磁性纳米粒子的制备及脂肪酶的固定化

建立了以纳米级磁性粒子为载体固定化脂肪酶的方法,优化了脂肪酶的固定化条件,考察了固定化酶的性质. 制备的磁性载体平均粒径20 nm,具有超顺磁性,分散和再分散效果好. 固定化酶的最适吸附时间为60 min,酶用量:载体量为1:1,固定化酶的酶活达到718 U/g. 结果表明,经纳米磁性粒子固定化后,脂肪酶得到活化,固定化酶比活为游离酶的1.8倍. 同时,固定化脂肪酶的pH稳定性显著提高.     

Fe_3O_4\SiO_2纳米粒子担载的固定化漆酶的稳定性和普施安染料的脱色研究

漆酶是一种生物蛋白酶,容易变性失活且有不可重复使用的特性,限制了漆酶的应用和发展。因此,如何提高漆酶的稳定性和重复使用性尤为重要。本文采用交叉偶联技术,将漆酶固定在具有核壳结构的磁性纳米粒子Fe3O4/SiO2上,探讨了密闭条件下热处理对固定化漆酶热稳定性的影响,及固定化漆酶降解不同浓度普施安的活性。结果表明:Fe3O4\SiO2纳米粒子担载的漆酶经70℃热处理后,仍有70%的活性,表现出良好的热稳定性;固定化漆酶对不同初始浓度普施安的脱色反应,符合一级反应。     

稀土元素铈对氧化锌形貌以及光催化性能的影响

为了进一步了解稀土元素铈修饰的氧化锌光催化剂的形貌特征和掺杂机理,通过将醋酸锌和硝酸铈溶液加入氢氧化钠溶液的共沉淀法合成了不同铈掺杂量的氧化锌光催化材料。采用粉末X射线衍射(XRD)、扫描电镜(SEM)和X射线能量色散谱(EDS)等技术,分析了催化剂的结构特征。结果表明,随着铈含量的增加,氧化锌形貌从一维棒状向二维纳米片结构转变;当铈的掺杂量达到2%(质量分数)时,氧化锌变成了尺寸均匀的圆盘状纳米粒子,并通过甲基橙的光催化降解实验证明2%铈掺杂的氧化锌纳米粒子具有更优越的光催化活性和稳定性。     

氧化锌/聚苯胺复合材料光催化性能研究

通过固相合成法制备氧化锌/聚苯胺复合材料。通过X射线衍射看出,制备了立方晶相氧化锌/聚苯胺复合材料;通过红外光谱看出,出现了氧化锌的吸收峰。氧化锌/聚苯胺复合材料对甲基橙的光催化降解效果较好。经过改性后的氧化锌/聚苯胺复合材料光催化效果更好,稳定性得到了提高,重复使用不影响光催化效率。     

核壳结构磁性树枝状纤维形有机硅固定化脂肪酶制备及其应用

为了提升脂肪酶的稳定性并构建新型固定化酶催化体系,利用改进的Winsor Ⅲ微乳液双连续相体系合成了超顺磁性Fe₃O₄内核和树枝状纤维形氧化硅外壳的核壳结构磁性有机硅纳米粒子（MMOSNs）,用于固定化南极假丝酵母脂肪酶B（CALB）。优化条件后CALB负载量为177.49 mg/g,比水解活性为27390 U/g。磁性有机硅通过与CLAB分子之间疏水相互作用及表面孔道结构,可有效激活CALB的界面活性并保护活性构象免受破坏,比游离酶和磁性无机硅固定化酶表现出更好的活性和稳定性。除此之外,将CALB@MMOSNs用于催化乙酰丙酸与十二醇的酯化反应最高转化率为85.05%,重复使用9次后仍保留68.94%转化率,而商业化N435只保留29.83%。证明疏水性磁性核壳结构有机硅是固定化CALB的良好载体,可有效扩展脂肪酶的工业应用。     

纳米氧化锌粒子的制备研究

氧化锌粒子的超细化,使其在磁、光、电和敏感材料等方面呈现出常规材料所不具备的特殊性能,具有广阔的应用前景.以尿素为沉淀剂,硝酸锌为原料,利用均匀沉淀法制备纳米氧化锌微粒.探索了影响纳米氧化锌制备的因素.通过透射电子显微镜(TEM)和X射线衍射分析(XRD),所制的纳米氧化锌微粒具有六方晶系纤锌矿结构,最小粒径可达25 nm,分散性较好,型貌为球型或类球型.     

梳状亲水性环氧基载体固定化Pseudomonas stutzeri LC2-8脂肪酶

以氯乙酰化聚苯乙烯微球(PS-acyl-Cl)为引发剂,亲水性丙烯酰胺(AM)和甲基丙烯酸缩水甘油酯(GMA)为单体,CuCl及联吡啶(Bipy)为催化体系,通过原子转移自由基聚合反应(ATRP)制备得到梳状亲水性环氧基柔性载体(PS-acyl-P(AM-co-GMA)),通过改变AM与GMA配比,使载体环氧基含量和亲水性得到控制.用该柔性载体固定Pseudomonas stutzeri LC2-8脂肪酶,优化了固定化条件,并对柔性固定化酶性质进行考察.结果显示,当n(AM)∶n(GMA)=20∶60,固定化时间为24 h,固定化温度为30℃,固定化pH为7.0时,固定化酶活力达到最高,为24.1U·g-1.固定化酶的最适pH为8.0,最适温度为30℃,其热稳定性比游离酶高,重复使用8次,剩余酶活力80％左右.以上表明,以ATRP法合成的载体PS-acyl-P(AM-co-GMA)可成功用于脂肪酶的固定化,有效提高脂肪酶的稳定性和实用性.     

改性硅藻土固定化脂肪酶催化蓖麻油制备生物柴油

采用改性硅藻土做为载体,用吸附法对脂肪酶进行固定化,对固定条件进行优化,利用固定化脂肪酶催化蓖麻油制备生物柴油,考察反应时间、温度、醇油比及酶用量对转化率的影响和固定化脂肪酶催化合成生物柴油的稳定性。研究表明,硅烷化试剂添加量0.4%、温度30℃和时间4~6 h时固定化脂肪酶的活性最高,在醇油比为9:1,固定化酶用量为蓖麻油质量的4%,温度为60℃,反应时间为10 h的条件下,生物柴油的产率最高,经过3个批次的反应后,其产率都在40%以上,该固定化酶催化合成生物柴油有良好的工业化前景。     

联氨还原法制备磁性钴纳米粒子

在表面活性剂聚乙烯吡咯烷酮(PVP)的保护下,采用水合肼于乙醇体系中还原CoCl2·6H2O而得到磁性钴纳米粒子,通过X射线衍射检验确认该种方法合成的钴纳米粒子同时具有hcp相和fcc相.X射线光电子能谱的表征结果显示钴粒子表面价态为零价,说明制备过程中没有被氧化.用透射电镜和激光光散射仪对粒子的表面形貌和粒径进行了表征分析,结果显示粒径在30nm左右,近似圆球形,在正己烷中分散效果较好.     

Cu~(2+)修饰低固载量固定化漆酶的活性研究

由于漆酶这种生物蛋白酶有容易变性失活且不可重复使用的特性,限制了漆酶的应用和发展。因此如何提高漆酶的活性,稳定性以及重复使用性尤为重要。本文采用交叉偶联技术,将漆酶固定在具有核壳结构的磁性纳米粒子Fe3O4/SiO2上,并研究了用Cu2+修饰后的低固载量固定化漆酶的活性变化以及修饰后固定化漆酶的稳定性。实验结果显示:Cu2+修饰后的低固载量固定化漆酶的相对活性提高了54%;而且在温度不太高的情况下,修饰后的低固载量固定化漆酶的相对活性优于修饰前的固定化漆酶;修饰后的固定化漆酶降解浓度为10mg·L-1的普施安染料,重复利用13次后降解率仍然可以达到92%。     

Effects of annealing temperature on some structural and optical properties of ZnO nanoparticles prepared by a modified sol-gel combustion method

Plate-shaped zinc oxide nanoparticles (ZnO-NPs) were successfully synthesized by a modified sol-gel combustion method. Zinc acetate, pure water and isopropanol were used as the starting materials. Acetic acid, diethanolamine and nitric acid were used as the polymerization agent, complexing agent and fuel, respectively. The precursors were formed by mixing aqueous solutions of zinc acetate, acetic acid and diethanolamine. Nitric acid was used to dry the produced gel. The resulting xerogel was annealed at 600 °C, 650 °C and 750 °C for 1 h. The synthesized ZnO-NPs were characterized by X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA) and high-magnification transmission electron microscopy (TEM). The XRD results revealed that the samples produced were crystalline with a hexagonal wurtzite phase. The TEM results showed single-crystal ZnO-NPs with nearly hexagonal plate shapes. The optical properties of the ZnO-NPs were studied by UV-visible and Fourier-transform infrared spectroscopy (FTIR). The UV-vis absorption spectra of the ZnO-NPs indicated absorption peaks in the UV region, which were attributed to the band gap of the ZnO-NPs. The results of the FTIR and UV-vis studies showed that the optical properties of the ZnO-NPs depended on the annealing temperature.     

Sm掺杂ZnO QDs的制备及其荧光性能研究

通过研究不同碱/锌、钐/锌物质的量比制备了分散性良好的Sm掺杂氧化锌量子点（ZnO QDs）。通过紫外可见光谱（UV-vis）、X射线衍射（XRD）、场致发射透射电子显微镜（TEM）、能量色散X射线谱（EDS）、X射线光电子能谱（XPS）对样品做了表征。研究结果表明,n（Zn）∶n（OH^-）=1∶1、Sm掺杂量为4%（物质的量分数）时制备的ZnO QDs在383 nm紫外光激发下的荧光发射强度最强。并发现稀土钐离子的掺杂与ZnO QDs的氧空位（OV）形成有关。Sm掺杂后的ZnO QDs的氧空位浓度比未掺杂的高,且ZnO QDs氧空位的浓度越大,其荧光发射强度越强。     

Chemically and Green Synthesized ZnO Nanoparticles Alter Key Immunological Molecules in Common Carp (Cyprinus carpio) Skin Mucus

This study was conducted to compare the effects of commercially available (C) and green synthesized (GS) Zinc oxide nanoparticles (ZnO-NPs) on immunological responses of common carp (Cyprinus carpio) skin mucus. GS ZnO-NPs were generated using Thymus pubescent and characterized by UV–vis diffuse reflectance spectroscopy (DRS), Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDX). Fish (n = 150) were randomly allocated into five groups in triplicate and received a waterborne concentration of 0% (control), 25%, and 50% of LC50 96 h of commercially available (C1 and C2) and green synthesized ZnO-NPs (GS1 and GS2) for 21 days. Results from XRD displayed ZnO-NPs with 58 nm in size and UV-vis DRS, EDX, and FT-IR analysis showed that some functional groups from plant extract bonded to the surface of NPs. The SEM images showed that ZnO-NPs have conical morphology. Acute toxicity study showed a higher dose of LC50_96h for green synthesized ZnO-NPs (78.9 mg.L⁻¹) compared to the commercial source (59.95 mg.L⁻¹). The highest activity of lysozyme and alternative complement activity (ACH50) were found in control and GS1 groups. A significant decrease in alkaline phosphatase activity (ALP) was found in C1 and C2 groups compared to other treatments. Protease activity (P) was significantly decreased in the C2 group compared to the control and GS groups. Total immunoglobulin (total Ig) content was the highest in the control. In addition, total Ig in the GS1 group was higher than GS2. The exposure to ZnO-NPs lowered total protein content in all experimental groups when compared to control. Present findings revealed lower induced immunosuppressive effects by green synthesized ZnO-NPs on key parameters of fish skin mucus.     

Immobilization of lipase on magnetic porous microspheres

开发了以磁性多孔微粒作为载体固定化脂肪酶的方法,进行了载体的FTIR、XRD、SEM、TEM、BET、TGA和VSM等测定与分析,考察了固定化时间、酶载量和缓冲液pH值等因素对固定化酶在有机相中催化烯丙醇酮转酯化反应性能的影响。结果表明,制备的磁性微粒是以Fe₃O₄为磁核,呈现多孔,比表面积12.16 m²/g,平均孔径为171.7 nm,磁铁含量38%并为超顺磁性;在酶与载体质量比为1∶1、pH值8.0及固定化时间6 h制得固定化酶的效果最佳,固定化酶的活力回收率可达240%。以其作为载体制备获得固定化酶操作稳定性得到显著提高,重复利用30批次后残余活力为74.5%,而游离酶7批次后仅为37.1%。     

Preparation of Polyglycidylmethacrylate Macropore Beads and Application in Candida species 99–125 Lipase Immobilization

Polyglycidylmethacrylate beads with macroporous structure were synthesized by suspension polymerization and directly used for Candida species 99–125 lipase immobilization because of their rich surface epoxy groups. The properties of the synthesized polymer beads were characterized by scanning electron microscopy and FT‐IR spectroscopy. To increase the enzyme activity, divinyl benzene and toluene/heptane were used as cross‐linker and porogen, respectively, and the effects of cross‐linker content and porogen content on lipase immobilization were studied. After optimizing the synthesis conditions, the optimum lipase concentration for immobilization was determined as 10 mg mL^–1. The immobilized lipase showed a broader pH stability and higher temperature stability. The immobilized enzyme could be reused for ten batches with 62 % of residual activity.     

固定化Candida sp. 99-125脂肪酶催化合成蜡酯(英文)

Wax esters were synthesized in a solvent free system catalyzed by immobilized lipase from Candida sp. 99-125, with oleic acid and cetyl alcohol. The effects of substrate molar ratio, lipase dosage and water removal were investigated in a 50 ml flask incubated in a thermostatic cultivation cabinet. The optimized conditions were: temperature 40 ℃, shaking at 170 r·min-1, acid/alcohol molar ratio 1:0.9, lipase dosage in 10% (by mass) of oleic acid, and open reaction for water removal. As a result, the conversion rate reached 98% for reaction of 8 h. The volume of reactor was scaled up to 1 L three-neck flask. The optimized parameters were: 200 r·min-1 agitation speed, 2.5% (by mass) lipase dosage, others were the same as the parameters described above. The conversion rate reached 95% for reaction of 24 h. The lipase retained 46% conversion rate after reuse for 6, 7 batches. The products were purified by removing remained cetyl alcohol and fatty acids with ethanol and saturated sodium carbonate so-lution, respectively. The purity of the wax ester, cetyl oleate, was 96%. The physical and chemical properties of cetyl oleate were tested and compared with those of jojoba oil. The results show that the product cetyl oleate has great potential to use as the substitute of natural jojoba oil.     

Green chemistry synthesized zinc oxide nanoparticles in Lepidium sativum L. seed extract and evaluation of their anticancer activity in human colorectal cancer cells

In recent years, extensive assessments were performed on metal oxide nanoparticles (MONs) for numerous biomedical implementations. This study aimed to describe a facile, environment-friendly and, green route for the synthesis of Zinc Oxide nanoparticles (ZnO-NPs) by exerting Lepidium sativum L. seed extract as a capping agent and to evaluate their anticancer activities on important human colorectal cancer cell lines, SW480, HT-29 and Caco-2. Characterization of the green chemistry synthesized ZnO-NPs were carried out using UV–visible (UV–Vis) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Field emission scanning electron microscope (FE-SEM) and, energy-dispersive X-ray (EDX) spectroscopy. UV–Visible spectra confirmed the biosynthesis of ZnO-NPs and showed a broad absorption peak at 325–450 nm. Microscopic results revealed the formation of the spherical and hexagonal shaped NPs having average size 36.96 and 44.50 nm. In addition, the XRD data demonstrated the crystalline structure of our green ZnO-NPs. In biological experiments, the outcomes of MTT assay indicated the significant cytotoxic effect of ZnO-NPs against SW480, HT-29 and Caco-2 cancer cells through a dosage reliant mechanism. Moreover, the real-time PCR data revealed the potent capability of ZnO-NPs in inducing apoptosis throughout colon cancer cells through the down-regulation of Bcl-2 gene expression and up-regulation of Bax and p53 genes. Overall, these results suggested the applicability of green fabricated ZnO-NPs from the extract of Lepidium sativum L. as a novel and hopeful therapeutic agent for colorectal cancer treatment.     

Optical properties of ZnO/BaCO3 nanocomposites in UV and visible regions

Pure zinc oxide and zinc oxide/barium carbonate nanoparticles (ZnO-NPs and ZB-NPs) were synthesized by the sol–gel method. The prepared powders were characterized by X-ray diffraction (XRD), ultraviolet–visible (UV–Vis), Auger spectroscopy, and transmission electron microscopy (TEM). The XRD result showed that the ZnO and BaCO₃ nanocrystals grow independently. The Auger spectroscopy proved the existence of carbon in the composites besides the Zn, Ba, and O elements. The UV–Vis spectroscopy results showed that the absorption edge of ZnO nanoparticles is redshifted by adding barium carbonate. In addition, the optical parameters including the refractive index and permittivity of the prepared samples were calculated using the UV–Vis spectra.

PACS

81.05.Dz; 78.40.Tv; 42.70.-a.     

Estimation of the surface interaction mechanism of ZnO nanoparticles modified with organosilane groups by Raman Spectroscopy

We investigated the surface modification of zinc oxide nanoparticles (ZnO-NPs) with 3-aminopropyltriethoxysilane (APTES). The ZnO-NPs were synthesized by the physical method of continuous arc discharge in controlled atmosphere (DARC-AC). The surface modification was performed using a chemical method with constant stirring and reflux for 24 h at room temperature. This surface functionalization of the ZnO nanoparticles (funct-ZnO-NPs) was experimentally confirmed by infrared spectroscopy (FT-IR), Raman spectroscopy, TGA, UV–Visible and XRD, while its morphological characterization was performed by HRTEM. Using Raman spectroscopy, it was possible to study the functionalization process after the change, as well as the appearance of new bands of the molecular vibrations produced by the chemical interaction of the surface of the nanoparticles with the silane coupling agent. Comparing the Raman spectra of the ZnO-NPs, APTES and funct-ZnO-NPs, it was observed that the area between 2700 and 3200 cm⁻¹ related to the vibrations of the CH₂ and CH₃ bonds of the APTES molecule. The funct-ZnO-NPs showed a decrease in the peak intensity, which indicates a deactivation of the degrees of freedom of the APTES at the time of the surface functionalization with the ZnO-NPs, suggesting a redistribution of the APTES CH₂ groups, as they interact with the surface of the ZnO-NPs. The APTES molecule is anchored to the surface of the ZnO-NPs via one or two Si-O-Zn bonds and not by three, as is commonly reported. The above finding is attributable to steric impediment of the side groups of the APTES and the strain of the Si-O-Zn bonds that hinders the trivalent interaction with the surface of the nanostructured ZnO. Similarly, the results obtained by Raman were verified and complemented by means of FT-IR due to the presence of bands at specific wavelengths.     

Optical and electrical properties of p-type Ag-doped ZnO nanostructures

Zn_1−xAg_xO nanoparticles (NPs) (x=0, 0.02, 0.04, and 0.06) were synthesized by a sol–gel method. The synthesized undoped ZnO and Zn_1−xAg_xO-NPs were characterized by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and UV–visible spectroscopy. The XRD patterns indicated that undoped and Ag-doped ZnO crystallize in a hexagonal wurtzite structure. The TEM images showed ZnO NPs with nearly spherical shapes, with particle size distributed over the nanometer range. Evidence of dopant incorporation is demonstrated in the XPS measurements of the Ag-doped ZnO NPs. The Raman measurements indicated that the undoped and Ag-doped ZnO-NPs had a high crystalline quality. From the result of UV–vis, the band-gap values of prepared undoped and Ag-doped ZnO were found to decrease with an increase in Ag concentration. The obtained undoped and Ag-doped ZnO nanoparticles were used as a source material to grow undoped and Ag-doped ZnO nanowires on n-type Si substrates, using a thermal evaporation set-up. Two probe method results indicated that the Ag-doped ZnO nanowires exhibit p-type properties.