Phase control and its mechanism of CuInS2 nanoparticles

CuInS₂ nanoparticles (NPs) usually take chalcopyrite-(CP) structure. Recently, CuInS₂ NPs with pseudo-wurtzite (WZ) structure, which is thermodynamically less favored, have been synthesized. However, the formation mechanism of this metastable-phase has not been understood yet. In this report, the key issue of phase selectivity of CuInS₂ (CIS) NPs has been investigated using various metal sources and ligands. Experimental results suggested that the crystalline structure and morphology of CIS NPs were decided by the stability of indium ligand complex; the active ligand reduces the precipitation rate of In₂S₃, resulting in pre-generation of Cu₂S seed NPs. Crystallographic analogy and superionic conductivity of Cu₂S remind us that the formation of WZ CIS NPs is attributed to the pre-generation of Cu₂S seed NPs and the following cation exchange reaction. In order to confirm this hypothesis, Cu_2-xS seed NPs with various structures have been annealed in indium-ligand solution. This experiment revealed that the crystalline structure of CIS NP was determined by that of pre-generation Cu_2-xS NPs. Our results provide the important information for the phase control and synthesis of ternary chalcogenide NPs with a novel crystalline structure.     

Targeted functionalisation of a hierarchically-structured porous coordination polymer crystal enhances its entire function

Spatiospecific functionalisation of a shell crystal was performed in a core-shell crystal of a porous coordination polymer (PCP) via post-synthetic modification (PSM). The shell crystal allowed the core crystal to selectively accumulate N,N-dimethylaniline (DMA) and afford the intense exciplex fluorescence.     

Agrocybynes A–E from the culture broth of Agrocybe praecox

Five novel compounds (1–3, 5, and 6), and two known ones (4 and 7) were isolated from the culture broth of Agrocybe praecox. Their structures were determined by the interpretation of spectroscopic data. Compounds 1–4 inhibited hypocotyl growth of lettuce, and 1, 3, and 4 inhibited the root growth.     

Electroless plating of honeycomb and pincushion polymer films prepared by self-organization

This report describes the fabrication and electroless plating of regular porous and pincushion-like polymer structures prepared by self-organization. Honeycomb-patterned films were prepared by simple casting of polymer solution under applied humid air and pincushion structures by peeling off the top layer of the former films. Silver-deposited honeycomb-patterned films and pincushion films were obtained by simple electroless plating of the respective original structures. XPS revealed Ag deposition on the honeycomb-patterned film. After thermal decomposition or solvent elution of the template polymer, unique metal mesoscopic structures were obtained.     

Quantitative analysis of the structure-hydrophobicity relationship for di- and tripeptides based on voltammetric measurements with an oil/water interface

The transfer of 18 di- and 27 tripeptides with un-ionizable amino acid side chains at a nitrobenzene/water (NB/W) interface was studied by cyclic voltammetry. The reversible half-wave potential (E(r)(1/2)), i.e., the midpoint potential could be accurately determined at pH 2 for both the facilitated and non-facilitated transfers, respectively, in the presence and absence of dibenzo-18-crown-6 (DB18C6) in NB. A multiple linear regression analysis was then performed for the E(r)(1/2) using the 'corrected' Dubois steric parameter for amino acid side chain substitutents. The result shows that the hydrophobicity of the peptides is governed not only by the intrinsic hydrophobicity of the peptide backbone and side chains, but also by the steric effects of side chain substituents. For the non-facilitated transfer of peptides, the steric effect of a bulky side chain is more significant at the N-terminus than at the C-terminus (and central for tripeptides). The more bulky the side chain at the N-terminus, the less hydrophobic the peptide becomes due to inhibition of the solvation of a terminal -NH(3)(+) group by organic solvents. For the facilitated transfer by DB18C6, however, the steric effect of a bulky side chain is the most significant at the central position of a tripeptide. A MOPAC calculation of optimized structures of DB18C6-peptide complexes has also shown that there is a notable steric hindrance between the central side chain and the benzene rings of DB18C6, which would reduce the 'apparent' hydrophobicity or transferability of the tripeptide.     

Visible light-induced partial oxidation of olefins on Cr-containing silica with molecular oxygen

Photocatalytic oxidation of olefins on Cr-containing silica with molecular oxygen by visible light irradiation (lambda > 400 nm) has been investigated. Cr-SiO(2) catalyst prepared by a conventional sol-gel method, containing highly dispersed chromate species, catalyzes efficient olefin oxidation with very high selectivity for partially oxidized products (>90%), whereas semiconductor TiO(2) promotes complete decomposition (CO(2) production). The Cr-SiO(2) catalyst shows much higher activity than Cr/SiO(2) prepared by an impregnation method or Cr proportional variant MCM-41 prepared by a templating method. ESR analysis reveals that photoirradiation of the chromate species with a tetrahedral coordination (T(d)(6+)) on Cr/SiO(2) and Cr proportional variant MCM-41 catalysts leads to the formation of excited state T(d)(5+) species (T(d)(5+*)), while irradiation to T(d)(6+) on Cr-SiO(2) produces T(d)(4+*) species. This can be explained by a homogeneous T(d)(6+) arrangement with Si species on the Cr-SiO(2) catalyst. On the strongly reduced T(d)(4+*), olefins are strongly attracted by an electron and/or proton donation, resulting in high oxidation activity. The Cr-SiO(2) catalyst is applicable to partial oxidation of various aliphatic and aromatic olefins with very high selectivity, and does not promote undesirable dimerization. The obtained findings suggest a potential use of Cr-SiO(2) as an efficient and recyclable heterogeneous photocatalyst for partial oxidation of olefins.     

A dendrimer approach to high-spin polycarbenes. Conversion of connectivity from disjoint to non-disjoint by perturbation of nonbonding molecular orbital coefficients

[structure: see text] Pentakis(diazo) compound was prepared by coupling 3,5-bis[4-[diazo(4-tert-butyl-2,6-dimethylphenyl)methyl]-3,5-dibromophenylethynyl]phenylacetylene with bis(4-iodo-2,6-dimethylphenyl)diazomethane under Sonogashira reaction conditions. Pentakis(carbene) generated by irradiation of the pentakis(diazo) compound was shown to have a high-spin state with S = 4.4 at 2.0 K.     

Germanium- and Tin-Catalyzed Living Radical Polymerizations of Styrene and Methacrylates

Summary : Ge and Sn (non-transition-metal) catalyzed living radical polymerizations were developed. Low-polydispersity (M_w/M_n ∼ 1.1–1.3) polystyrenes, poly(methyl methacrylate)s, poly(glycidyl methacrylate)s, and poly(2-hydroxyethyl methacrylate) with predicted molecular weights were obtained with a fairly high conversion in a fairly short time. The pseudo-first-order activation rate constant k_act for the styrene/GeI₄ (catalyst) system was large enough, even with a small amount of GeI₄, to explain why the system provides low-polydispersity polymers from an early stage of polymerization. The retardation in the polymerization rate observed for the styrene/GeI₄ system was kinetically proved to be mainly due to the cross-termination between the propagating radical with GeI. Attractive features of the Ge and Sn catalysts include their high reactivity hence small amounts (1–5 mM) being required under a mild condition (at 60–80 °C), high solubility in organic media without ligands, insensitivity to air hence sample preparation being allowed in the air, and minor color and smell. The Ge catalysts may also be attractive for their low toxicity.     

A white-light interferometer using a lamp source and heterodyne detection with acousto-optic modulators

A heterodyne technique for white-light interferometer with a lamp source, which uses two acousto-optic modulators, is developed for high-sensitivity detection of weak light. By using converging input beams input into a Michelson interferometer with spherical mirrors, the spectral dependence of the modulators is canceled, and the white-light heterodyne interference fringes are generated at 200 kHz. Using a tandem interferometer, the object surface which has a low surface reflectivity of less than 10⁻⁴ was detected with a good signal-to-noise ratio.