Formation of different gold nanocrystal core-resin shell structures through the control of the core assembly and shell polymerization

The formation of different Au nanocrystal core-resin shell structures through the control of the nanocrystal assembly and shell polymerization is investigated. 4-Mercaptophenol is employed together with formaldehyde as the resin monomers. 4-Mercaptophenol molecules bond to the surface of Au nanocrystals so that the resultant phenolic resin can intimately encapsulate Au nanocrystals. The morphologies of the obtained structures are determined by the nanocrystal assembly and the monomer polymerization behaviors, which are controlled by the solution pH as well as the monomer amounts. At pH = 8-9, Au nanorods are assembled and fused together under hydrothermal conditions in a preferential end-to-end manner. The fused structures are coated with a layer of resin, with the thickness controlled by the supplied amounts of the monomers. At pH = ～10, Au nanorods are coated with resin of controllable thicknesses and separated from each other. The resin-coated Au nanorods are stable in both aqueous and nonaqueous solutions. At pH = ～12, Au nanorods are coated with a thin layer of resin and assembled together in a side-by-side manner. A similar assembly and resin coating behavior is also observed with Au nanopolyhedrons. Moreover, plasmonic-fluorescent bifunctional structures are readily produced by incorporating CdTe nanocrystals in the resin shell that is coated on Au nanocrystals, owing to the presence of a number of thiol groups in the resin shell.     

Synthesis by neutral surfactant assembly of ordered mesoporous organic-inorganic hybrid materials incorporating phosphorus centres

The co-condensation of tetraethoxysilane (TEOS) and organotrialkoxysilane R'Si(OEt)₃ (R' group containing a phosphorus atom) in the presence of a neutral surfactant (n-C₁₆H₃₃NH₂) template provides ordered mesoporous hybrid materials. We show that further chemical reactions (sulfuration and quaternization) at phosphorus centres do not disrupt the ordered structure and the textural characteristics of the materials.     

Pore structure characterization of organic-inorganic materials by inverse size exclusion chromatography

Summary In Inverse Size (or Steric) Exclusion Chromatography (ISEC) measurements, the investigated material is used as a stationary phase in a chromatographic column and the elution volumes of a series of standard solutes with different molecular size are measured. By an appropriate choice of mobile phase and type of standard solutes, specific (enthalpic) interactions between investigated material and solutes are eliminated so that the elution volumes depend on the porous structure of the column filling only. Then, a mathematical treatment of elution data can provide detailed information on both the macropores and the microporous structure of e.g. a swollen polymer gel in a polymer that is grafted onto silica. The basic principle of the evaluation of porosimetric information from chromatographic data is the assumption that the real porous structure of an investigated sample can be modelled as a collection of discrete pore fractions, each containing pores of different but uniform size and of simple geometrical shape. Problem then is to determine the combination of volumes of these fractions which yields the best agreement between computed and experimental values of the elution volumes of standard solutes. It is possible to perform the ISEC measurements either in an organic solvent or non-solvent (e.g. tetrahydrofuran or methanol) or in water, depending on the compatibility of the investigated material with the respective environment. For non-polar polymers, like copolymers of styrene and divinylbenzene, the use of tetrahydrofuran as the mobile phase with alkanes and polystyrenes as standard solutes has been recommended. Alternative ISEC investigation of the same material in an organic and an aqueous environment can provide additional information on its lipo- or hydrophilicity. This method has provided specific information, not obtainable by mercury porosimetry, when modifying silica by a coupling agent, polymerizing different monomers to different extents.     

Studies of the functionalisation of organic-inorganic hybrid materials by using the Heck reaction

Cogelation of 4-styryltrimethoxysilane was performed using NH4F as catalyst. The functionalisation of the styryl group was then studied by using Heck's reaction with ethyl 4-bromobenzyl- or 4-bromoarylvinylbenzyl-phosphonates. The efficiency of the solid-phase reaction was highly dependent on the texture of the solids.     

Templated assembly of biomembranes on silica microspheres using bacteriorhodopsin conjugates as structural anchors

Membrane proteins are some of the most sophisticated molecules found in nature. These molecules have extraordinary recognition properties; hence, they represent a vast source of specialized materials with potential uses in sensing and screening applications. However, the strict requirement of the native lipid environment to preserve their structure and functionality presents an impediment in building biofunctional materials from these molecules. In general, the purification protocols remove the native lipid support structures found in the cellular environment that stabilize the membrane proteins. Furthermore, the membrane protein structure is often highly complex, typified by large, multisubunit complexes that not only span the lipid bilayer but also contain large (>2 nm) cytoplasmic and extracellular domains that protrude from the membrane. The present study is focused on using a biomimetic approach to build a stable, fluid microenvironment to be used to incorporate larger membrane proteins of interest into a tether-supported lipid bilayer membrane adequately spaced above a substrate passivated to liposome fusion and nonspecific adsorption. Our aim is to reintroduce the supporting structures of the native cell membrane using self-assembled supramolecular complexes constructed on microspheres in an artificial cytoskeleton motif. Central to our architecture is to utilize bacteriorhodopsin (bR), a transmembrane protein, as a biomembrane anchoring molecule to be tethered to surfaces of interest as a sparse structural element in the design. Compared to a typical lipid tether, which inserts into one leaflet of the lipid bilayer, bR anchoring provides an over 8-fold greater hydrophobic surface area in contact with the bilayer. In the work presented here, the silica microsphere surface was biofunctionalized with streptavidin to make it a suitable supporting interface. This was achieved by self-assembly of (p-aminophenyl)trimethoxysilane on the silica surface followed by subsequent conjugation of biotin-PEG3400 (PEG = poly(ethylene glycol) and PEG2000 for further passivation and the binding of streptavidin. We have conjugated bR with biotin-PEG3400 through amine-based coupling to use it as a tether. The biotin-PEG-bR conjugate was further labeled with Texas Red to facilitate localization via fluorescence imaging. Confocal microscopy was utilized to analyze the microsphere surface at different stages of surface modification by employing fluorescent staining techniques. Sparely tethered supported lipid bilayer membranes were constructed successfully on streptavidin-functionalized silica particles (5 mum) using a detergent-based method in which tethered bR nucleates self-assembly of the bilayer membrane. The fluidity of the supported membranes was analyzed using fluorescence recovery after photobleaching in confocal imaging detection mode. The phospholipid diffusion coefficients obtained from these studies indicated that nativelike fluidity was achieved in the tether-supported membranes, thus providing a prospective microenvironment for insertion of membrane proteins of interest.     

核壳结构微球的制备方法与展望

核壳结构微球作为一种功能性聚合材料已得到广泛的关注,本文介绍了国内外关于核壳结构微球制备方法的研究进展,包括种子聚合法、大分子单体法、自组装法、逐步异相凝聚法,并对各种方法的反应机理和影响因素进行了阐述;进而对该领域研究的热点工作进行了概述性的展望。     

Templated assembly of a pseudorotaxane of gold rectangles

A nanoscopic pseudorotaxane (1)2 subset2 composed of the gold rectangle [Au4(mu-PAnP)2(mu-bipy)2](OTf)4 and the linear template 4,4'-bis(9'-anthryl)biphenyl was assembled (PAnP = 9,10-bis(diphenylphosphino)anthracene); bipy = 4,4'-bipyridine).     

Ag@C core/shell structured nanoparticles: controlled synthesis, characterization, and assembly

Silver nanoparticles with tunable sizes were encapsulated in a carbonaceous shell through a green wet chemical route-the catalyzed dehydration of glucose under hydrothermal condition. In this one-pot synthesis, glucose was used as the reducing agent to react with Ag+ or Ag(NH3)2+, and it also served as the source of carbonaceous shells. The effects of hydrothermal temperature, time, and the concentrations of reagents on formation of the final nanostructures were systematically studied. The presence of competitive molecules poly(vinyl pyrrolidone) was found to be able to relieve the carbonization process, to incorporate themselves into carbonaceous shell, and to make the carbonaceous shell colorless. All these approaches provided diverse means to tailor the Ag@C nanostructures. By evaporation of the solvents gradually in a moist atmosphere, the monodispersed nanoparticles could self-assemble into arrays. Transmission electron microscopy, scanning electron microscopy, and UV-vis extinction spectra and surface-enhanced Raman spectra were used to characterize the core/shell nanostructures. These Ag@C core/shell nanoparticles have hydrophilic, organic-group-loaded surfaces and characteristic optical properties, which indicated their promising applications in optical nanodevices and biochemistry.     

Thermal degradation of epoxy-silica organic-inorganic hybrid materials

Degradation kinetics of organic-inorganic hybrid materials based on epoxy resin were investigated by thermogravimetric analysis (TGA). The hybrid materials were prepared from diglycidyl ether of bisphenol A (DGEBA) and 3-glycidyloxypropyltrimethoxysilane (GLYMO) polymerised simultaneously by poly(oxypropylene)diamine (Jeffamine D230). Nanometric level of homogeneity in the hybrids was verified by electron microscopy. Energy of activation of degradation for the hybrids with varying inorganic content, as well as for the unmodified epoxy-amine system, was determined by the isoconversional Kissinger-Akahira-Sunose method, and was found to be significantly higher for the hybrid materials than for the unmodified epoxy-amine system. The degradation process was described by empirical kinetic models. The results indicated that presence of the inorganic network influences the mechanism of degradation of organic phase. Greater thermal stability of hybrid materials was confirmed by other parameters obtained from TGA curves.     

Radical carboazidation: expedient assembly of the core structure of various alkaloid families

A procedure for one-pot intermolecular radical addition of 2-iodoesters to terminal alkenes followed by azidation of the radical adduct has been developed. This sequential reaction represents an alkene carboazidation process. Its efficacy is demonstrated by the two-step preparation of various lactams such as pyrrolidinones, pyrrolizidinones, and indolizidinones. An easy access to spirolactams bearing an amino-substituted quaternary carbon center is also described. These compounds are important building blocks for the synthesis of numerous alkaloids such as, for instance, FR901483.     

The supramolecular chemistry of organic-inorganic hybrid materials

The combination of nanomaterials as solid supports and supramolecular concepts has led to the development of hybrid materials with improved functionalities. These "hetero-supramolecular" ideas provide a means of bridging the gap between molecular chemistry, materials sciences, and nanotechnology. In recent years, relevant examples have been reported on functional aspects, such as enhanced recognition and sensing by using molecules on preorganized surfaces, the reversible building of nanometer-sized networks and 3D architectures, as well as biomimetic and gated chemistry in hybrid nanomaterials for the development of advanced functional protocols in three-dimensional frameworks. This approach allows the fine-tuning of the properties of nanomaterials and offers new perspectives for the application of supramolecular concepts.     

Synthesis,crystal structure,photoluminescence properties of organic-inorganic hybrid materials based on ethylenediamine bromide

In this work, a new orthorhombic organic-inorganic hybrid single crystal (C₂H₁₀N₂)₂MnBr₄.2Br with-Zero-dimensional structure was synthesized by slow evaporation method at 75 °C. The crystal structure and intermolecular interactions were performed by single crystal X-ray diffraction and Hirshfeld surface. Optical properties of (C₂H₁₀N₂)₂MnBr₄.2Br were systematically studied by Raman, infrared spectrum, UV–vis, photoexcitation spectra, and photoluminescence spectra. The optical band gap (E_g = 2.61 eV) were calculated from the absorption spectra of (C₂H₁₀N₂)₂MnBr₄.2Br. This hybrid materials also had shown good thermal stability (decomposition temperature: 288–660 °C). Finally, photoluminescence measurements showed a strong excitation line at 362 nm and a strong fluorescence at 537 nm which makes it a promising material in luminescence field.     

Preparation and characterization of multiresponsive polymer composite microspheres with core–shell structure

Fe₃O₄/SiO₂/poly (N-isopropylacrylamide-co-N,N-dimethylaminoethyl methacrylate) [P(NIPAM-co-DMA)] multiresponsive composite microspheres with core–shell structure were synthesized by template precipitation polymerization. First, the magnetite nanoparticles were coated with silica and then modified with 3-(trimethoxysilyl)-propyl methacrylate (MPS). Subsequently, the Fe₃O₄/SiO₂ particles grafted with MPS were used to seed the precipitation copolymerization of NIPAM and DMA. The composite microspheres with core–shell structure were superparamagnetic, pH-sensitive, and thermoresponsive. The swelling ratio (D_{25 °C, pH = 3}/D_{50 °C, pH = 9})³ coupling of pH and temperature increased up to 21.2, which was much higher than that without comonomer DMA.     

Study of cure kinetics of epoxy-silica organic-inorganic hybrid materials

Cure kinetics of organic-inorganic hybrids based on epoxy resin was investigated, using differential scanning calorimetry (DSC). Thermoset hybrid materials were prepared from diglycidyl ether of bisphenol A (DGEBA) as organic precursor, and 3-glycidyloxypropyltrimethoxysilane (GLYMO) as inorganic precursor. Precursors were polymerised simultaneously using poly(oxypropylene)diamine (Jeffamine D230) as a curing agent. Isothermal DSC characterisation of DGEBA/Jeffamine system and two hybrid DGEBA/GLYMO/Jeffamine systems, with DGEBA and GLYMO mixed in mass ratios of 2:1 and 1:1, respectively, was performed at different temperatures. Applicability of empirical models, commonly used to describe the curing kinetics of thermosets, to hybrid systems was investigated, and the resulting parameters were tested on dynamic DSC scans. Additionally, prepared materials were studied by FTIR and the extraction in tetrahydrofuran. The presence of inorganic phase was found to hinder complete cross-linking of organic phase and influence the kinetics of cure.