Isatin-Schiff base functionalized graphene oxide as a highly selective turn-on fluorescent probe for the detection of Pd(II) via photoinduced electron transfer pathway

Hamed Barzinmehr; Maryam Mirza-Aghayan; Maryam Heidarian

doi:10.1016/j.saa.2023.123673

Isatin-Schiff base functionalized graphene oxide as a highly selective turn-on fluorescent probe for the detection of Pd(II) via photoinduced electron transfer pathway

Spectrochim Acta A Mol Biomol Spectrosc. 2024 Mar 15:309:123673. doi: 10.1016/j.saa.2023.123673. Epub 2023 Nov 20.

Authors

Hamed Barzinmehr¹, Maryam Mirza-Aghayan², Maryam Heidarian³

Affiliations

¹ Department of Chemistry and Biochemistry, Baylor University, One Bear Place, Waco, TX 76798-7348, USA; Chemistry and Chemical Engineering Research Center of Iran (CCERCI), P. O. BOX 14335-186, Tehran, Iran.
² Chemistry and Chemical Engineering Research Center of Iran (CCERCI), P. O. BOX 14335-186, Tehran, Iran. Electronic address: m.mirzaaghayan@ccerci.ac.ir.
³ Chemistry and Chemical Engineering Research Center of Iran (CCERCI), P. O. BOX 14335-186, Tehran, Iran.

PMID: 38198996
DOI: 10.1016/j.saa.2023.123673

Abstract

We investigated the use of isatin-Schiff base functionalized graphene oxide (ISBGO) as a selective fluorescent chemosensor for the detection of palladium ions. Selectivity tests indicated that over 23 metal ions tested, ISBGO (λ_ex = 340 nm, λ_em = 504 nm) showed the highest affinity for Pd(II), displaying a 10.1-fold enhancement. Also, interference tests proved that in the presence of both Pd(II) and other metal ions, there was still high fluorescence intensity and no considerable quenching occurred. According to DFT and TD-DFT calculations, photo-induced electron transfer (PET) is responsible for the turn-on response produced by the chemosensor. Coordination of Pd(II) with ISBGO in fact blocks PET from imine nitrogen of 3-iminoindolin-2-one moiety to the benzene ring, which in turn leads to a turn-on response. In addition, Job's plot analysis and Benesi-Hildebrand approach suggest that ISBGO preferably forms a 1:1 complex with Pd(II) with an association constant of 1.020 × 10⁵ M^-1. Moreover, FT-IR spectroscopy and DFT study showed that amide oxygen and imine nitrogen of 3-iminoindolin-2-one moiety acted as binding sites of ISBGO. High sensitivity, fast response, great degree of sensitivity, short life time, low detection limit of 32 nM combined with high association constant (K_f) of 1.020 × 10⁵ M^-1 and increased fluorescence quantum yield (Φ_f) of roughly 1.5-fold in the presence of Pd (II), highlight the role of ISBGO as an excellent probe for sensing Pd(II) in aqueous solution.

Keywords: Chemosensor; Fluorescence; Graphene oxide; PET; Palladium; Turn-on response.