Optical detection of Al(III) and Cu(II) ions in an aqueous medium by using a simple probe possessing O,O-donor moiety

Abstract

A commercially available probe (RS) has been reported for instantaneous selective colorimetric detection of Cu(II) and fluorescent detection of Al(III) ions in H₂O:DMSO (90:10% v/v) medium. The probe displays a color change from pale yellow (λ_ab 352 nm) to yellowish-green (λ_ab 411 nm) with Cu(II) and a change in emission from green (λ_ex 340 nm; λ_em 522 nm) to bluish-green (λ_em 489 nm) with Al(III) ions. The optical detection of these metal ions by RS is via the formation of tetragonally distorted octahedral RS-Cu(II) and tetrahedral RS-Al(III) complexes as evidenced from the results of UV-Vis, ²⁷Al & ¹H NMR, HRMS, EPR and thermal analysis studies. Job’s method indicates that the stoichiometry of both these complexes is 1:1. The probe's corresponding optical changes are particular for Cu(II) and Al(III) ions in the presence of other metal ions. RS displays high selectivity to these ions in a wide pH range. The limits of the detection of Cu(II) and Al(III) are as low as 66 nM and 0.83 µM, respectively. Further, RS could be applied as a fluorescent probe for observing Al(III) ions in living HeLa cells by carrying out cell image studies.

Graphical Abstract

Keywords:

• Copper sensor
• aluminum sensor
• fluorescence
• colorimetric
• complex formation

Acknowledgment

The authors thank the NMR facility established in the Department of Chemistry under the DST-FIST Scheme. One of the authors (Prof. KPE) acknowledges the University Grants Commission, New Delhi, for financial support in the form of BSR, Mid-Career Award.