A sensitive “on-off-on” fluorescent probe for sequential Cu2+/S2− detection in actual water samples and living cells

Aquatic organism is far less tolerant to Cu2+ than that of mammals, and the excessive Cu2+ can also be harmful to human by bioconcentration. Herein, a fluorescent probe (DPA-SAA) that can be easily synthesized was developed for detecting traces of Cu2+ in actual aqueous environment and cells. The experimental and theoretical results showed that the fluorescence of DPA-SAA could be evidently quenched by only 1% equivalent of Cu2+. The limit of detection (LOD) was calculated to be 0.66 nM, which is far below the Chinese standard of fishery water quality (157 nM). Simultaneously, the Cu2+ of complex DPA-SAA/Cu2+ could be captured by S2−, thus realizing sequential S2− detection with a low LOD of 13.93 nM. Moreover, DPA-SAA was proved qualified for Cu2+ detection in actual water samples with good recovery, and sequential Cu2+/S2− sensing in living cells.