A new lipophilic cationic rhodamine-based chemosensor for detection of Al (III)/Cu(II) and intracellular pH change and its application as a smartphone-assisted sensor in water sample analysis

A new probe, RTPP was prepared by condensation of rhodamine B hydrazide with (3-formyl-4-hydroxybenzyl) triphenylphosphonium chloride. The structure of sensor RTPP was elucidated using spectroscopic methods and single crystal X-ray diffraction. Colourless and non-fluorescence sensor RTPP solution turns pink in the presence of Cu2+ and showed orange fluorescence enhancement in the presence of Al3+. Cation recognition performance and binding mechanisms of the probe were studied through UV, fluorescence, IR, MS, and NMR spectroscopic studies; where the results revealed that sensor RTPP has a high affinity towards Al3+/Cu2+ with the limit of detection down to at least 10-7 M. The developed system was applicable for tracing Cu2+ through colorimetric method in two selected water samples with satisfactory results. More significantly, "naked-eye" detection of Cu2+ using RTPP has been effectively incorporated with a smartphone RGBColorDetector application to make it suitable for on-site qualitative and quantitative colorimetric investigation. In addition, RTPP can act as a sensor for detecting acidic pH change in HCT 116 human colorectal carcinoma cell line through fluorescence response.