Activation analysis activities in China

The history, the major achievements in both methodology and application studies, the current trends and the future perspectives of activation analysis in China are biefly described.     

Parametric normalization for full-energy peak count rates obtained at different geometries

The Effective Interaction Depth (EID) law has been systematically studied and applied to parametric normalization for peak count rates obtained at different source-detector distances (S-D). The errors caused by EID normalization are less than 4% over the full range of S-D (from to several mm) for true coincidence-free -rays. Parametric corrections for the true coincidence (summing) effect are also established, based on simplified decay schemes and P/T ratio determinations. The total response of Ge detector for single-energy -rays (T) is clearly defined with scattering contributions from surroundings included. Errors from summing effect corrections are also less than 4%. The combined EID normalization and summing effect corrections give an error no greater than 5.7% for the worst situations (several mm S-D and cascade-crossover decay scheme), acceptable for most practical K₀ NAA.     

Synthesis and characterization of UV-curable polydimethylsiloxane epoxy acrylate

UV-curable polydimethylsiloxane epoxy acrylate (PSEA) was synthesized by hydrosilylation of allyl glycidyl ether with hydrogen-containing polydimethylsiloxane to give polydimethylsiloxane-type epoxy resin which modified with acrylic acid. The curing speed and the double bond conversion in the UV cured film were influenced by the purity of PSEA with Fourier transform infrared spectroscopy (FT-IR) measurements. The influences of the synthetic process, such as, the reaction temperature, the concentration of reactants and the catalyst which determined the purity and activity of resins were discussed in detail. The structures of this resin were characterized by ¹H-NMR and FT-IR spectra. The molecular weight was checked by gel permeation chromatography, and M_n is 45,000. The properties of the cured film were also investigated by thermogravimetric analyzer, dynamical thermal mechanical analysis, and etc. For example, tensile strength (6.9 Mpa), elongation (20%), hardness (A; 18), water absorption (24 h; 2%), weight loss (40 min, 300 °C; 5%) and etc.     

Palladium‐Catalyzed One‐Pot Three‐ or Four‐Component Coupling of Aryl Iodides,Alkynes, and Amines through CN Bond Cleavage: Efficient Synthesis of Indole Derivatives

An efficient synthesis of N‐substituted indole derivatives was realized by combining the Pd‐catalyzed one‐pot multicomponent coupling approach with cleavage of the C(sp³)?N bonds. Three or four components of aryl iodides, alkynes, and amines were involved in this coupling process. The cyclopentadiene–phosphine ligand showed high efficiency. A variety of aryl iodides, including cyclic and acyclic tertiary amino aryl iodides, and substituted 1‐bromo‐2‐iodobenzene derivatives could be used. Both symmetric and unsymmetric alkynes substituted with alkyl, aryl, or trimethylsilyl groups could be applied. Cyclic secondary amines such as piperidine, morpholine, 4‐methylpiperidine, 1‐methylpiperazine, 2‐methylpiperidine, and acyclic amines including secondary and primary amines all showed good reactivity. Further application of the resulting indole derivatives was demonstrated by the synthesis of benzosilolo[2,3‐b]indole.     

Transfer of Aryl Halide to Alkyl Halide: Reductive Elimination of Alkylhalide from Alkylpalladium Halides Containing syn‐β‐Hydrogen Atoms

β‐Hydride abstraction is a well‐accepted elementary step for catalytic cycles in organometallic chemistry. It is usually anticipated that alkylpalladium halides containing syn‐β‐hydrogen atoms will undergo β‐hydride abstraction to afford the Heck‐type products. However, this study discloses that the above general knowledge is only conditionally correct. Our experimental results demonstrate that the reductive elimination of alkylhalides from alkylpalladium halides containing syn‐β‐hydrogen atoms may surpass the β‐hydride abstraction or even become exclusive in certain cases.     

VPE生长CdS外延膜的光学性质与光学双稳态

本文报导了在透明的CaF2衬底上采用气相外延(VPE)方法生长的高质量CdS薄膜。通过对其发射和吸收光谱以及光双稳特性的研究,表明这种外延膜的性质与体单晶相似。     

Preparation,morphology, and biolabeling of fluorescent nanoparticles based on conjugated polymers by emulsion polymerization

Novel nanoparticles based on conjugated polymer with good fluorescent properties were synthesized by Suzuki coupling reaction using certain surfactants as one kind of special emulsion polymerization. The luminescent properties of the prepared nanoparticles could be controlled by selecting different monomers. Without using substances comprising any heavy metal element, these fluorescent nanoparticles show very good biocompatibility with cells, thus showing potential applications in cell biolabeling, drug delivery tracing, organic light‐emitting diodes, flat displays, and other areas. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Graphene Nanoribbons from Tetraphenylethene‐Based Polymeric Precursor: Chemical Synthesis and Application in Thin‐Film Field‐Effect Transistor

Graphene nanoribbons (GNRs) with a non‐zero bandgap are regarded as a promising candidate for the fabrication of electronic devices. In this study, large‐scale solution synthesis of narrow GNRs was firstly achieved by the intramolecular cyclodehydrogenation of kinked tetraphenylethene (TPE) polymer precursors prepared by A₂B₂‐type Suzuki‐Miyaura polymerization. After the cyclization reaction, the nanoribbons have a better conjugation than the twisted polymer precursor, resulting in obvious red shift in UV/vis absorption and photoluminescence (PL) spectra. The efficient formation of conjugated nanoribbons was also investigated by Raman, FTIR spectroscopy, and microscopic studies. Furthermore, such structurally well‐defined GNRs have been successfully developed for top‐gated field‐effect transistor (FET) by directly solution processing. The AFM images show that the prepared‐GNRs thin films form crystalline fibrillar intercalating networks, which can effectively facilitate the charge transport. These FET devices with ion‐gel gate dielectrics exhibit low‐voltage operation (<5 V) with excellent mobility up to 0.41 cm²·V^?1·s^?1 and an on‐off ratio of 3×10⁴, thus opening up new opportunities for flexible GNRs‐based electronic devices.