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Tran, Chinh Hoang,Pham, Linh Thi Thuy,Lee, Yechan,Jang, Han Byeol,Kim, Suna,Kim, Il Elsevier 2019 Journal of catalysis Vol.372 No.-
<P><B>Abstract</B></P> <P>Electron donating complexing agents (CAs) are one of the key components to achieve active Zn(II)–Co(III) double metal cyanide (DMC) catalysts for the ring-opening polymerization (ROP) of propylene oxide (PO). The effect of the type of CAs on the ROP of PO is mechanistically studied by exploiting a series of dicarbonyl compounds, α-, β-, and γ-diketones and β-ketoesters, as CAs for DMC catalysts. The keto and/or enol modes of complexation of CAs on the catalyst surface is defined by combining structure-sensitive characterization tools such as infrared, absorption and X-ray photoelectron spectroscopies, finding keto complexation exhibits higher activity than enol complexation. Polymerizations of 1,2-epoxyhexane, glycidyl isopropyl ether, epichlorohydrin, and 1,2-epoxytetradecane are also conducted to get further insights on the mechanistic pathways of DMC-catalyzed ROP of epoxides. The interaction of oxygen atoms from both CAs and PO with the dormant sites during the activation of catalyst and the consequent formation of active sites by the removal of the coordinated CAs has been investigated using <SUP>1</SUP>H NMR analysis combined with DFT calculations. Once the active sites are initiated in cationic pathway and started to propagate, the DMC catalysts are fragmented into small pieces, allowing the unexpected high activity of the DMC catalysts. The propagation proceeds in either cationic or coordinative route depending on the presence of polyol initiator. The further understanding of the mechanistic pathways using a series of new dicarbonyl CAs expands the variety and scope of DMC-catalyzed ROP of epoxides.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The effect of complexing agents on double metal cyanide (DMC) catalysis is investigated. </LI> <LI> The β-, and γ-dicarbonyl compounds are highly effective complexing agents. </LI> <LI> The adsorption of complexing agents in keto form is favorable for high activity. </LI> <LI> The fragmentation of catalyst occurs at the early period of polymerization. </LI> <LI> Plausible mechanistic pathways of DMC-catalyzed polymerizations are proposed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Hydroxyapatite Nano-Rods/Chitosan Modified Glassy Carbon Electrode for Cu(II) Ions Determination
Hoang V. Tran,Chinh D. Huynh,Thu D. Le,Hong S. Hoang 대한금속·재료학회 2020 ELECTRONIC MATERIALS LETTERS Vol.16 No.4
In this work, we propose a simple approach for fabrication of an electrochemical sensor for copper (II) ion determination in aqueous solution based on using a hydroxyapatite nano-rods/chitosan (HA/CS) nanocomposite coated on glassy carbon electrode (GCE) surface. Firstly, hydroxyapatite (HA) nano-rods has been synthesized by a simple precipitation reactions using Ca(OH)2 slurry and orthophosphoric acid (H3PO4) as precursors. After that, as-synthesized HA was dispersed into chitosan (CS) matrix to HA/CS-modify GCE by a drop casting technique. Characteristic of HA and HA/CS coating on GCE have been analysed by Transmission/Scanning Electron Microscope (TEM/SEM), X-ray Diffraction (XRD) and Fourier-Transform infrared spectroscopy (FT-IR) techniques. Electrochemical activities of neat GCE, CS-modified GCEs (GCE/CS) and HA/CS-modified GCE (GCE/HA/CS) have been evaluated in sodium acetate (NaAc-HAc) buffer with presence/absence of Ni2+, Co2+ or Cu2+ ions to test whether sensitive and selective of these developed Cu2+ sensors. Evaluated results demonstrated that GCE/HA/CS sensor has a sensitivity to Cu2+ ion of 7.688 ± 0.5324 µA mM− 1, it is the most sensitive to Cu2+ ions compared with GCE or GCE/CS. In additional, proposed Cu2+ electrochemical sensor has been applied to determine Cu2+ ions concentration in tap water with a high recoveries was found.