简易方法制备交叉碳纳米管-石墨烯异质结

发展了一种通过两次高分子辅助转移和选择性氧等离子体刻蚀技术大量制备交叉碳纳米管-石墨烯异质结的无损方法. 拉曼光谱和导电性测试证明, 制备的单层石墨烯薄片在大面积范围内质量均一、导电性好. 而且, 本文所讨论的单层石墨烯的生长和随后的器件制备也提供了大面积制备石墨烯薄片图案化的可重复性方法. 该方法与传统的薄膜技术兼容, 只需简易的几步便可把图案化的石墨烯集成到大规模的微电子器件回路中, 有望实现流线型和自动化的石墨烯微电子器件的大量生产. 这些研究结果为进一步制备分子整流器和其它功能纳米/分子器件提供了技术基础.     

石墨烯狭缝受限孔道中水分子的分子动力学模拟

石墨烯是一种具有广泛应用前景的纳米材料,特别是由石墨烯片层自组装形成的二维纳米通道能够应用于物质的过滤分离.本文采用分子动力学模拟方法研究了原态石墨烯/羟基改性石墨烯狭缝孔道中水分子的微观行为,模拟计算了水的界面结构性质和扩散动力学性质,所研究的石墨烯孔宽为0.6-1.5 nm.模拟结果表明,在石墨烯狭缝孔道中,水分子受限结构呈现层状分布,在超微石墨烯孔道(0.6-0.8 nm)中水分子可形成特殊的环状有序结构,石墨烯表面可诱导产生特殊的水分子界面取向.在石墨烯孔道中,水分子的扩散运动低于主体相水分子的扩散运动,羟基化石墨烯孔道可以促使水分子的扩散能力降低.对于改性石墨烯狭缝孔道,由于羟基的作用,水分子可以自发渗入0.6 nm的石墨烯孔道内.模拟所得到的受限水分子的动力学性质与水分子在石墨烯孔道内的有序结构有关.本文研究结果将有助于分析理解水分子通过石墨烯纳米通道的渗透机理,为设计基于石墨烯的纳米膜提供理论指导.     

基于石墨烯修饰电极的电化学生物传感

石墨烯是一种具有单原子厚度的二维碳纳米材料,具有大的比表面积、高的导电性和室温电子迁移率,以及优异的机械力学性能.石墨烯还具有电化学窗口宽,电化学稳定性好,电荷传递电阻小,电催化活性高和电子转移速率快等电化学特性.化学修饰石墨烯,特别是氧化石墨烯(GO)和还原氧化石墨烯(rGO),可以被宏量、廉价地制备出来.它们具有可加工性能,可以被组装、加工或复合成具有可控组成和微结构的宏观电极材料.因此,石墨烯及其化学修饰衍生物是用于电化学生物传感的独特而诱人的电极材料.例如,GO是一种化学修饰石墨烯,也是石墨烯的重要前驱体;其边缘具有大量的羧基可用于共价固定酶,从而能实现酶电极的生物检测.在GO上的不可逆蛋白吸附也可以促进蛋白质的直接电子转移以提高其电化学检测性能.但是,GO大量的含氧官能团破坏了石墨烯本征的共轭结构,降低了其电学性能并限制了其实际应用.GO可以通过化学、电化学、热还原等技术转化成rGO,从而能部分修复其共轭结构,提高其导电性与传感性能.另一方面,石墨烯是一种零带隙材料;原子掺杂可以调控其能带结构,提高其电催化性能.石墨烯材料也常常需要通过与其它功能材料的复合进一步改善其可分散与可加工性能,提高其电催化活性和电化学选择性.本文综述了本征石墨烯(包括GO,rGO和掺杂石墨烯)以及石墨烯与生物分子、高分子、离子液体、金属或金属氧化物纳米粒子等复合材料修饰电极在检测各种生物分子方面的研究进展,并对该研究领域进行了展望.     

石墨烯表界面化学修饰及其功能调控

石墨烯属于碳纳米材料家族中的一员,是一种单层的二维原子晶体,具有高硬度、高导热性、高载流子迁移率等诸多优良特性,被认为是新一代电子学器件的重要基础材料.近年来我们课题组利用石墨烯的这些优良特性在其表界面化学修饰及其功能调控方面开展了一系列研究工作.我们对石墨烯表界面进行了共价或非共价化学修饰,在一定程度上打开了石墨烯的带隙,并发展了具有传感功能的石墨烯器件.我们还制备了基于石墨烯的纳米电极,发展了新一代分子电子器件的普适性制备方法,实现了单分子器件的功能化.展望未来,以石墨烯为代表的碳基纳米材料将继续在纳电子器件研究领域发挥重要作用.     

气体分子在二维石墨烯纳米孔中的选择性渗透特性

二维石墨烯纳米孔中气体分子的选择性渗透对多孔石墨烯分离膜非常重要。本文采用分子动力学方法研究了气体分子在氮氢修饰石墨烯纳米孔中的渗透特性,从分子的大小和结构、纳米孔的构型以及分子与石墨烯之间的作用强度等角度阐明了分子出现选择性渗透的原因。结果表明,不同分子的渗透率不同,即H₂O＞H₂S＞CO₂＞N₂＞CH₄。渗透率跟分子的质量和直径以及分子在石墨烯表面上的吸附密度有关;根据气体分子动理学理论,渗透率跟分子质量成反比关系;而分子在石墨烯表面上的高吸附密度对渗透起促进作用。对于H₂O和CH₄分子,分子直径起主导作用;H₂O分子直径最小,其渗透率最大;同理,CH₄分子的渗透率最小。对于H₂S和CO₂分子,H₂S分子的直径较大,但其与石墨烯之间的作用强度较大(吸附密度较高),导致渗透率较高;对于CO₂和N₂分子,CO₂分子的直径较小,并且与石墨烯之间的作用强度较大,渗透率较高。同时发现,分子在纳米孔中的渗透使得其在石墨烯表面的密度分布极不均匀。纳米孔左右两侧的功能化氮原子使CH₄分子容易从孔两侧区域穿过,而其它分子由于直径较小在纳米孔中心区域穿过的概率最大。分子与石墨烯之间的作用越强,导致分子在石墨烯表面区域内停留的时间越长,最终使其在渗透纳米孔的过程中所经历的时间越长。本文所采用的氮氢修饰石墨烯纳米孔中,分子渗透速率达到~10^-3 mol·s^-1·m^-2·Pa^-1,并且其它分子相对于CH₄分子的选择性也很高,说明基于该类型纳米孔的多孔石墨烯分离膜在天然气处理等工业气体分离领域具有很好的应用前景。     

环糊精-石墨烯超分子体系

环糊精是由D型吡喃葡萄糖通过α-1,4-糖苷键连接而成的环状超分子主体化合物,其特殊的结构赋予了其良好的分子识别性能;石墨烯是仅由单层sp杂化的碳原子构筑的具有良好的电化学性能的材料.作为著名的"明星分子",石墨烯类材料无疑是近5年来研究热点之一.在各种各样的石墨烯材料中,由环糊精-石墨烯联合构筑的超分子体系在保留二者优良性能的同时又引入了新的功能特点.综述了近些年来新发展起来的环糊精-石墨烯超分子体系:通过二者作用方式进行了分类,分为共价键连接和非共价键连接;综述了该超分子体系在药物运输及释放、电化学检测(包括对药物分子、污染物和生物分子的检测)等领域的应用;最后对该体系在药物负载及释放、模拟生物固氮、燃料电池、研究电子传导等应用前景进行了展望.     

对乙酰氨基酚分子印迹传感器的制备研究

将石墨烯(GR)与三氯化铁和铁氰化钾混合反应,合成了一种具有良好分散性的石墨烯-普鲁士蓝(GRPB)复合纳米材料,将GR-PB滴涂在玻璃碳电极(GCE)上,以邻甲苯胺为功能单体,对乙酰氨基酚为模板分子进行电化学聚合,制备了一种基于分子印迹的电化学传感器,用于定量测量对乙酰氨基酚的含量。通过扫描电镜、循环伏安和交流阻抗对该传感器进行了表征。实验结果表明,石墨烯-普鲁士蓝可以有效提高传感器的电化学灵敏度;在对乙酰氨基酚浓度范围为1.0×10^-5mol·L^-1至2.0×10^-7 mol·L^-1之间,传感器表现出良好的线性响应,检测限为7.37×10^-8 mol·L^-1。以药物中的对乙酰氨基酚作为实际样品,制备的传感器具有良好的准确性和精密度。     

分子轨道图形理论的应用——求a_k的断键公式

本文应用分子轨道图形理论公式,推导出求HMO本征多项式系数a_k的图形公式。应用该公式,求出了常见同系列共轭分子a_k的封闭公式。     

酞菁铅在石墨烯表面吸附行为的拉曼光谱研究

利用石墨烯增强拉曼散射效应可以获得与石墨烯接触的某些分子的拉曼增强信号, 并且对于不同的分子或振动模, 其拉曼增强因子不同. 根据这一特征, 本工作利用拉曼光谱技术对石墨烯表面上酞菁铅(PbPc)分子Langmuir-Blodgett (LB)膜在退火过程中吸附构型的变化进行了跟踪研究. 发现随着退火温度的升高, 石墨烯表面上PbPc分子的拉曼信号经历了一个先增强后减弱的过程, 在升华温度点附近强度达到最大, 表明PbPc发生了由直立向平躺取向的转变; 同时, 在PbPc分子升华温度点附近, 由于对称性破坏导致散射截面低的振动模出现, 并且该振动模强度随着退火温度的进一步升高而增强, 表明非平面的PbPc分子受石墨烯π-π相互作用的影响而形变加剧, 向平面结构转变; 在更高的退火温度下, 则出现一些不属于PbPc分子的拉曼振动峰, 表明PbPc分子在石墨烯表面由Pb(II)被还原成Pb(0).     

石墨烯修饰电极分子印迹电化学传感器的研制及其对多巴胺的测定

以石墨烯为电极增敏材料,多巴胺印迹聚合物为特异性识别材料,采用滴涂法组装石墨烯修饰电极的分子印迹电化学传感器。考察了pH值、石墨烯浓度、印迹聚合物浓度对传感器的影响,优化的实验条件为:pH 7.0,石墨烯浓度为0.5g/L,印迹聚合物浓度为20g/L。实验表明,该印迹传感器对多巴胺的响应电流远大于非印迹电极,同时该印迹传感器对多巴胺具有较好的选择性,检测范围为2.0×10-7～1.0×10-4mol/L,检出限(S/N=3)为6.8×10-8mol/L。该传感器用于盐酸多巴胺注射液的测定,其回收率为98%～105%。     

Spectroscopic Studies of a Three-dimensional,Five-coordinated Copper(Ⅱ） Complex via Hydrogen Bonds:[Cu(PPD)(H2O)2](H2PDA=Pyridine-2,6-dicarboxylic Acid)

A new copper(Ⅱ） complex[Cu(PDA)(H2O)2] was synthesized and its structure was determined.Cu(Ⅱ）is five-coordinated in a tetragonal pyramid geometry.The two coordinating water molecules are different and the two Cu-O bond lengths differ by nearly 0.02nm.The whole crystal is linked to form a three-dimensional network by means of hydrogen bonds.The X-band ESR spectrum shows three different g tensors with a well-resolved hyperfine structure in the gz signal,giving the ESR parameters gx=2.05,gy=2.065 and gz=2.29.The covalency of the coordinate bonds and the deviation from tetragonal pyramid geometry for the complex are discussed based on the ESR spectra.     

The Balance between Hydrogen Bonds,Halogen Bonds,and Chalcogen Bonds in the Crystal Structures of a Series of 1,3,4-Chalcogenadiazoles

In order to explore how specific atom-to-atom replacements change the electrostatic potentials on 1,3,4-chalcogenadiazole derivatives, and to deliberately alter the balance between intermolecular interactions, four target molecules were synthesized and characterized. DFT calculations indicated that the atom-to-atom substitution of Br with I, and S with Se enhanced the σ-hole potentials, thus increasing the structure directing ability of halogen bonds and chalcogen bonds as compared to intermolecular hydrogen bonding. The delicate balance between these intermolecular forces was further underlined by the formation of two polymorphs of 5-(4-iodophenyl)-1,3,4-thiadiazol-2-amine; Form I displayed all three interactions while Form II only showed hydrogen and chalcogen bonding. The results emphasize that the deliberate alterations of the electrostatic potential on polarizable atoms can cause specific and deliberate changes to the main synthons and subsequent assemblies in the structures of this family of compounds.     

无金属参与的氧原子邻位C(sp3)—S键的构筑

以二叔丁基过氧化物(DTBP)为氧化剂, 苯硫酚为硫化试剂, 在无金属参与的条件下, 于120 ℃下采用一步法合成了硫代苄醚. 这种构筑C(sp³)—S键的方法具有高原子经济性和高选择性的优点, 并以较高的收率获得了一系列目标化合物.     

Infrared study of νOD modes in isotopically dilute (HDO) isostructural compounds M(HCOO)2·2H2O (M=Mn,Fe,Co,Ni,Cu,Zn) with matrix-isolated guest ions (Cu in M(HCOO)2·2H2O and M in Cu(HCOO)2·2H2O)

The infrared spectra of isotopically dilute (matrix-isolated HDO molecules) isostructural compounds M(HCOO)₂·2H₂O (M=Mn,Fe,Co,Ni,Zn,Cu) are presented and discussed in the region of the OD stretching modes. According to the structural data the compounds under study are divided into two groups: in M(HCOO)₂·2H₂O (M=Mn,Ni,Zn) the H₂O(1) molecules form stronger hydrogen bonds as compared to H₂O(2); in M(HCOO)₂·2H₂O (M=Fe,Co,Cu) the H₂O(2) molecules form stronger hydrogen bonds as compared to the H₂O(1) molecules. The influence of the metal–water interactions (synergetic effect) and the unit-cell volumes (repulsion potential of the lattice) on the hydrogen bond strength within the isostructural series is discussed. The wavenumbers of the uncoupled OD stretching modes of the HDO molecules influenced by guest ions (Cu²⁺ ions matrix-isolated in M(HCOO)₂·2H₂O and M²⁺ ions matrix-isolated in Cu(HCOO)₂·2H₂O) are presented and commented. For example, the analysis of the spectra reveals that when Cu²⁺ ions are included in the structure of M(HCOO)₂·2H₂O the hydrogen bonds of the type M–OH₂OCHO–Cu are considerably weaker as compared to those of the same type formed when M²⁺ ions are included in the structure of Cu(HCOO)₂·2H₂O if the cations remain unchanged.     

Electronic structures and chemical bonding in diatomic ScX to ZnX (X = S, Se, Te)

Bond distances, vibrational frequencies, electron affinities, ionization potentials, dissociation energies, and dipole moments of the title molecules in neutral, positively, and negatively charged ions were studied using density functional method. Ground electronic state was assigned for each molecule. The bonding patterns were analyzed and compared with both the available data and across the series. It was found that, besides ionic component, covalent bonds are formed between the metal s, d orbitals, and the p orbital of S, Se, and Te. For neutral and cationic molecules, the covalent character increases from ScX to CrX and from FeX to CuX with an exception of decrease at MnX and ZnX, while for anionic molecules, the trend is not obvious. For both neutral and charged molecules, the sulfides have the shortest bond distance and largest vibrational frequency, while tellurides have the largest bond distance and smallest vibrational frequency. For neutral and anionic molecules, the dissociation energy of sulfides is the largest, that of tellurides is the smallest, while this only remains true for cationic molecules from ScX(+) to FeX(+).     

葡萄糖、肌醇与抗坏血酸的相互作用研究

利用电化学、密度泛函理论和分子中的原子理论,从微观角度研究了葡萄糖、肌醇与抗坏血酸的相互作用。两种混合体系在水溶液及磷酸盐缓冲溶液中的电化学结果表明,抗坏血酸中烯二醇羟基上的氢原子可与葡萄糖/肌醇羟基上的氧原子形成氢键,使得抗坏血酸的电氧化反应难以发生。量子化学计算进一步证明了上述两种混合体系中氢键的存在。     

Description of collective effects in computer models of water

The dynamics of a system containing 3456 water molecules in a cubic cell with periodic boundary conditions at 297 K was simulated. The time dependence of distances between oxygen atoms was examined for many pairs of molecules. These distances often oscillate around a certain average value over long periods of time (10 ps and longer). These average values can be about 2.8 Å (hydrogen bond) or much larger, up to 12–13 Å and more. This suggests that big groups of molecules are involved in a concerted motion. Lists of hydrogen bonds in 50 configurations divided by an interval of about 1 ps are compared. The average lifetime of a hydrogen bond is about 7 ps. The network of hydrogen bonds is colored according to their lifetimes for one of the configurations. The bonds that live longer than 7 ps form an infinite cluster. The bonds that live longer than 8 ps join to form a great number of finite clusters including several hundreds of nodes (molecules). These clusters contain few closed cycles. Even the bonds that live longer than 20 ps are united into clusters each containing two or three nodes (molecules). The self-diffusion coefficient for molecules involved in long-lived bonds is likely to be slightly smaller than that for molecules which do not participate in these bonds.     

单笼形水分子簇中心水分子对类型关系

随机产生单笼形水分子簇(H2O)n(n=8~36),经分类统计后发现,在笼形水分子簇中,其1221,1212,2121和2112四类氢键的个数与水分子和氢键总数之间有定量关系,且1212类氢键的个数与2121类的氢键始终相等.如果笼形水分子簇中某一类氢键数已知,则它的其余三类氢键的个数也随即确定.     

水与乙醇分子在金管内吸附作用的分子动力学研究

使用分子动力学研究了乙醇与水分子在纳米金管内按照不同比例混合时的吸附现象,并利用径向密度分布函数及水和乙醇分子所形成的平均氢键数来探讨纳米限制效应.结果表明,径向密度分布函数和氢键数目受纳米金管影响较大.另外,水与金管之间的作用力比乙醇与金管之间的大,导致水分子形成的平均氢键数不同于乙醇分子的.     

Selenium containing macrocycles:transformation between Se-N/Se-S/Se-Se bonds

Macrocycles possess potential applications in supramolecular chemistry and biosystems.Thus development of new kinds of macrocycles is of significance.Herein,novel macrocycles containing Se-Se/Se-S bonds were synthesized via transformation between selenium related dynamic covalent bonds.A monomer containing two ebselen moieties was synthesized(M1).The Se-N bonds in M1 were reduced by dithiothreitol,forming Se-S linked dimer(D1).To realize the transformation from Se-S bonds to Se-Se bonds,guest molecules were added as template,triggering the formation of Se-Se linked dimer(D2).The formation of these two new kinds of macrocycles was determined by ~1H NMR and ~(77)Se NMR,and the necessity of guest molecules was also confirmed.The introduction of ebselen moieties and Se-S bonds or Se-Se bonds into macrocycles may endow it with new responsiveness and bioactivities,as well as new types of host-guest chemistry.