Synthesis of CdTe quantum dots using a heterogeneous process at low temperature and their optical and structural properties

Luminescent CdTe quantum dots (QDots) have been synthesized through a low-temperature process employing a heterogeneous reaction between cadmium acetate and tri-n-octyl phosphine tellurium (TOPTe) in the presence of tri-n-octyl phosphine oxide (TOPO). UV-visible absorption spectra revealed that monodispersed CdTe QDots were synthesized at 70 °C for 240 min. The as-synthesized CdTe QDots exhibited photoluminescence (PL) with a narrow spectral distribution (FWHM41 nm). Highly luminescent CdTe QDots with PL quantum yield (QY) up to 33% were size selected from the ensemble. X-ray and electron diffraction measurements revealed that CdTe crystallized in a wurtzite-type structure at 70 °C. High-resolution transmission electron microscopic measurements revealed that the CdTe particles were of regular spherical morphology with an average diameter of 2.8 nm. The present experiment demonstrates, in addition to an advantage in green chemistry, that a low-temperature process allows an extended period of time for crystallization that is useful for synthesizing defect-free QDots with higher PL QY. PACS 81.07.-b; 81.20.-n; 81.07.Ta; 78.67.-n; 61.46.+w     

Epoxidation with an electrocatalytic p-450 model system in an acidic solution

An electrochemical P-450 model system using meso-tetraphenylporphyrinatomanganese(III) chloride (MnTPP), imidazole and acetic acid was tested in an acetonitrile solution, and epoxide was obtained with a good current efficiency. The results of cyclic voltammetry revealed that acid plays an important role in the second electron transfer.     

Growth conditions for oscillation of nonlinear differential equations with p-Laplacian

In this paper, oscillation criteria are established for all solutions of second-order nonlinear differential equations of the form

     

Characteristics of germanium avalanche photodiodes in the wavelength region of 1-1.6 µm

Dark current, quantum efficiency, multiplication noise, and pulse response of germanium avalanche photodiodes with n+-p junction were studied to find an optimum structure. The dark current can be separated by graphical means into a leakage current component and a multiplied component which flows through the junction. The dark current components are also evaluated by using diodes with various diameters. The quantum efficiency and the multiplication noise are shown to be strongly affected by the n+ layer thickness. An n+ layer thickness optimized for signal-to-noise ratio is estimated from experimental and calculated results, using a figure of merit for avalanche photodiodes. The response waveform for mode-locked Nd:YAG laser shows a rise time of 100 ps and a half pulsewidth of less than 200 ps.     

Radical pair formation in dihalogenated benzene derivatives at 77K

Radical pair formation in dihalogenated benzene derivatives irradiated at 77 K has been revealed by the EPR detection of ΔM = 2 transitions. In some specimens, the hydrogen atom signal has been observed, suggesting the presence of the phenyl radical.     

Structure-activity relationships of new N-acylanthranilic acid derivatives as plasminogen activator inhibitor-1 inhibitors

Novel anthranilic acid derivatives having substituted N-acyl side chains were designed and synthesized for evaluation as plasminogen activator inhibitor-1 (PAI-1) inhibitors. Compounds with a 4-diphenylmethyl-1-piperazinyl moiety on the acyl side chains in general exhibited potent in vitro PAI-1 inhibitory activity and good pharmacokinetic profiles after oral administration in rats. Compound 16f (TM5275) was identified as a promising candidate for further pharmacological evaluation.     

Efficient Synthesis of a Regioregular Oligothiophene Photovoltaic Dye Molecule,MK‐2, and Related Compounds: A Cooperative Hypervalent Iodine and Metal‐Catalyzed Synthetic Route

We have successfully established an efficient route to the core structure of donor–acceptor head‐to‐tail (H–T)‐linked regioregular oligothiophenes, which includes the following key synthetic steps, that is, hypervalent iodine induced direct and regioselective coupling of thiophenes and the use of the obtained bithiophenes as excellent coupling substrates for the Suzuki and Stille couplings. The versatility of this new approach is highlighted in the dramatic improvement of the yield (ca. 59 % overall yield) of MK‐2, a high‐performance organic dye, for photovoltaic applications.     

Quantum degenerate mixtures of alkali and alkaline-earth-like atoms

We realize simultaneous quantum degeneracy in mixtures consisting of the alkali and alkaline-earth-like atoms Li and Yb. This is accomplished within an optical trap by sympathetic cooling of the fermionic isotope ?Li with evaporatively cooled bosonic 1??Yb and, separately, fermionic 1?3Yb. Using cross-thermalization studies, we also measure the elastic s-wave scattering lengths of both Li-Yb combinations, |a(?Li-1??Yb)| = 1.0 ± 0.2 nm and |a(?Li-1?3Yb)| = 0.9 ± 0.2 nm. The equality of these lengths is found to be consistent with mass-scaling analysis. The quantum degenerate mixtures of Li and Yb, as realized here, can be the basis for creation of ultracold molecules with electron spin degrees of freedom, studies of novel Efimov trimers, and impurity probes of superfluid systems.