Synthesis of GaN nanocrystallites by pulsed laser ablation in pure nitrogen background gases

GaN is a promising material not only for electronic devices but also for photocatalysts. Synthesis of GaN nanocrystal is a key issue to improve performance for these applications. In the present study, GaN nanocrystallites have been synthesized by pulsed laser ablation (PLA), where safe and inactive pure N₂ gases were used as reactive background gases. The third harmonics beam of a Q-switched Nd:YAG laser (355 nm, 10 mJ/pulse, 4 J/(cm² pulse)) was used to ablate a sintered high purity GaN target. The deposition substrates were not heated. It was clarified that the formed GaN nanoparticles contained a hexagonal system with the wurtzite structure. The diameter of the nanocrystallites was about 10 nm, and showed only little dependence on the background gas pressure, while the porosity of the assembly of nanocrystallites and content of GaN nanocrystallites in the assembly increased with background gas pressure. Highly porous nanometer-sized GaN film obtained at higher gas pressure is considered to be candidate structures for the photocatalysts.     

Spatiotemporal sub-cellular biopatterning using an AFM-assisted electrochemical system

The integration of electrochemical-based biolithography (ECBL) with an ordinary atomic force microscope (AFM) enables in situ lithography adjacent to a single, cultured cell, consequently allowing the morphological shape of the cell to be manipulated. The tip of a commercially available AFM cantilever was modified to serve as an electrode that could generate the oxidant HBrO for local, controlled etching of a cytophobic material (heparin or albumin) previously layered adjacent to a living cell. A NIH-3T3 fibroblast, initially confined to a patterned area, extended along a bioadhesive surface that had been newly exposed using the ECBL-AFM system.     

A ladder polysilane wrapped with amylose

A mixture of tricyclic ladder polysilane 1 and amylose, upon pH adjustment of aqueous media from very basic to neutral, affords a supramolecular complex in which a preferential twisted (helical) conformation is induced on the ladder polysilane to display optical activity. Under the experimental conditions used, 1 assumes a left-handed twisted structure in the left-handed helical channel of amylose.     

An Infinite Family of Non-Invertible Surfaces in 4-Space

A proof is given that for each non-negative integer g, thereis an infinite family of knotted surfaces of genus g, none ofwhich is ambient isotopic to itself with the orientation reversed.2000 Mathematics Subject Classification 57Q45, 57R42.     

Diazadibora[1.1.1.1]m,p,m,p‐cyclophanes: Ambipolar Conjugated Macrocycles with Different B–π–N Embedded Patterns

Are different B(boron)–π–N(nitrogen) embedded patterns to bring about significant different (opto)electronic properties for the same macrocyclic molecular backbone? A series of B–π–N‐embedded alternate‐meta‐para‐linked cyclophanes 1 – 3 have been prepared and characterized as a new class of ambipolar π‐conjugated B–π–N macrocycles. The answer to the opening question is yes. These macrocycles revealed the intramolecular charge transfer in the oxidized states and the intriguing photophysical proprerties in accordance with the embedded patterns, suggesting the electronic structures are tunable by introducing multiple B–π–N moieties.     

Effect of underlying coronene and perylene adlayers for [60]fullerene molecular assembly

Supramolecularly assembled layers of C60 on coronene- and perylene-modified Au(111) surfaces were investigated and the structure of the C60 adlayer was found to be strongly influenced by the underlying organic layers, suggesting that the latter underlying organic adlayers play an important role in the process of formation of the C60 molecular adlayer.     

Adlayers of C60-C60 and C60-C70 fullerene dimers formed on au(111) in benzene solutions studied by STM and LEED

Scanning tunneling microscopy (STM) and low-energy electron diffraction were used to reveal the structures of ordered adlayers of [2+2]-type C60-C60 fullerene dimer (C120) and C60-C70 cross-dimer (C130) formed on Au(111) by immersingit in abenzene solution containing C120 or C130 molecules. High-resolution STM images clearly showed the packing arrangements and the electronic structures of C120 and C130 on the Au(111) surface in ultrahigh vacuum. The (2 square root3 x 4square root3)R30 degrees, (2square root3 x 5square root3)R30 degrees, and (7 x 7) structures were found for the C120 adlayer on the Au(111) surface, whereas C130 molecules were closely packed on the surface. Each C60 or C70 monomer cage was discerned in the STM image of a C130 molecule.     

Highly selective and simple synthesis of C(2)(m)--X--C(2)(n) fullerene dimers

Energetic-radiation-induced dimerization reaction of fullerenes was found to be a simple and highly selective method for synthesis of C2m-X-C2n (m = n or m not equal n) type molecules without formation of other products. Utilizing the new method, C70-C-C70, C60-C-C70, C60-C-C60, and C70-O-C70 were prepared and characterized. The method is capable of synthesizing new C2m-X-C2n molecules by introducing X (different atoms) into the reaction system. Energetic radiation created reactive sites for covalently bonded bridges between fullerene molecules originally only weakly bound by van der Waals force. This observation may open a new subject and practicable approach for polymer sciences of fullerenes.     

Analysis of an antibody pharmaceutical, tocilizumab, by capillary electrophoresis using a carboxylated capillary

Antibody pharmaceuticals are becoming more and more prevalent due to their excellent effectiveness in clinical medications, and are expected to allow tailor-made medical treatment for rheumatic diseases, immunosuppression in cardiac transplantation, and cancer. Antibody-type pharmaceuticals of immunoglobulin G (IgG) commonly have N-glycosylated carbohydrate chains attached to heavy chains. The carbohydrate chains play important roles in the effectiveness of antibodies. Therefore evaluation of a glycosylated species is important in the first step of quality control of antibody pharmaceuticals. In the present work, we examined capillary electrophoresis with a newly developed, chemically modified capillary, the inner surface of which is modified with carboxyl groups, for evaluation of IgG molecular species which have carbohydrate chains; tocilizumab was used as a model. The analytical system developed in the present study is useful for determining the content of non-glycosylated peptides. In the analysis of tocilizumab, the ratio of non-glycosylated peptide was estimated to be 1.23% with a relative standard deviation of 3.05%. The method affords high reproducibility with simple operation, and analysis can be completed within 6 min.     

Electrochemical Condensation of Methylviologen on Specifically‐adsorbed Anion Layers

The adsorption of methylviologen dications (MV²⁺) on single‐crystalline Au electrodes in both H₂SO₄ and HClO₄ was examined. MV²⁺ strongly interacted with sulfate and bisulfate anions adsorbed on the Au(111) electrode surface in 0.05 M H₂SO₄ under a controlled potential of 1.25 V vs. the reversible hydrogen electrode (RHE). A characteristic non‐Faradaic current was observed at 1.10 V vs. RHE. When adsorption of MV²⁺ was carried out in 0.1 M HClO₄, the electrochemical response of MV²⁺ was less than that obtained in H₂SO₄. The results show that the formation of a highly ordered sulfate/bisulfate adlayer plays an important role in the formation of condensed MV²⁺ layers. Examination of polycrystalline Au and Au(100) electrodes revealed a poor electrochemical response due to the surface roughness of the Au substrate, but the electrochemical detection was applicable to polycrystalline Au electrodes. A systematic investigation of the structural dependency of viologen derivatives showed that molecular size is important for electrostatic interactions with a highly ordered sulfate/bisulfate adlayer. The findings of the present study demonstrate successful detection of MV²⁺ at a concentration of ≤1 pM with a non‐Faradaic current.