Fluorescent Triphenyl Substituted Maleimide Derivatives: Synthesis,Spectroscopy and Quantum Chemical Calculations

In this paper we describe a semi-empirical quantum method for predicting the wavelength of maximum fluorescence excitation and emission for several known and new maleimide derivatives. All new maleimides, containing a N-Benzyl attachment, were successfully synthesised via a tandem Suzuki reaction with aryl boronic acids containing either an electron donating, electron withdrawing functional groups. Absorption and emission spectra calculated using the semi-empirical AM1 method with excited state ZINDO calculations proved more reliable than either Hartree-Fock Configuration interaction or time dependent density functional methods. Calculated absorption and emission wavelengths were compared with 26 experimental spectra from known or newly synthesised maleimides and found to have provide reasonable predictions, with an average deviation of less the 6% for absorption maxima and less than 4% for emission peaks. The described method provides a strong benchmark for the accuracy that can be expected from theoretical predictions of fluorescence spectra.     

Nanoporous polyimide film from poly(ethylene glycol-co-imide) using a one-step heat calcination process

Polyamic acid (PAA) made from 3,3, 4,4-biphenyltetracarboxylic dianhydride and 4,4-diaminodiphenyl ether was synthesized and used as the backbone of nanoporous polyimide. Thermally labile polyethylene glycol (PEG) at 10, 20 or 30 wt% was introduced to the end group of PAA. Self-assembled PAA-b-PEG micelle-like nanoparticles could be formed as a result of amphiphilic characteristics of hydrophobic PAA and hydrophilic PEG. Thermal imidization and degradation of spin-coated amphiphilic PAA-b-PEG film were performed sequentially through one-step heat treatment to obtain polyimide film with nanopores. Pore sizes decreased with increasing amount of PEG block and their dielectric constants decreased from 2.71 ± 0.13 to 2.38 ± 0.11.     

Slit Holomorphic Stochastic Flows and Gaussian Free Field

It was realized recently that the chordal, radial and dipolar Schramm–Löwner evolution (SLEs) are special cases of a general slit holomorphic stochastic flow. We characterize those slit holomorphic stochastic flows which generate level lines of the Gaussian free field. In particular, we describe the modifications of the Gaussian free field (GFF) corresponding to the chordal and dipolar SLE with drifts. Finally, we develop a version of conformal field theory based on the background charge and Dirichlet boundary condition modifications of GFF and present martingale-observables for these types of SLEs.     

Palladium-Catalyzed Coupling of Allylic Cyclic Carbonates with Aryl- and Vinylstannanes in Aqueous Medium

The palladium-catalyzed reaction of allylic cyclic carbonates with aryl-and vinyltin reagents afforded the cross-coupled products at room temperature in an aqueous medium.     

Direct Synthesis of Hydrogen Peroxide from Hydrogen and Oxygen Using Tailored Pd Nanocatalysts: A Review of Recent Findings

Direct synthesis of hydrogen peroxide from hydrogen and oxygen is being actively studied as an alternative to the current manufacturing process. The direct synthesis route has not reached the point of commercialization because of low yields, but significant effort is being spent on enhancing the productivity. With advances in computational capacity, simulation studies based on DFT calculations now offer directions for catalyst improvement, but such modifications can only be realized through the application of nanoparticle synthesis techniques that allow for nanocrystal morphology and size control and unique immobilization. To date, there have only been a small number of studies on such nanoparticles with size and crystallographic homogeneity for the direct hydrogen peroxide synthesis. According to our knowledge no other group has systematically investigated application of nanoparticles in direct synthesis of hydrogen peroxide, and thus included in this review are primarily previous studies conducted by our group. In this review, we discuss the utilization of nanotechnology for the synthesis of Pd catalysts and its effect on the direct synthesis of hydrogen peroxide, and we suggest a direction for future studies.     

The concerted and stepwise chemisorption mechanisms of isothiazole and thiazole on Si(100)?2?��?1 surface

The surface reaction pathways of isothiazole and thiazole on Si(100)?2?×?1 surface were theoretically investigated using multireference wavefunctions. In the case of isothiazole, the Si?CN dative adduct turned out to be the major surface product. In contrast, a direct reaction competition between a concerted [4?+?2]_CC cycloaddition and Si?CN dative adduct was found in the adsorption of thiazole. Therefore, it is concluded that the particular geometric arrangements of heteroatoms exhibit distinctly different initial surface reaction mechanisms.     

Non-contact evaluation of the resonant frequency of a microstructure using ultrasonic wave

This paper presents a novel non-contact method for evaluating the resonant frequency of a microstructure, Firstly, the microstructure under test is excited by ultrasonic waves. This excitation method does not impose any undefined load on the specimen like the electrostatic excitation and also this is the first actual use of ultrasonic wave for exciting a microstructure in the literature. Secondly, the amplitudes of the microstructure are determined by image edge detection using a Mexican hat wavelet transform on the vibrating images of the microstructure. The vibrating images are captured by a CCD camera when the microstructure is vibrated by ultrasonic waves at a series of discrete high frequencies （〉30 kHz）. Upon processing the vibrating images, the amplitudes at various excitation frequencies are obtained and an amplitude-frequency spectrum is obtained from which the resonant frequency is subsequently evaluated. A micro silicon structure consisting of a perforated plate （192 × 192 μm） and two cantilever beams （76 × 43 μm） which is about 4 μm thickness is tested. Since laser interferometry is not required, thermal effects on a test object can be avoided. Hence, the setup is relatively simple. Results show that the proposed method is a simple and effective approach for evaluating the dynamic characteristics of microstructures.