高介电性能石墨烯/聚合物纳米复合材料研究进展

石墨烯作为一种新型二维平面纳米材料,表现出许多优异的物理性质.将石墨烯与聚合物复合,利用其独特的结构及物理性质,有望开发一类具有卓越介电性能的纳米复合电介质材料.本文总结了高介电石墨烯/聚合物纳米复合材料这一研究方向的最新进展,重点介绍了石墨烯提高聚合物基体介电性能的基本理论、石墨烯/聚合物界面对复合电介质性能的影响等,并简要展望了这类材料的发展前景.     

PTh / ZnO复合纳米粉的固相合成及其光谱特性

0引言导电聚合物/无机物纳米复合材料具有纳米材料和导电聚合物的共同特性,因此在电催化、二次充电电池材料、超级电容器材料等方面具有良好的应用前景[1]。聚噻吩(PTh)以及取代聚噻吩是导电聚合物领域中较早发现的具有环境稳定性和可加工性的材料之一。近年来,有关聚噻吩/无机物纳米复合材料的制备及其光电性能的研究倍受关注,Gebeyehu等[2]用PTh敏化纳米晶TiO2光伏电池,发现其光伏效率明显优于固态光伏电池;Jayant等[3]研究了PTh中的羧基基团的影响以及在纳米晶TiO2     

纳米晶/聚合物太阳能电池

纳米晶/聚合物太阳能电池作为一种新型光伏器件成为近年来的研究热点。通过改变纳米晶的形貌及尺寸来调节材料本身的带隙从而改善光吸收特性,并且无机半导体材料本身具有高的电子迁移率和良好的热稳定性,以上特性使该类电池具有巨大的发展潜力。本文从纳米晶的种类、形状和尺寸、表面配体及纳米晶与聚合物界面性能等方面综述了纳米晶/聚合物太阳能电池的研究现状。纳米晶形貌、太阳光利用率和载流子传输效率是影响电池效率的主要因素。文中指出开展窄带隙纳米晶的合成、优化纳米晶/聚合物电池结构、解析纳米晶与聚合物界面激子传输机理等改善该类电池性能的途径,旨在为提高纳米晶/聚合物太阳能电池的效率提供借鉴经验。     

聚合物-二氧化硅复合基材中CdS纳米晶的合成

本文报道在Sol-gel基材中制备由聚合物稳定的CdS纳米晶的新方法， 即通过甲基丙烯酸镉与甲基丙烯酸羟乙酯共聚合合成了含有Cd 2+的聚合物微凝胶, 在聚合物微凝胶网络中原位聚合正硅酸乙酯形成聚合物互穿的Sol-gel复合基材. 再向该聚合物/二氧化硅复合基材中通入H2S气体得到CdS纳米晶. 在聚合物网络中原位聚合正硅酸乙酯可以降低纯二氧化硅材料的脆性; 另一方面, 二氧化硅可以作为增强剂增加聚合物材料的强度. 因此, 在我们合成的聚合物/二氧化硅复合基材中制备的CdS纳米晶将具有很好的应用前景.     

一种提高SiO2凝胶玻璃中ZnSe纳米晶稳定性的方法

半导体纳米品材料具有很大的应用潜力，然而非氧化物半导体纳米晶在空气中通常不稳定．因此其应用受到限制．纳米品不稳定主要是因为其表面原子配位不足，存在大量的悬空键，d使其很容易与环境中的物质发生反应而逐渐变质．人们通常采用惰性介质包覆的方法来提高纳米晶的稳定性，     

用于透射电子显微镜表征的单层纳米晶/聚合物复合薄膜的制备

为了提高纳米晶的TEM表征质量, 通过在水/气两相界面上铺展纳米晶/聚合物复合单层膜的方法, 制备了质量较高的TEM样品. 对于水相纳米晶采用表面活性剂再包覆的方法, 将其转移到油相. 与传统制样方法(尤其是水相合成纳米晶)相比, 嵌入聚合物膜中的纳米晶更容易分散(受到空间位阻与分子间弱相互作用等因素的影响), 并且聚合物膜可以自支持在空的铜网上, 从而提高了TEM照片的清晰度. 研究了系统中聚合物、纳米晶、表面活性剂和溶剂的种类及配比关系对于样品和成像质量的影响, 结果表明, 该方法对各种金属及半导体纳米晶的TEM表征具有一定的普适性.     

粒子-聚合物相互作用与粒子-粒子相互作用对聚合物基纳米复合物力学性能的影响

聚合物基纳米复合物(PNCs)具有比传统高分子材料更加优异的光学、力学、热力学等性能,广泛应用于各个工程领域.而纳米粒子(NPs)对材料性能提高的机理则是当前聚合物纳米复合物领域研究的重要问题,聚合物纳米复合体系相互作用的影响因素众多,至今尚未明确并完整建立复合体系相互作用与性能增强之间的关系.本文总结了近年来关于纳米粒子填充聚合物基体力学性能的研究,从粒子-聚合物相互作用和粒子-粒子相互作用角度阐述了聚合物纳米复合体系力学性能的增强机理,并根据体系中不同的结构关系分别总结了聚合物/未改性纳米粒子复合体系和聚合物/聚合物接枝纳米粒子复合体系中影响力学性能的因素.该部分内容具有重要的理论和实践意义,有助于构建复合体系微观结构与宏观性能之间的关系,进而对微观层面调控PNCs的力学性能提供指导.     

聚合物纳米杂化材料的控制合成、自组装及功能化

聚合物纳米杂化材料的制备及功能化是当前国际前沿研究课题之一.特殊结构的聚合物可以通过分子间特殊相互作用,在纳米尺度上自发地组装成具有特殊结构和形态的集合体,这类材料在新材料、电子以及生物医学等领域具有广泛的应用前景.本文介绍国内外,特别是厦门大学在双亲性分子及嵌段共聚物的模板自组装、基于POSS单体纳米构筑单元以及POSS嵌段聚合物自组装的有机/无机纳米杂化材料、模板控制导电高分子材料纳米形态构筑等领域材料的可控合成和组装,与此同时对相关材料的性能及功能化应用进行了简要的讨论.     

氧化物与稀土磷酸盐复合陶瓷的切削加工性评价

应用模糊综合评判原理, 评价可加工陶瓷材料的切削加工性, 判断材料的切削加工性等级.通过Ce-ZrO2/CePO4复合陶瓷的材料制备、性能测试、模糊综合评判和加工实验, 研究了氧化物与稀土磷酸盐复合陶瓷的材料切削加工性.根据模糊数学提出一种可加工陶瓷材料切削加工性的综合评判方法.以陶瓷材料的力学性能参数为因素集, 选择5种切削加工性等级, 根据隶属函数计算模糊矩阵, 通过模糊变换确定出氧化物与稀土磷酸盐复合陶瓷的切削加工性.综合评判结果将所制备的几种Ce-ZrO2/CePO4复合陶瓷材料分为3个切削加工性等级, 材料的切削加工性等级随CePO4含量的增加而提高, 评判结果与钻削实验的材料去除率结果相符.Ce-ZrO2/CePO4复合陶瓷材料的钻削加工表面具有明显的塑性变形加工痕迹.还分析了含LaPO4的其它氧化物复合陶瓷材料的切削加工性等级.材料切削加工性的评价方法建立了材料性能与加工技术之间的关系, 可提供一种新的材料设计方法.     

聚吡咯及其复合热电材料研究进展

聚吡咯(PPy)以其环境稳定性好、低毒、可调的导电性等优点,在热电材料研究方面日益受到人们的关注。采用纳米结构导电聚合物或将有机导电聚合物材料与高导电性的碳纳米粒子进行复合制备聚合物/碳纳米粒子复合材料,可以有效地改善其热电性能。本文结合该领域近年来的研究进展,重点讨论了PPy及其复合热电材料的研究结果,对一维纳米结构PPy的制备也进行了论述。     

聚合物稳定的金纳米簇催化：理论计算与实验的相互影响

平均粒径为2–10 nm的聚合物稳定的Au纳米簇(NCs)表现出独特的催化性能。多个研究表明，影响聚合物稳定的Au NCs催化活性的主要因素为： Au NC尺寸的控制、聚合物的选择以及反应条件的优化。这是由于聚合物稳定的Au NCs在多个催化反应中表现出明显的尺寸效应，其催化活性也因所采用的聚合物和反应条件的不同而不同。为了阐明影响聚合物稳定的Au NCs催化活性的内在原因，众多研究者关注于聚合物稳定的Au NCs催化中的理论计算与实验的相互影响。本文主要总结了聚合物稳定的Au NCs中这种相互影响的研究进展。     

A generalized ligand-exchange strategy enabling sequential surface functionalization of colloidal nanocrystals

The ability to engineer surface properties of nanocrystals (NCs) is important for various applications, as many of the physical and chemical properties of nanoscale materials are strongly affected by the surface chemistry. Here, we report a facile ligand-exchange approach, which enables sequential surface functionalization and phase transfer of colloidal NCs while preserving the NC size and shape. Nitrosonium tetrafluoroborate (NOBF4) is used to replace the original organic ligands attached to the NC surface, stabilizing the NCs in various polar, hydrophilic media such as N,N-dimethylformamide for years, with no observed aggregation or precipitation. This approach is applicable to various NCs (metal oxides, metals, semiconductors, and dielectrics) of different sizes and shapes. The hydrophilic NCs obtained can subsequently be further functionalized using a variety of capping molecules, imparting different surface functionalization to NCs depending on the molecules employed. Our work provides a versatile ligand-exchange strategy for NC surface functionalization and represents an important step toward controllably engineering the surface properties of NCs.     

Poly(vinyl alcohol) Chains Grafted onto the Surface of Copper Oxide Nanoparticles: Application in Synthesis and Characterization of Novel Optically Active and Thermally Stable Nanocomposites Based on Poly(amide-imide) Containing N-trimellitylimido-L-valine Linkage

Green polymer nanocomposites (NCs) show unique properties of combining the advantages of nanofillers and organic polymers. In this study, in order to control the dispersion of nanoparticles (NPs) in a polymer matrix, first, poly(vinyl alcohol) (PVA) as a green modifier was grafted on the surface of the CuO NPs to obtain CuO-PVA nanohybrid. Then poly(amide-imide) (PAI) was synthesized by the direct step growth polymerization of N-trimellitylimido-L-valine and 4,4′-methylenebis(3-chloro-2,6-diethylaniline) in ionic liquid medium. Finally, CuO-PVA hybrids were incorporated into the PAI matrix using ultrasonic technique for the preparation of PAI/CuO-PVA NCs. The obtained PAI/CuO-PVA NCs were characterized by different methods. The results of thermogravimetric analysis showed that thermal stability of the NCs was enhanced by incorporation of CuO-PVA nanohybrid compared to the pure PAI.     

Silicon Nanocrystals and Silicon‐Polymer Hybrids: Synthesis,Surface Engineering,and Applications

Silicon nanocrystals (Si‐NCs) are emerging as an attractive class of quantum dots owing to the natural abundance of silicon in the Earth's crust, their low toxicity compared to many Group II–VI and III–V based quantum dots, compatibility with the existing semiconductor industry infrastructure, and their unique optoelectronic properties. Despite these favorable qualities, Si‐NCs have not received the same attention as Group II–VI and III–V quantum dots, because of their lower emission quantum yields, difficulties associated with synthesizing monodisperse particles, and oxidative instability. Recent advancements indicate the surface chemistry of Si‐NCs plays a key role in determining many of their properties. This Review summarizes new reports related to engineering Si‐NC surfaces, synthesis of Si‐NC/polymer hybrids, and their applications in sensing, diodes, catalysis, and batteries.     

Polyethylene-based nanocomposite: Structure and properties of poly(vinyl alcohol)/organofunctionalized Mg-doped fluorapatite hybrid

We report here the production and characterization of polymer nanocomposites (NC)s containing nanoceramics of organofunctionalized Mg-doped fluorapatite (MDFA) in a poly(vinyl alcohol) matrix. First, the MDFA materials were functionalized with N-trimellitylimido-L-leucine modifier through ultrasonic irradiation. The numerous experimental techniques like Fourier transform infrared spectroscopy, X-ray diffraction, atomic force microscopy, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis were applied to characterize the prepared materials. Thermal analysis of the obtained NCs showed an increase in thermal stability of the NCs when compared to the neat macromolecule.     

CdSe nanocrystal based chem-/bio- sensors

Semiconductor nanocrystals (NCs) have found application in biology mostly as optical imaging agents where the photophysical properties of the NCs are insensitive to species in their environment. This tutorial review examines the application of CdSe NCs as optical sensing agents where the NC's photophysical properties are sensitive to species in their environment. For this case, the NC is modified at the surface with a conjugate, which interacts with an external agent by physical (i.e. recognition) or chemical means. Signal transduction in these chem-bio (CB) sensitive NCs is derived primarily from energy transfer between the NC and the external agent, which functions as the energy transfer acceptor or donor. Signaling may be obtained by directly detecting luminescence from the NC and/or the conjugate. New developments for the use of NCs as gain materials in micro-lasing cavities (distributed feedback gratings and spherical resonators) opens the way to designing CB-sensitive NCs for high-gain sensing applications.     

Linking Semiconductor Nanocrystals into Gel Networks through All‐Inorganic Bridges

For colloidal semiconductor nanocrystals (NCs), replacement of insulating organic capping ligands with chemically diverse inorganic clusters enables the development of functional solids in which adjacent NCs are strongly coupled. Yet controlled assembly methods are lacking to direct the arrangement of charged, inorganic cluster‐capped NCs into open networks. Herein, we introduce coordination bonds between the clusters capping the NCs thus linking the NCs into highly open gel networks. As linking cations (Pt²⁺) are added to dilute (under 1 vol %) chalcogenidometallate‐capped CdSe NC dispersions, the NCs first form clusters, then gels with viscoelastic properties. The phase behavior of the gels for variable [Pt²⁺] suggests they may represent nanoscale analogues of bridged particle gels, which have been observed to form in certain polymer colloidal suspensions.     

Synthesis and properties of transparent luminescent nanocomposites with surface functionalized semiconductor nanocrystals

5-Amino-1,10-phenanthroline (Aphen) was used as an organic ligand to functionalize CdS nanocrystals (NCs) by a ligand-exchange process. The functional Aphen-CdS NCs have strong luminescent emission at 552 nm and good dispersibility in the polar organic monomers. The Aphen-CdS NCs were dispersed in polymeric monomers to prepare a series of transparent luminescent nanocomposites with excellent thermal stability via in-situ bulk polymerization. The fluorescent properties of the Aphen-CdS NCs were well retained in the polymer matrix. It was found that when the methacrylic acid (MAA) and glycidyl methacrylate (GMA) as the comonomers were introduced into the polymer matrix, the emission peaks of the resultant nanocomposites had a blue shift and the fluorescent intensities also increased due to the interaction between NCs and the polymer matrices. The transparent NCs/polymer nanocomposites with tunable fluorescent emission can be potentially used for the fabrication of optoelectronic devices.     

Synthesis of polyolefin composition in the presence of supported catalysts

Polyolefins are basic materials in the plastics. Their application is limited by their low thermostability, adhesion, hardness and other physico-mechanical properties. The following treatments are known to improve and modify polyolefin properties: the incorporation of inorganic or organic fillers with a greater hardness and rigidity into the polyolefin matrix, the grafting of functional groups to polyolefins, and crosslinking with the formation of a network structure in the polyolefin matrix. In the case of polymers and inorganic materials, the activation of their surface by the functionalizing and fixing of transition metals allows one to perform polymerization of monomers on a surface to obtain a polymer–polymer composites and a highly filled polymer–inorganic composites.     

Temperature and Composition Dependent Optical Properties of CdSe/CdS Dot/Rod-Based Aerogel Networks

Employing nanocrystals (NCs) as building blocks of porous aerogel network structures allows the conversion of NC materials into macroscopic solid structures while conserving their unique nanoscopic properties. Understanding the interplay of the network formation and its influence on these properties like size-dependent emission is a key to apply techniques for the fabrication of novel nanocrystal aerogels. In this work, CdSe/CdS dot/rod NCs possessing two different CdSe core sizes were synthesized and converted into porous aerogel network structures. Temperature-dependent steady-state and time-resolved photoluminescence measurements were performed to expand the understanding of the optical and electronic properties of these network structures generated from these two different building blocks and correlate their optical with the structural properties. These investigations reveal the influence of network formation and aerogel production on the network-forming nanocrystals. Based on the two investigated NC building blocks and their aerogel networks, mixed network structures with various ratios of the two building blocks were produced and likewise optically characterized. Since the different building blocks show diverse optical response, this technique presents a straightforward way to color-tune the resulting networks simply by choosing the building block ratio in connection with their quantum yield.