A FRET-based rhodamine–benzimidazole conjugate as a Cu2+-selective colorimetric and ratiometric fluorescence probe that functions as a cytoplasm marker

On the basis of fluorescence resonance energy transfer (FRET) from benzimidazole to a rhodamine moiety, a rhodamine–benzimidazole conjugate (RBC) ratiometric fluorescent probe has been designed and synthesized. The RBC selectively binds to Cu2+, showing visually observable changes in absorption and emission behavior, and demonstrates an effective intracellular Cu2+ imaging ability, allowing it to function as a cytoplasm marker.