–gel method

This paper describes the preparation and characterization of glass films consisting of SiO₂, Li₂O, Na₂O, K₂O or MgO in varying compositions on stainless steel and aluminum substrates by sol–gel method. Silver phosphate or silver incorporated zeolite was also introduced into the sols for obtaining antibacterial effect. The SiO₂/Li₂O/Na₂O system having the composition of 85:5:10 wt% was found as the optimum for obtaining a stable sol and film formation. The films were investigated by scanning electron microscopy (SEM) and electron dispersive analysis by X-ray (EDX), Fourier transformed infrared (FTIR) spectroscopy, thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA). Homogenous films having 300 ± 20 nm thicknesses were formed by spin coating and then by curing at 500 °C for 1 h. Obtained films had high adherence to the metal substrates and they were also durable in acidic, basic or NaCl environments. They also presented a powerful antibacterial effect against E. coli.     

Synergism in binary mixtures of Thermobifida fusca cellulases Cel6B,Cel9A,and Cel5A on BMCC and Avicel

In an earlier binding study conducted in our laboratory using Thermobifida fusca cellulases Cel6B, Cel9A, and Cel5A (formally Thermomonospora fusca E₃, E₄, and E₅), it was observed that binding capacities for these three cellulases were 18–30 times higher on BMCC than on Avicel. These results stimulated an interest in how the difference in accessibility between the two cellulosic substrates would affect synergism observed with cellulase mixtures. To explore the impact of substrate, accessibility on the extent of conversion and synergism, three binary T. fusca cellulase mixtures were tested over a range of cellulase ratios and total molar cellulase concentrations on Avicel and BMCC. Higher extents of conversion were observed for BMCC due to the higher enzyme to substrate ratio resulting from the higher binding The processive endoglucanase, Cel9A, had four times the extent of conversion of the end endocellulase Cel5A, while the exocellulase Cel6B had three times the extent of conversion of Cel5A. Approximately 500 nmol/g of the cel9A+Cel6B mixture was needed to obtain 80% conversion, while the Cel6B+Cel5A and Cel9A+Cel5A mixtures required 1500 and 1250 nmol/g, respectively, to obtain 80% conversion. Thus, it appears that the more accessible structure of BMCC, as reflected by its binding capacity, results in relative higher processive activity.     

Catalysis of enantiomeric ester hydrolysis by N-decanoyl-L-histidine in polymer domains

Catalytic hydrolysis of enantiomeric substrates by N-decanoyl-L -histidine was studied at pH 7.30, 0.02M phosphate buffer, and 25°C in the presence of quaternized polymers. The rate of reaction is remarkably accelerated in the presence of polyethylenimine derivatives, but the observed stereoselectivity depends on the structure of the substrates.     

Hazards associated with the use of electrochemically prepared substrates in the qualitative analysis of aqueous solutions by surface-enhanced Raman spectroscopy

The different spectral behaviour of silver surface-enhanced Raman spectroscopy (SERS) substrates roughened electrochemically in and without the presence of an analyte has been shown clearly. These differences are associated with anomalous local pH conditions within the cavities in surfaces of high microporosity in the in-situ roughened silver substrates. In-situ roughened silver electrodes appeared to have a much higher porosity compared with ex-situ roughened surfaces.     

Visible absorption of iodine-doped polysilane with p-N,N-dialkylaminophenyl substituents

The doping effects on optical and electrical properties of polysilanes were investigated by in-situ measurement. When polysilanes bearing a p-N,N-dialkylaminophenyl substituent were doped with iodine vapor, drastic spectral changes were observed. The evolved visible absorption up to 700 nm was found to be strong and stable compared to that of iodine-doped polysilanes such as poly(methylphenylsilane). On the basis of the studies concerning iodine doping of the related p-N,N-dimethylaminophenyl-substituted silane and disilane, and also theoretical calculations, this new absorption can be best interpreted by the result of charge transfer consisting of the strong interaction between iodine and dialkylamino substituents in the polysilanes. © 1996 John Wiley & Sons, Inc.