用于检测多巴胺的荧光增强型适体传感器

利用贵金属纳米颗粒独特的物理特性,设计具有信号放大功能的荧光适体传感器用于多巴胺的浓度检测。基于金属荧光增强效应通过在金纳米颗粒与荧光基团之间添加隔离层的手段实现荧光信号放大。将化学修饰了SH键的核酸适体与金纳米颗粒溶液混合,形成稳定的Au-S键结构并与标记荧光基团的DNA互补链利用碱基互补配对原则结合。然后,通过调节所设计的核酸适体5′所添加的碱基A的数量,从而调节荧光基团与金纳米颗粒表面的距离。同时,优化核酸适体与金纳米颗粒之间的浓度比以及所处的反应环境的pH值,获得最佳的放大效率。最后对不同浓度的多巴胺进行测试。实验结果表明:金纳米颗粒溶液与核酸适体在一定的浓度比之下,在隔离层厚度为27个碱基A时,最大的荧光增强倍数为2.35。多巴胺浓度检测的线性范围为20～100nmol/L,最低检测限为20nmol/L。该传感器可以在纳米级有效调控隔离层厚度,提供了一种稳定的信号放大策略。     

长度标准器超声清洗参数设计研究

针对提高激光诱导击穿光谱技术(LIBS)中等离子体的发射光谱强度的问题,提出一种在铜样品表面沉积金纳米颗粒的方法。在样品表面沉积纳米金颗粒后对铜进行激光诱导击穿(NELIBS),得到NELIBS和LIBS下的发射光谱强度增强因子、信噪比等参数。实验表明,通过在铜样品表面沉积金纳米颗粒的LIBS(NELIBS)可以有效增强等离子体辐射光谱信号强度,铜元素谱线增强因子最高可达8.01,微量元素镁元素谱线增强因子最高为6.01,且增强因子均随激光能量的增加而逐渐减小并趋于稳定;NELIBS可以明显改善信噪比,铜元素在激光脉冲能量为80 mJ时达到最优,镁元素在激光能量为50 mJ时达到最优。对谱线Cu I 521.8 nm和Mg II 279.569 nm进行洛伦兹拟合,并得到半高全宽,发现纳米金颗粒使谱线半高全宽增加,谱线Mg II 279.569 nm的半高全宽增加了165.58%,谱线Cu I 521.8 nm的半高全宽增加了30%。样品中的微量元素因谱线强度低、信噪比差而无法探测到,通过此方法可以有效提高探测能力。     

纳米金改善激光诱导等离子体探测方法研究

针对提高激光诱导击穿光谱技术(LIBS)中等离子体的发射光谱强度的问题,提出一种在铜样品表面沉积金纳米颗粒的方法。在样品表面沉积纳米金颗粒后对铜进行激光诱导击穿(NELIBS),得到NELIBS和LIBS下的发射光谱强度增强因子、信噪比等参数。实验表明,通过在铜样品表面沉积金纳米颗粒的LIBS(NELIBS)可以有效增强等离子体辐射光谱信号强度,铜元素谱线增强因子最高可达8.01,微量元素镁元素谱线增强因子最高为6.01,且增强因子均随激光能量的增加而逐渐减小并趋于稳定;NELIBS可以明显改善信噪比,铜元素在激光脉冲能量为80 mJ时达到最优,镁元素在激光能量为50 mJ时达到最优。对谱线Cu I 521.8 nm和Mg II 279.569 nm进行洛伦兹拟合,并得到半高全宽,发现纳米金颗粒使谱线半高全宽增加,谱线Mg II 279.569 nm的半高全宽增加了165.58%,谱线Cu I 521.8 nm的半高全宽增加了30%。样品中的微量元素因谱线强度低、信噪比差而无法探测到,通过此方法可以有效提高探测能力。     

热处理对金纳米颗粒活性衬底的影响

利用退火工艺对拉曼增强衬底进行热处理,得到粒径和密度不同的金纳米颗粒拉曼增强衬底,并且此工艺不引入杂质离子。通过用生物大分子龙胆紫作为探针分子,对金纳米颗粒表面的表面增强拉曼散射(SERS)和表面增强荧光(SEF)进行研究发现,拉曼和荧光强度存在相同的变化趋势。研究结果表明:热处理可以优化SERS和SEF增强效果,为高效率、低成本的基于SERS和SEF效应生物化学传感器件的研究提供参考。     

IFD和SCFD在制备纳米TiO2中的比较研究

采用Sol—gel法制备纳米TiO2,对生成的凝胶湿颗粒,分别采用红外辐射（IFD）和超临界流体干燥（SCFD）技术进行干燥,然后对样品进行XRD、SEM及BET表征,同时考察样品对苏丹红Ⅰ的光催化氧化降解活性。测试结果表明,红外干燥法制备的纳米TiO2是锐钛矿和金红石的混晶,粒径10-30nm,对苏丹红光催化降解性能优于采用SCFD法制备的样品。红外干燥法具有干燥时间短、制备步骤简便、无需特殊设备、产品催化活性高等优点。     

Synthesis and optical properties research of gold nanoparticles with different morphologies

本文制备了不同形貌的金纳米颗粒,并对其形貌对光学性能的影响进行了研究。本文用还原法制备了不同粒径的金纳米颗粒,采用晶种生长法成功地制备出了星形、梭形和棒状的金纳米颗粒。颗粒的形貌和大小并采用投射电子显微镜(TEM)进行了表征,结果说明,本文成功制备出了不同形貌大小的金纳米颗粒。UV-Vis光谱和拉曼光谱仪对制备的颗粒的表征测试说明,不同形貌大小对颗粒有着不同的光学性能。拉曼光谱的结果说明,不同形貌大小的金纳米颗粒可以用作不同浓度分子的探针,对物质进行检测。     

基于等离激元热电子效应的光电晶体管制备及其特性

为了解决典型宽禁带半导体光电探测器件的工作波段限制材料禁带宽度的问题,对基于表面等离激元热电子效应的光电晶体管进行了制备和光电性能研究,提出一种采用重掺杂的硅片作为背栅极、二氧化硅(SiO_2)氧化层作为绝缘层,且能利用等离激元热电子效应的光电晶体管,有望实现响应光谱的调控。利用热退火方法在绝缘层表面修饰金纳米颗粒,并结合射频溅射、物理掩模和真空热蒸镀的方法实现了热电子效应铟镓锌氧化物(IGZO)光电晶体管。器件的光学和电学性能测试结果表明:修饰金纳米颗粒的光电晶体管在658nm红光入射下产生明显的光电响应,外加90V栅极偏压时,光电流提升约为2.2倍。金纳米颗粒修饰的等离激元热电子结构有效调控了该型晶体管的响应光谱范围,不受材料禁带宽度的限制,而且晶体管的背栅调控进一步放大光电流,提高了器件的量子效率。     

金标免疫试纸条反射式光度计的研制

为使金标免疫分析术能对目标被检物进行高灵敏度快速定量检测,成功研制一种金标免疫试纸条反射式光度计.根据纳米金颗粒对绿光的强烈吸收特性,以绿光激光器为照明光源,以扫描方式测量金标免疫试纸条上经生物反应而结合上去的纳米金颗粒的分布,通过特定算法计算出样品中目标被检物的浓度.该光度计对人绒毛膜促性腺激素标准样品的检测灵敏度达到5 mIU/ml,在5～500 mIU/ml浓度范围内具有良好的线性响应特性,相关系数R2～0.99,使用研制的光度计对同一生物反应稳定的金标试纸条进行20次重复测量,测量结果的变异系数(CV)小于2%.该光度计具有快速、稳定、灵敏的工作性能.     

镍(Ⅱ)-血清蛋白配合物极谱催化前波及其应用

实验发现 ,在 p H8.8的 H3BO3- Na OH介质中 ,镍 ( ) -血清蛋白配合物在单扫示波极谱上 ,在- 0 .6 0 V处 (vs.SCE)会产生吸附性质的催化前波 ,该波二阶导数波高与蛋白质浓度在一定范围内呈线性关系 ,对于牛血清蛋白 (BSA) ,线性范围为 1～ 2 9μg/ m L,检出限为 0 .5 μg/ m L;对于人血清蛋白 (HSA) ,线性范围为 0 .8～2 6 μg/ m L,检出限为 0 .4 μg/ m L。应用该法测定了人血清样品总蛋白含量。研究了实验条件的选择 ,探讨了方法的机理     

基于自组装金钯核壳纳米颗粒单层膜的光纤H2传感器

低维纳米材料的大比表面积极大提升了材料与环境气体分子的反应效率,对提高光纤氢气传感器中关键氢敏器件的灵敏度及响应速度有着至关重要的作用。提出了一种在油水界面自组装制备高性能金钯(Au-Pd)核壳纳米颗粒单层氢敏薄膜的方法,并制备了基于该薄膜的透射式光纤氢气传感器。实验中采用水热合成法制备粒径约12 nm的球形Au核,然后在Au核水溶液中加入Pd生长液,得到粒径约为20 nm的Au-Pd核壳纳米颗粒。采用十八胺修饰Au-Pd核壳纳米颗粒并通过相转移技术将颗粒转移到甲苯溶液中,最后在甲苯-水界面提拉制备覆盖率高并且空洞和堆积少的纳米颗粒单层氢敏薄膜。表征分析结果表明,形成的Au-Pd核壳纳米颗粒粒径均匀且结晶度好,制备的纳米颗粒单层薄膜排列致密覆盖率达87%。搭建了透射式光纤氢气器并测试了制备的Au-Pd核壳纳米颗粒单层膜在不同氢气浓度下的感氢响应特性。实验结果表明,单层纳米颗粒氢敏膜对4%的氢气响应时间约为3 s,对0.1%的氢气(氮气为载气)响应时间约为13 s,在多个循环的测试中表现出良好的稳定性,该传感器在低浓度氢气的快速、准确检测上具有良好的应用前景。     

Electrostatic force microscopy measurements of charge trapping behavior of Au nanoparticles embedded in metal–insulator–semiconductor structure

Charge trapping properties of electrons and holes in Au nanoparticles embedded in metal–insulator–semiconductor (MIS) on p-type Si (1 0 0) substrates were investigated by electrostatic force microscopy (EFM). The Au nanoparticles were prepared with a unique laser irradiation method and charged by applying a bias voltage between EFM tip and sample. The EFM system was used to image charged areas and to determine quantitatively the amount of stored charge in the Au nanoparticle-inserted MIS structure. In addition, charge trapping characteristics of the samples were carried out with electrical measurements, such as capacitance–voltage and current–voltage measurement for memory characteristics. Finally, the comparison of EFM results with the electrically measured data was done to determine the amount of stored charge in the Au nanoparticle-inserted MIS structure, confirming the usefulness of EFM system for the characterization of nanoparticle-based non-volatile devices.     

Electrostatic force microscopy measurements of charge trapping behavior of Au nanoparticles embedded in metal-insulator-semiconductor structure

Charge trapping properties of electrons and holes in Au nanoparticles embedded in metal-insulator-semiconductor (MIS) on p-type Si (100) substrates were investigated by electrostatic force microscopy (EFM). The Au nanoparticles were prepared with a unique laser irradiation method and charged by applying a bias voltage between EFM tip and sample. The EFM system was used to image charged areas and to determine quantitatively the amount of stored charge in the Au nanoparticle-inserted MIS structure. In addition, charge trapping characteristics of the samples were carried out with electrical measurements, such as capacitance-voltage and current-voltage measurement for memory characteristics. Finally, the comparison of EFM results with the electrically measured data was done to determine the amount of stored charge in the Au nanoparticle-inserted MIS structure, confirming the usefulness of EFM system for the characterization of nanoparticle-based non-volatile devices.     

Interference microscopic studies on wood plastic and cell wall—liquid interactions in beech

A method is described to measure the content of methylmethacrylate-polymer (poly-MMA) in wood-plastic composites and the influence of MMA on water and ethanol accessibility of beech wood fibre walls using interference microscopy. Although the S₂-layer of the fibre wall is capable of containing about 12% volume of plastic, the effect of treatment on ultimate water absorption of the cell wall is negligible. The ultimate absorption of ethanol is, however, completely reduced to zero. Increased dimensional stability of wood-poly-MMA composites is probably due to hindrance by the plastic in the lumina of the wood elements. The interference microscopic method is also shown to be suitable for determination of the fibre saturation point of cell wall areas.     

Boundary Lubrication Properties of Nanoperiod Solid Lubricant Multilayer Films Composed of Diamond-Like Carbon and Gold Layers

To develop electroconductive and high-endurance solid lubricant nanoperiod multilayer (DLC/Au)_n films, diamond-like carbon (DLC) and gold layers were deposited while controlling the time the substrate was exposed graphite and gold targets. The electrical resistivity of the (DLC/Au)_n multilayer films was ~12.4 Ω cm. The hardness of the (DLC/Au)_n multilayer films was similar to that of DLC films and much higher than that of gold monolayer films. According to the results of oscillating sliding tests under water boundary lubrication and dry conditions, (DLC/Au)_n multilayer films exhibited the low friction coefficient, little damage, and high sliding durability than the monolayer films. (DLC/Au)_n films also have a lower friction coefficient and exhibit less damage than a Au monolayer under polyalphaolefin boundary lubrication.     

Long-term water absorption behavior of thermoplastic composites produced with thermally treated wood

Wood plastic composites (WPCs) were produced from thermally treated beech (Fagus orientalis L.) wood and polypropylene (PP) polymer with coupling agent, by using injection molding. The wood chips were thermally treated for 30 or 120 min at three different temperatures (120 °C, 150 °C, or 180 °C) under saturated steam in a digester and then grounded (40-mesh size) by wood mill. Long-term water absorption kinetics of the composites were investigated with water immersion test. It was found that the water absorption decreased with increasing severity of the thermal-treatment and water immersion time as compared to the control composites. Furthermore, the composites produced with wood treated at 180 °C for 120 min exhibited the least water absorption. Microstructures of the composites were examined by SEM analysis to understand the mechanisms for the wood–plastic interaction which affected the water absorption. Further studies were conducted to model the water diffusion of the composites. Diffusion coefficient parameter in the models was obtained by fitting the model predictions with the experimental data. Water absorption of the studied composites was proved to follow the kinetics of a Fickian diffusion process.     

Size-dependent flocculation behavior of colloidal Au nanoparticles modified with various biomolecules

Au nanoparticles with different sizes were prepared and modified with various biomolecules including amino acids (arginine, lysine and cysteine), glutathione (GSH), oligopeptides, and proteins (bovine serum albumin (BSA), human serum albumin (HSA) and mouse IgG). The flocculation behaviors of the modified Au nanoparticles were investigated by observing their colorimetric and morphological changes with UV-vis spectrophotometer and transmission electron microscope (TEM), respectively. Consequently, we found that the flocculation behavior of the modified Au nanoparticles was quite different depending on both the size of the Au nanoparticles and the modified biomolecules. When modified with an amino acid, small-sized Au nanoparticles flocculated more easily than large ones while the modification with oligopeptides resulted in the flocculations of all tested Au nanoparticles due to the large number of hydrogen bonding between adjacent particles. The small Au nanoparticles were very effectively stabilized by protein capping, while the stabilization effect was not so good with large ones. The possible explanations for these size-dependent flocculation behaviors were discussed. This study would widen the understanding for the interaction involved in the Au nanoparticles modified with biomolecules.     

A comparison of the microstructure of silicon nitride-silicon carbide composites made with and without deoxidized starting material

Two different types of silicon carbide (SiC) matrix composites, with either 10 wt% or 20 wt% silicon nitride (Si₃N₄) reinforcement, were fabricated to investigate the effect of pretreatment on the resulting composite micro-structure. The first type of composite was prepared from as-received α-SiC and α-Si₃N₄ powders, while the second type was prepared from powder compacts that had been deoxidized to eliminate surface silica on the powder particles. The composites were hot isostatically pressed in tantalum cans at 2373 K for 1h under a pressure of 200 MPa. Density measurements showed that full theoretical density was achieved for the composites prepared from the as-received powders, while much lower densities were obtained for the composites prepared from the deoxidized green compacts. Almost all of the α-SiC transformed into β-SiC, and almost all the α-Si₃N₄ transformed into α-Si₃N₄ in the composites made from the as-received powders, while in the composites made from the deoxidized material the α-SiC remained untransformed and both α-Si₃N₄ and β-Si₃N₄ phases were present in significant quantities. High-resolution transmission electron microscopy and Fresnel fringe imaging were used to identify the grain boundary and interphase boundary structure. Most interfaces were found to be covered with ? 1 nm thick amorphous intergranular films in the composites prepared from as-received powders, whereas most interfaces were found to be free of such amorphous intergranular films in the composites prepared from the deoxidized material. Taken together, the presence of intergranular films at the interfaces and the results from density measurements are consistent with the densification and reverse α → β-SiC transformation taking place in the composites made from as-received powders by a liquid-phase sintering route. An incomplete liquid-phase sintering mechanism is also able to explain the microstructure observed in the composites made from the deoxidized material.     

Friction and wear behaviors of C/C-SiC composites containing Ti3SiC2

In the present paper, friction and wear behaviors of a carbon fiber reinforced carbon–silicon carbide–titanium silicon carbide (C-SiC–Ti₃SiC₂) hybrid matrix composites fabricated by slurry infiltration and liquid silicon infiltration were studied for potential application as brake materials. The properties were compared with those of C/C-SiC composites. The composites containing Ti₃SiC₂ had not only higher friction stability coefficient but also much higher wear resistance than C/C-SiC composites. At an initial braking speed of 28 m/s under 0.8 MPa pressure, the weight wear rate of the composites containing 5 vol% Ti₃SiC₂ was 5.55 mg/cycle, which was only one-third of C/C-SiC composites. Self-lubricious film-like debris was formed on the composites containing Ti₃SiC₂, leading to the improvement of friction and wear properties. The effect of braking speed and braking pressure on the tribological properties of modified composites were investigated. The average friction coefficient was significantly affected by braking speed and braking pressure, but the wear rate was less affected by braking pressure.     

The Effect of Hot Extrusion on Mechanical and Tribological Behavior of Ag-Cu/MoS2 Composites

Silver–copper/molybdenum disulfide (Ag-Cu/MoS₂) composites, prepared by powder metallurgy and hot press sintering, were extruded at a temperature of 680°C with extrusion ratios of 10 and 70. Mechanical tests and tribotests were carried on both the hot-pressed and hot-extruded composites. The tribological properties of the composites against a silver coin disc were investigated on a pin-on-disc tester with normal load and sliding speed of 5 N and 0.27 m/s, respectively. The microstructure, wear morphology, and cross section of the worn subsurface were observed by scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) analyses were performed on the worn surfaces of Ag-Cu/MoS₂ composites. The results indicated that the distribution of the MoS₂ particles in the composites was improved and the interfacial strength of Ag/MoS₂ was enhanced during the process of hot extrusion. The hardness, bending strength, and wear resistance of hot-extruded composites increased remarkably due to the presence of the continuous matrix skeleton and the stronger interfacial bonding of Ag/MoS₂. XPS revealed that a chemical reaction had occurred at the worn surface due to the friction heat. Although the dominant wear mechanism was fatigue wear for both the hot-pressed and hot-extruded composites, finer debris and a lower wear rate were observed in hot-extruded composites due to the fact that the nucleation and growth of cracks in the worn subsurface were restrained in the process of tribotest.     

Effect of fiber orientation on friction and wear of fiber reinforced polymeric composites

The friction and wear behavior of composites (i.e. uniaxially oriented graphite fiber-epoxy, Kevlar fiber-epoxy and biaxially oriented glass fiber-MoS₂-polytetrafluoroethylene (PTFE)) was investigated as a function of varying fiber orientations with respect to the sliding direction. In graphite fiber-epoxy composites, both wear and friction coefficients were minimum when the orientation of the fibers was normal to the sliding surface. In Kevlar-epoxy composites when the fibers were oriented normal to the surface and the sliding direction, the wear rate was also minimum but the friction coefficient was the highest. In glass fiber-MoS₂-PTFE composites wear was minimum when the largest fraction of fibers was oriented normal to the sliding surface.