Deman Han

On-line solid phase extraction coupled to flame atomic absorption spectrometry for the determination of trace copper and zinc in environmental and biological samples

In this work, bamboo charcoal (BC) was used as a sorbent for on-line solid phase extraction (SPE) coupling with flame atomic absorption spectrometry (AAS) for trace copper and zinc determination in environmental and biological samples. Under the optimum pH of 5.5 (for Zn) and 7.0 (for Cu), trace copper and zinc were effectively adsorbed on the microcolumn and the retained cations were efficiently eluted with HCl or HNO3 with an appropriate concentration and flow rate for on-line AAS determination. With a sample loading time of 60 s at a sample flow rate of 7.6 mL min−1, the enhancement factors of 39 (for Cu) and 30 (for Zn) and detection limits (3σ) of 0.60 µg L−1 (for Cu) and 0.36 µg L−1 (for Zn), respectively, were achieved. The sample throughput was 45 h−1. At the level of 20 µg L−1of Cu(II) and Zn(II), the precision (RSD, nu2009=u200911) were found to be 0.26% and 1.6%, respectively. The proposed method has been successfully applied to the determination of copper and zinc in environmental and biological samples.

A turn-on fluorescent probe for simultaneous sensing of cysteine/homocysteine and hydrogen sulfide and its bioimaging applications

Hydrogen sulfide and biothiol molecules such as Cys, Hcy, and GSH play important roles in biological systems. Exploiting a probe to simultaneously detect and distinguish them is quite important. In this work, a versatile fluorescent probe that can simultaneously detect and discriminate Cys/Hcy and H2S is reported. The probe easily prepared by the Knoevenagel condensation of cyanoacetylindole with chlorinated phenyl-propenal possessed three potential sites that could react with biothiols and H2S. This probe also exhibited rapidity, high selectivity, and sensitivity for Cys/Hcy and H2S with distinct optical signal changes. The probe was able to display obvious fluorescence enhancement at 480u202fnm for Cys/Hcy and unique absorbance enhancement at 500u202fnm for H2S. We also demonstrated that the probe can be successfully applied to image Cys in MCF-7 cells suing a confocal fluorescence microscope.

An Additive-Free, Base-Catalyzed Protodesilylation of Organosilanes

We report an additive-free, base-catalyzed C-, N-, O-, and S-Si bond cleavage of various organosilanes in mild conditions. The novel catalyst system exhibits high efficiency and good functional group compatibility, providing the corresponding products in good to excellent yields with low catalyst loadings. Overall, this transition-metal-free process may offer a convenient and general alternative to current employing excess bases, strong acids, or metal-catalyzed systems for the protodesilylation of organosilanes.

Gold Promotion of MCM-41 Supported Ruthenium Catalysts for Selective Hydrogenation of α,β-Unsaturated Aldehydes and Ketones

In the challenging α,β-unsaturated aldehydes and ketones hydrogenation to unsaturated alcohols (UA), Ru–Au/MCM-41 exhibits superior high activity and selectivity compared with monometallic Ru. TEM and XRD measurements were applied to characterize as-prepared Ru/MCM-41 and Ru–Au/MCM-41 catalysts. The results indicated that the addition of Au significantly improved the dispersion of the metallic Ru components, thus enhancing the activity of the catalyst. The enhancement of selectivity to UA could be attributed to the interaction of Ru and Au components in the support and the morphology effect of Ru, which are revealed by in-suit DRIFTS, H2-TPD, XPS, and FTIR measurements. The morphological and electronic aspects of Ru particles lead to a favorable adsorption of C=O bond versus C=C bond. A dramatic increase in activity and selectivity of the reactions were observed upon the addition of Au, suggesting that the significant synergistic effects between Ru and Au play an important role in the activity and selectivity of the reaction. It is the first time that chemoselective hydrogenation of α,β-unsaturated aldehydes and ketones were studied on Ru–Au/MCM-41 catalysts.Graphical Abstract