A highly selective colorimetric, absorption and fluorescence probe for Al(3+)detection based on a new Schiff base compound

Aluminum is the most affluent metal element in many living organisms. However, excessive Al3+ is considered to be harmful for biological activities. In the past decades, many of sensing techniques and probes were widely developed for Al3+ detection. But the low sensitivity and nonquantitative detection still need to be improved. Multi-signal probes may sweep away the obstacle. In this article, a Schiff base based on carbazole and triphenylamine as a multi-signal (colorimetric, absorption and fluorescence) probe was successfully designed, prepared and characterized. This newly designed probe, 4, 4-(9-ethyl-carbazol) methylenimine-triphenylamine(L), exhibited a "turn-on" fluorescence mode for the qualitative and quantitative detection of Al3+. The color of L changes from light yellow to orange, and the limit of detection (LOD) is 2 x 10(-6) mol/L. The LODs by absorption and fluorescence methods were found to be 6.7 x 10(-7) mol/L and 6.3 x 10(-8) mol/L, respectively. The data of the Job's plot, H-1 NMR and LC-MS imply that L will be hydrolyzed in the presence of Al3+, and a new complex is formed based on the carbazole amide molecule and Al3+ to push the "turn-on" fluorescence. Furthermore, the fluorescence image of HeLa cells facilitating intracellular detection of Al3+ was successfully captured by the probe of L.