中空Fe_3O_4-PB复合纳米粒类Fenton催化降解苯酚

针对广泛存在于水体中的酚类污染物,本研究制备了磁性中空四氧化三铁(Fe_3O_4)纳米颗粒,在其表面包覆普鲁士蓝(PB)纳米壳层,记为Fe_3O_4-PB,利用Fe离子体系(Fe~(2+),Fe~(3+))的类芬顿(Fenton)效应降解水体中的苯酚污染物。首先对所得复合纳米粒子的理化性能及纳米酶性质进行表征,研究材料在H_2O_2存在条件下的Fenton效应,进而考察其对苯酚的降解移除以及循环使用性能。结果显示,Fe_3O_4-PB在H_2O_2存在的条件下能使3,3′,5,5′-四甲基联苯胺(TMB)发生显色反应,证明其具有纳米酶效应。此外,与辣根过氧化氢酶(HRP)相比,Fe_3O_4-PB在不同pH值、温度范围情况下均表现出更稳定高效的过氧化物模拟酶性能。同时Fe_3O_4因内核具有良好的磁响应性,在外加磁场辅助下,易于从反应体系中磁分离并进行循环利用,而经八次循环使用后,Fe_3O_4-PB仍保持约60%的活性,显示了良好的循环使用性能。     

两种磁性纳米颗粒(Fe_3O_4、Fe_3O_4@柠檬酸)的制备及其在DNA提取分离中的应用

采用溶剂热法制备表面修饰柠檬酸的磁性Fe_3O_4纳米粒子和磁性Fe_3O_4纳米粒子,并对其粒径大小、晶体结构和磁性能进行表征,并考察其用于DNA提取分离的效果。结果表明,两产物均为立方晶系的Fe_3O_4纳米颗粒。磁性Fe_3O_4纳米粒子和表面修饰柠檬酸的磁性Fe_3O_4纳米粒子的平均粒径为411.1nm和586.3nm。当全血体积200μL、磁性纳米粒子用量2.0mg时,提取的DNA浓度最高分别为270.6ng/μL(Fe_3O_4)和466.4ng/μL(Fe_3O_4@柠檬酸)。     

基于Pd/Fe3O4/rGO纳米复合材料的H2O2无酶传感器

环境监测、食品工业、临床、制药等领域对过氧化氢(H_2O_2)的快速、准确检测有极大的需求,而电化学检测方法由于灵敏度高、响应快、检测限低等特点被认为是最理想的H_2O_2检测方法.本文利用电化学沉积的方法将Pd纳米颗粒沉积到四氧化三铁/石墨烯(Fe_3O_4/rGO)纳米复合材料修饰的玻碳电极表面,形成基于新型磁性纳米复合材料的H_2O_2无酶传感器;并采用循环伏安和计时安培电流等方法对修饰电极的电化学性能进行了表征.结果表明:制备的Pd/Fe_3O_4/r GO/GCE对H_2O_2的催化还原显示出较好的电催化活性,Pd纳米颗粒和Fe_3O_4/rGO在催化H_2O_2还原的过程中表现出了良好的协同作用.测定H_2O_2的线性范围为0.05~1 m M和1~2.6 m M两段,最低检测限达到3.918μM(S/N=3).并且该传感器具有较高的灵敏度和较好的重现性和抗干扰性,具有一定的实际应用价值.     

纳米纤维素/Fe3O4纳米球的原位合成及其电化学性能

利用实验室自制茶梗纳米纤维素原位合成纳米纤维素(CNC)/四氧化三铁(Fe_3O_4)纳米球,并对其粒径大小、结晶性质、磁性性能和电化学性能进行分析表征。结果表明,通过原位合成法所制得CNC/Fe_3O_4纳米球,粒子间分散性良好,直径约为10～30 nm;CNC/Fe_3O_4纳米球具有磁化强度34.9 A·m~2/kg的磁特性;CNC/Fe_3O_4纳米球表现出良好的电化学性能,CNC/Fe_3O_4电极的比电容主要是Fe_3O_4产生的赝电容,在电流密度0.03 A/g时,比容量可达30.14 F/g,在0.04 A/g电流密度下,经过500次充放电后容量保持率为78.76%。CNC/Fe_3O_4电极中离子的扩散为Warburg机理。     

纤维素水凝胶包覆Fe_3O_4类Fenton纳米催化剂的制备及其催化降解性能

采用纤维素水凝胶包覆Fe_3O_4颗粒,制备得到核壳结构的羧甲基纤维素聚丙烯包覆Fe_3O_4类Fenton纳米催化剂(CMC-co-AA/Fe_3O_4),并应用于降解偶氮染料酸性大红GR。考察了体系pH值、催化剂用量、染料初始浓度等参数对降解效果的影响。SEM和FT-IR分析结果表明水凝胶成功地包覆在Fe_3O_4颗粒表面,且壳层厚度为20~30nm。XRD分析显示,包覆层不影响纳米Fe_3O_4的晶型结构,纳米催化剂在使用过程中仍保持Fe_3O_4磁响应性能,能够有效地分离回收。相比传统的Fe_3O_4纳米催化剂,包覆型CMC-co-AA/Fe_3O_4纳米催化剂水溶液显示出了较好的均一分散性。且当pH3直至中性条件下,此时传统未包覆的Fe_3O_4纳米催化剂对酸性大红GR的降解率为0,而CMC-co-AA/Fe_3O_4纳米催化剂的降解率仍能维持36%,说明了水凝胶壳层结构赋予CMC-co-AA/Fe_3O_4纳米催化剂较宽的pH适用范围。重复试验表明,该纳米催化剂在循环使用四次后,对染料的降解率仍能保持98%左右。     

磁热双重响应纳米Fe_3O_4/环氧树脂复合材料的形状记忆性能

以形状记忆环氧树脂EP5-60%为基体,掺杂改性磁性Fe_3O_4纳米粒子,制备了一系列磁和热双重响应纳米Fe_3O_4/环氧树脂形状记忆复合材料。红外测试表明,KH550成功改性了磁性Fe_3O_4纳米粒子,DSC测试确定热响应回复温度为80℃。当改性磁性Fe_3O_4纳米粒子质量分数为7%时,Fe_3O_4-7%/EP5-60%复合材料力学性能最佳,拉伸强度为29 MPa、断裂伸长率为37.3%。弯曲回复测试Fe_3O_4-7%/EP5-60%热响应形状记忆性能,其热响应形状记忆固定率(R_f)为99%,回复率(R_r)为97.9%。录像法记录Fe_3O_4-7%/EP5-60%磁响应形状回复过程时,25 min内能回复形变,磁响应回复率为93.3%。以上结果表明,利用Fe_3O_4纳米粒子的磁性,通过改性并控制好掺杂含量,可以制备性能较好的磁和热双重响应的纳米Fe_3O_4/环氧树脂形状记忆复合材料。     

Fe_2O_3-AgBr纳米纤维光催剂的制备及其光催化性能研究

采用静电纺丝技术合成Fe_2O_3纳米纤维,然后采用沉积沉淀法将AgBr颗粒沉积在Fe_2O_3纳米纤维上,制备了Fe_2O_3-AgBr纳米纤维光催化剂。SEM测试表明该材料纤维直径为50~100nm,TEM和XRD结果表明Fe_2O_3-AgBr是由Fe_2O_3和AgBr组成的半导体纳米纤维。同时,研究了该材料的光催化性能。结果表明:在可见光照射下,经过90min后,Fe_2O_3-AgBr纳米纤维光催化剂对罗丹明B(RhB)的降解效率达到了93.25%,且循环测试实验表明,经过4次循环后该材料仍能降解81.6%的RhB,具有较高的稳定性和回收再利用性。     

Fe_3O_4@SiO_2@COOH@NTA-Ni的制备及其对生物分子荧光检测的研究

采用溶剂热法制备了Fe_3O_4纳米团簇,利用溶胶凝胶法对其进行SiO_2包覆,然后用羧基硅烷化试剂进行羧基化修饰,使其表面连接NTA,引入不同浓度Ni~(2+),制备了Fe_3O_4@SiO_2@COOH@NTA-Ni磁性纳米功能组装体。并对制备的各中间体进行了形貌、Zeta电位、化学组成、羧基密度、Ni~(2+)含量、磁性能的表征。最后,我们利用该磁性纳米功能组装体检测荧光素标记的His标签蛋白和非His标签蛋白,研究了组装体本身荧光对于检测的影响。结果表明Fe_3O_4纳米团簇和Fe_3O_4@SiO_2具有良好的分散性,羧基化后表面羧基密度可达0.5μmol/mg,各中间体在去离子水中有良好的稳定性,1g磁性纳米功能组装体的Ni~(2+)含量高达8.693×10~(-5)mol,具有较高的饱和磁化强度并保持了超顺磁性;同时,我们通过加入洗脱液,检测上清液,解决了该磁性纳米功能组装体自身荧光对检测的影响,从而拓展了其在药物筛选、酶检测等领域的应用。     

Fe3O4@SiO2核壳磁性纳米材料的制备及其对Cu(Ⅱ)的吸附研究

首先通过溶剂热法制备了磁性Fe_3O_4纳米粒子,随后采用SiO_2对其进行包覆形成了Fe_3O_4@SiO_2核壳磁性纳米材料。通过XRD、SEM、TEM、磁性能分析和吸附性能分析等对Fe_3O_4@SiO_2核壳磁性纳米材料进行了表征。结果表明,合成的Fe_3O_4@SiO_2核壳磁性纳米材料具有Fe_3O_4和SiO_2两种晶型结构,SiO_2成功包覆在磁性Fe_3O_4纳米粒子上,SiO_2并没有对各组织的结构和成分产生较大影响;Fe_3O_4@SiO_2核壳磁性纳米材料的粒径在200～400 nm左右,且呈核壳式的结构,内层Fe_3O_4纳米粒子的颜色较深,外层SiO_2的颜色较浅;Fe_3O_4@SiO_2核壳磁性纳米材料在室温下的饱和磁化强度为76.31 A·m~2/kg,剩余磁化强度几乎为0;Fe_3O_4@SiO_2核壳磁性纳米材料对Cu(Ⅱ)的吸附在1 500 min时达到饱和,去除率最高为63%,最大吸附容量可达120 mg/g,其对Cu(Ⅱ)具有较好的吸附效果。     

Fe_3O_4@SiO_2与PAC、PAM联合去除污水中磷的研究

采用共沉淀法制备四氧化三铁(Fe_3O_4)磁性纳米球,并采用St9ber溶胶-凝胶法制备四氧化三铁@二氧化硅(Fe_3O_4@SiO_2)纳米复合粒子,Fe_3O_4@SiO_2具有超顺磁性,可在外加磁场作用下实现从水中快速分离。并对Fe_3O_4@SiO_2进行了表征,同时系统研究了不同pH和不同浓度的Fe_3O_4@SiO_2与聚合氯化铝(PAC)、聚丙烯酰胺(PAM)联合使用时对污水中磷酸盐的吸附行为,结果表明Fe_3O_4@SiO_2用量为5mg/L,PAC用量为3mg/L,PAM用量为0.413mg/L,pH=9的条件下,Fe_3O_4@SiO_2对磷的去除率达到86.441%,采用Fe_3O_4@SiO_2与PAC和PAM联合除磷效果较好。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Numerical study of methods of linearization of the output characteristics of radio-frequency sensors of the level of dielectric media

Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or) the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15% for control media with dielectric permittivity in the range 2.2–30.     

Possibilities of Decreasing the Errors of Determination of the Height of the Pole of a Sessile Drop of Melt

We analyze the possibilities of decreasing the errors of measuring the height of the pole of a sessile drop of melt above its equator by determining the position of the equator according to the midpoints of vertical chords of the image of the drop. The optimal distance between these chords and the edge of the image of the drop is chosen within 10–20% of the radius of the equator. The proposed method guarantees the same level of errors of evaluation of the height of the pole and the radius of the equator, which enables one to substantially increase the accuracy of evaluation of the capillary constant and the surface energy of the melt according to the geometric parameters of the sessile drop.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Analysis of anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.