Nanohybridization of Low-Dimensional Nanomaterials: Synthesis,Classification, and Application

Nanomaterials have attracted much attention from academic to industrial research. General methodologies are needed to impose architectural order in low-dimensional nanomaterials composed of nanoobjects of various shapes and sizes, such as spherical particles, rods, wires, combs, horns, and other non specified geometrical architectures. These nanomaterials are the building blocks for nanohybrid materials, whose applications have improved and will continuously enhance the quality of the daily life of mankind. In this article, we present a comprehensive review on the synthesis, dimension, properties, and present and potential future applications of nanomaterials and nanohybrids. Due to the large number of review articles on specific dimension, morphology, or application of nanomaterials, we will focus on different forms of nanomaterials, such as, linear, particulate, and miscellaneous forms. We believe that almost all the nanomaterials and nanohybrids will come under these three categories. Every form or dimension or morphology has its own significant properties and advantages. These low-dimensional nanomaterials can be integrated to create novel nano-composite material applications for next-generation devices needed to address the current energy crisis, environmental sustainability, and better performance requirements. We discuss the synthesis, properties, and morphology of different forms of nanomaterials (building blocks). Moreover, we elaborate on the synthesis, modification, and application of nanohybrids. The applications of these nanomaterials and nanohybrids in sensors, solar cells, lithium batteries, electronic, catalysis, photocatalysis, electrocatalysis, and bio-based applications will be detailed. The time is now ripe to explore new nanohybrids that use individual nanomaterial components as basic building blocks, potentially affording additionally novel behavior and leading to new, useful applications. In this regard, the combination or integration of linear nanorods/nanowires and spherical nanoparticles to produce mixed-dimensionality, higher-level nanocomposites of greater complexity is an interesting theme, which we explore in this review article.     

Enantiomeric separation of some flavanones using shinorhizobial linear octasaccharides in CE

Succinoglycan, a shinorhizobial exopolysaccharide produced by Shinorhizobium meliloti, is composed of an octasaccharide subunit. S. meliloti produces both high-molecular-weight and low-molecular-weight (M(r)<10 000) succinoglycans that consisted of monomer, dimer, or trimer of an octasaccharide unit. We isolated and purified the monomer among low-molecular-weight succinoglycans and used this microbial linear octasaccharide as a novel chiral additive for enantiomeric separation of some flavanones such as homoeriodictyol, hesperetin, naringenin, and isosakuranetin in CE. Throughout the present investigation, we firstly used noncyclic oligosaccharides for the chiral separation of flavanones. We also found that successful enantioseparation of four flavanones depends on the presence of succinate substituents of the linear monomeric octasaccharide in CE, suggesting that succinylation of succinoglycan monomer is decisive for the effective enantiomeric separation.     

Inhibition of acyl-coenzyme A:cholesterol acyltransferase stimulates cholesterol efflux from macrophages and stimulates farnesoid X receptor in hepatocytes

We investigated the mechanism of spontaneous cholesterol efflux induced by acyl-coenzyme A:cholesterol acyltransferase (ACAT) inhibition, and how an alteration of cholesterol metabolism in macrophages impacts on that in HepG2 cells. Oleic acid anilide (OAA), a known ACAT inhibitor reduced lipid storage substantially by promotion of cholesterol catabolism and repression of cholesteryl ester accumulation without further increase of cytotoxicity in acetylated low-density lipoprotein-loaded THP-1 macrophages. Analysis of expressed mRNA and protein revealed that cholesterol 7alpha-hydroxylase (CYP7A1), oxysterol 7alpha- hydroxylase (CYP7B1), and cholesterol 27-hydroxylase (CYP27) were highly induced by ACAT inhibition. The presence of a functional cytochrome P450 pathway was confirmed by quantification of the biliary cholesterol mass in cell monolayers and extracelluar medium. Notably, massively secreted biliary cholesterol from macrophages suppressed the expression of CYP7 proteins in a farnesoid X receptor (FXR)-dependent manner in HepG2 cells. The findings reported here provide new insight into mechanisms of spontaneous cholesterol efflux, and suggest that ACAT inhibition may stimulate cholesterol-catabolic (cytochrome P450) pathway in lesion-macrophages, in contrast, suppress it in hepatocyte via FXR induced by biliary cholesterol (BC).     

Mixed-ligand metal-organic frameworks with large pores: gas sorption properties and single-crystal-to-single-crystal transformation on guest exchange

Two isomorphous 3D metal-organic frameworks, {[Cu2(BPnDC)2(bpy)].8 DMF.6 H2O}n (1) and {[Zn2(BPnDC)2(dabco)].13 DMF.3 H2O}n (2), have been prepared by the solvothermal reactions of benzophenone 4,4'-dicarboxylic acid (H2BPnDC) with Cu(NO3)(2).2.5 H2O and 4,4'-bipyridine (bpy), and with Zn(NO3)(2).6 H2O and 4-diazabicyclo[2.2.2]octane (dabco), respectively. Compounds 1 and 2 are composed of paddle-wheel {M2(O2CR)4} cluster units, and they generate 2D channels with two different large pores (effective size of larger pore: 18.2 A for 1, 11.4 A for 2). The framework structure of desolvated solid, [Cu2(BPnDC)2(bpy)]n (SNU-6; SNU=Seoul National University), is the same as that of 1, as evidenced by powder X-ray diffraction patterns. SNU-6 exhibits high permanent porosity (1.05 cm3 g(-1)) with high Langmuir surface area (2910 m2 g(-1)). It shows high H2 gas storage capacity (1.68 wt % at 77 K and 1 atm; 4.87 wt % (excess) and 10.0 wt % (total) at 77 K and 70 bar) with high isosteric heat (7.74 kJ mol(-1)) of H2 adsorption as well as high CO2 adsorption capability (113.8 wt % at 195 K and 1 atm). Compound 2 undergoes a single-crystal-to-single-crystal transformation on guest exchange with n-hexane to provide {[Zn2(BPnDC)2(dabco)].6 (n-hexane).3 H2O}n (2hexane). The transformation involves dynamic motion of the molecular components in the crystal, mainly a bending motion of the square planes of the paddle-wheel units resulting from rotational rearrangement of phenyl rings and carboxylate planes of BPnDC2-.     

Benzofurans and sterol from the seeds of <Emphasis Type="Italic">styrax obassia</Emphasis>

Two benzofurans (1, 2) along with five known compounds (3.7) were isolated from the seeds of S. obassia. Their structures were elucidated as methyl 3-[7-methoxy-2-(3′,4′-methylenedioxyphenyl)-5-benzofuranyl]-propionate (1), methyl 3-[2-(3′,4′-methylenedioxyphenyl)-5-benzofuranyl]-propionate (2), egonol (3), egonolacetate (4), egonol-2-methylbutanoate (5), 7-demethoxyegonol-2-methylbutanoate (6), and stigmasterol (7) on the basis of their comprehensive spectroscopic analysis including 2D NMR data. Compounds 1, 2 are obtained for the first time from nature, while this is the first record of compound 7 from the Styrax species. Published in Khimiya Prirodnykh Soedinenii, No. 4, pp. 350-353, July-August, 2008. Original article submitted May 4, 2007.     

Effect of the amounts of glycidyl methacrylate on the mechanical and dynamic properties of styrene–butadiene–glycidyl methacrylate terpolymer/silica composites

GMA-SBRs with GMA contents in the range of 0.06–0.71 wt.% were synthesized and used to evaluate the properties of the silica composites for fuel-efficient tires. The chemical structures of the GMA-SBRs were analyzed using Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance (¹H NMR), size exclusion chromatography (SEC), and differential scanning calorimetry (DSC). GMA-SBRs can enhance filler–rubber interaction through covalent bond formation between the silica filler and rubber molecules. After compounding, the cure characteristics and mechanical and dynamic properties of the GMA-SBR silica-filled composites were analyzed. The mechanical properties, including the Mooney viscosity, bound rubber, swelling ratio, and moduli, exhibited obvious differences with increasing GMA content. However, the optimum content of GMA in the GMA-SBR, in terms of dynamic properties such as the Payne effect which represents the change in dynamic modulus against the strain to determine the extent of filler flocculation and tan δ at 60 °C representing tire rolling resistance, was ~0.6 wt.%. These results are due to improved silica dispersion, resulting from increased covalent bond formation between GMA-SBR and the silica surface. This approach assists in the determination of functional group contents in functionalized emulsion styrene–butadiene rubber for fuel-efficient tires, leading to a decrease in vehicular greenhouse gas emission.     

Reversible transformation of ZnII coordination geometry in a single crystal of porous metal-organic framework [Zn3(ntb)2(EtOH)2].4 EtOH

A 3D porous metal-organic framework [Zn3(ntb)2(EtOH)2]n.4nEtOH (1) that generates 1D channels of honeycomb aperture has been prepared by the solvothermal reaction of Zn(NO3)(2).6 H2O and 4,4',4'-nitrilotrisbenzoic acid (H3NTB) in EtOH at 110 degrees C. Framework 1 exhibits reversible single-crystal-to-single-crystal transformations upon removal and rebinding of the coordinating EtOH as well as the EtOH guest molecules, which give rise to desolvated crystal [Zn3(ntb)2]n (1') and resolvated crystal [Zn3(ntb)2-(EtOH)2]n.4nEtOH (1'). The X-ray structures indicate that 3D host framework is retained during the transformations from 1 to 1' and from 1' to 1', but the coordination geometry of ZnII ions changes from/to trigonal bipyramid to/from tetrahedron, concomitant with the rotational rearrangement of a carboxylate plane of the NTB3- relative to its associated phenyl ring. To retain the single crystal integrity, extensive cooperative motions must exist between the molecular components throughout the crystal. Framework 1' exhibits permanent porosity, thermal stability up to 400 degrees C, and blue luminescence, and high storage capabilities for N2, H2, CO2, and CH4.     

Synthesis and characterization of graft copolymers of poly(vinyl chloride) with styrene and (meth)acrylates by atom transfer radical polymerization

Graft copolymers of poly(vinyl chloride) with styrene and (meth)acrylates were prepared by atom transfer radical polymerization. Poly(vinyl chloride) containing small amount of pendent chloroacetate units was used as a macroinitiator. The formation of the graft copolymer was confirmed with size exclusion chromatography (SEC), ¹H NMR and IR spectroscopy. The graft copolymers with increasing incorporation of butyl acrylate result in an increase of molecular weight. One glass transition temperature (T_g) was observed for all copolymers. T_g of the copolymer with butyl acrylate decreases with increasing content of butyl acrylate.     

Novel silicon-based alternating copolymers: synthesis,photophysical properties,and tunable EL colors

We synthesized novel silicon-based alternating copolymers for tunable electroluminescent (EL) colors by Heck synthetic method. Their thermal, photophysical and electroluminescent properties were studied. Most of them exhibited a blue-green EL color at the operating voltage of lower than 12 V. Unusually, we observed the white EL color from a EL device based on SiPhPVK. From photophysical studies and the time-resolved PL spectroscopies, it might be attributed to the formation of stabilized excited state in SiPhPVK. Furthermore, in order to reduce the operating voltage of their LED with increasing the electron affinity of the main chain in silicon-based alternating copolymers, we synthesized the silicon-based copolymers containing electron transporting oxadiazole units in main chain. We also studied their photophysical and electroluminescent properties.