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Issue 2, 2016
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ESIPT blocked CHEF based differential dual sensor for Zn2+ and Al3+in a pseudo-aqueous medium with intracellular bio-imaging applications and computational studies

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Abstract

A novel 3-hydroxymethyl-5-methylsalicylaldehydenaphthyl-hydrazone (H3SAL-NH) exhibits ESIPT behaviour due to proton transfer from the phenolic OH group to the azomethine N atom in the excited state. Through this ESIPT behaviour together with cistrans isomerization of the azomethine group, the free ligand becomes very weakly fluorescent. However, in the presence of Zn2+ and Al3+ the ESIPT and isomerization are blocked due to coordination to the metal ions thereby causing turn on fluorescence for Al3+ and Zn2+. Moreover, Zn2+ can easily be displaced from the [H2SAL-NH–Zn2+] complex by Al3+ thereby enhancing the differential selectivity for Al3+ over Zn2+. This probe was found to be selective for Al3+ over Zn2+ in the presence of Na2H2EDTA, under both intra- and extracellular conditions. The LODs for Zn2+ and Al3+ were determined by 3σ methods and were found to be 3.1 nM and 0.92 nM, respectively. Thus, the differentially selective turn-on fluorescence behaviour of H3SAL-NH for Zn2+ and Al3+ is based on the combined blocking of ESIPT and C[double bond, length as m-dash]N isomerization, and a chelation-enhanced fluorescence (CHEF) effect. The coordination modes of the complexes were investigated through spectroscopic and computational studies. H3SAL-NH also exhibits good photostability and very low cytotoxicity and is useful for fluorescence imaging of Zn2+ and Al3+ ions in live HepG2 cells.

Graphical abstract: ESIPT blocked CHEF based differential dual sensor for Zn2+ and Al3+in a pseudo-aqueous medium with intracellular bio-imaging applications and computational studies

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Publication details

The article was received on 10 Sep 2015, accepted on 01 Dec 2015 and first published on 03 Dec 2015


Article type: Paper
DOI: 10.1039/C5RA18424J
RSC Adv., 2016,6, 1268-1278

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    ESIPT blocked CHEF based differential dual sensor for Zn2+ and Al3+in a pseudo-aqueous medium with intracellular bio-imaging applications and computational studies

    R. Alam, T. Mistri, R. Bhowmick, A. Katarkar, K. Chaudhuri and M. Ali, RSC Adv., 2016, 6, 1268
    DOI: 10.1039/C5RA18424J

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