Dual sensing performance of a rhodamine-derived scaffold for the determination of Cu2+ and Ce4+ in aqueous media

•The dual mode sensor R6G-CB for Cu2+ and Ce4+ has developed based on rhodamine 6G-carbazole derivative.•The dual sensing mechanisms were proposed for Cu2+ (CHEF) and Ce4+ (TBET).•The R6G-CB-Cu2+ complex and R6G-CB-Ce4+ adduct structures were confirmed via ESI-Mass, FT-IR and DFT calculations.•Reversible “Turn-Off” fluorescence was demonstrated using EDTA binding studies in organic-aqueous media.•R6G-CB sensing capabilities developed as practical applications for its low cost filter paper strip systems. A rhodamine 6G-based probe bearing a carbazole unit (R6G-CB) was developed as a fluorescent chelation agent for Cu2+ and a chemodosimeter for Ce4+ in acetonitrile:aqueous (5:5, v/v) media. The R6G-CB chemosensor exhibited selectivity toward Cu2+ ions over other metal cations by showing “off-on”-type changes in its absorption and emission spectra, which were attributed to the transformation of the non-fluorescent and colorless spirolactam derivative to the ring-opened, fluorescent, pink amide. The Cu2+-induced chelation-enhanced fluorescence (CHEF) is associated with the spirolactam ring opening of the rhodamine unit. This R6G-CB chemosensor also showed a fast response (