Preparation and Characterization of a Sol-Gel Prepared Ferroelectric Sandwich Structure

A novel silicon-based PbTiO₃/Pb(Zr,Ti)O₃/PbTiO₃ (PT/PZT/PT) sandwich structure has been prepared using a sol-gel method. The annealing temperature is greatly reduced compared with those structures without PT layers. Capacitance-voltage (C-V), leakage current-voltage (I-V), polarization-field (P-E), dielectric-frequency response and polarization fatigue of the sandwich structure are examined. The relative dielectric constant, the coercive field and the remanent polarization of the PZT films are measured to be about 900, 18 kV/cm and 16 C/cm² respectively. The current density is less than 5 × 10^–9 A/cm² below 200 kV/cm. The dielectric constant of the structure remains constant at low frequency, and decreases to some degree at high frequency. The retained polarization does not change significantly after 8 × 10⁹ read/write cycles. The PZT films are proved to have very good dielectric and ferroelectric properties. The new PT/PZT/PT sandwich structure can be valuable for memory devices and other applications.     

基于异构三联苯-2，2″，4，4″-四羧酸构筑的单水桥钴(Ⅱ)、镍(Ⅱ)配位聚合物的合成、结构及磁性质

使用异构三联苯-2,2″,4,4″-四羧酸配体(m-H₄tpta和p-H₄tpta),通过水热法合成了2例新的单水桥Co (Ⅱ)/Ni (Ⅱ)金属链状配位聚合物[Co (m-H₂tpta)(H₂O)₃]_n(1)和{[Ni₂(p-tpta)(H₂O)₆]·2H₂O}_n(2)。其结构通过FT-IR、元素分析、X射线单晶及粉末衍射进行了表征。在结构上,金属离子呈现出轻微扭曲的八面体几何构型,通过单水分子桥连接形成了一维金属链,异构H₄tpta配体分别采用μ₁-η¹∶η⁰∶η¹∶η⁰和μ₄-η¹∶η¹∶η¹∶η¹配位模式与金属离子连接,形成一维链和三维网状结构,配合物2表现出(4,4)-连接的NbO型的三维拓扑网络结构。磁性方面,配合物1的Co(Ⅱ)离子间通过μ₂-H₂O桥传递表现出反铁磁相互作用。配合物2也展现出Ni(Ⅱ)离子间的反铁磁耦合作用,与磁耦合Ni—Ow—Ni角有关。     

活性碳纤维阴极电芬顿反应降解微囊藻毒素研究

以具有高比表面积的活性碳纤维作为阴极,通过电芬顿反应降解水中微囊藻毒素(MCRR,MCLR)的电化学方法系统考察了电流密度、pH值和Fe2+浓度等因素对微囊藻毒素降解效果的影响.实验结果表明,在Fe2+浓度为1.0mmol/L和电流密度为6.6mA/cm2条件下,电化学处理60min,MCRR(8.81mg/L)去除率为75%,MCLR(6.36mg/L)去除率为94%.证明过氧化氢可以通过电化学还原在活性碳纤维阴极表面高效产生,微囊藻毒素可被高效降解去除.     

盐酸2-芳基-3,5,5-三甲基-2-吗啉醇的合成

盐酸2-芳基-3; 5; 5-三甲基-2-吗啉醇的合成;盐酸芳基三甲基吗啉醇; 胺化; 合成     

Cryptanalysis and improvement of a digital image encryption method with chaotic map lattices

A digital image encryption scheme using chaotic map lattices has been proposed recently. In this paper, two fatal flaws of the cryptosystem are pointed out. According to these two drawbacks, cryptanalysts could recover the plaintext by applying the chosen plaintext attack. Therefore, the proposed cryptosystem is not secure enough to be used in the image transmission system. Experimental results show the feasibility of the attack. As a result, we make some improvements to the encryption scheme, which can completely resist our chosen plaintext attack.     

Structures and photocatalytic performance of two d10 metal-based coordination polymers containing mixed building units

The linker 1,4-bis(2-methyl-imidazole-yl)-butane (bib) was used to construct two coordination polymers, specifically [Cd(bib)(ipa)]_n (1) and [Zn(bib)(tpa)]_n (2), in the presence of isophthalic acid (H₂ipa) and terephthalic acid (H₂tpa), respectively, under solvothermal conditions. Topological analyses reveal that the crystal of complex 1 consists of a 3D threefold interpenetrating network with Schläfli symbol {6⁵.8}, while complex 2 possesses a 2D wavelike layer structure with Schläfli symbol {6⁶}. The photocatalytic properties of both complexes for the degradation of methyl violet have been explored, revealing that complex 2 is a better photocatalyst than 1. A mechanism for the photocatalytic properties of the complexes is proposed, based on the results of density of states (DOS) and partial DOS calculations.

     

Atomic Force Microscopic Studies of the Ligand-DNA Interactions on Mica

Atomic force microscopy (AFM) can reliably generate high-resolution images of nucleic acids and proteins.     

侧链液晶聚硅氧烷langmuir膜的原子力显微镜观察

通过原子力显微镜观测了含手性基团侧链液晶聚硅氧烷在空气/水界面上的单层膜,观测了成膜物在界面形成微畴结构以及表面压力升高时微畴聚集、重排过程,分析了纳米级微畴形成、聚集和重排的机理和规律。     

Theranostic gold cluster nanoassembly for simultaneous enhanced cancer imaging and photodynamic therapy

As one of near-infrared (NIR) fluorescent (FL) nanoprobes, gold nanoclusters (Au NCs) are delicated to passive-targeting tumors for NIR FL imaging, but which easily cleared by the kidneys for the small size (<1.5 nm). Herein, the well-defined gold clusters nanoassembly (Au CNA) was synthesized by the selfassembly of Au NCs based on protein cross-linking approach. The as-prepared Au CNA demonstrated highly effective cellular uptake and precise tumor targeting compared to that of Au NCs. Moreover, with the irradiation of 660 nm laser, Au CNA generated largely reactive oxygen species (ROS) for photodynamic therapy (PDT). In vitro and in vivo PDT revealed that Au CNA exhibited largely cell death and significantly tumor removal at a low power density of 0.2 W/cm². It could be speculated that the laser-excited Au CNA produced photon energy, which further obtained electron from oxygen to generate radical species. Therefore, Au CNA as a photosensitizer could realize NIR FL imaging and NIR laser induced PDT.     

Two CoII coordination polymers of biphenyl‐2,2′,5,5′‐tetracarboxylic acid with flexible N‐donor ligands: syntheses,structures and magnetic properties

Two Co^II‐based coordination polymers, namely poly[(μ₄‐biphenyl‐2,2′,5,5′‐tetracarboxylato){μ₂‐1,3‐bis[(1H‐imidazol‐1‐yl)methyl]benzene}dicobalt(II)], [Co₂(C₁₆H₆O₈)(C₁₄H₁₄N₄)₂]_n or [Co₂(o,m‐bpta)(1,3‐bimb)₂]_n ( I ), and poly[[aqua(μ₄‐biphenyl‐2,2′,5,5′‐tetracarboxylato){1,4‐bis[(1H‐imidazol‐1‐yl)methyl]benzene}dicobalt(II)] dihydrate], {[Co₂(C₁₆H₆O₈)(C₁₄H₁₄N₄)₂(H₂O)₂]·4H₂O}_n or {[Co₂(o,m‐bpta)(1,4‐bimb)₂(H₂O)₂]·4H₂O}_n ( II ), were synthesized from a mixture of biphenyl‐2,2′,5,5′‐tetracarboxylic acid, i.e. [H₄(o,m‐bpta)], CoCl₂·6H₂O and N‐donor ligands under solvothermal conditions. The complexes were characterized by IR spectroscopy, elemental analysis, single‐crystal X‐ray diffraction and powder X‐ray diffraction analysis. The bridging (o,m‐bpta)^4? ligands combine with Co^II ions in different μ₄‐coordination modes, leading to the formation of one‐dimensional chains. The central Co^II atoms display tetrahedral [CoN₂O₂] and octahedral [CoN₂O₄] geometries in I and II , respectively. The bis[(1H‐imidazol‐1‐yl)methyl]benzene (bimb) ligands adopt trans or cis conformations to connect Co^II ions, thus forming two three‐dimensional (3D) networks. Complex I shows a (2,4)‐connected 3D network with left‐ and right‐handed helical chains constructed by (o,m‐bpta)^4? ligands. Complex II is a (4,4)‐connected 3D novel network with ribbon‐like chains formed by (o,m‐bpta)^4? linkers. Magnetic studies indicate an orbital contribution to the magnetic moment of I and II due to the longer Co…Co distances. An attempt has been made to fit the χ_MT results to the magnetic formulae for mononuclear Co^II complexes, the fitting indicating the presence of weak antiferromagnetic interactions between the Co^II ions.