Synthesis and Two‐Photon Absorption Property Characterizations of Small Dendritic Chromophores Containing Functionalized Quinoxaliniod Heterocycles

A series of star‐shaped multi‐polar chromophores (compounds 1 – 3 ) containing functionalized quinoxaline and quinoxalinoid (indenoquinoxaline and pyridopyrazine) units has been synthesized and characterized for their two‐photon absorption (2PA) properties both in the femtosecond and the nanosecond time domain. Under our experimental conditions, these model fluorophores are found to manifest strong and wide‐dispersed two‐photon absorption in the near‐infrared region. It is demonstrated that molecular structures with multi‐branched π frameworks incorporating properly functionalized quinoxalinoid units would possess large molecular nonlinear absorptivities within the studied spectral range. Effective optical‐power attenuation and stabilization behaviors in the nanosecond time domain of a selected representative dye molecule (i.e., compound 2 ) from this model compound set were also investigated and the results indicate that such structural motif could be a useful approach for the molecular design toward strong two‐photon‐absorbing material systems for quick‐responsive and broadband optical‐suppressing‐related applications, particularly to confront long laser pulses.     

改进型合成甲醇铜基催化剂NC208的低氢活化(英文)

用TPR、DTA和XRD方法研究了改进型合成甲醇铜基催化剂NC208,成功地建立了对该催化剂进行低氢活化的程序升温还原程序并把它用于工业生产,取得了很高的甲醇收率。     

Growth of InGaAs-capped InAs quantum dots characterized by Atomic Force Microscope and Scanning Electron Microscope

Atomic force microscopy (AFM) is typically used to measure the quantum dot shape and density formed by lattice mismatched epitaxial growth such as InAs on GaAs. However, AFM images are distorted when two dots are situated in juxtaposition with a distance less than the AFM tip width. Scanning electron Microscope (SEM) is much better in distinguishing the dot density but not the dot height. Through these measurements of the growth of In_xGa_1-xAs cap layer on InAs quantum dots, it was observed that the InGaAs layer neither covered the InAs quantum dots and wetting layer uniformly nor 100% phase separates into InAs and GaAs grown on InAs quantum dots and wetting layer, respectively.     

A Drying‐Free,Water‐Based Process for Fabricating Mixed‐Matrix Membranes with Outstanding Pervaporation Performance

Despite much progress in the development of mixed matrix membranes (MMMs) for many advanced applications, the synthesis of MMMs without particle agglomeration or phase separation at high nanofiller loadings is still challenging. In this work, we synthesized nanoporous zeolitic imidazole framework (ZIF‐8) nanoparticles with a particle size of 60 nm and a pore size of 0.34 nm in water and directly added them into an aqueous solution of the organic polymer poly(vinyl alcohol) (PVA) without an intermediate drying process. This approach led to a high‐quality PVA/ZIF‐8 MMM with enhanced performance in ethanol dehydration by pervaporation. The permeability of this MMM is three times higher than that of pristine PVA, and the separation factor is nearly nine times larger than that of pristine PVA. The significantly improved separation performance was attributed to the increase in the fractional free volume in the membranes.     

Stereoselective Michael-alkylation and Michael-oxidation reactions of chiral 1,3-dioxolanones

A highly diastereoselective Michael-alkylation/oxidation methodology has been developed for the synthesis of optically active α-hydroxy-1,5-diester subunits. Inverse stereochemistry at the C_2′ position could be achieved by using a Michael acceptor equipped with a suitable group followed by a highly stereoselective protonation. This methodology has been applied to the enantioselective synthesis of the upper fragment of (+)-retusine.