Supramolecular Science最新文献

Small and large unilamellar biotinylated liposomes (SUVs and LUVs) composed of egg phosphatidylcholine and 2 mol% of biotinylated phosphatidylethanolamine were assembled in the presence of avidin at a low concentration (0.05–0.1 mg ml^-1) and simultaneously immobilized in fused-silica capillary tubing. LUV assemblies were immobilized to 21 nmol phospholipid in one capillary, about twice as high as found for the SUV assemblies. Estimated values showed that the capillary inner surface was coated by 4–15 liposome layers. The liposome-coated capillary can be used in capillary electrophoresis for microanalysis of drug-membrane interactions. This avidin–biotin-assembly method may also be applied to immobilize liposomes or proteoliposomes in a high order on a planar solid surface for construction of biomaterials.

A novel C₆₀ pyrrolidine derivative, C₆₀(C₈H₁₅NO₂) (1), has been synthesized and its Langmuir and LB films were investigated. The monolayer of 1 can be transferred on to hydrophilic substrates. Photocurrent generation of the LB film modified ITO electrode has been measured. The anodic photocurrent can be suppressed by oxygen and enhanced by the electron donor Vc (ascorbic acid). The quantum yield is 1.9% with the concentration of Vc at 0.5 mg ml^-1 in the KCl solution.

The effects of macromolecules as soluble additives and solid matrices have been examined for the crystallization of CaCO₃. A vaterite form grows on a glass substrate in the presence of poly(glutamic acid) (PGA) containing a carboxylic acid group as a soluble additive. In contrast, no crystal growth has been observed when poly(acrylic acid) (PAA) exists as an additive though it has the same functional group. The conformation or the backbone structure of the polymers may have an influence on the crystal polymorph of CaCO₃. Thin film states of CaCO₃ crystals have been obtained as organic/inorganic composites with chitosan that acts as a solid matrix in the presence of PAA or PGA as a soluble additive.

Photopolymerizations of intercalated 4-vinylbenzoate (VBA) and p-(or m-) phenylenediacrylates (PDA) were investigated in the presence of an anion exchange clay, hydrotalcite. UV irradiation of clay powder adsorbing VBA and 4-benzoylbenzoate (BBA) ions gave rise to the cyclodimerization of the olefin and a radical polymerization to form polyvinylbenzoate. The degree of the polymerization was 10–10³. The stereoregularity was investigated by NMR analysis and is discussed in relation to the state of molecular aggregation in the clay interlayers. In contrast to VBA, photoreaction of the intercalated PDAs resulted in the formation of oligomers in [2+2] cycloaddition manner, of which the polymerization degrees were rather low (up to ten at most). The stereochemistry of the oligomer was revealed to be of a syn-head-to-head structure by NMR analysis. Dianionic molecules such as PDAs showed an interesting intercalation behavior in contrast to monoanions, i.e. just one double-negatively charged molecule was estimated to occupy three anion exchange sites of the hydrotalcite layer. Also, the relatively low polymerization degrees of the PDAs were found to be due to the above intercalation characteristics. Powder X-ray diffraction analysis showed that the molecular aggregation state was remarkably changed by desiccating the clay composite in vacuum, thus suppressing the efficiency of the photoreaction.

Polymeric receptors for cholesterol were synthesized by crosslinking β-cyclodextrin (β-CyD) with hexamethylene diisocyanate or toluene 2,4-diisocyanate in dimethyl sulfoxide (DMSO) in the presence of cholesterol as the template. Non-imprinted β-CyD polymers were much poorer in the cholesterol adsorption. When β-CyD was cross-linked by epichlorohydrin in aqueous alkaline solutions (even in the presence of cholesterol), the cholesterol adsorbing activity was nil. Use of DMSO as the cross-linking solvent is necessary for the imprinting, since β-CyD molecules form inclusion complexes with cholesterol in this solvent and thus their mutual conformation in the polymer is regulated appropriately for cholesterol binding. The adsorbed cholesterol was completely removed from the polymers by treating the adducts with ethanol, indicating a strong potential for practical applications.

Electron beam lithography was investigated using a cross-linkable polymer Langmuir–Blodgett (LB) film. Cross-linking reaction occurs in the LB film with electron beam irradiation as well as UV light irradiation and the irradiated LB film becomes insoluble in the organic solvents to form a two-dimensional network in the LB film. The sensitivity and contrast of the cross-linkable polymer LB film are 3 μC cm^-2 and 0.64, respectively. The limiting resolution of patterning is 0.2 μm line-and-space. The electron beam lithography using the cross-linkable polymer LB film is applicable to the future nanotechnology.

Ordered mesoporous silicas with spherical morphology and average particle size in the range between 100 nm and 2 μm were synthesised according to two novel routes. Both synthesis routes used tetraethoxysilane, water, alcohol and aqueous ammonia for producing spherical silica beads. The porosity was created by adding two different kinds of pore structure directing agents to the starting solution: one was an n-alkyltrialkoxysilane which was covalently bonded to the silica framework, the other was an n-alkylamine which acted as a nonionic template. After calcination and post treatment the resulting particles showed a specific surface area up to 1000 m² g^-1, a specific pore volume of up to 0.8 cm³g^-1 and an average pore diameter between 2 and 6 nm.

Zeolites are one of the most important materials currently used in the petroleum industry for a wide variety of catalytic transformations. However, they are increasingly being considered for other applications such as for designing quantum-confined materials in their spaces. With such applications in mind, precise characterisation of zeolites and related porous materials has never been more necessary. Here we show how electron diffraction coupled with high-resolution imaging can reveal the detailed fine structure in both the bulk and at the surface of these materials. A variety of case studies are considered which include ETS-10, FAU, LTL and FSM-16.

Ultrathin polymer films incorporating amphiphilic ruthenium (II) polypyridine complex (Ru2C16B) or viologen (LPV) were prepared by casting a mixed solution on a water surface. Interfacial photoinduced energy-transfer from coumarin dye (CoD) on the glass plate to Ru2C16B in the polymer film indicated asymmetric population of Ru2C16B at a single surface of the film. Phoinduced electron-transfer from Ru2C16B to LPV across the films also verified asymmetric enrichment of these amphiphilic dyes. The results establish a novel and simple method of asymmetric self-organization of amphiphilic dyes in the thin polymer film.

Transmission electron microscopy observation was carried out for nanometric Cr clusters deposited on microgrids at room temperature using plasma–gas-condensation (PGC) method. In order to obtain optimum conditions for monodisperse cluster formation we have studied effects of an Ar gas pressure, an Ar gas flow rate, and a mixing rate of He gas with Ar gas on the size distribution of formed clusters. It has been found that monodisperse clusters with the size rage of 9–13 nm in diameter are producible at a low Ar gas pressure (≤1.3 Torr) and a low Ar gas flow rate (≤600 sccm). The mean cluster size decreases with decreasing Ar gas pressure, while it is not sensitive to the Ar gas flow rate. When He gas is mixed with Ar gas, the mean cluster size further decreases to 6 nm and the cluster beam intensity becomes stronger probably because He gas with the high thermal conductivity enhances supersaturation for cluster nucleation.