A rhodamine–quinoline type molecular switch as a highly selective sequential sensor for Al³⁺and F⁻in aqueous solution

Abstract

A novel optical rhodamine-quinoline type chemosensor (REQ) was successfully synthesized and characterized as a reversible molecular switch. It displayed high selectivity toward Al 3+ among 19 metal ions and the resultant complex [REQ-Al 3+ ] acted as a sequential chemosensor toward F À among 16 anions in neutral aqueous media (ethanol-water, v/v ¼ 3/7, Tris-HNO 3 , 20 mM, pH 7.0). Moreover, detecting fluoride at concentrations below the maximum contaminant level in drinking water defined by the U. S. Environmental Protection Agency (4.0 mg L À1 , 211 mM) could be achieved with a detection limit (LOD) estimated to be down to 8.0 mM. The reversible ring-open mechanism of the rhodamine spirolactam induced by Al 3+ binding and the 1 : 1 stoichiometric structure between REQ and Al 3+ were adequately supported by Job plot evaluation, optical titration, and 1 H NMR study. Finally, it could be conveniently used for the determination of Al 3+ and F À with the "naked eye" due to the obvious color change of the testing solution, showing its potential practical application.

Rhodamine–naphthalene conjugate as a novel ratiometric fluorescent probe for recognition of Al3+

“…FRET is a distance-dependent interaction between the electronic excited states of two different fluorophores in which excitation is transferred from donor moiety to acceptor moiety without photoemission, the transfer efficiency of the excitation primarily depend on the scope of spectral overlap between donor emission with acceptor absorption and the distance between donor and acceptor [23][24][25][26][27][28][29][30].…”

A new rhodamine-based colorimetric chemosensor for naked-eye detection of Cu 2+ in aqueous solution

“…19,20 Specifically, it is based on spirolactam (colorless and nonfluorescent) to ring-opened amide (color and fluorescent) process utilized for the detection of metal ions. [21][22][23][24][25][26][27][28][29][30][31] Based on this mechanism, our ambition was to design and synthesize a new colormetric probe for detection of Cu 2+ in aqueous media. Herein, we introduce a novel and simple method to prepare rhodamine B-based chemosensor by two steps reaction.…”

A novel ratiometric fluorescent probe for detection of Fe3+ by rhodamine–quinoline conjugate

“…In order to explain the phenomenon, Based on the above experiments and some reported fluorescent probes which shared some similarities to HL [40][41][42][43][44][45][46][47][48], the sensing mechanism is schematically illustrated in Scheme 2. …”