Observation of ultra-broadband terahertz emission from ZnTe films grown by metaloganic vapor epitaxy

ZnTe films were grown on (0001) sapphire substrates by the metalorganic vapor phase epitaxy (MOVPE) method. Single crystalline (111) ZnTe epitaxial layers were confirmed by x-ray diffraction, reflection high-energy electron diffraction, and cathodoluminescence measurements. Emission of THz radiation with a spectral distribution up to 40 THz was clearly observed from the ZnTe film with a thickness of 10 μm. The results show that MOVPE is a promising growth method for obtaining high-quality ZnTe epitaxial films on sapphire substrates, which paves the way for obtaining thinner ZnTe films to provide a flatter frequency response in THz device applications.     

Radical addition of ethers to imines initiated by dimethylzinc

Ethers undergo addition to imines in the presence of dimethylzinc and air through a radical process. [reaction: see text]     

Hydrolysis products of flavins (isoalloxazines)

Hydrolysis of flavin (I) with Triton B gave the 4a-spirohydantoin (II) as the main product along with III, showing that a main nucleophilic attack of hydroxide ion was initiated on the 10a position of I.     

Reaction of β-phenylthioalkyltitanium reagents with carbonyl compounds

β-Phenylthioalkyltitanium reagent prepared by the hydrotitanation of alkenyl sulfide using triethylsilane and titanium tetrachloride is found to react with aromatic aldehyde or α,β-unsaturated ketone to give the corresponding γ-hydroxyalkyl sulfide or δ-phenylthio ketone, respectively.     

Development of high-resolution optical scanning fluorescence microscopy

Instrumentation of a high-resolution optical scanning fluorescence microscope is presented. This instrument provides a fluorescent image of the structural surface of various kinds of thin membrane samples with high resolution on the molecular scale. For this instrument, a new excitation optical tip and a three-dimensional scanning unit have been designed. The optical tip consists of a sharpened optical fibre covered with evaporated aluminium in vacuo, on which the top has a pinhole. The optical tip is mounted in the centre of a crosslinked piezoelectric scanning head. On thez-axis, a piezoelectric positioner is equipped with a differential micrometer mechanism. All operations are controlled with a micro-computer system.The scanning area in this instrument is 4000*4000 nm₂ for measurements of biological specimens. Several optical scanning microscopic images as well as the STM image are presented.     

Hemilabile amidomonophosphine ligand-rhodium(I) complex-catalyzed asymmetric 1,4-addition of arylboronic acids to cycloalkenones

The asymmetric 1,4-addition reaction of arylboronic acids with cycloalkenones was catalyzed by 1 mol % of an amidomonophosphine-rhodium(I) catalyst in a 10:1 mixture of 1,4-dioxane and water at 100 degrees C, affording 3-arylcycloalkanones in reasonably high enantioselectivity and high yields. It was revealed by NMR, IR, and X-ray spectroscopies that this bidentate amidomonophosphine behaves as a hemilabile ligand that contains a hard donor site in addition to the soft donor in a molecule. Phosphorus atom strongly bonds to rhodium(I), and the amide carbonyl oxygen is coordinatively labile. The reaction efficacy of phenylboronic acid with cyclopent-2-en-1-one was significantly dependent on the possibility of coordination of the amide carbonyl oxygen to rhodium(I).