Morphological control of multifunctionalized mesoporous silica nanomaterials for catalysis applications

I found an efficient method to control the morphology of the organically monofunctionalized mesoporous silica materials by introducing different types of organoalkoxysilanes in a base-catalyzed co-condensation reaction. The monofunctionalized materials exhibit different particle morphologies relative to the pure MCM-41 material. The concentration dependence of the morphology is a critical factor to determine the final particle shape. A proposed mechanism of the shape evolution is also offered. After understanding the role of organoalkoxysilanes in producing various well-shaped nanomaterials, I also obtained a series of bifunctional mesoporous silica materials with certain particle morphology. A series of bifunctional mesoporous silica nanospheres (MSNs) whose physicochemical properties was investigated via solid state NMR techniques and Cu 2+ adsorption capacity tests. The ratio of two different organic groups inside of mesopores of these MSNs could be fine-tuned. These MSNs serve as a useful model system to study substrate selectivity in catalytic reactions and sorption phenomena. For example, the Cu2+ adsorption capacity of these materials was dictated by the chemical nature of the mesopores generated by the different organic functional groups.;An investigation of the substrate selectivity of the bifunctionalized MSNs in a competitive nitroaldol reaction using an equimolar amount of two competing 4-nitrobenzaldehyde derivatives was performed. Shape-controlled bifunctional MSNs were employed as the catalysts. The properties of the MSNs were investigated using various spectroscopic methods and electron microscopy. The more hydrophobic the surface organic groups are, the higher the ratio of hydrophobic final product. This is the first example to demonstrate the selection of substrate using physicochemical nature of the mesopore surface other than the conventional shape selection in zeolite systems.;I also created a cooperative dual catalyst system that is capable of activating two different substrates in aldol reaction, Henry reaction and cyanosilylation. One catalytic group activates the nucleophile, another organic group simultaneously activates the electrophile to enhance the total reaction rate. I systematically varied the amount of two organic groups and performed the three model reactions to compare rate enhancements

[1,1′-Bis(diphenyl­phosphino)ferrocene]carbon­yl[dihydro­bis(pyrazol-1-yl)borato]hydridoruthenium(II) acetone solvate

In the title compound, [FeRu(C17H14P)2(C6H8BN4)H(CO)]·C3H6O, the RuII ion is coordinated in a distorted octa­hedral environment involving a hydride ligand, a carbonyl ligand and two bidentate ligands. Of the two bidentate ligands, the bulky 1,1′-bis­(diphenyl­phosphino)ferrocene (dppf) ligand chelates with a larger bite angle of 101.90 (2)°, whereas the bite angle of the [H2Bpz2]− ligand (pz = pyrazol­yl) is 85.67 (7)°. The latter ligand creates an RuN4B six-membered ring with a boat conformation, which puckers towards the site of the small hydride ligand. The hydride ligand is cis with respect to the carbonyl ligand and trans to one of the P atoms of the dppf ligand. In the crystal structure, there are weak inter­molecular C—H⋯O hydrogen bonds between complex mol­ecules and acetone solvent mol­ecules

Morphological Control of Multifunctional Mesoporous Silica Nanomaterials for Catalysis Applications

I found an efficient method to control the morphology of the organically monofunctionalized mesoporous silica materials by introducing different types of organoalkoxysilanes in a base-catalyzed co-condensation reaction. The monofunctionalized materials exhibit different particle morphologies relative to the pure MCM-41 material. The concentration dependence of the morphology is a critical factor to determine the final particle shape. A proposed mechanism of the shape evolution is also offered. After understanding the role of organoalkoxysilanes in producing various well-shaped nanomaterials, I also obtained a series of bifunctional mesoporous silica materials with certain particle morphology. A series of bifunctional mesoporous silica nanospheres (MSNs) whose physicochemical properties was investigated via solid state NMR techniques and Cu{sup 2+} adsorption capacity tests, The ratio of two different organic groups inside of mesopores of these MSNs could be fine-tuned. These MSNs serve as a useful model system to study substrate selectivity in catalytic reactions and sorption phenomena. For example, the Cu{sup 2+} adsorption capacity of these materials was dictated by the chemical nature of the mesopores generated by the different organic functional groups. An investigation of the substrate selectivity of the bifunctionalized MSNs in a competitive nitroaldol reaction using an equimolar amount of two competing 4-nitrobenzaldehyde derivatives was performed. Shape-controlled bifunctional MSNs were employed as the catalysts. The properties of the MSNs were investigated using various spectroscopic methods and electron microscopy. The more hydrophobic the surface organic groups are, the higher the ratio of hydrophobic final product. This is the first example to demonstrate the selection of substrate using physicochemical nature of the mesopore surface other than the conventional shape selection in zeolite systems. I also created a cooperative dual catalyst system that is capable of activating two different substrates in aldol reaction, Henry reaction and cyanosilylation. One catalytic group activates the nucleophile, another organic group simultaneously activates the electrophile to enhance the total reaction rate. I systematically vaned the amount of two organic groups and performed the three model reactions to compare rate enhancements

catena-Poly[[bis­(dimethyl­ammonium) [cadmate(II)-bis­(μ-1,1′:4′,1′′-terphenyl-3,3′′-dicarboxyl­ato)]] dimethyl­formamide disolvate]

In the title compound, {(C2H8N)2[Cd(C20H12O4)2]·2C3H7NO}n, the CdII ion lies on a twofold rotation axis and is in a distorted octa­hedral CdO6 environment, defined by four O atoms of two μ2-coordinated 1,1′:4′,1′′-terphenyl-3,3′′-dicarboxyl­ate (DCT) ligands and two O atoms of two μ1-coordinated DCT ligands. Both types of DCT ligands act as bridging, forming a one-dimensional polymeric structure propagating parallel to [10]

511 keV γ\gamma-ray emission from the galactic bulge by MeV millicharged dark matter

We propose a possible explanation for the recently observed anomalous 511 keV line with a new "millicharged" fermion. This new fermion is light [${\cal O}({\rm MeV})$]. Nevertheless, it has never been observed by any collider experiments by virtue of its tiny electromagnetic charge $\epsilon e$. In particular, we constrain parameters of this millicharged particle if the 511 keV cosmic $\gamma$-ray emission from the galactic bulge is due to positron production from this new particle.Comment: 3 pages, 1 figure, A talk given by J.C.Park at the 16th International Conference on Supersymmetry and the Unification of Fundamental Interactions (SUSY08), Seoul, Korea, June 16-21, 200

Nanostructured ZnO Arrays with Self-ZnO Layer Created Using Simple Electrostatic Layer-by-Layer Assembly

Formation of unique ZnO nanoarrays utilizing photodynamic polymer, surface-relief grating structures, and unique electrostatic layer-by-layer assembly as a simple and economical methodology was demonstrated. Atomic force microscope (AFM), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDAX) analysis were employed to characterize elemental composition and morphology of the resulting ZnO nanostructures with self-ZnO layer. Optical behavior of the final product was studied by UV-vis-NIR absorption and photoluminescence (PL) spectra

Influence of Mg Deficiency on the Superconductivity in MgB2 Thin Films Grown by using HPCVD

The effects of Mg deficiency in MgB2 films grown by using hybrid physical-chemical vapor deposition were investigated after vacuum annealing at various temperatures. High-quality MgB2 films grown on c-cut Al2O3 substrates with different superconducting transition temperatures (Tc) of 40.2 and 41 K were used in this study. As the annealing temperature was increased from 200 to 800 C, the Mg contents in the MgB2 films systemically decreased, but the Tc's did not change, within 0.12 K, until the annealing temperature reached 700 C. For MgB2 films annealed at 800 C for 30 min, however, no superconductivity was observed, and the temperature dependence of the resistivity showed a semiconducting behavior. We also found that the residual resistivity ratio decreased with increasing annealing temperature.Comment: 7 pages including 4 figure