Highly Selective and Reversible Optical, Colorimetric, and Electrochemical Detection of Mercury(II) by Amphiphilic Ruthenium Complexes Anchored onto Mesoporous Oxide Films

Authors

  • M. K. Nazeeruddin,

    1. Laboratory for Photonics and Interfaces, Institute of Chemical Science and Engineering, Faculty of Basic Science, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland
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  • D. Di Censo,

    1. Laboratory for Photonics and Interfaces, Institute of Chemical Science and Engineering, Faculty of Basic Science, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland
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  • R. Humphry-Baker,

    1. Laboratory for Photonics and Interfaces, Institute of Chemical Science and Engineering, Faculty of Basic Science, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland
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  • M. Grätzel

    1. Laboratory for Photonics and Interfaces, Institute of Chemical Science and Engineering, Faculty of Basic Science, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland
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  • We acknowledge financial support of this work by the Swiss National Science Foundation under NRP 47 and thank E. Palomares, J. R. Durrant, P. Comte, Q. Wang, and A. Agrios for their support. Supporting Information is available online from Wiley InterScience or from the author.

Abstract

The colorimetric, fluorimetric, and electrochemical detection of mercury ions by functionalized ruthenium sensitizers in aqueous and non-aqueous solutions and on anchored TiO2 films are investigated. Mercury ions coordinate reversibly to the ruthenium sensitizers, inducing a color change and increasing the phosphorescence intensity significantly. The electrochemical data of the adsorbed sensitizer on TiO2 films show a reversible couple, owing to the percolation through electronic couplings between –NCS ligands of neighboring molecules; upon exposure to a Hg2+-containing solution, the electrical signal is appreciably reduced. The detection limit for mercury(II) ions using UV-vis spectroscopy in homogeneous aqueous solutions is estimated to be ∼ 20 ppb. The results presented herein have important implications in the development of reversible colorimetric, fluorimetric, and electrochemical on–off sensors based on nanocrystalline semiconductor films for the simple, swift, and selective detection of mercury ions in solution.

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