基于EPR方法的天然产物抗氧化性能研究(英文)

自旋捕捉EPR、用于动物模型的低温EPR以及自旋标记EPR等多种EPR方法已经用于天然产物的抗氧化活性研究中.虽然对于抗氧化剂而言其必备条件之一就是具有体外清除自由基的能力,但是外源性抗氧化剂在生物体内抗氧化剂抗氧化能力评价的方法更有实际意义.通过对超过200种中药和一些传统中药处方的研究,已经建立并详细描述了用于评价天然产物抗氧化能力的EPR筛选方法.通过EPR方法可以获得天然产物在分子水平、细胞水平以及组织水平抗氧化能力的比较全面的评价.     

晶体PZCST:VO2+的EPR谱及光吸收谱的理论研究

采用双旋-轨耦合参量模型和3d¹电子组态在四角对称下的能级公式,计算了KZnClSO₄·3H₂O(PZCST): VO²⁺的EPR谱和光吸收谱,所得EPR谱和光吸收谱的理论结果与实验发现符合得很好. 研究发现,该晶体沿C₄轴局域对称结构呈压缩的四角畸变,其大小为0.47 nm;大的κ值表明VO²⁺的未配对电子的自旋极化对超精细结构常数有着较大的贡献.     

光合作用水裂解机理与EPR应用研究

在绿色植物放氧光合作用中,光系统II（PSII）催化着自然界利用光能将水裂解并释放出氧气的化学反应. 在研究PSII的生物催化机理中,电子顺磁共振（EPR）波谱学发挥着非常重要的作用. 该文综述了与水裂解有关的EPR应用研究,如锰簇Mn₄O₅Ca的不同氧化中间态,以及这些不同氧化态的锰簇与酪氨酸Y-Z自由基的磁性相互作用等,这些进展揭示了水裂解过程是一个逐步的与质子耦联的电子传递过程.     

CuGeO3晶体自旋-佩尔斯态的EPR

报道了CuGeO₃单晶在96GHz频率,1 4K温度下的电子顺磁共振(EPR)实验,测量了主轴g因子.导出了Cu²⁺离子在CuGeO₃自旋佩尔斯系统中的混合d轨道基态波函数.采用近似自洽场方法计算了CuGeO₃的主轴g因子.使实验结果得到了解释.     

纳米掺N TiO2的制备及光谱分析

以钛酸四丁酯(TBT)及乙二胺(EDA)为前驱体,乙醇为溶剂,冰醋酸为抑制剂,通过溶胶-凝胶法制备了纳米掺NTiO2,并对其结构及光谱性质进行了表征,根据差热-热重分析(TG-DTA)确定了所制备样品的晶型转换温度及最佳的煅烧温度;根据紫外-可见漫反射光谱(UV-Vis/DRS)表征了其光谱吸收特性;根据X射线衍射光谱(XRD)确定了其粒径及晶相结构;根据X射线光电子能谱(XPS)分析了其表面组成。实验考察了光谱吸收带红移程度与乙二胺、钛酸四丁酯的配比及煅烧温度的关系。研究结果表明,制备的纳米掺NTiO2为锐钛矿相,其光谱吸收带发生了明显的红移,乙二胺与钛酸四丁酯的配比及煅烧温度对其光谱吸收有明显的影响。当乙二胺与钛酸四丁酯的摩尔比为1:10,煅烧温度为600℃时,所制备样品对可见光的吸收最强。     

负载型二氧化钛光催化材料的制备及其光催化性能研究

以球形氧化铝为载体,采用溶胶-凝胶法和浸渍涂覆过程制备了负载型二氧化钛光催化材料。以扫描电子显微镜(SEM)和X-射线衍射仪(XRD)等手段对所合成的样品形貌及晶型进行了表征。结果表明,氧化铝载体经负载二氧化钛后,在球形氧化铝表面沉积了一层粒径为10~20nm的锐钛型二氧化钛纳米颗粒。通过能量色散X射线光谱(EDX)对氧化铝载体和所合成的样品进行进一步分析,表明样品中明显存在Ti元素。另外,提高氧化铝载体在二氧化钛溶胶中的浸渍次数能够有效提高二氧化钛的负载量。当浸渍次数增加到5次时,Ti元素的含量由3.8Wt.%提高至15.7Wt.%。另外,以亚甲基蓝为目标降解物,详细研究了不同浸渍次数获得的负载型二氧化钛催化材料的催化性能。结果表明:随着浸渍次数的增加,负载型二氧化钛催化材料的表面形貌不仅得到明显改善,而且显著提高了样品的光催化活性。当浸渍次数由1次提高至4次时,亚甲基蓝的降解率由40%上升至83.1%。然而,当二氧化钛负载量达到一定程度时,由于不断浸渍导致下层的二氧化钛受光照机会和光照强度减弱,导致其光催化活性提高缓慢。当浸渍次数提高至5次时,亚甲基蓝降解率仅为85.6%。所制备的负载型二氧化钛光催化材料重复使用5次,其光催化活性保持相对稳定。     

Fabrication and Magnetic Properties of Co-Doped TiO2 Powders Studied by Nuclear Magnetic Resonance

Co0.04 Ti0.96O2 powders are fabricated by sol-gel method. The structure and magnetic properties are investigated under different annealing conditions systematically with emphasis on the influence of oxygen pressure. Pure anatase structure was acquired for all the samples annealed at 450℃ for one hour. The samples annealed in air exhibit evident room-temperature ferromagnetism (RTFM) with a small magnetic moment of 0.029μB per Co atom and coercivity Hc of 26 Oe, while the samples annealed in vacuum have strong RTFM with a larger magnetic moment of 1.18μB per Co atom and Hc of 430 Oe. The zero-field spin echo nuclear magnetic resonance spectrum of ^59Co is obtained to prove the existence of Co dusters in the latter samples, implying that the Co dusters are responsible for the strong RTFM in the samples annealed in vacuum. No Co cluster could be observed using both XPS and NMR techniques in the samples annealed in air, implying that the RTFM found in these sample sis intrinsic.     

在体EPR专用磁场装置性能的改进

为测试在体EPR牙齿辐射剂量测量专用磁场装置,开展了初步性能试验. 针对扫描磁场非线性造成谱线的畸变情况,对在体EPR专用磁场装置性能进行了改进,给出了一种校正扫描磁场非线性的实现方法,通过对扫描磁场驱动电流进行反向刻度校正,可有效改善EPR谱线的畸变情况. 初步试验进一步证明了水平磁场在体测量方案的可行性,磁场装置性能的改进为实现X波段EPR辐射剂量在体测量向实际应用奠定基础.     

掺铁TiO2纳米薄膜的制备及光催化性能研究

采用溶胶-凝胶提拉法制备了掺铁改性TiO2纳米材料镀膜玻璃,研究了掺铁、PEG用量、镀膜层数等因素对TiO2纳米膜透光率和光催化降解性的影响,并对相关机理进行了探讨。研究发现,掺铁能提升TiO2纳米膜的光催化活性,催化降解速率为不掺铁时的1．38倍;溶胶前驱体中PEG用量为0．1g（0．13wt％）时制取的薄膜具有最佳的光催化活性和较好的透光率,低于或超过这个值,催化降解效果都不理想;镀膜层数为2～5层时,均有较高的透光率,光催化活性依次递增,其中综合效果最佳的为2层镀膜。纳米TiO2镀膜玻璃是一种性能优异的新型自净节能环保材料,在高楼建筑、灯具制造、城市照明系统等领域具有潜在的广泛用途。     

中国电子顺磁共振(EPR)发展50年回顾

自从1945年前苏联科学家Zavoisky在固体中观察到电子顺磁共振（EPR）这一奇妙的物理现象以来,电子顺磁共振波谱学已经经历了60多年漫长的发展历程. 在世界上,20世纪50、60年代是EPR的基本理论、实验技术和实验方法迅速发展的时期,同时对我国产生了很大的影响. 从60年代开始至今,EPR波谱学在我国已有50多年的发展,其间大约可以分为3个阶段： (一) 20世纪60~80年代初是EPR波谱设备研制和技术发展的初始阶段;(二) 20世纪80年代到21世纪初主要是EPR实验技术进一步发展和实验方法及其在化学、物理学、生物学、医学等学科中的应用研究阶段;(三) 21世纪以来,开始了新的实验技术和开展更加广泛深入的应用研究,特别是开始脉冲EPR波谱学的应用和相关设备的研制.     

金-二氧化钛（Au-TiO_2）复合薄膜的制备及局域表面等离子体共振（LSPR）效应

利用溶胶凝胶法在玻璃衬底上制备了金-二氧化钛（Au-TiO2）复合纳米薄膜,研究了热处理温度对复合薄膜表面纳米颗粒沉积的影响。利用原子力显微镜对样品进行了形貌表征,结果显示：复合薄膜是由纳米微晶组成的致密膜,温度越高越有利于Au粒子的形成。在550℃的热处理温度下,薄膜表面沉积的纳米微晶的粒径约为100nm。利用紫外-可见分光光度计测量了反射谱线,结果表明：由于局域表面等离子体共振（LSPR）的产生,在不同的热处理温度下,第一个反射峰（短波长处）不发生变化,第二个反射峰（长波长处）发生漂移（红移）。     

镧掺杂介孔TiO2光催化剂的制备、表征及其光催化性能

以钛酸四正丁酯和硝酸镧为原料, 以P123为模板剂,采用模板法合成了La掺杂型介孔TiO₂光催化剂, 借助TGA-DSC、BET、XRD及UV-Vis等测试手段对样品进行了表征,并以苯酚为模型污染物考察了镧掺杂量对样品光催化活性的影响．结果表明: La掺杂介孔TiO₂光催化剂孔径分布较均匀(～10 nm),比表面积可达165 m²/g．与纯介孔TiO₂相比,经掺杂改性后的样品在紫外光区及可见光区的吸收显著增强,对光具有更高的利用率,La掺杂可显著提高介孔TiO₂的光催化活性.     

铁和镧共掺杂纳米二氧化钛光催化剂的制备、表征及其光催化活性

以葡聚糖为模板,钛酸四正丁酯、硝酸铁和硝酸镧为前驱体采用模板法制备了一系列铁、镧单掺杂及共掺杂纳米TiO₂光催化剂. 利用SEM、XRD、BET比表面积测定和UV-Vis等技术对其形貌、晶体结构及表面结构、光吸收特性等进行了表征. 以甲基橙溶液的光催化降解为模型反应,考察了不同掺杂的样品在紫外和可见光下的光催化性能. TiO₂材料具有较大的比表面积(约150 m²/g),铁和镧共掺杂纳米TiO₂在可见光区域有较强的吸收,在紫外和可见光条件下较纯TiO₂和单掺杂TiO₂对甲基橙溶液具有更好的光催化降解效果,且铁和镧的掺杂量显著影响该材料的催化性能. 当铁掺杂量为0.5mol%、镧掺杂量为0.3mol%,在500 ℃焙烧2 h所得光催化材料的催化性能最佳,焙烧4 h即可使甲基橙的降解率达98.8%,且该复合材料有较高的循环回收利用率,重复使用4次仍可使甲基橙的降解率保持在88%以上.     

羧酸型聚芴/二氧化钛杂化材料的制备及其荧光猝灭行为

通过Suzuki偶合反应合成了聚[9,9-二辛基芴-9,9-双(丙酸基)芴](PF8COOH),并采用溶胶-凝胶法制备了羧酸型聚芴/二氧化钛(TiO₂)杂化材料。通过核磁共振氢谱(¹H NMR)、凝胶渗透色谱(GPC)、紫外-可见吸收光谱(UV-Vis)、X射线衍射(XRD)和荧光发射光谱对聚合物及其杂化材料进行了表征,并研究了杂化材料的荧光猝灭行为。结果表明,所合成的PF8COOH数均分子量为19 600,PF8COOH的紫外-可见吸收和荧光发射光谱较聚(9,9-二辛基芴)(PF8)均发生红移。通过溶胶-凝胶法制得了PF8COOH/TiO₂杂化材料,其中TiO₂主要为金红石型。杂化材料出现明显的荧光猝灭现象,TiO₂含量越大则杂化材料的荧光猝灭现象越明显。羧基的引入可使聚芴与TiO₂之间的相互作用增强,电子更容易从聚芴向TiO₂转移,因而PF8COOH/TiO₂杂化材料的荧光猝灭现象比PF8/TiO₂杂化材料更明显。     

EPR Spectra of Hydrazyl Biradicals

Electron paramagnetic resonance is the most effective method of studying the electron exchange in biradicals. Experimental EPR spectra for the solutions of some hydrazyl biradicals are available in the literature (see Refs. [I,2]), however, the interpretation of the spectra is not given.     

Gas-phase Crystallization of Titanium Dioxide Nanoparticles

We have investigated the development of crystal morphology and phase in ultrafine titanium dioxide particles. The particles were produced by a droplet-to-particle method starting from propanolic titanium tetraisopropoxide solution, and calcined in a vertical aerosol reactor in air. Mobility size classified 40-nm diameter particles were conveyed to the aerosol reactor to investigate particle size changes at 20–1200°C with 5–1-s residence time. In addition, polydisperse particles were used to study morphology and phase formation by electron microscopy. According to differential mobility analysis, the particle diameter was reduced to 21–23-nm at 600°C and above. Precursor decomposition occurred between 20°C and 500°C. The increased mobility particle size at 700°C and above was observed to coincide with irregular particles at 700°C and 800°C and faceted particles between 900°C and 1200°C, according to transmission electron microscopy. The faceted anatase particles were observed to approach a minimized surface energy by forming {101} and {001} crystallographic surfaces. Anatase phase was observed at 500–1200°C and above 600°C the particles were single crystals. Indications of minor rutile formation were observed at 1200°C. The relatively stable anatase phase vs. temperature is attributed to the defect free structure of the observed particles and a lack of crystal–crystal attachment points.     

In Vitro Analyses of Effect of Light on Toxicity of Titanium Dioxide Nanoparticles to Tetrahymena pyriformis Using Fourier Transform Infrared Spectra

ABSTRACT

The wide application of titanium dioxide nanoparticles (TiO₂ NPs) has caused a large number of TiO₂ NPs to be released into the water environment without treatment, which would inevitably result in unexpected toxic damage to aquatic animals. The objects of this research were to discuss the toxic effects of TiO₂ NPs to Tetrahymena pyriformis (T. pyriformis) under dark and light conditions. The Fourier transform infrared (FTIR) spectra were utilized to investigate the biochemical constituent changes of T. pyriformis under the exposure of TiO₂ NPs. The results showed that illumination had little effect on the cell numbers of T. pyriformis after 24 hr exposure at 5 mg/L of TiO₂ concentration. However, the cell viability of TiO₂ NP–exposed T. pyriformis under light illumination (81.4%) decreased compared with that in the dark environment (96.1%). The FTIR results showed that the typical absorption band of the CH₂ asymmetric stretching vibration shifted from 2924.64 to 2925.49 cm^?1 in the dark, which indicated an increase in membrane fluidity without illumination. A decreased intensity (p < 0.05) was observed in amide I and amide II from 98.57 ± 9.62 and 41.88 ± 3.63 to 75.65 ± 4.07 and 25.25 ± 1.12 in the irradiated T. pyriformis, respectively, which suggested that the coexistence of TiO₂ NPs and light could induce an obvious decrease of protein. In the light condition, the overproduction of ROS led to the breakdown of balance of the oxidative/antioxidative system, resulting in the lipid peroxidation and the death of cells. The results further reveal that TiO₂ NPs under light conditions are more toxic than in the dark.     

Titanium Dioxide/Carbon Fabric Prepared by a Controlled Pyrolysis Method

Titanium dioxide/carbon fabrics were prepared through pyrolysis of cellulosic fabrics in the presence of titanium ions. The influence of sintering temperature on the characteristics of the TiO₂/carbon fabrics was investigated. The properties of the samples were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The photocatalytic efficiency was evaluated by degradation of methylene blue (MB) solution. The results showed that the sample sintered at 300°C exhibits high photocatalytic efficiency.     

Substructure of Titanium Dioxide Agglomerates from Dry Ball-milling Experiments

The calciner discharge of TiO₂ white pigments from the sulphate process is ground batchwise in a planetary ball mill, varying the energy of comminution between 0 and 5.1 times the earth's gravitational constant. Particle sizes and specific surfaces of the ground products reveal that the calciner discharge consists of aggregates of 430nm diameter built from 160–210nm TiO₂ crystals. The contact area of a primary particle in an aggregate is about 15% of its surface. The success in comminution of aggregates as a function of grinding energy follows Kick's law. The theory by Rose and Weichert is used to quantify the mechanical strength of the aggregates. Ca. 20% of the aggregates are further agglomerated to granules of ca. 35µm. At all energy levels above a certain threshold, agglomerates break directly into aggregates.     

Effect of Particle Size and Phase Composition of Titanium Dioxide Nanoparticles on the Photocatalytic Properties

Titanium dioxide (TiO₂) nanoparticles were prepared by the oxidation of titanium tetrachloride (TiCl₄) in a diffusion flame reactor. The average diameter of particles was 15–30 nm and mass fraction of anatase ranged from 40% to 80%. Effects of particle size and phase composition of those TiO₂ nanoparticles on photocatalytic properties such as decomposition of methylene blue, bacteria and ammonia gas were investigated. The degree of decomposition of methylene blue by the TiO₂ nanoparticles under the illumination of the black light was directly proportional to the anatase mass fraction, but inversely to the particle size. The decomposition of bacteria and ammonia gas by the TiO₂ nanoparticles under the illumination of the fluorescent light showed the same trend as in the case of the methylene blue.