Thermally programmable gas storage and release in single crystals of an organic van der Waals host

A single crystal of a low density form of guest-free p-tert-butylcalix[4]arene can take up and release small guest molecules by controlling the temperature and pressure without changing the structure. Using NMR spectroscopy with flowing hyperpolarized xenon, we have shown that at room temperature access of xenon to the pore system is difficult, whereas it is relatively easy at 100 degrees C. There are good prospects for simple van der Waals materials such as the title material to be used as programmable zeolite mimics.     

碳纳米管的快速糖基化及用于糖-凝集素特异性识别作用的研究

将含糖基的简单两亲分子N-十八烷基麦芽糖酰胺(N-n-Octadecyl-D-maltonamide, NOMA)非共价修饰到单壁碳纳米管(SWNT)表面形成糖-碳纳米管复合体(NOMA-SWNT), 谱学和形态学结果表明, NOMA不仅能快速、高效地吸附到SWNT表面, 而且能有效地改善SWNT在水溶液中的分散性能. 以NOMA-SWNT管束为导通沟道构建了碳纳米管场效应管(CNTFET)器件, 检测了麦芽糖和伴刀豆凝集素蛋白(Con A)的特异性识别作用. 检测器件在每个修饰阶段的电学性能的变化证明了NOMA对SWNT的非共价糖基化修饰及用CNTFET来检测糖-凝集素特异性识别作用的可能性.     

Synthesis and characterization of cross-linked reverse micelles

The design and synthesis of a new cross-linkable amphiphile is reported. Solutions of the amphiphile in a toluene/water mixture form reverse micelles as indicated by dynamic light scattering and NMR spectroscopy. As indicated by dynamic light scattering, TEM, and NMR spectroscopy data, these reverse micelles can be cross-linked without drastically changing the radius of the reverse micelles. Mixed reverse micelles are also characterized and cross-linked. The cross-linked reverse micelles are demonstrated to facilitate phase transfer and can be used to site isolate a catalyst.     

Dithienylethene-Based Single Molecular Photothermal Linear Actuator

By employing a mechanically controllable break junction technique, we have realized an ideal single molecular linear actuator based on dithienylethene (DTE) based molecular architecture, which undergoes reversible photothermal isomerization when subjected to UV irradiation under ambient conditions. As a result, open form (compressed, UV OFF) and closed form (elongated, UV ON) of dithienylethene-based molecular junctions are achieved. Interestingly, the mechanical actuation is achieved without changing the conductance of the molecular junction around the Fermi level over several cycles, which is an essential property required for an ideal single molecular actuator. Our study demonstrates a unique example of achieving a perfect balance between tunneling width and barrier height change upon photothermal isomerization, resulting in no change in conductance but a change in the molecular length, which results in mechanical actuation at the single molecular level.     

Supramolecular Assembly through Interactions between Molecular Dipoles and Alkali Metal Ions

Establishing a way to fabricate well‐ordered molecular structures is a necessary step toward advancement in organic optoelectronic devices. Here, we propose to use interactions between electric dipoles of molecules and alkali metal ions to form a well‐developed homogeneous monolayer of diarylethene molecules on the Cu(111) surface with the aid of NaCl co‐deposition. Scanning tunneling microscopy and density functional theory calculation results indicate that the formation of a row‐type structure occurs as a result of interactions between the Na⁺ ions and the diarylethene molecular dipoles, drastically changing the adsorption configuration from that without Na⁺.     

The detection of laser-induced structural change of MnO2 using in situ Raman spectroscopy combined with self-modeling curve resolution technique

In this paper, we present the use of one of the self-modeling curve resolution techniques, band-target entropy minimization (BTEM), which is independent of any spectral library, to elucidate Raman pure component spectra of two different manganese oxides arising from laser-induced structural changes. It is often extremely difficult to obtain the pure Raman spectrum of MnO₂ without changing it to another structural form. However, using BTEM to analyze the collected in situ Raman spectra measured as a function of laser exposure time, has enabled us to obtain both the pure component spectra of the original sample and the product due to laser irradiation. This technique proves to be an efficient Raman spectral interpretation method for thermal sensitive solid samples.     

Surfactant-assisted one-pot synthesis of superparamagnetic magnetite nanoparticle clusters with tunable cluster size and magnetic field sensitivity

Magnetic nanoparticles (MNPs) have many potential biomedical applications. Improvements in their magnetic properties and solubility are necessary for these applications to realize their full potential. In this study, MNPs in the form of raspberry-like magnetite (Fe(3)O(4)) nanoparticle clusters, consisting of tiny Fe(3)O(4) particles with a diameter of approximately 20 nm, were prepared under hydrothermal conditions at 200 °C in the presence of 3,4-dihydroxyhydroxysinnamic acid (DHCA). The primary particles were connected by DHCA molecules to form the clusters, which were well dispersed in water media because a COOH group from DHCA appeared on their surfaces. The cluster size could be tuned from 50 to 400 nm without changing the primary particle size by controlling the reaction time. Therefore, all prepared clusters displayed superparamagnetic properties at room temperature. In addition, the sensitivity of Fe(3)O(4) to an external magnetic field could also be controlled by the cluster size.     

Surface patterning and its application in wetting/dewetting studies

Recent advances in microfabrication have allowed one to pattern the surface of a solid substrate with patches of different wettabilities on the micrometer-sized scale. These textured surfaces provide a well-characterized model system for studying the wetting and dewetting behaviors of liquids on heterogeneous surfaces. They also present a well-defined template to direct the self-organization of liquids on the surfaces of solid substrates, and to form patterned microstructures of various materials without using expensive, clean-room facilities. As demonstrated in a number of studies, the three-dimensional morphologies of the liquid microstructures could be easily controlled by changing the two-dimensional features patterned on the surface of a solid substrate. These demonstrations suggest that microfabrication based on surface patterning and selective wetting or dewetting will offer immediate advantages in applications such as fabrication of microreactor arrays and microfluidic devices, where a liquid (or solution) is the primary material to be patterned.     

Thermodynamics of sublimation of calix[4]arene complexes with solvent molecules

The inclusion of small neutral organic guests (C₆H₁₄, CH₂Cl₂, CH₃OH) by calix[4]arene receptors was found by ¹H NMR spectroscopy and microanalysis. The studied calix[4]arenes can form stable intramolecular complexes with solvent molecules which keep the stoichiometric composition without changing under conditions of the sublimation experiment. The saturated vapour pressures of calix[4]arenes and complexes of calix[4]arenes with solvent molecules were determinated for the first time by the Knudsen’s effusion method in the wide temperature range. The changing of standard thermodynamic parameters of complexation by transfer process from condensed state to vapour phase was estimated. It was shown that the large flexibility of the calixarene ligand structure corresponds to a strongly negative entropic contribution as well as negative enthalpy term to the Gibbs energy of formation of host–guest complexes in the gas phase.     

Hydrogen-bonding dynamics in photoinduced electron transfer in a ferrocene-quinone linked dyad with a rigid amide spacer

A newly designed ferrocene-quinone dyad with an amide space (Fc-Q) is employed to examine formation of the hydrogen bonding in the one-electron reduced form (Q*-) and the dynamics in the photoinduced electron-transfer reaction from the ferrocene to the quinone moiety. Photoexcitation of the Q moiety in Fc-Q in deaerated PhCN with 388 nm results in intramolecular electron transfer from Fc to the singlet excited state of Q to produce Fc+-Q*- without changing the conformation (<1 ps), followed by hydrogen bond formation with the amide proton of the spacer (tau = approximately 5 ps). The resulting radical ion pair decays via a back electron transfer to the ground state at a longer time scale with a rate constant of 2.6 x 108 s-1.     

RHODOPSIN-PHOSPHOLIPID INTERACTION IN DETERGENT AND IN THE DISK

Abstract— Solubilization of cattle disk membrane in deoxycholate shifted the fluorescence emission maximum from 324 to 331 nm without changing the intensity. Tryptophyl residues are probably located at the hydrophobic interface between rhodopsin and phospholipid. Depletion of deoxycholate concentration from the solubilized disk by Sephacryl 200 column chromatography produced rhodopsin-phospholipid complexes with different characteristics that are the intermediate stages of membrane formation from homogeneous molecular solution. Association of rhodopsin takes place in a two-dimensional way even in the appreciably low content of phospholipid.
Sedimentation velocity studies showed that reassociation of lipid and rhodopsin occurs in 0.2% deoxycholate as well as in 0.05% sodium dodecylsulfate.
By using Sephacryl column we can now prepare, within 60 min, the rhodopsin-lipid complex that can form large vesicles in response to the addition of MgCl₂ without dialysis. This type of lipoprotein complex will be useful to the study of the mechanism of the two dimensional membrane formation.     

Photocatalytically Renewable Micro‐electrochemical Sensor for Real‐Time Monitoring of Cells

Electrode fouling and passivation is a substantial and inevitable limitation in electrochemical biosensing, and it is a great challenge to efficiently remove the contaminant without changing the surface structure and electrochemical performance. Herein, we propose a versatile and efficient strategy based on photocatalytic cleaning to construct renewable electrochemical sensors for cell analysis. This kind of sensor was fabricated by controllable assembly of reduced graphene oxide (RGO) and TiO₂ to form a sandwiching RGO@TiO₂ structure, followed by deposition of Au nanoparticles (NPs) onto the RGO shell. The Au NPs‐RGO composite shell provides high electrochemical performance. Meanwhile, the encapsulated TiO₂ ensures an excellent photocatalytic cleaning property. Application of this renewable microsensor for detection of nitric oxide (NO) release from cells demonstrates the great potential of this strategy in electrode regeneration and biosensing.     

Protein Labelling with Versatile Phosphorescent Metal Complexes for Live Cell Luminescence Imaging

To take advantage of the luminescent properties of d⁶ transition metal complexes to label proteins, versatile bifunctional ligands were prepared. Ligands that contain a 1,2,3‐triazole heterocycle were synthesised using Cu^I catalysed azide–alkyne cycloaddition “click” chemistry and were used to form phosphorescent Ir^III and Ru^II complexes. Their emission properties were readily tuned, by changing either the metal ion or the co‐ligands. The complexes were tethered to the metalloprotein transferrin using several conjugation strategies. The Ir^III/Ru^II–protein conjugates could be visualised in cancer cells using live cell imaging for extended periods without significant photobleaching. These versatile phosphorescent protein‐labelling agents could be widely applied to other proteins and biomolecules and are useful alternatives to conventional organic fluorophores for several applications.     

Selective reactions of enantiomeric-mixtures

Enantiomers in solution have a tendency to form associations of various compositions. This phenomenon is used to separate partially resolved mixtures of enantiomers.Possibilities for improving separation by changing various parameters have been investigated. A new method for determination of optical purity is described.     

不同浸润性多孔电极表面的气泡行为

采用氢气模板法制备了具有多孔结构的电极; 通过改变电镀电流密度和电镀时间实现了电极表面多孔结构孔径和分布的控制; 通过改变表面化学组成有效调控了电极表面的浸润性质. 比较了具有不同微观结构和表面化学组成的电极在给定条件下电解水过程中气泡的产生及行为机制. 实验结果表明: 相对于亲水的多孔电极, 疏水的多孔电极表面能够黏附气泡, 更易倾向于形成稳定的气膜; 多孔结构对于亲水电极表面气泡行为的影响比对疏水电极表面气泡行为的影响更为显著; 与没有多孔结构的亲水电极相比, 具有多孔结构的亲水电极表面产生的气泡数量多, 速率快; 与较小孔径的多孔亲水电极相比, 较大孔径的多孔亲水电极表面产生气泡速率快且黏附气泡数量少. 该研究结果为微气泡减阻电极的设计提供了理论依据.     

Design of a universal reversible bidirectional current switch based on the fullerene-phthalocyanine supramolecular system

A novel bidirectional current ON-OFF switch controlled by electron injection and deprivation was proposed on the basis of the density functional theory (DFT) calculation over a fullerene-phthalocyanine supramolecular system PcCoC(60) for the first time. The electron density for PcCoC(60) was revealed to move from fullerene to phthlocyanine only in the oxidized form and from phthlocyanine to fullerene only in the reduced form, reaching the control of electron movement direction by changing the oxidation state of this supramolecular system.     

General shape control of colloidal CdS, CdSe, CdTe quantum rods and quantum rod heterostructures

We report a general synthetic method for the formation of shape-controlled CdS, CdSe and CdTe nanocrystals and mixed-semiconductor heterostructures. The crystal growth kinetics can be manipulated by changing the injection rate of the chalcogen precursor, allowing the particle shape-spherical or rodlike-to be tuned without changing the underlying chemistry. A single injection of precursor leads to isotropic spherical growth, whereas multiple injections promote epitaxial growth along the length of the c-axis. This method was extended to produce linear type I and type II semiconductor nanocrystal heterostructures.     

Evolution of interparticle capillary forces during drying of colloidal crystals

Photonic crystals are periodic structures that have the capability to manipulate the photons in the same way as semiconductors do for electrons. The self-assembly strategy that utilizes colloidal crystals as a template to form photonic crystals has received a great deal of recent research interest because it is simple and cost-effective. Experimental studies and theoretical analysis have speculated that capillary forces play a pivotal role in forming the colloidal crystals during the crystal growth process and that particularly during the drying stage the changing of the magnitude of capillary forces is critical to the resultant microstructure. This paper presents a computational analysis of the changing capillary forces, which may throw light on a refined strategy for controlling colloidal crystal growth.     

以阴离子表面活性剂/阳离子聚铵复合胶束为模板合成有序介孔二氧化硅

基于静电作用, 阴离子表面活性剂可与阳离子聚铵组装形成复合胶束. 借助阳离子聚铵,复合胶束可以作为模板与硅源协同组装, 形成高度有序的介孔二氧化硅. 本文通过调变不同种类阴离子表面活性剂、合成体系pH值、合成温度及阳离子聚铵和硅源用量等因素, 合成了具有不同介观结构和形貌的介孔二氧化硅. 实验证实阴离子表面活性剂/阳离子聚铵复合胶束模板法是合成介孔二氧化硅的一种通用方法.     

Crystallization of s-polypropylene: a qualitative change in the kinetics induced by the temperature of the melt

The crystallization of syndiotactic polypropylene (sPP) can be strongly affected by the temperature of the melt prior to cooling to the crystallization temperature. We observed, for a commercial sample, a variation in the form of the crystallization isotherm that cannot be explained simply on the basis of a changing number of growing hedrites.