电活性分子L-B膜修饰CdSe薄膜电极的光电化学研究

用电活性分子——硬脂酸二茂铁酯L-B膜修饰了薄膜CdSe电极,在单色光650nm光照下用循环伏安法研究修饰的薄膜电极的光电化学性能。研究结果指出经多层L-B膜修饰后,薄膜CdSe电极的,I-V性能和光稳定性都有明显改善。用界面能级关系讨论了硬脂酸二茂铁酯L-B膜在光照的CdSe薄膜/Fe(CN)_6~(4-)溶液界面起传递电荷的中介作用,加速了界面的电荷转移。     

脂肪酶催化合成环十五内脂的酸碱效应

以15-羟基十五烷酸甲酯为底物,进行了脂肪酶催化合成环十五内酯研究,考察了酶活性与pH值的关系,探讨了酶粉pH值记忆和有机相酸碱性对内酯化反应的影响。结果表明,pH=6~7时脂肪酶的水解活力最高,pH=6~6.5时15-羟基十五烷酸甲酯转化环十五内酯的转化率最高,添加有机酸碱对内酯化反应产生不利影响。     

硬脂酸二茂铁酯L—B膜修饰SnO2电极的阻抗研究

测定了二茂铁衍生物——硬脂酸二茂铁酯L-B膜修饰SnO_2电极在Fe(CN)_6~(3-/4-)溶液中的阻抗性能,用单纯形法求出了等效电路中的元件参数值,计算了电极反应速度常数K_s。从分析SnO_2电极修饰不同层的硬脂酸二茂铁酯L-B膜的界面阻抗和电极反应的动力学性能,表明与在固相中研究的硬脂酸二茂铁酯L-B膜的阻抗性能明显不同,在Fe(CN)_6~(3-/4-)溶液中表现了电活性分子修饰电极的界面阻抗行为,进一步证实了修饰在SnO_2电极上的硬脂酸二茂铁酯L-B膜在Fe(CN)_6~(3-/4-)的氧化还原电极反应过程中,起电荷传递的中介作用。     

吐温修饰脂肪酶的研究

分别用甲醛和戊二醛作为偶联剂,共价连接吐温80和猪胰脂肪酶,回收共价修饰脂肪酶,并且比较修饰酶与自然酶在性质上的差异。当甲醛和戊二醛浓度相同时,用甲醛连接的修饰酶的活力最高,而用戊二醛连接的修饰酶的氨基连接效率高。当用不同浓度的甲醛修饰时,发现浓度为1．25mg·mL的甲醛连接的修饰酶的活力最高。在碱性条件下,修饰酶比自然酶的活力高,在中性、酸性条件下,自然酶的活力高     

利用醋酸纤维/聚四氟乙烯复合膜中的微结构固定化脂肪酶

脂肪酶的固定化是降低其使用成本的有效途径之一.提出了利用亲水/疏水复合膜中的微结构固定化脂肪酶的新思路.首先制备由致密的亲水层和多孔的疏水层组成的醋酸纤维素/聚四氟乙烯（CA/PTFE）复合膜,然后利用复合膜的特殊微结构,用超滤的方法实现了脂肪酶的固定化.扫描电镜照片结果表明,大部分被截留的酶位于复合膜的界面处.制备得到的固定化酶膜应用于水解橄榄油的反应,其最高催化活力达到1.24 μmol FFA·min^-1·cm^-2,大大高于文献报道值.同时研究了固定化脂肪酶膜的催化动力学,考察了亲水层厚度和脂肪酶负载量对固定化效果的影响,优化了固定化条件.在经过10次（50 h以上）的重复使用后,固定化酶膜的活力仅降低了20%.     

葡萄糖硬脂酸酯的非水相酶法制备及其动力学研究

研究了脂肪酶催化合成葡萄糖硬脂酸酯（GSAE）的非水相转化条件及其效果。从7种商品化脂肪酶中筛选适于非水相酶法制备GSAE的酶;在50 ml锥形瓶中加入一定量的葡萄糖、硬脂酸、脂肪酶、吸水剂、助溶剂等,分别探讨脂肪酶种类及用量、助溶剂种类及用量、酸糖比、水份、分子筛用量、摇床速率、反应温度、反应时间等因素对GSAE合成反应产率的影响。结果表明,丙酮是适宜的助溶剂,在丙酮反应体系中脂肪酶Novozyme 435 保持较高活性,适宜酶法制备GSAE,水份明显降低脂肪酶活性和酯化反应产率,底物、助溶剂和反应过程的除水对于该酯化反应是十分必要的。正交试验设计优化的酯化反应条件为：Novozyme 435酶用量0.08 g、分子筛用量0.8 g、硬脂酸 : 葡萄糖(摩尔比) = 3 : 1、反应温度45℃,丙酮用量10ml、摇床转速150r/min、反应时间5 h。此条件下最大反应速率Vm=0.749μmol/min?g和Km = 0.0203 mmol/L,GSAE产率达到64.11%。     

葡萄糖硬脂酸酯的非水相酶法制备

考察了脂肪酶催化合成葡萄糖硬脂酸酯(GSAE)的非水相转化条件及其效果。从7种商品化脂肪酶中筛选适于非水相酶法制备GSAE的酶,分别探讨脂肪酶种类及用量、助溶剂种类及用量、底物摩尔比、水分、分子筛用量、摇床速率、反应温度、反应时间等因素对GSAE合成反应产率的影响。结果表明,丙酮是适宜的助溶剂,在丙酮反应体系中固定化脂肪酶Novozyme 435是适宜GSAE酯化反应的最好催化剂,水分明显降低脂肪酶活性和酯化反应产率,底物、助溶剂和反应过程的除水对于该酯化反应是十分必要的。正交实验设计优化的酯化反应条件为:Novozyme 435酶用量0.08 g、分子筛用量0.8 g、n(硬脂酸)∶n(葡萄糖)=3∶1、反应温度45℃、丙酮用量10 mL、摇床转速150 r/min、反应时间5 h。该条件下最大反应速率Vm=0.749μmol/(min.g)和Km=0.020 3mmol/L,GSAE产率达64.11%。     

膜材料的亲疏水性对固定化脂肪酶的影响

用吸附法固定脂肪酶时,膜材料的亲疏水性对固定化酶的量、比活力和活力稳定性等有很大影响.今以柱状假丝酵母脂肪酶和猪胰脂肪酶为研究对象,选取了8种亲疏水性不同的膜材料(醋酸纤维素、聚丙烯腈、聚酰胺、聚砜、聚醚砜、聚偏二氟乙烯、聚丙烯和聚四氟乙烯)作为固定化载体,用吸附法制备了固定化脂肪酶膜.研究结果表明,强疏水性聚四氟乙烯和聚丙烯膜对两种酶的吸附量都比较大,且固定化酶的比活力和活力回收率比较高,聚四氟乙烯固定化柱状假丝酵母酶比游离态酶的半衰期提高了6倍以上.强亲水性醋酸纤维素膜对猪胰脂肪酶的吸附量比聚四氟乙烯高,但是固定化酶的比活力、活力回收率比强疏水性膜低,而接触角在40°～50°的聚酰胺膜和聚砜膜的吸附量最小.因此吸附法制备固定化脂肪酶膜,选择聚丙烯膜和聚四氟乙烯膜是合适的,制备的优化条件为吸附温度25℃,酶溶液的pH为7.5,吸附时间10 h.     

乳化中的表面活性剂

涂料树脂乳化液是水性涂料的主要形式之一。它是藉表面活性剂在树脂（油）／水界面上,通过自组集而形成的单分子层（界面膜）来稳定。此界面膜以表面活性剂的亲油部分（尾）指向油相,以亲水部分（头）指向水相,并拥有3个与乳化相关的现象,即界面张力,自发曲率（spontaneous curvature）和弯曲刚性来发挥作用。     

溶胶-凝胶法固定化Candida sp.99-125脂肪酶

利用正硅酸甲酯(TMOS)和丙基三甲氧基硅烷(PTMS)为复合硅源,以PEG(MW=20000)为稳定剂,以HCl为催化剂,经过溶胶-凝胶过程包埋假丝酵母99-125脂肪酶. 研究得到最适的固定化条件为：PTMS与TMOS的摩尔比4: 1, R值(水与硅源的摩尔比)20, 给酶量(酶占硅源的质量百分数)3.71%, PEG与酶的质量比(1~1.5):1, 硅源水解时间35 min. 在该条件下,固定化脂肪酶的最高酯化活力是游离酶最高酯化活力的2.02倍. 固定化脂肪酶在100℃保温2 h后酶活仍维持为59.1%,固定化酶催化特定酯化反应,经过8批连续反应96 h后酶活维持不变.     

Esterification kinetics of long-chain fatty acids and fatty alcohols with a surfactant-coated lipase in n-hexane

The esterification reaction kinetics of long-chain fatty acids and fatty alcohols catalyzed with a surfactant-coated lipase in a microaqueous n-hexane system were studied. The biocatalytic complex, surfactant-lipase adduct, showed 40 times the activity after a reaction time of 5 h compared to the unmodified lipase in the same reaction system. Various factors that may affect the activity of the modified lipase were studied, such as the influence of substrate fatty acid chainlength, water content, and temperature. By varying the concentration of each of the two substrates while keeping that of the other substrate constant, it was found that the esterification reaction follows Michaelis-Menten kinetics. The surfactant-enzyme complex kinetic parameters were determined with respect to both substrates. It was suggested that the kinetics of the lipase-catalyzed esterification reaction model follow a Ping-Pong Bi Bi mechanism with no substrate or product inhibition.     

Synthesis, Characterization, Biodegradation and Evaluation of the Surface Active Properties of Nonionic Surfactants Derived from Jatropha Oil

Four nonionic surface active agents were synthesized using the fatty acids obtained from the hydrolysis of Jatropha oil. The fatty acids obtained contained different fatty acids including: palmitic, stearic, oleic, linoleic and linolenic acids in different proportions. The chemical structures of the obtained surfactants were characterized using elemental analysis and FTIR spectroscopy. The surface activities of the different surfactants were determined using surface and interfacial tension measurements. The surfactants showed good surface and interfacial activities, which are dependent on their chemical structures. Thermodynamic parameters of adsorption and micellization confirmed these results. The biodegradation tests in river water showed that the surfactants are readily biodegradable, and reached the European standards after 24 days. Surfactants containing longer nonionic chains formed stable emulsions with paraffin oil, while shorter chains exhibit a lower emulsion stability performance.     

Wettability of Surface Oxyfluorinated Polypropylene Fibres and Its Effect on Interfacial Bonding with Cementitious Matrix

The surface of high molecular weight polypropylene monofilament fibre was modified using a oxyfluorination method. The oxyfluorination treatment level was varied and a hydrolysis post-treatment was also applied. Contact angles of oxyfluorinated, hydro-lyzed oxyfluorinated and unmodified polypropylene fibres were obtained by dynamic contact angle (DCA) measurement using three liquids of known dispersion, acid and base surface free energy components. The surface free energies were then calculated according to the acid-base theory developed by Good, van Oss and Chaudhury. Surface oxyfluorination largely increased the acid and base components of the fibres' surface free energy compared with unmodified polypropylene fibres. The oxyfluorinated and unmodified polypropylene fibre surfaces were observed by Scanning Electronic Microscopy and Photoacoustic Infrared Spectroscopy. It was found that the surface oxyfluorination largely increases the roughness of the polypropylene surfaces and the carbonyl group content increases as the treatment level increases. The interfacial shear bond strengths between the cementitious matrix and the polypropylene fibres treated under various conditions were determined by embedded fibre pull-out tests. Results showed that the fibre surface oxyfluorination treatments increase the interfacial bond strengths. The correlations between the shear bond strengths and surface free energy components were established. Results showed that fibre/concrete interfacial bonding was best correlated with the acid component of surface free energy of polypropylene fibres.     

Gemini Cationic Surfactants: Synthesis and Influence of Chemical Structure on the Surface Activity

Three cationic gemini surfactants were synthesized and characterized using different methods. Their surface activities were measured using surface and interfacial tension measurements. The effect of the spacer chain length on the surface activity, emulsification power and interfacial tension was studied. The thermodynamic parameters showed the tendency towards micellization and adsorption. The results showed that longer spacers increased the micellization tendencies of the surfactants, while shorter spacers increased the adsorption tendency at the air–water interface.     

Suspension stabilizers for PVC production I: Interfacial tension measurements

The effect of commonly used suspension stabilizers on the interfacial tension of the vinyl chloride (VCM)/water interface was studied at 50°C, using the drop volume method. The measurements covered drop times from a few seconds to about 1000 s. The interfacial tension between VCM and pure water was found to be 32 mN/m. In the presence of additives, the interfacial tension varied with drop time. An equilibrium situation was probably not reached in any of these experiments. The surface activity of the poly(vinyl alcohol) increased with increasing acetate content. The interfacial tension decreased much more slowly with time in the presence of the poly(vinyl alcohol)s than with the cellulose ether tested. However, this polymer, Methocel F50, on adsorption at the interface formed a solid, mechanically strong surface film. The formation of such films was delayed by addition of ammonium laurate and/or Span 20.     

邻苯二甲酸单醇酯钠盐的合成及性能研究

分别用十二醇、十四醇、十六醇和十八醇与邻苯二甲酸酐反应合成邻苯二甲酸单醇酯,再用氢氧化钠中和得钠盐。研究了催化剂、醇、原料配比、酯化温度及溶剂等对单酯酯化率的影响,用红外光谱和核磁共振波谱对产物结构进行了表征,测定其泡沫性能和界面性能。确定了最佳酯化条件为:以自制催化剂BN-1作催化剂,二甲苯为溶剂,n(醇)∶n(酸酐)=1∶1.6,酯化温度100℃,酯化时间5 h。随着醇碳链增加,邻苯二甲酸单醇酯钠盐泡沫能力降低,但界面活性增强。     

Correlation between adhesion of aqueous solutions of nonionic and anionic surfactant mixture with short-chain alcohols to polymer surface and their adsorption at interfaces. I. Adhesion tension and adsorption

Contact angle measurements of aqueous solutions of a p-(1,1,3,3-tetramethylbutyl) phenoxypoly(ethylene glycol) (Triton X-100)/sodium dodecylsulfate (SDDS) mixture with a short-chain alcohol (methanol, ethanol or propanol) on polytetrafluoroethylene (PTFE) and nylon-6 surfaces were made. Complete spreading of the studied solutions was observed only in the case of nylon-6. Contact angle isotherms were considered with regard to alcohol activity as well as the adsorption of the surfactant mixture and alcohol at the polymer-solution interface. For this analysis solid-liquid interfacial tension and changes of adhesion tension as a function of the surface tension of the solution were taken into account. It appeared that in the range of alcohol concentration in which it is present in the monomeric form in the bulk phase, the Gibbs surface excess concentration of the surfactant mixture and alcohol at the PTFE-solution interface is close to that at the solution-air interface. However, alcohol activity at these interfaces differ from each other. The adsorption of the surface active agents at the nylon-6-solution interface is much lower than at the solution-air interface.     

Production of biodiesel by esterification of natural fatty acids over modified organoclay catalysts

Biodiesel has been produced by esterification of natural fatty acids with methanol in the presence of a modified bentonite with 1-benzyl-1H-benzimidazole-based Brønsted acidic ionic liquids as catalysts. The effect of reaction temperature, type and amount of catalyst, molar ratio and reaction time was investigated. The results showed that MB3B (bentonite modified with 3,3′-(butane-1,6-diyl)bis(6-sulfo-1-(4-sulfobenzyl)-1H-benzimidazolium) hydrogensulfate) has the highest catalytic activity and best recyclability under the optimized reaction conditions. Thus, this modified bentonite is able to catalyze the esterification of oleic acid to its methyl ester in 6 h with yields of more than 92%. The catalytic activity of MB3B for the esterification of natural other fatty acids and alcohols has also been studied.     

Synthesis of fatty esters by polyethylene glycol-modified lipase

Monomethoxypolyethylene glycols (PEG) of molecular masses 1900 and 5000 were activated using p-nitrophenyl chloroformate to form PEG–nitrophenyl carbonates (activated PEG) with high yield (96–98%). The activated PEG was covalently attached to Candida rugosa lipase. Increasing the molar ratio of activated PEG to the enzyme increased the degree of lipase modification. These modified lipases exhibited specific ester synthesis activities on organic solvents compared with native lipase. The degree of activity enhancement depended on the size of activated PEG used and the degree of modification of the enzyme. Maximal activity was attained after exhaustive of modification. The effects of different solvents, reaction temperature, and fatty acids on the esterification activity and the stability of the modified enzyme were investigated. The optimum esterification temperature (40° C) and preference of fatty acids as acyl donors of the modified lipase were very similar to those of the native enzyme. The modified lipase exhibited higher activity non-polar solvents than in polar solvents, and showed higher temperature, solvent and storage stability then the native lipase.     

Synthesis and Surface Active Properties of Sulfonated Acrylate Esters Based on Al‐Cedre Oil

Sulfonated acrylate esters have been synthesized by using renewable raw materials such as fatty alcohols of Al‐Ceder oil. Mixed fatty acids were isolated from Al‐Ceder oil by hydrolysis; both saturated and unsaturated fatty acids were isolated from the mixed fatty acids. The methyl esters of mixed fatty acid, saturated and unsaturated acids of Al‐Cedre oil were subjected to reduction with (LiAlH4) to give the corresponding fatty alcohols. The products of the reduction process were saponified and the hydroxyl values were estimated to further confirm the reduction occurrence. The acrylate esters were synthesized by esterification of acrylic acid with fatty alcohols of C_16:0, C_18:0, C_18:1, and C_18:2 mixed saturated, mixed unsaturated and mixed fatty acids of Al‐Cedre oil, respectively. This esterification was followed by addition of NaHSO₃ to form bisulfite adducts. The structures of the prepared surfactants were characterized by IR and ¹HNMR spectroscopy. A series of useful surface parameters, stability towards acids and base hydrolysis and calcium stability have been determined.