Nanopattern formation on Cu(0 0 1) surface coadsorbed with nitrogen and oxygen

Strain-induced nanopatterns formed by the coadsorption of nitrogen and oxygen atoms are studied on the Cu(0 0 1) surface by scanning tunneling microscopy. A square grid pattern similar to that on the N-adsorbed surface appears, and consists of square c(2 × 2) areas with adsorbed N and O atoms when the total density of the adsorbates is around 30% of the Cu atom density on the clean surface. We evaluated the surface strain using a first-principles calculation for a coadsorbed surface and compared it with those on the clean and N-adsorbed surfaces. The strain on the coadsorbed surface is smaller than that of the N-adsorbed surface. The observed size of the square c(2 × 2) area on the coadsorbed surface is larger than that on the N-adsorbed surface with increasing the density of the adsorbates on average as expected by the strain reduction. On the other hand, there is no significant difference in the period of the grid pattern.     

X-ray photoelectron spectroscopic study of perovskite titanates and related compounds: An example of the effect of polarization on chemical shifts

The differences of the binding energy of the Ti 2P_{$\text{3}\text{2}$} electrons obtained by X-ray photoelectron spectroscopy in various perovskite type titanates and related compounds have been studied. The titanium compounds studied were titanium dioxide (anatase and rutile), calcium titanate, strontium titanate, lead titanate and barium titanate. The oxidation number of the titanium ion for all of these compounds is formally 4+. However, the X-ray photoelectron spectra show small shifts in the Ti 2p_{$\text{3}\text{2}$} binding energy as the cation is varied. An analysis of data led to the conclusion that this shift is mainly due to differences in polarization energy between these compounds.     

Effects of benzyl ether type dendrons as hole-harvesting antennas, and shielding for the neutralization of stilbene core radical cations with chloride ion during two-photon ionization of stilbene dendrimers having stilbene core and benzyl ether type dendrons

The two-photon ionization (TPI) process (308 and 266 nm) of stilbene dendrimers having a stilbene core and benzyl ether type dendrons has been investigated in an acetonitrile and 1,2-dichloroethane mixture (3:1) in order to elucidate the dendrimer effects. The quantum yield of the formation of stilbene core radical cation during the 308-nm TPI was independent of the dendron generation of the dendrimers, whereas a generation dependence of the quantum yield of the radical cation was observed during the 266-nm TPI, where both the stilbene core and benzyl ether type dendron were ionized, suggesting that the subsequent hole transfer occurs from the dendron to the stilbene core, and that the dendron acts as a hole-harvesting antenna. The neutralization rate of the stilbene core radical cation with the chloride ion, generated from the dissociative electron capture by 1,2-dichloroethane, decreased with the increase in the dendrimer generation, suggesting that the dendron is an effective shield of the stilbene core radical cation against the chloride ion.     

Synthesis,crystal structures,spectral, electrochemical and magnetic properties of di-µ-phenoxido-bridged dinuclear copper(II) complexes with N-salicylidene-2-hydroxybenzylamine derivatives: axial coordination effect of dimethyl sulphoxide molecule

The template reaction of salicylaldehyde and its substituted derivatives and 2-hydroxy-5-bromobenzylamine or 2-hydroxy-5-chlorobenzylamine with copper(II) acetate in dimethyl sulphoxide (dmso) afforded eight dinuclear Cu(II) complexes, [Cu₂(L)₂(dmso)₂] (H₂ L = N-salicylidene-2-hydroxy-5-bromobenzylamine, N-salicylidene-2-hydroxy-5-chlorobenzylamine and their 5-bromo, 5-nitro and 5-methyl-substituted salicylidene derivatives). These Cu(II) complexes were characterised by IR and UV-VIS-NIR spectroscopy, electric conductivity, cyclic voltammetry, and temperature dependence of magnetic susceptibilities (4.5–300 K). In the THF solution, the complexes are nonelectrolytes and exhibit a characteristic CT band due to phenoxido-bridging at 360–384 nm. In the cyclic voltammograms, an irreversible reduction process was observed at ?1.18–1.54 V vs Fc/Fc⁺. Single-crystal X-ray crystallography revealed that two Cu(II) ions were bridged by the two phenoxido-oxygen atoms of the two Schiff-base ligands with axial coordination of dmso molecules forming a square pyramid with a Cu-Cu distance of 3.0628(8)–3.0931(6) °A. In accordance with the crystal structures, the magnetic interaction between the two Cu(II) ions is relatively anti-ferromagnetic with ?2J value of 386–575 cm^?1. The axial coordination effect of the dmso molecule was discussed in relation to the correlation between the Cu-O-Cu angle and the ?2J value.     

Size-controlled, one-pot synthesis, characterization, and biological applications of epoxy-organosilica particles possessing positive zeta potential

Epoxy-organosilica particles made from 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (EpoMS) as a single silica source were synthesized by means of a one-pot method. We evaluated three sets of synthesis conditions, including traditional Stober conditions and two variations. Although the traditional conditions did not afford EpoMS particles, the variations did. The size distributions of the particles were evaluated by means of transmission electron microscopy. The mean diameters and size distributions of the particles depended on the EpoMS concentration, and the best coefficient of variation for the size distribution was 5.9%. The surface of the particles had unique properties, such as a positive zeta potential. The particles bound strongly to proteins as well as to DNA. The particles made from EpoMS, allowing particles internally functionalized with fluorescent dye to be prepared by means of a one-pot synthesis. EpoMS particles doped and tuned with fluorescent dye showed strong fluorescence signals and distinct peaks on flow cytometry, and the fluorescent particles could be used to label cells. The labeled cells showed clear fluorescence under a fluorescence microscope, and electron microscopy showed many particles in the cytoplasm. This is the first report describing the synthesis of epoxy-organosilica particles with a positive zeta potential and describing differences in the characteristics of particle formations due to changes in synthesis conditions. We also discuss the advantages of EpoMS particles, as well as the potential biological applications of these particles.     

Angle-controlled arrangement of single-walled carbon nanotubes solubilised by 8-quinolinol metal chelate derivatives on mica

We solubilised SWNTs of short length using a mechanochemical high-speed vibration milling (HSVM) through formation of complexes between the SWNTs and chelate complexes; the mixture formed a network structure on mica.     

Novel drug delivery system of hollow mesoporous silica nanocapsules with thin shells: preparation and fluorescein isothiocyanate (FITC) release kinetics

Core-shell nanoparticles of Au@silica with a diameter of approximate 45–60 nm and wall thickness in range of 3–10 nm were synthesized by using 40 and 50 nm gold nanoparticles as the templates. The mesoporous particles are regulated by 3-aminopropyltrimethoxysilane addition. Hollow mesoporous silica nanocapsules (HMSNs) were prepared by using sodium cyanide to dissolve the gold cores. The characterization of Au@silica and HMSNs by transmission electronic microscope indicated that the silica shells were uniform and smooth, and also the porosity was proved by fluorescein isothiocyanate (FITC) release experiments. The ratio of hollow core to HMSNs is more than 70%. HMSNs were subsequently used as drug carrier to investigate FITC (as a model drug) release behaviors in vitro. Fluorescent spectrometry was performed to determine the release kinetics from the HMSNs. The release profiles are significantly different as compared with the control (free FITC), which show that HMSNs are good drug carriers to control drug release, and have high potential in therapeutic drugs delivery in future applications.     

Tetraplatinum precursors for supramolecular assemblies: syntheses, crystal structures, and stereoselective self-assemblies of [Pt4(micro-OCOCH3)6(kappa4-N4-DArBp)] (DArBp = 1,3-bis(arylbenzamidinate)propane)

Treatment of the cisoid-capped complex [Pt(4)(micro-OCOCH(3))(6)(kappa(4)-N(4)-DAr'Bp)] (), which was obtained from the reaction of [Pt(4)(micro-OCOCH(3))(8)] (1) with Na(2)D(t)BuPhBp (D(t)BuPhBp = 1,3-bis(para-tert-butylphenylbenzamidinate)propane), with an equimolar amount of 1,1'-ferrocenedicarboxylic acid undergoes a stereoselective self-assembly to afford an indented-quadrangle tetramer [Pt(4)(micro-OCOCH(3))(4)(kappa(4)-N(4)-D(t)BuPhBp){Fe(C(5)H(4)COO)(2)}](4) as a single diastereomer.     

A neoceptor approach to unraveling microscopic interactions between the human A2A adenosine receptor and its agonists

Strategically mutated neoceptors, e.g., with anionic residues in TMs 3 and 7 intended for pairing with positively charged amine-modified nucleosides, were derived from the antiinflammatory A(2A) adenosine receptor (AR). Adenosine derivatives functionalized at the 5', 2, and N(6) positions were synthesized. The T88D mutation selectively enhanced the binding of the chain-length-optimized 5'-(2-aminoethyl)uronamide but not 5'-(2-hydroxyethyl)uronamide, suggesting a critical role of the positively charged amine. Combination of this modification with the N(6)-(2-methylbenzyl) group enhanced affinity at the Q89D- and N181D- but not the T88D-A(2A)AR. Amino groups placed near the 2- or N(6)-position only slightly affected the binding to mutant receptors. The 5'-hydrazide MRS3412 was 670- and 161-fold enhanced, in binding and functionally, respectively, at the Q89D-A(2A)AR compared to the wild-type. Thus, we identified and modeled pairs of A(2A)AR-derived neoceptor-neoligand, which are pharmacologically orthogonal with respect to the native species.