Urea-type ligand-modified CdSe quantum dots as a fluorescence “turn-on” sensor for CO 3 2− anions

A new fluorescence “turn-on” nanosensor for carbonate determination was reported based on CdSe quantum dots (QDs) modified with thio ligands containing urea groups: N -(5-mercapto-1,3,4-thiadiazol-2-ylcarbamoyl)-2-( o -tolyloxy)acetamide (AASH-CdSe QDs). The AASH-CdSe QDs were prepared through a ligand exchange process and characterized by transmission electron microscopy (TEM), fluorescence spectroscopy, UV-vis spectroscopy and FT-IR spectroscopy. The synthesized AASH-CdSe QDs allowed a selective fluorescence “turn-on” response towards carbonate. Under optimal conditions, the relative fluorescence intensity increases linearly with carbonate concentration in the range 1 × 10 −7 –1 × 10 −4 M with a detection limit of 2.3 × 10 −8 M. A Langmuir-type binding model was highly effective in describing the carbonate concentration dependence of the luminescence intensity of the AASH-CdSe QDs. The possible mechanism was discussed.