A fluorescence and colorimetric bifunctional probe for recognition of Al3+ and Cu2+ and its applications in cells and environmental water systems

A highly sensitive bifunctional probe (1) for Al3+ and Cu2+ by the reaction of 2-hydroxyl-1-naphthalene formaldehyde with indole-3-formyl hydrazine was synthesized. In THF-H2O (v/v = 3:7) solution, 1 only shows fluorescence enhanced recognition for Al3+ in 17 common metal ions, which shows that 1 can be used as a highly selective fluorescence enhancement probe for Al3+. When the concentration of Al3+ is 20.0 µM (1.0 equivalent), the fluorescence intensity of 1 is increased by 195 times, and the detection limit of 1 for Al3+ is calculated to be 3.8 nM, which shows that 1 is fluorescence probe for Al3+ with an ultra-high sensitivity. Trace Al3+ (For example, the WHO drinking water quality standard 7.4 μM) can be clearly observed by the fluorescence test paper covering 1 through the change of fluorescence color. In addition, the vivo-detection ability of 1 is verified by detected the Al3+ in living GS cells of epinephelus coioides. Furthermore, 1 can also be used as a high selective and sensitive colorimetric probe for Cu2+. In THF-H2O (v/v = 3:7) buffer solution (pH = 7.0), the addition of Cu2+ results in a 69 nm red shift in the UV–visible absorption spectrum of 1 solution, causing the color of 1 solution to change from colorless to yellow. In addition, 1 shows a low detection limit of 39.3 nM, a fast response time, excellent recyclability and anti-interference for Cu2+. Therefore, 1 can be used for fluorescence detection of Cu2+ in environmental water systems.