Control of Crystal Structure and Orientation of Ni(salen) by Epitaxial Growth on Alkali Halide

Thin films of N,N′-bis(salicylaldehydo)ethylenediaminato nickel(II) (Ni(salen)) are fabricated by vacuum epitaxy on (001) surfaces of KBr, KCl, and NaCl substrates and characterized by transmission electron microscopy. Two new monoclinic polymorphs of Ni(salen), β (a = 2.59 nm, b = 1.54 nm, c = 0.670 nm, β = 92.6°) and γ (a = 2.56 nm, b = 0.787 nm, c = 0.743 nm, β = 93.7°), are successfully identified by electron diffractions and high resolution images. The β form is produced on all three substrates by deposition at room temperature, while the γ form is produced on NaCl and KCl at 90 °C. The orientation of these polymorphs is controlled by lattice matching. Although the γ form is energetically favorable with better lattice matching to these substrates, the faster-growing β form is preferentially produced at lower substrate temperature. The polymorphic structure of the deposited film is thus governed by both the substrate surface structure and the growth temperature

Diastereoselective Addition of Alcohol to Diastereotopic Silylenes

The successful example of diastereoselective addition of alcohol to diastereotopic silylenes is reported

Diastereoselective Addition of Alcohol to Diastereotopic Silylenes

The successful example of diastereoselective addition of alcohol to diastereotopic silylenes is reported

Supramolecular Nanotube Hydrogels: Remarkable Resistance Effect of Confined Proteins to Denaturants

Nanotube networks self-assembling from asymmetric bolaamphiphile, N-(β-d-glucopyranosyl)-N′-(2-glycylglycylglycineamideethyl)-octadecanediamide 1, acted as hydrogelators. The obtained nanotube hydrogel was able to separately fix a green fluorescent protein (GFP) and a myoglobin (Mb) into not only independent nanospaces consisting of three-dimensional meshworks formed in between nanotubes but also a one-dimensional hollow cylinder of the nanotube itself. Especially, the fixed GFP and Mb into the nanotube hollow cylinder with 9 nm inner diameter showed strong resistance to denaturants such as guanidinium chloride and urea at high concentrations. The oxygen binding ability of the fixed Mb into the nanotube hollow cylinder was remarkably superior to those of the fixed Mb into the nanotube meshworks and the free Mb in bulk. The nanotube hydrogel also showed slow release behavior depending on pH conditions. Such a unique fixation property of the nanotube hydrogel has never been seen for preceded supramolecular and polymer hydrogels having three-dimensional meshworks formed in between nanofibers. Hence, the nanotube hydrogel can function as a novel soft material applicable to biological and medical fields

Self-Assembling Structures of Long-Chain Phenyl Glucoside Influenced by the Introduction of Double Bonds

Four long-chain phenyl glucoside amphiphiles possessing a saturated or unsaturated long alkyl chain group as the self-assembling unit of a highly organized molecular architecture were synthesized. Their self-assembling properties were investigated by EF-TEM, SEM, CD, FT-IR, and XRD. Compound 2 possessing one double bond in the lipophilic portion showed twisted helical fibers, which formed a bilayered structure with a 3.59 nm period, while compound 3 showed the helical ribbons and left-handed nanotubular structures with 150−200 nm inner diameters and ca. 20 nm of wall. Very interestingly, compound 4 possessing three double bonds showed a nanotubular structure with ca. 70 nm of inner diameter through a helical ribbon, which formed a loose bilayered structure with 4.62 nm. These results indicate that self-assembling properties strongly depend on the number of cis double bonds

Spontaneous Fiber Formation and Hydrogelation of Nucleotide Bolaamphiphiles

Nucleotide-appended bolaamphiphiles 1−7, in which two 3‘-phosphorylated thymidine moieties are connected to both ends of a long oligomethylene spacer, have been first synthesized. Their self-assembling behavior in aqueous solutions was investigated in terms of gelling ability of water molecules. The longer homologues 6 and 7 with the C18 and C20 oligomethylene spacers, respectively, proved to be capable of gelling water very effectively (>25 000 water molecules per molecule) through spontaneous formation of a fibrous network. Gelation behavior of both bolaamphiphiles strongly depended on the pH and temperature of the aqueous solutions used. The gel-to-sol transition temperature (TGS) of 7 was determined to be approximately 85 °C. XRD measurement of a freeze-dried hydrogel from 7 suggested the presence of lamellar organization consisting of monolayer sheets. Hydrogen bonds involving the 5‘-hydroxyl group of the deoxyribose moiety, hydrophobic interaction between the long oligomethylene chains, and π−π stacking of the thymine residues are responsible for the effective hydrogel formation

Sol−Gel Synthesis of Low-Dimensional Silica within Coordination Nanochannels

Sol−Gel Synthesis of Low-Dimensional Silica within Coordination Nanochannel

Effects of Fullerene Substituents on Structure and Photoelectrochemical Properties of Fullerene Nanoclusters Electrophoretically Deposited on Nanostructured SnO₂ Electrodes

Two kinds of fullerene derivatives have been designed to examine the effect of the fullerene substituents on the structure and photoelectrochemical properties of fullerene clusters electrophoretically deposited on nanostructured SnO2 electrodes. The cluster sizes increase and the incident photon-to-current efficiencies decrease with introduction of large substituents into C60. The trend for photocurrent generation efficiency as well as surface morphology on the electrode can be explained by the steric bulkiness around the C60 molecules. A C60 molecule with two alkoxy chains is suggested to give a bilayer vesicle structure, irrespective of the hydrophobic nature of both the C60 and alkoxy chain moieties. Such information will be valuable for the design of photoactive molecules, which are fabricated onto electrode surfaces to exhibit high energy conversion efficiency

Bead-Milling and Postmilling Recrystallization: An Organic Template-free Methodology for the Production of Nano-zeolites

Organic template-free synthesis of nano-zeolite has been an important subject of both scientific and industrial applications. Most research has focused on the fabrication of nano-zeolite by a bottom up approach, that is, control of zeolite nucleation and crystal growth during the hydrothermal synthesis. This communication reports a new method for the production of nano-zeolite powder by a top-down approach. In this study, the zeolite was first milled to produce a nanopowder. This technique can cause destruction of the outer portion of the zeolite framework and hence cause pore blocking, which deactivates various properties of the zeolite. To remedy this, the damaged part was recrystallized using a dilute aluminosilicate solution after bead milling. As a result of the combination of bead milling and postmilling recrystallization, nano-zeolite A (LTA type zeolite) about 50 nm in size with high crystallinity was successfully obtained

Electrophoretic Deposition of Single-Walled Carbon Nanotubes Covalently Modified with Bulky Porphyrins on Nanostructured SnO₂ Electrodes for Photoelectrochemical Devices

Single-walled carbon nanotubes (SWNTs) covalently modified with large porphyrin molecules have been prepared to construct photoelectrochemical devices with nanostructured SnO2 electrodes on which the multiporphyrin-linked SWNTs are deposited electrophoretically. The film of the porphyrin-linked SWNTs on the nanostructured SnO2 electrode exhibited an incident photon-to-photocurrent efficiency as high as 4.9% under an applied potential of 0.08 V vs SCE. The more uniform film and moderate photocurrent generation in the porphyrin-linked SWNT devices can be rationalized by the exfoliation abilities of the bulky porphyrins that yield large steric hindrance around the SWNTs. Direct electron injection from the excited states of the SWNTs to the conduction band of the SnO2 electrode is responsible for the photocurrent generation. Despite the efficient quenching of the porphyrin-excited singlet state by the SWNTs in the porphyrin-linked SWNTs, the photocurrent action spectra revealed that the excitation of the porphyrin moieties makes no contribution to the photocurrent generation. The evolution of an exciplex between the porphyrin-excited singlet state and the SWNTs and the subsequent rapid decay to the ground state without generating the charge-separated state is proposed to explain the unusual photoelectrochemical behavior. The results obtained here will provide valuable information on the design of SWNT-based photoelectrochemical devices