Retrievable Photoelectrochemical Sensing Platform for Hg~(2+) Based on the Alternation of a Multifunctional Photosensitizer

【Author】

Yuanqiang Hao;Yali Cui;Yintang Zhang;Wenzhong Sun;Shuping Liu;Maotian Xu;

【Abstract】

A novel photoelectrochemical(PEC) sensing platform was devised and constructed for reversible detection of Hg2+. Herein, the ideology for developing molecular probe, which based on the direct spectral feature changes of the probe induced by targets, was resourcefully employed for the construction of photoelectrochemical sensor. N3 dye, bis(4,4'-dicarboxy-2,2'-bipyridine) dithiocyanato ruthenium(II), was selected as a multifunctional model molecule for photo-sensitization, target-recognition and interface conjugation. First, N_3 was covalently tethered on the surface of amino-functionalized Ti O_2 nanowires via amide coupling. Under visible illumination(~ 540 nm), the highly efficient photoinduced charge-transfer from N_3 dye into Ti O_2 nanoarchitecture could produce a sensitive photocurrent response. Then, the introduced target Hg~(2+) ions can coordinate to SCN groups of N_3 dye and lead to the formation of N~(3-)Hg~(2+) complex which would remarkably change the absorption feature and attenuate the photocurrent response of the original photosensitizer. DFT calculations demonstrated that N~(3-)Hg~(2+) complex have a larger HOMO-LOMO gap, a higher LOMO energy level and a reduced electron density of LUMO localized on the anchoring groups with respect with N3 dye, which contributed to the decreased photocurrent. Under optimized conditions, the photocurrent was decreased with the increasing Hg2+ concentration in a dynamic range of 0.5 n M to 50 μM, with a detection limit of 0.13 n M. Moreover, the N_3 grafted Ti O_2 phtoanode could be restored by being treated with cysteine due to the extraction of Hg~(2+) by thiols. And the covalent attachment of the photosensitizer to the Ti O_2 nanowire ensured the long-term stability of the PEC sensor. The proposed sensing strategy, by utilizing the multifunctional molecule photosensitizers for direct responding to targets, presents a novel methodology for the development of high performance PEC sensors in future.

【Keywords】

bioelectrochemical system;;3-HP;;Shewanella oneidensis MR-1

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