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Sequential recognition of La3+ and CN ions using isophthalic dihydrazide derivative via aggregation induced enhanced emission (AIEE): a fluorescence relay enhancement in aqueous medium

Vaishali Yadav and Vimal K. Bhardwaj

Department of Chemistry, Dr B R Ambedkar National Institute of Technology, Jalandhar, India



Received: 3 October 2022  Accepted: 12 December 2022


An isophthalic dihydrazide based Schiff base receptor H2L has been explored for the sequential sensing of La3+ and CN ions in aqueous medium with fluorescence relay enhancement, having a detection limit of 5.90 × 10–8 M and 4.47 × 10–7 M, respectively. The fluorescent aggregates of H2L have been synthesized by re-precipitation method to overcome the weak fluorescence property of La3+ion via aggregation induced enhanced emission (AIEE) mechanism. The absorption and emission sensing studies of receptor H2L have been performed towards various metal ions such as Th3+, Ce3+, Eu3+, Ho3+, Pr3+, Cd2+, Hg2+,Co2+, Zn2+, Cu2+, Ni2+ as their nitrate salts in 20 mM N-(2-hydroxyethyl)-piperazine-N′-ethanesulfonic acid (HEPES) buffer solution at neutral pH in H2O–DMSO (95%, v/v). The addition of La3+ ion solution to H2L aggregates results in a remarkable emission enhancement at 748 nm with a detection limit of 5.90 × 10–8 M. The aggregates of resultant H2L-La complex have also been investigated for the sensing of different anions such as F, Cl, Br, SO4, H2PO4, N3, AcO, I, NO3 in H2O–DMSO (60%, v/v) at neutral pH. However, the presence of CN ion to H2L-La complex solution further exhibits a fluorescence relay enhancement with 4.47 × 10–7 M limit of detection. The observed behaviour is due to chelation enhanced fluorescence (CHEF) by metal ion and effective interference in the photoinduced electron transfer (PET) quenching by anion. The interaction studies of receptor with La3+ and resultant H2L-La complex with CN ion are supported by mass spectrometry. It is the first report on fluorescence relay enhancement for the sequential recognition of La3+ and CNions.

Keywords: Chelation enhanced fluorescence (CHEF); Fluorescent sensors; Imine receptor; Excited state intramolecular proton transfer (ESIPT); Nano-aggregates

Full paper is available at

DOI: 10.1007/s11696-022-02633-y


Chemical Papers 77 (5) 2425–2435 (2023)

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