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A tetraphenylporphyrin (1b) bearing amide groups at the 3,5-positions of the meso-phenyl groups is assembled into a two-dimensional sheetlike structure and acts as an organogelator. When [60]fullerene was added, the sheetlike structure was dramatically changed into a one-dimensional fibrous structure, and both the gelation ability and the gel stability were improved. The stoichiometry between [60]fullerene and 1b was determined to be 1:2. Examination utilizing SEM and TEM observations, UV-vis and ATR IR spectral analyses, and XRD analysis revealed that an amide-amide hydrogen-bonding interaction creates a cavity, the size of which is complementary to that of [60]fullerene, and these cavities are connected by another amide-amide hydrogen-bonding interaction to provide a one-dimensional multicapsular structure. This is a novel example that the superstructure constructed in an organogel system is drastically changed by added [60]fullerene.
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PMID:[60]fullerene-motivated organogel formation in a porphyrin derivative bearing programmed hydrogen-bonding sites. 1291 35

Methyl methacrylate/1,2-divinylbenzene (MMA/DVB) in an opaque emulsion were successfully grafted onto the surface of polymeric substrate under the irradiation of UV light with benzophenone (BP) as a photoinitiator that was previously coated on the substrate surface. Monomer conversion, grafting efficiency, and grafting yields were determined by the gravimetric method. ATR-IR, AFM, and TEM were used to characterize the surface composition, to observe the topography of the grafted substrates, and to view inter-film colloid particles formed by cross-linking. The results reveal that, with the opaque MMA/DVB emulsion system and CPP film as substrate, the monomer conversion is in the range of 15-55%, the grafting efficiency is about 80%, the grafting yield reaches 5%, and the thickness of the graft layer can be controlled in the range 0.09-1.5 microm. Images of AFM show that the graft layer is piled up by nanoparticles (about 30-50 nm in diameter), which are linked together and tied to the substrate surface with covalent bonds. A possible model of surface graft polymerization including surface initiating, nucleation, and shish kebab growing is put forward to interpreting the above results.
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PMID:MMA/DVB emulsion surface graft polymerization initiated by UV light. 1524 6

The synthesis of four bis(trialkoxysilylated) organic molecules capable of self-assembly--(EtO)3Si(CH2)3NHCONH-(CH2)n-NHCONH(CH2)3Si(OEt)3 (n = 9-12)--associating urea functional groups and alkylidene chains of variable length is described. These compounds behave as organogelators, forming supramolecular assemblies thanks to the intermolecular hydrogen bonding of urea groups. Whereas fluoride ion-catalysed hydrolysis in ethanol in the presence of a stoichiometric amount of water produced amorphous hybrids, acid-catalysed hydrolysis in an excess of water gave rise to the formation of crystalline lamellar hybrid materials through a self-organisation process. The structural features of these nanostructured organic/inorganic hybrids were analysed by several techniques: attenuated Fourier transformed infrared (ATR-FTIR), solid-state NMR spectroscopy (13C and 29Si), scanning and transmission electron microscopy (SEM and TEM) and powder X-ray diffraction (PXRD). The reaction conditions, the hydrophobic properties of the long alkylidene chains and the hydrogen-bonding properties of the urea groups are determining factors in the formation of these self-assembled nanostructured hybrid silicas.
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PMID:Lamellar bridged silsesquioxanes: self-assembly through a combination of hydrogen bonding and hydrophobic interactions. 1566 78

A multilayer comprising nanogold particles and organic molecules was constructed by self-assembly of the small organic molecule 1-phenyl-5-mercaptotetrazole onto the octadecylamine-protected nanogold monolayer in the course of transferring the monolayer, layer by layer, from a Langmuir-Blodgett trough to solid substrates. The structure and properties of the constructed multilayer were characterized by TEM images and ATR-IR, XPS, and UV-vis spectra. It is evidenced for the first time that the combination of Langmuir-Blodgett and self-assembly techniques provides a new way to organize functional nanoparticles such as organic-nanogold complexes.
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PMID:A novel nanogold multilayer constructed by Langmuir-Blodgett and self-assembly techniques. 1575 24

An end-to-end assembly of spherical Ag nanoparticles takes place in the presence of biotin to form long fiberlike microstructures. These microstructures are about 4 mum long with a thickness of 1 mum, obtained from SEM studies. TEM studies showed the presence of spherical silver nanoparticles having an average size of 20 nm. ATR-FTIR studies revealed that silver ions interact with biotin involving the carboxylate group. A weak binding of the silver particles with the thioether and ureido groups helps in connecting the Ag nanoparticles to form long fiberlike structures. Elucidation of the mechanism of formation of the spherical Ag clusters was done by pulse radiolysis.
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PMID:Self-assembly of Ag nanoparticle-biotin composites into long fiberlike microstructures. 1637 26

The apatite forming ability of biopolymer bacterial cellulose (BC) has been investigated by soaking different BC specimens in a simulated body fluid (1.5 SBF) under physiological conditions, at 37 degrees C and pH 7.4, mimicking the natural process of apatite formation. From ATR-FTIR spectra and ICP-AES analysis, the crystalline phase nucleated on the BC microfibrils surface was calcium deficient carbonated apatite through initial formation of octacalcium phosphate (OCP) or OCP like calcium phosphate phase regardless of the substrates. Morphology of the deposits from SEM, FE-SEM, and TEM observations revealed the fine structure of thin film plates uniting together to form apatite globules of various size (from <1 mum to 3 mum) with respect to the substrates. Surface modification by TEMPO (2,2,6,6-tetramethylpyperidine-1-oxyl)-mediated oxidation, which can readily form active carboxyl functional groups upon selective oxidation of primary hydroxyl groups on the surface of BC microfibrils, enhanced the rate of apatite nucleation. Ion exchanged treatment with calcium chloride solution after TEMPO-mediated oxidation was found to be remarkably different from other BC substrates with the highest deposit weight and the smallest apatite globules size. The role of BC substrates to induce mineralization rate differs according to the nature of the BC substrates, which strongly influences the growth behavior of the apatite crystals.
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PMID:Surface functional group dependent apatite formation on bacterial cellulose microfibrils network in a simulated body fluid. 1711 6

Single step and completely green room temperature biosynthesis of microscale size triangular gold prisms (approximately 25 nm thick) using remnant water collected from soaked Bengal gram beans (Cicer arietinum L.) is reported for the first time. Extracellular transport of protein and biomolecules from protein rich gram beans mediate the reduction of aqueous Au3+ ions and direct the growth of triangular prisms. The growth of triangular gold prisms is monitored by UV-vis spectrometer and supported by complementary characterizations using UV-vis/NIR, TEM, EDS, light microscope, XRD, XPS, ATR-FTIR, and ESI-MS. Plausible mechanism for the formation of microscale size triangular gold prisms is discussed. Effect of varying compositions of gram bean extract and aqueous Au3+ solution governing the morphology of the resultant gold particles is also investigated. Procuring the reducing, growth directing, and stabilizing molecules from the remnant water (extract), which normally would have been a kitchen waste, and water as a universal solvent makes it a completely green process displaying both environmental and economic advantages. Furthermore, this biosynthesis approach is simple, green, and an eco-friendly alternative to chemical synthesis of triangular gold prisms with rates comparable to chemical methods.
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PMID:Microscale size triangular gold prisms synthesized using Bengal gram beans (Cicer arietinum L.) extract and HAuCl4x3H20: a green biogenic approach. 1725 24

The morphology of micrometer-sized beta-hematin crystals (synthetic malaria pigment) was determined by TEM images and diffraction, and by grazing incidence synchrotron X-ray diffraction at the air-water interface. The needle-like crystals are bounded by sharp {100} and {010} side faces, and capped by {011} and, to a lesser extent, by {001} end faces, in agreement with hemozoin (malaria pigment) crystals. The beta-hematin crystals grown in the presence of 10% chloroquine or quinine took appreciably longer to precipitate and tended to be symmetrically tapered toward both ends of the needle, due to stereoselective additive binding to {001} or {011} ledges. Evidence, but marginal, is presented that additives reduce crystal mosaic domain size along the needle axis, based on X-ray powder diffraction data. Coherent grazing exit X-ray diffraction suggests that the mosaic domains are smaller and less structurally stable than in pure crystals. IR-ATR and Raman spectra indicate molecular based differences due to a modification of surface and bulk propionic acid groups, following additive binding and a molecular rearrangement in the environment of the bulk sites poisoned by occluded quinoline. These results provided incentive to examine computationally whether hemozoin may be a target of antimalarial drugs diethylamino-alkoxyxanthones and artemisinin. A variation in activity of the former as a function of the alkoxy chain length is correlated with computed binding energy to {001} and {011} faces of beta-hematin. A model is proposed for artemisinin activity involving hemozoin nucleation inhibition via artemisinin-beta-hematin adducts bound to the principal crystal faces. Regarding nucleation of hemozoin inside the digestive vacuole of the malaria parasite, nucleation via the vacuole's membranous surface is proposed, based on a reported hemozoin alignment. As a test, a dibehenoyl-phosphatidylcholine monolayer transferred onto OTS-Si wafer nucleated far more beta-hematin crystals, albeit randomly oriented, than a reference OTS-Si.
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PMID:Crystal nucleation, growth, and morphology of the synthetic malaria pigment beta-hematin and the effect thereon by quinoline additives: the malaria pigment as a target of various antimalarial drugs. 1729 Sep 93

This work has presented a typical example to reveal the great influence of the terminal groups on the self-assembly of hyperbranched polymers. The hyperbranched polymers with hydroxyl terminal groups (HBPO-OH) were hydrophobic and precipitated in water, however, they displayed a pH-responsive self-assembly behavior when the terminal groups were replaced by carboxyl groups. The obtained carboxyl-terminated hyperbranched polymers (HBPO-COOH) existed as unimolecular micelles at high pH (12.21) due to the ionization of carboxyl groups, while the polymers aggregated into multimolecular micelles from 10 to 500 nm with the decrease of pH as a result of the partial protonation of the carboxyl groups. The size of the obtained micelles depended strongly on the solution pH - the lower the pH, the bigger the micelles. TEM, DLS, ATR-FT-IR, (1)H NMR and AFM measurements substantiated that the multimolecular micelles were formed by the secondary aggregation of unimolecular micelles driven by the hydrogen bonding interaction depending on the solution pH.
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PMID:pH-responsive self-assembly of carboxyl-terminated hyperbranched polymers. 1732 72

Due to its poor solubility in water and oil, silybin is hardly absorbed orally and cannot be dissolved directly for parenteral preparations. In this study, a silybin-phospholipid complex was prepared by single-factor design and orthogonal experimental design. Lipophilicity was improved to a large extent, which was determined by solubility experiments and oil/water partition studies. Various methods were used to confirm the formation and explore the properties of the silybin-phospholipid complex, such as UV, IR, ATR, CNMR, XRD,DSC, SEM and TEM. The structure of the phytosome when the complex was dispersed in aqueous solution is suggested.
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PMID:Preparation and properties of a silybin-phospholipid complex. 1827 1


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