Toward a highly sensitive and selective indole-rhodamine-based light-up probe for Hg2+ and its application in living cells

•A novel light-up fluorescent probe (L1) based on indole derivative and Rhodamine fluorophore for Hg2+ species was developed.•The probe L1 can show a linear response to Hg2+ with high sensitivity and selectivity, and its detection limit was 5.0×10−8M.•Futhermore, probe L1 can be successfully applied to monitor Hg2+ species in living MCF-7 cells by fluorescence imaging.