以卵磷脂为手性添加剂制备手性介孔二氧化硅

以十六烷基三甲基溴化铵(CTAB)的自组装体为模板,卵磷脂(PC)为手性添加剂,在n_PC:n_CTAB=1:21时,通过溶胶-凝胶法制备了螺旋介孔二氧化硅纳米棒。利用扫描电镜(FESEM)、透射电镜(TEM)、X-射线衍射以及氮气吸附-脱附等测试手段,对该纳米棒的形貌以及孔结构进行了表征。TEM显示该纳米棒的长度约为50~200nm,直径约为30~50nm。X-射线衍射表明孔道呈二维六方排列,虽然FESEM显示纳米棒左右手比例约为1:1,但通过圆二色谱表征证明该纳米棒在埃尺度下倾向于形成单一手性。结果表明,卵磷脂的手性可以传递到螺旋介孔二氧化硅纳米棒中。     

以联二萘酚衍生物为手性添加剂制备介孔二氧化硅

通过溶胶-凝胶法以十八烷基三甲基溴化铵(STAB)自组装体为模板和非离子型联二萘酚衍生物(S)作为手性添加剂制备螺旋介孔二氧化硅。样品利用扫描电镜、透射电镜、X-光衍射以及氮气吸附-脱附进行了表征。结果表明:反应混合物中S与STAB的物质的量之比对介孔二氧化硅的形貌及孔结构有很大影响。改变nS∶nSTAB比,从0.1∶1到0.4∶1时,其结构从螺旋纳米棒状变为表面具有环形层状孔的纳米棒,孔道由沿着纳米棒长轴方向转变为同心环状。当nS∶nSTAB=0.5∶1时,得到类似皱缩花瓣的纳米颗粒。该手性添加剂的引入并没有改变左右手螺旋纳米棒的比例。     

乳酸类合成子构建的四连接螺旋手性配位聚合物的合成、结构和光催化性质

通过乳酸衍生物和3-溴-4-羟基苯甲酸的组合得到对映体3-溴-4-(((1R)-1-羧基乙基)氧基)苯甲酸(R-H₂bba)和3-溴-4-(((1S)-1-羧基乙基)氧基)苯甲酸(S-H₂bba)。以其为手性合成子在水热条件下分别与1,3-二(吡啶-4-基)丙烷(1,3-dpp)和Ni²⁺反应,构建了对映手性配位聚合物{[Ni(R-bba)(1,3-dpp)(H₂O)_0.5]·1.5H₂O}_n (HU12-R)和{[Ni(S-bba)(1,3-dpp)(H₂O)_0.5]·1.5H₂O}_n (HU12-S)。结构分析揭示HU12-R和HU12-S是具有dia网络特征的三维螺旋骨架。在骨架中,阴离子配体R-bba^2-和S-bba^2-分别与Ni²⁺中心连接在一起围绕2₁螺旋轴得到一对小的对映螺旋链,而1,3-dpp与Ni²⁺中心则围绕4₁螺旋轴构建出另外一对大的对映螺旋链。电化学测试显示HU12-R属n型半导体,具有低阻抗性质,对紫外可见光有很强的吸收能力。进一步光催化实验证实在紫外光照射下所得配合物对染料降解有明显催化效果。     

立方介孔相含钕氧化硅的合成与表征

以十六烷基三甲基溴化铵为结构导向剂，通过水热法合成了具有立方结构的含钕Nd-MCM-48介孔分子筛材料。XRD和TEM测试表明当n_Nd/n_Si<0.05时可以获得典型的长程有序介孔立方结构相，随n_Nd/n_Si比的增加，晶胞参数的增大和红外吸收光谱(FT-IR)的变化为Nd进入介孔分子筛骨架中提供了有力证据。N₂吸附-脱附实验给出了其BET表面积为1 195 m²·g^-1，BJH平均孔径为3.6 nm。紫外-可见漫反射光谱(UV-Vis)证明钕氧形成一种八面体结构。X射线光电子能谱(XPS)进一步证明钕主要以三价形式存在于立方介孔分子筛骨架中。     

以卵磷脂为手性添加剂制备手性介孔二氧化硅

以十六烷基三甲基溴化铵(CTAB)的自组装体为模板,卵磷脂(PC)为手性添加剂,在n PC∶nCTAB=1∶21时,通过溶胶-凝胶法制备了螺旋介孔二氧化硅纳米棒。利用扫描电镜(FESEM)、透射电镜(TEM)、X-射线衍射以及氮气吸附-脱附等测试手段,对该纳米棒的形貌以及孔结构进行了表征。TEM显示该纳米棒的长度约为50～200 nm,直径约为30～50 nm。X-射线衍射表明孔道呈二维六方排列,虽然FESEM显示纳米棒左右手比例约为1∶1,但通过圆二色谱表征证明该纳米棒在埃尺度下倾向于形成单一手性。结果表明,卵磷脂的手性可以传递到螺旋介孔二氧化硅纳米棒中。     

两对由乳酸衍生物和刚性辅助配体构建的螺旋单一手性配位聚合物：合成、结构和性质

利用水热合成条件,在辅助配体帮助下,乳酸衍生物与Zn²⁺反应合成出了2对单一手性的配位聚合物,即{[Zn（（R）-CBA）（1,3-DIMB）]·H₂O}_n（1-D）、{[Zn（（S）-CBA）（1,3-DIMB）]·H₂O}_n（1-L）、[Zn₂（（R）-CBA）₂（1,4-BMIP）]_n（2-D）和[Zn₂（（S）-CBA）₂（1,4-BMIP）₂]_n（2-L）。结构分析揭示上述所有配合物都包含由CBA^2-配体与Zn（Ⅱ）离子构建而成的螺旋链。此外,刚性的辅助配体1,3-DIMB和1,4-BMIP在结构多样性中发挥了重要作用。测试了配合物的热稳定性、固态圆二色谱、荧光性质等。研究结果表明半刚性乳酸配体可以有效地合成螺旋结构的单一手性配位聚合物。     

两个基于半刚性双甲基苯并咪唑配体的螺旋型镉配位聚合物

以1,4-双（2-甲基苯并咪唑-1-亚甲基）苯（bmb）为主配体与Cd（NO₃）₂反应,通过改变辅助双羧酸配体2个羧基间的连接基团,得到了2个配位聚合物{[Cd（bmb）（tba）]·DMF}_n（1）和[Cd（bmb）（ada）]_n（2）（H₂tda=5-叔丁基间苯二甲酸,H₂ada=1,3-金刚烷二乙酸）。结构分析表明聚合物1显示二维三明治结构,带有交替的左手和右手螺旋链。聚合物2也显示了二维三明治结构,带有meso-螺旋和微孔。聚合物1和2都显示了强的荧光发射和高的热稳定性。     

基于轴手性配体的两个镧系金属配合物的合成、表征及其荧光性质

通过水热法,合成了2个基于轴手性配体2,2''-dinitro-4,4''-biphenyldicarboxylic acid（H₂nbpdc）的配位聚合物[La（nbpdc）（phen）（FA）]_n（1）,[Eu（nbpdc）（phen）（FA）]_n（2）（phen=菲咯啉,FA=甲酸根）,并且对2个化合物进行了红外、单晶X射线衍射、热重、荧光、CD谱及介电性质的研究。晶体结构测试表明,2个化合物结晶在正交晶系P2₁2₁2₁手性空间群,且具有相同的三维拓扑结构。荧光性质测定表明化合物1和2分别在606和615.5 nm处有强的发射光谱。与此同时,固体CD谱测试进一步证实2个化合物具有手性。     

基于轴手性配体的两个镧系金属配合物的合成、表征及其荧光性质

通过水热法，合成了2个基于轴手性配体2，2''-dinitro-4，4''-biphenyldicarboxylic acid（H₂nbpdc）的配位聚合物[La（nbpdc）（phen）（FA）]_n（1），[Eu（nbpdc）（phen）（FA）]_n（2）（phen=菲咯啉，FA=甲酸根），并且对2个化合物进行了红外、单晶X射线衍射、热重、荧光、CD谱及介电性质的研究。晶体结构测试表明，2个化合物结晶在正交晶系P2₁2₁2₁手性空间群，且具有相同的三维拓扑结构。荧光性质测定表明化合物1和2分别在606和 615.5 nm处有强的发射光谱。与此同时，固体CD谱测试进一步证实2个化合物具有手性。     

基于链状SemSn(2≤m+n≤4)小分子的硒硫碳复合正极材料的制备及其电化学性能

将Se固溶复合到链状小硫分子S_2~4中,利用超微孔碳(UMC)的空间限域效应,在UMC中成功构建了链状Se_mS_n(2≤m+n≤4)小分子,并用作锂硫(Li-S)电池正极材料。与链状S_2~4小分子相比,改性后的Se_mS_n(2≤m+n≤4)小分子电导率更高,锂化能更低,放电锂化过程更容易。所制得的UMC/Se_mS_n(2≤m+n≤4)复合正极材料的放电过程为一步固相转化反应,从而有效抑制了活性物质的穿梭流失。与UMC/S_2~4复合正极材料相比,UMC/Se_mS_n(2≤m+n≤4)复合正极材料的电荷传递阻抗更小,放电比容量更高。因此,UMC/Se_mS_n-40(2≤m+n≤4,w_SeS2∶w_UMC=4∶6)复合正极材料在0.1C时循环100次后,比容量依然保持有844 mAh·g^-1;在0.5C下长时间循环500次时,每次循环容量损失仅约为0.07%,表现出优异的循环稳定性。     

Preparation of Mesoporous 1,4‐Phenylene‐silica Nanorings through a Dual‐templating Approach

Mesoporous 1,4‐phenylene‐silica nanorings were prepared using cetyltrimethylammonium bromide (CTAB) and (S)‐2‐methyl‐1‐butanol as a chiral dopant in concentrated aqueous NH₃ solutions. Transmission electron microscopy images of the samples indicated that the nanorings were formed by bending nanorods 360°. With increasing the stirring speed or the (S)‐2‐methyl‐1‐butanol/CTAB molar ratio, the morphologies of mesoporous 1,4‐phenylene‐silicas changed from helical nanofibers to nanorings, and then to nano‐saddles. Circular dichroism spectra of these hybrid silicas indicated that they were chiral.     

Synthesis and characterization of PbS nanorods in W/O microemulsion system

PbS nanorods have been successfully synthesized in water-in-oil (W/O) microemulsion containing non-ionic surfactant OP, n-pentanol, cyclohexane, and aqueous solution. The effects of the molar ratio of water to surfactant (ω₀), the concentration of reactants and the ageing time on the morphologies of PbS nanoparticles were investigated. The microstructures, morphologies and properties of the synthesized products were characterized by means of X-ray diffraction, transmission electron microscopy, and ultraviolet-visible (UV-VIS) absorption spectroscopy, respectively. The results showed that the synthesized rod-like products are composed of cubic phase PbS. These nanorods have an average diameter of about 100 nm, and an average length of about 500 nm. In the UV-VIS absorption spectrum, the absorption edge of PbS nanorods exhibit a blue shift compared with that of bulk PbS, indicating the quantum confinement effect of PbS nano-particles     

Preparation of Helical Mesoporous Ethenylene-silica Nanofibers with Lamellar Mesopores on Their Surface

The morphologies and pore architectures of mesoporous ethenylene‐silica were controlled using cetyltrimethylammonium bromide (CTAB) as template and (S)‐β‐citronellol as a co‐structure‐directing agent under basic conditions. When the (S)‐β‐citronellol/CTAB molar ratios are in the range of 0.75–2.0, helical nanofibers were obtained. With increasing the (S)‐β‐citronellol/CTAB molar ratio, the lengths of the nanofibers increases. Lamellar mesopores were identified on the surfaces of the nanofibers prepared in the (S)‐β‐citronellol/CTAB molar ratio range of 1.5–2.0. At the (S)‐β‐citronellol/CTAB molar ratio of 2.5:1, nanoparticles with nanoflakes on the surfaces were obtained. The field emission scanning electron microscopy images taken after different reaction times indicated that the helical pitches of the nanofibers decreased with increasing the reaction time. Helical 1,4‐phenylene‐silica and methylene‐silica nanofibers were also prepared. The results indicated that the morphologies and pore architectures of the obtained organic‐inorganic hybrid silicas are also sensitive to the hybrid silica precursors. Helical ethenylene‐silica nanofibers with lamellar mesopores on their surfaces can be also prepared using the mixtures of CTAB and racemic citronellol within a narrower citronellol/CTAB molar ratio range.     

Cholesteric mixture containing a chiral azobenzene-based dopant: material with reversible photoswitching of the pitch of the helix

A new low molar mass chiral-photochromic dopant was synthesized. It contains a menthyl fragment as the chiral group and an azobenzene group, capable of E - Z photoisomerization, as the photochromic component. The substance obtained was used as a chiral dopant in mixtures with a comb-shaped cholesteric acrylic copolymer with menthyl-containing chiral side groups and phenyl benzoate nematogenic side groups. Such mixtures form a cholesteric mesophase. The chiral dopant led to an additional twisting of the cholesteric helix, i.e. to a shift of the selective light reflection peak to a shorter wavelength region of the spectrum. The initial copolymer gave selective light reflection in the spectral range 1200-1400 nm; the mixture containing 3.5 mol % of chiral-photochromic dopant reflects light with λ_max~ 850 nm. The action of light with λ_ir~ 440 nm results in E - Z isomerization of the azo-group of the chiral dopant and in a shift of the selective light reflection peak to the long wavelength region of the spectrum (amplitude of shift = 30 nm). This is explained by a lower helical twisting power of the Z-isomer of the chiral dopant. This process is thermally reversible: annealing of irradiated films leads to a back shift of the selective light reflection peak to the short wavelength region of the spectrum due to Z - E isomerization. Kinetic features of the direct and backward processes of isomerization were studied: it was shown, that mixtures of the chiralphotochromic azobenzene-containing dopant with cholesteric polymers give new possibilities for the creation of polymer materials with a reversibly regulated helical supramolecular structure which determines their optical properties.     

Morphology Control of Bi2S3 Nanostructures and the Formation Mechanism

Bismuthinite (Bi₂S₃) nanostructures were prepared by a hydrothermal method with sodium ethylenediaminetetraacetate (EDTA‐Na₂). The morphology of Bi₂S₃ nanostructures was changed from a nanorod to a nanoplate by presence of the EDTA‐Na₂. The altered morphology was caused by the capping effect of EDTA‐Na₂ with Bi³⁺ ions, which induces the suboptimal growth direction due to partially blocking the preferential orientation direction. When the EDTA‐Na₂/Bi³⁺ molar ratio=1, the growth of Bi₂S₃ nanostructures was not allowed due to the chelating effect of EDTA‐Na₂. The obtained Bi₂S₃ nanorods, stacked nanorods, nanoplates and nanoparticles were characterized using X‐ray diffraction (XRD), transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) pattern. A possible formation mechanism of these morphologies was proposed. The successful synthesis of various morphologies of nanostructured Bi₂S₃ may open up new possibilities for thermoelectric, electronic and optoelectronic uses of nanodevices based on Bi₂S₃ nanostructure.     

微波水热法制备CdS单分散纳米球及其形貌控制

采用微波水热法,以醋酸镉(Cd(CH3COO)2.2H2O)为镉源,硫脲(CS(NH2)2)为硫源,制备出了具有单分散球形形貌的CdS纳米晶。应用X射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、能量色散谱仪(EDS)、高分辨透射电子显微镜(HR-TEM)、紫外可见吸收光谱(UV-Vis)等测试手段对样品的物相、形貌、元素组分及吸光性能进行了表征,并以罗丹明B溶液的降解脱色反应来考察了其的光催化活性。结果表明:随着S/Cd物质的量比(nS/nCd)逐渐增大,产物会出现由刺球链状向分散球形过渡的规律性变化。在一定的nS/nCd比的条件下可以合成出大小均匀、分散性较好的六方相CdS纳米球。样品对可见光有较强吸收,存在着一定的红移现象。在可见光照射下,硫化镉单分散纳米球具有更高的光催化活性。     

Synthesis and hierarchical superstructures of side‐chain liquid crystal polyacetylenes containing galactopyranoside end‐groups

Three kinds of chiral saccharide‐containing liquid crystalline (LC) acetylenic monomers were prepared by click reaction between 2‐azidoethyl‐2,3,4,6‐tetraacetyl‐β‐D ‐galactopyranoside and 1‐biphenylacetylene 4‐alkynyloxybenzoate. The obtained monomers were polymerized by WCl₆‐Ph₄Sn to form three side‐chain LC polyacetylenes containing 1‐[2‐(2,3,4,6‐tetraacetyl‐β‐D ‐galactopyranos‐1‐yl)‐ethyl]‐1H‐[1,2,3]‐triazol‐4′‐biphenyl 4‐alkynyloxybenzoate side groups. All monomers and polymers show a chiral smectic A phase. Self‐assembled hiearchical superstructures of the chiral saccharide‐containing LCs and LCPs in solution state were studied by field‐emission scanning electron microscopy. Because of the LC behavior, the LC molecules exhibit a high segregation strength for phase separation in dilute solution (THF/H₂O = 1:9 v/v). The self‐assembled morphology of LC monomers was dependent upon the alkynyloxy chain length. Increasing the alkynyloxy chain length caused the self‐assembled morphology to change from a platelet‐like texture ( LC‐6 ) to helical twists morphology ( LC‐11 and LC‐12 ). Furthermore, the helical twist morphological structure can be aligned on the polyimide rubbed glass substrate to form two‐dimensional ordered helical patterns. In contrast to LC monomers, the LCP‐11 self‐assembled into much more complicate morphologies, including nanospheres and helical nanofibers. These nanofibers are evolved from the helical cables ornamented with entwining nanofibers upon natural evaporation of the solution in a mixture with a THF/methanol ratio of 3:7. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6596–6611, 2009