Naked-eye fluorescence sensing of aluminum using a bis(rhodamine)-phenyl hybrid for environmental monitoring and in vitro/in vivo bioimaging

A new probe, Rh-Ph-Rh, featuring two rhodamine groups attached to a phenyl ring, was developed. This hybrid compound serves multiple purposes: it turns on with a strong fluorescent signal in the presence of aluminum ions (Al3+) and can detect them at concentrations as low as 358 nM. When both Al3+ and cyanide ions (CN⁻) are present, fluorescence is quenched, enabling sensitive detection of CN¯ (619 nM). Beyond sensing, Rh-Ph-Rh can act as a molecular “memory” unit and displays notable electrical properties. Practical applications include rapid detection of Al3+ and CN⁻ ions using filter paper strips and smartphone-based RGB colorimetric analysis. In biological assays using MCF-7 cancer cells, Rh-Ph-Rh exhibited anticancer effects that increased with higher doses (IC50 = 31.357 µg/mL), enabling fluorescence-based imaging of aluminum ions within cells. Tests in live Daphnia magna (water fleas) confirmed that a visible green glow could selectively identify Al3+. Taken together, these results suggest that Rh-Ph-Rh could be a valuable tool for environmental monitoring, biological imaging, and cancer treatment and diagnosis.