A novel rhodamine-chromone Schiff-base as turn-on fluorescent probe for the detection of Zn(II) and Fe(III) in different solutions

An easily available Schiff-base as a dual probe (L) was designed and synthesized through a simple condensation reaction between chromone and rhodamine B hydrazide. This probe L showed obvious responses to Zn2+ and Fe3+ in different solutions. When excited at a wavelength of 420 nm, this probe L displayed a significant fluorescence enhancement at 490 nm with addition of Zn2+ in EtOH/HEPES buffer solution (9/1, 20.0 mu M HEPES, pH 7.24) because of the inhibition of the photo-induced electron transfer (PET) process and the chelation-enhanced fluorescence (CHEF) effect. Whereas, at different excitation and emission wavelengths, this probe L exhibited high selectivity towards Fe3+ due to ring-opening mechanism of the rhodamine spirolactam in DMSO/EtOH (2/3, V/V) accompanied by a change in color, which could be easily observed by the naked eye. Additionally, the detection limits of probe L for sensing Zn2+ and Fe3+ were both as low as 10(-7) M, and this probe L had a great utility for rapid detection of Zn2+ and Al3+ by simple test strips.