Electrochemical Behavior of the 1,10-Phenanthroline Ligand on a Multiwalled Carbon Nanotube Surface and Its Relevant Electrochemistry for Selective Recognition of Copper Ion and Hydrogen Peroxide Sens

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• 作者：Prakasam Gayathri ; Annamalai Senthil Kumar
• 刊名：Langmuir
• 出版年：2014
• 出版时间：September 2, 2014
• 年：2014
• 卷：30
• 期：34
• 页码：10513-10521
• 全文大小：2699K
• ISSN：1520-5827

文摘

1,10-Phenanthroline (Phen) is a well-known benchmark ligand and has often been used in the coordination chemistry for the complexation of transition metal ions, such as Fe²⁺, Ni²⁺, and Co²⁺. Because the electro-oxidation potential of Phen is much higher (>2 V versus Ag/AgCl) than the water decomposition potential, i.e., 鈭?.5 V versus Ag/AgCl, in pH 7, it is practically difficult to electro-oxidize Phen in aqueous medium using any conventional electrodes, such as glassy carbon electrode (GCE), gold, and platinum. Interestingly, herein, we report an unexpected oxidation of Phen to a highly redox active 1,10-phenanthroline-5,6-dione (Phen-dione) and its confinement on a multiwalled carbon nanotube (MWCNT)-modified glassy carbon electrode (GCE/MWCNT@Phen-dione) surface by potential cycling of Phen-adsorbed GCE/MWCNT (GCE/MWCNT@Phen) from 鈭? to 1 V versus Ag/AgCl in pH 7 phosphate buffer solution. GCE/MWCNT@Phen-dione showed selective recognition of copper ion (GCE/MWCNT@Phen-dione鈥揅u²⁺) by catalyzing the hydrogen peroxide reduction reaction in a neutral pH solution. The precise structure of the Phen electro-oxidized product has been identified after characterizing the electrode and/or ethanolic extract of the product by various techniques, such as Raman, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) (for copper complex), liquid chromatography鈥搈ass spectrometry (LC鈥揗S), electrospray ionization鈥搈ass spectrometry (ESI鈥揗S) (for copper complex), cyclic voltammetry (CV), and in situ electrochemical quartz crystal microbalance (EQCM) and comparing electrochemical behavior of several control compounds, such as phenanthrene and 9,10-phenanthrenequinone. It is concluded that the product formed is 1,10-phenanthroline-5,6-dione, wherein the dione position is ortho to each other and the copper ion is complexed with nitrogen of the phenanthroline ring. With extended electrochemical oxidation of a structurally similar ligand, 2,2鈥?bipyridine failed to show any such electrochemical dynamics. Finally, applicability of GCE/MWCNT@Phen-dione鈥揅u²⁺ for electrochemical sensing of hydrogen peroxide in a couple of real samples is successfully demonstrated.