Synthesis and Tunable Reactivity of N‐Heterocyclic Germylene

Modifying the β‐diketimine ligand LH 1 (LH=[ArN?C(Me)? CH?C(Me)? NHAr], Ar=2,6‐iPr₂C₆H₃) through replacement of the proton in 3‐position by a benzyl group (Bz) leads to the new ^BzLH ligand 2, which could be isolated in 77 % yield. According to ¹H NMR spectroscopy, 2 is a mixture of the bis(imino) form [(ArN?C(Me)]₂CH(Bz) 2a and its tautomer [ArN?C(Me)? C(Bz)?C(Me)NHAr] 2b. Nevertheless, lithiation of the mixture of 2a and 2b affords solely the N‐lithiated β‐diketiminate [ArN?C(Me)? C(Bz)?C(Me)? NLiAr], ^BzLLi 3. The latter reacts readily with GeCl_2?dioxane to form the chlorogermylene ^BzLGeCl 4, which serves as a precursor for a new zwitterionic germylene by dehydrochlorination with LiN(SiMe₃)₂. This reaction leads to the zwitterionic germylene ^BzL′Ge: 5 (^BzL′=ArNC(?CH₂)C(Bz)?C(Me)NAr) which could be isolated in 83 % yield. The benzyl group has a distinct influence on the reactivity of zwitterionic 5 in comparison to its benzyl‐free analogue, as shown by the reaction of 5 with phenylacetylene, which yields solely the 1,4‐addition product 6, that is, the alkynyl germylene ^BzLGeCCPh. Compounds 2–8 have been fully characterized by multinuclear NMR spectroscopy, mass spectrometry, elemental analyses, and single‐crystal X‐ray diffraction analyses.     

A novel electromagnetic induction detector with a coaxial coil for capillary electrophoresis

A novel electromagnetic induction detector with two inductors for CE was described here.The two inductors were used as signal detection and reference,respectively.The parameters affecting the detector performance(including coil turns,detection distance, excitation frequency,voltage,etc.) were optimized.Under the optimum condition,the feasibility of the detector was examined by analyzing inorganic ions.The fabricated detector showed good linear relationship between the response and the analytes concentrations,with a detection limit of 13μmol/L for Na~+(S/N = 3).A variety of advantages,such as simple construction, ease of operation,and considerably universal response,suggested this novel detector a promising application prospect in analytical area.     

Simultaneous determination of 20 food additives by high performance liquid chromatography with photo-diode array detector

An efficient and accurate analytical method was developed for the simultaneous determination of 20 synthetic food additives, including three sweeteners,seven food colorants,nine synthetic preservatives and caffeine,by high performance liquid chromatography (HPLC) with photodiode array detector(PDA).This method permits the detection of food additives at very low concentrations(0.005-0.150μg/mL).The applicability was verified by the determination of food additives present in various foodstuffs.     

CO selective methanation in hydrogen-rich gas mixtures over carbon nanotube supported Ru-based catalysts

Series of carbon nanotube supported Ru-based catalysts were prepared by impregnation method and applied successfully for complete removal of CO by CO selective methanation from H2-rich gas stream conducted in a fixed-bed quartz tubular reactor at ambient pressure.It was found that the metal promoter,reduction temperature and metal loading affected the catalytic properties significantly.The most excellent performance was presented by 30 wt% Ru-Zr/CNTs catalyst reduced at 350℃.Since it decreased CO concentration to below 10ppm from 12000ppm by CO selective methanation at the temperature range of 180-240℃,and kept CO selectivity higher than 85% at the temperature below 200℃.Characterization using XRD,TEM,H2-TPR and XPS suggests that Zr modification of Ru/CNTs results in the weakening of the interaction between Ru and CNTs,a higher Ru dispersion and the oxidization of surface Ru.Amorphous and high dispersed Ru particles with small size were obtained for 30 wt% Ru-Zr/CNTs catalyst reduced at 350℃,leading to excellent catalytic performance in CO selective methanation.     

Self-supported interconnected Pt nanoassemblies as highly stable electrocatalysts for low-temperature fuel cells

In it for the long haul: Clusters of Pt nanowires (3D Pt nanoassemblies, Pt?NA) serve as an electrocatalyst for low-temperature fuel cells. These Pt nanoassemblies exhibit remarkably high stability following thousands of voltage cycles and good catalytic activity, when compared with a commercial Pt?catalyst and 20?%?wt Pt?catalyst supported on carbon black (20?% Pt/CB).     

Probing the electronic structure and chemical bonding of the "staple" motifs of thiolate gold nanoparticles: Au(SCH3)2- and Au2(SCH3)3-

Thiolate-protected gold nanoparticles have been found recently to be coordinated by the so-called "staple" bonding motifs, consisting of quasi-linear [RS-Au-SR] and V-shaped [RS-Au-(SR)-Au-SR] units, which carry a negative charge formally. Using photoelectron spectroscopy (PES) in conjunction with ab initio calculations, we have investigated the electronic structure and chemical bonding of the simplest staples with R = CH(3): Au(SCH(3))(2)(-) and Au(2)(SCH(3))(3)(-), which were produced by electrospray ionization. PES data of the two Au-thiolate complexes are obtained both at room temperature (RT) and 20 K. The temperature-dependent study reveals significant spectral broadening at RT, in agreement with theoretical predictions of multiple conformations due to the different orientations of the -SCH(3) groups. The Au-S bonds in Au(n)(SCH(3))(n+1)(-) (n = 1, 2) are shown to be covalent via a variety of chemical bonding analyses. The strong Au-thiolate bonding and the stability of the Au-thiolate complexes are consistent with their ubiquity as staples for gold nanoparticles and on gold surfaces.     

Sensitive detection of H(2)O(2) and H(2)O(2)-related reactant with Ru(bipy)(2)(7,8-dimethyl-dipyridophenazine)(2+) and oligodeoxyribonucleotide

A sensor for H(2)O(2) and H(2)O(2)-related reactant was constructed with oligonucleotides and Ru(bipy)(2)dppx(2+) (bipy = 2,2'-bipyridine, dppx = 7,8-dimethyl-dipyridophenazine), which was performed by converting the H(2)O(2)-induced DNA cleavage into the change of luminescence. The 'DNA light switch' Ru(bipy)(2)dppx(2+) could emit strong luminescence in the presence of dsDNA. DNA cleavage occurred upon addition of H(2)O(2) due to the Fenton reaction, which resulted in the decrease of the luminescence of Ru(bipy)(2)dppx(2+). Therefore, the luminescence intensity depended on the concentration of H(2)O(2) and H(2)O(2)-related reactants, and the detection limits for H(2)O(2), uric acid and cholesterol were 0.20 μM, 0.46 μM and 1.25 μM, respectively. The recovery varied between 94.0% and 105.0% when the assay was applied to the determination of uric acid and cholesterol in biological samples, which demonstrated the good practicability of the assay.     

Carbon‐Decorated Single‐Crystalline Ni2P Nanotubes Derived from Ni Nanowire Templates: A High‐Performance Material for Li‐Ion Batteries

Single‐crystalline Ni₂P nanotubes (NTs) were facilely synthesized by using a Ni nanowire template. The mechanism for the formation of the tubular structures was related to the nanoscale Kirkendall effect. These NTs exhibited a core/shell structure with an amorphous carbon layer that was grown in situ by employing oleylamine as a capping agent. Galvanostatic charge/discharge measurements indicated that these Ni₂P/C NTs exhibited superior high‐rate capability and good cycling stability. There was still about 310 mAh g^?1 retained after 100 cycles at a rate of 5 C. Importantly, the tubular nanostructures and the single‐crystalline nature of the Ni₂P NTs were also preserved after prolonged cycling at a relatively high rate. These improvements were attributed to the stable nanotubular structure of Ni₂P and the carbon shell, which enhanced the conductivity of Ni₂P, suppressed the aggregation of active particles, and increased the electrode stability during cycling.     

Comparing microcrystalline with spherical nanocrystalline cellulose from waste cotton fabrics

Microcrystalline cellulose (MCC) and spherical nanocrystalline cellulose (SNCC) were successfully prepared from waste cotton fabrics through acid hydrolysis. The comparative analysis of the morphology and structure between the obtained MCC and SNCC was carried out. The SNCC suspension exhibited higher stability than the MCC suspension. Transmission electron microscopy in combination with atomic force microscopy showed that the cellulose nanospheres with average size of 35?nm were achieved, while the average particle size of MCC was 49?μm. The MCC and SNCC had similar functional groups and crystalline structure as confirmed by Fourier transform infrared spectroscopy and X-ray diffraction analysis, respectively. Viscometric average molecular weight measurement and thermo gravimetric analysis indicated that the degree of polymerization and thermal stability of SNCC was lower than that of MCC. These results should improve understanding of the characteristics of MCC and SNCC derived from waste cotton fabrics and lead to many new applications.     

GMA和共单体对聚乙烯木塑复合材料的直接反应增容

通过甲基丙烯酸缩水甘油酯(GMA)、聚乙烯(PE)、木粉和其它助剂的熔融挤出,实现了GMA及GMA与共单体对PE和木粉的直接反应增容.通过扫描电镜(SEM)观测了PE基木塑复合材料(WPC)的冲击断面形貌.测试了WPC经抽提后所得木粉的傅立叶变换红外光谱(FTIR)和WPC的力学性能及热变形温度(HDT).研究了共单体苯乙烯(St)和抑交联剂亚磷酸三苯酯(TPP)对反应增容的影响.结果显示,经GMA和引发剂反应增容后,有部分PE分子键合到了木粉粒子上,从而增强了木塑两相的结合力;St的加入有利于提高GMA的接枝率,导致更多PE分子键合到了木粉粒子上,而TPP的加入则使GMA的接枝率有所下降.经GMA和引发剂直接反应增容后,WPC的力学性能和HDT均明显改善;St的加入有助于抑制PE的交联,但并未造成WPC力学性能和HDT的明显劣化;同时加入St和TPP后,WPC的HDT有所下降,而断裂伸长率和冲击强度则明显提高.