石墨烯用于金属腐蚀防护的研究

单层无缺陷石墨烯具有优异的屏蔽性能,能阻隔氧气、水分子等腐蚀因子到达金属基体表面,被认为是已知最薄的腐蚀防护涂层。基于石墨烯在金属腐蚀防护领域巨大的应用潜力,本文从石墨烯薄膜防护涂层、石墨烯/有机防护涂层以及石墨烯-导电高分子/有机防护涂层等方面进行系统总结,重点围绕石墨烯薄膜存在的问题以及石墨烯在有机涂层中均匀分散等进行详细分析和介绍,同时对石墨烯基防腐涂料的未来发展进行了展望。     

改性聚苯胺及其衍生物涂层的防腐性能

导电聚合物作为一种新型高分子材料,由于具有可逆的氧化还原特性,在金属腐蚀防护领域具有潜在的应用前景。在众多的导电聚合物中,聚苯胺因其具有独特的抗点蚀、抗划伤和防止海洋生物附着等特殊性能,被广泛应用于金属材料、化学工业和航海航天等领域, 逐渐成为防腐涂料领域的研究热点。本文通过对单一聚苯胺涂层防腐性能不足的分析,系统总结了近年来改性聚苯胺涂层在金属腐蚀防护领域的研究进展,包括单一环取代聚苯胺涂层和N取代聚苯胺涂层、改性聚苯胺复合涂层和改性聚苯胺复合材料/树脂共混复合涂层;通过各种腐蚀测试手段比较了改性聚苯胺涂层与未改性聚苯胺涂层之间防腐性能的优劣,进一步证明了供电子取代基（如烷基、烷氧基和氨基等）能够提高聚苯胺涂层的防腐性能,复合改性或与树脂共混也能够提高聚苯胺及其衍生物涂层的防腐性能;同时展望了聚苯胺及其衍生物涂料未来发展的新趋势。     

氮化硼纳米片及其凝胶材料的研究进展

氮化硼纳米片具有高机械强度、良好的化学惰性和热稳定性等优点.除了这些性质,基于纳米氮化硼的凝胶材料还有高比表面积、大孔隙率等特点.因此它在催化、储氢、除污和气体吸附等领域具有潜在的应用前景.这篇综述主要介绍了氮化硼纳米片及其凝胶材料的制备,举例说明了氮化硼凝胶的关键应用并加以展望.     

水热法制备低维氮化硼纳米结构的研究进展

作为一种宽禁带绝缘材料，氮化硼由于其高导热性、强化学惰性和高热稳定性在热界面材料、光催化和电催化以及储能材料方面引起了广泛的研究兴趣.低维氮化硼纳米结构，如二维纳米片、一维纳米管、纳米棒、纳米线、零维纳米球和量子点等，具有高热导率（600 W/mK）和超宽带隙（5～6 eV），在高导热复合材料、热电材料及电子封装材料等领域具有很好的应用前景，其制备技术及相关性能研究是近年来材料科学领域的热点之一.主要详述了目前水热法制备低维氮化硼（BN）纳米结构的研究进展及存在的问题，并指出深入研究合成机理、研发新型水热制备方法将是今后本领域的重点研究方向.     

氮化硼负载的高分散Au-CuOx纳米颗粒用于低温CO氧化

负载型金催化剂显示出高的低温CO氧化活性,其催化性能与载体的性质密切相关.近年来,六方氮化硼作为一种新型催化材料引起了极大关注.已有研究表明,二维结构的氮化硼纳米片有利于传质扩散,并且暴露出大量的表面和边缘,作为新型非金属催化剂在烷烃氧化脱氢中表现出优异的活性.同时,CO氧化反应是强放热过程,氮化硼具有优良的导热性能,能够减少反应过程中热点的形成.然而氮化硼是非还原性载体,与活性组分金之间的相互作用较弱,需要通过改性来加强金与氮化硼载体间的相互作用.基于此,本文首先通过球磨处理来获得具有高比表面积和富缺陷的氮化硼纳米片载体,采用浸渍法在氮化硼纳米片上引入铜物种,实现对载体的改性,然后采用传统的沉积-沉淀法制备Au-CuO_x/BN催化剂.经氧化性气氛预处理后,Au-CuO_x/BN催化剂表现出良好的低温CO氧化活性,80℃下即可实现CO的完全转化.采用X射线衍射(XRD),高分辨透射电镜(HRTEM),氢气程序升温还原(H₂-TPR),X射线光电子能谱(XPS),CO吸附原位漫反射红外光谱(CO-DRIFT)等表征手段深入分析了Au-CuO_x/BN的结构与催化活性的关系.XRD测试结果未观察到明显的金和铜物种衍射峰,表明二者在氮化硼载体上高度分散.HRTEM和元素分析面扫描结果进一步表明,氧化铜主要分布于BN边缘的官能团和缺陷位上,金纳米粒子与铜物种的空间分布位置一致,表明BN通过稳定CuO_x物种进而实现了金纳米粒子(2.0 nm)的高分散,且反应后的金纳米粒子未发生明显团聚.H₂-TPR结果表明金和铜物种间的相互作用可促进铜物种的还原,XPS分析进一步证实了金和铜物种之间存在电子转移.CO-DRIFT结果表明,Au-CuO_x/BN催化剂对CO的吸附能力和提供活性氧物种的能力显著强于Au/BN催化剂,从而促进了CO氧化反应.综上,铜物种作为连接金和氮化硼载体之间的桥梁,促进了金纳米粒子在氮化硼载体上的分散和稳定,同时增强了CO的吸附和氧的活化.本文拓展了氮化硼在多相催化中的应用,为发展新型二维催化材料提供新的思路.     

新型多孔氮化硼材料

多孔氮化硼材料是一种新型多孔非氧化物材料,具有高比表面积、可调孔径、良好的化学惰性和热稳定性等特点,在催化、储氢、气体吸附和分离等领域具有巨大的应用潜力,是材料领域研究热点之一。依孔径的不同,多孔氮化硼材料被分为微孔氮化硼、介孔氮化硼、大孔氮化硼和多级孔氮化硼。本文综述了微孔、介孔、大孔及多级孔等类型氮化硼材料的研究进展。重点介绍了不同类型氮化硼材料的制备和性能,并分析了各种制备方法的优缺点,最后探讨了多孔氮化硼材料的发展前景。     

多孔氮化硼掺杂聚吡咯-2,3,3-三甲基吲哚固相微萃取涂层的制备及多环芳烃的检测

多环芳烃(PAHs)是持久性有机污染物中的一种，大部分具有较强的致癌、致畸和致突变性，对生态环境和人类健康易造成严重威胁。由于环境样品基质复杂且其中PAHs含量低，因此在仪器分析之前需要对环境样品进行必要的前处理。萃取材料的特性是决定大部分前处理技术萃取效率的关键。基于此，本文以低成本且富含较多官能团的吡咯(py)、2,3,3-三甲基吲哚(2,3,3-TMe@In)为单体，多孔氮化硼为掺杂物，采用电化学循环伏安法制备出多孔氮化硼掺杂聚吡咯-2,3,3-三甲基吲哚(Ppy/P2,3,3-TMe@In/BN)复合涂层，通过扫描电子显微镜、热稳定性分析、傅里叶红外光谱等手段对Ppy/P2,3,3-TMe@In/BN进行表征，结果表明：该涂层呈现出多孔、多褶皱的枝状结构，该结构有利于增加涂层的比表面积，从而实现对PAHs的大量富集；在320℃解吸温度下，涂层材料的色谱基线基本稳定，表明该涂层具有良好的热稳定性。将其修饰在不锈钢丝表面制成固相微萃取涂层，结合气相色谱-氢火焰离子化检测器，对影响萃取和分离萘(NAP)、苊(ANY)、芴(FLU)3种PAHs的条件进行优化，建立了用于以上3种PAHs...     

有机 无机纳米复合光电材料研究进展

很久以来人们就尝试着结合有机材料和无机材料的性质于一种复合材料。在还没有复合材料这一概念时,有机/无机复合结构已被广泛用于聚合物工业中——无机添加剂(矿物、粘土、滑石等)被加入聚合物中以改善其性能。过去十年中,关于有机/无机纳米复合材料的研究工作已成为材料学科的一个重要领域。不同于传统的复合材料,有机无机纳米复合材料其相微区通常为纳米尺度,有时甚至减小到分子水平的复合。复合材料的性质不但与各组分的性质有关,而且各组分相的形态和其间界面性质密切相关,后两者对决定材料的整体性质起着至关重要的作用^[1,2].     

有机涂层失效过程的电化学阻抗和电位分布响应特征

结合使用电化学阻抗谱(EIS)和扫描Kelvin探针(SKP)技术研究了在质量分数为3.5%的NaCl溶液中的铁基有机涂层劣化过程特征. 结果表明, 根据EIS和SKP的响应特征, 可将涂层劣化过程分为3个主要阶段: (Ⅰ) 涂层渗水阶段. 此时, 涂层渗水阶段的EIS阻抗持续减小, 但保持单容抗弧特征, SKP特征是电位持续降低, 但分布保持均匀; (Ⅱ) 基底金属腐蚀发生阶段. 此时, EIS阻抗快速下降, 并产生第二时间常数; SKP特征为表面电位差增大; (Ⅲ) 基底金属腐蚀发展与涂层失效阶段. 此时, EIS出现扩散尾, SKP电位差保持较大数值. 实验结果表明, 在研究有机涂层劣化过程中, EIS和SKP的结合使用能够互相补充完善, 获得涂层劣化过程中更为准确\, 可靠的变化信息.     

石墨烯/碳纳米管复合材料的制备及应用进展

石墨烯和碳纳米管都是纳米尺寸的碳材料,具有极大的比表面积、良好的导电性以及优秀的机械性能等特性. 选择合适的方法制备出石墨烯/碳纳米管复合材料,它们之间可以产生一种协同效应,使其各种物理化学性能得到增强,因而这种复合材料在很多领域有着极大的应用前景. 以石墨烯/碳纳米管复合材料为综述对象,详细地介绍了它的制备、掺杂和应用等方面的进展,同时也对其发展前景进行了展望. 这种复合材料不仅被成功地应用在电容器、光电器件、储能电池、电化学传感器和其它领域,而且也会在这些领域内深化并向其它领域延伸.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.