A julolidine-chalcone-based fluorescent probe for detection of Al3+ in real water sample and cell imaging.

A fluorescent probe 1 based on julolidine-chalcone derivative, which can specifically recognize aluminum ion with high selectivity and anti-interference, was developed. Probe 1 has good fluorescence stability and can detect Al3+ with turn-on fluorescence in a wide pH range of 4.0-9.0. The probe has good repeatability for the detection of Al3+ and fluorescence turn-on and off can be repeated with the alternate Al3+ and EDTA. The sensing mechanism is speculated that Al3+ will coordinate with hydroxyl oxygen and carbonyl oxygen on the probe through in situ 1H NMR and HRMS combing with Job's plot. The probe can also detect Al3+ in actual water samples and applied to monitor Al3+ in biological system.

Fluorescent N-functionalized carbon nanodots from carboxymethylcellulose for sensing of high-valence metal ions and cell imaging.

A convenient and sensitive reversible-fluorescence sensing platform for accurate monitoring of high-valence metal ions is still very challenging. As a green kind of fluorescent carbon nanomaterials, carbon dots (CDs) have captured considerable attention because of the stable fluorescence property and low cost. Herein, we fabricated a type of nitrogen-functionalized carbon dots (N-CDs) from CMC as a fluorescent reversible sensing platform for detecting various high-valence metal ions. N-CDs with a mean size of 2.3 nm were obtained and possessed 22.9% quantum yields (QY). A label-free fluorescent probe for detection of high-valence metal ions (Fe3+, Cr6+, Mn7+) was established via the fluorescence quenching response. Among them, the detection limit (LOD) toward Fe3+ ions reached 0.8 µM. We have explored the quenching mechanism of N-CDs to explain the valence state-related electron-transfer fluorescence quenching between high-valence metal ions and N-CDs. Moreover, the valence state-related fluorescence quenching phenomenon of N-CDs in aqueous solution could be effectively recovered by introducing a reducing agent (Ti3+). This "turn off-on" fluorescence recovery system of N-CDs could be applied in different applications covering the selective detection of environmental high-valence metal ions and cellular imaging.