Ratiometric fluorescence and visual imaging detection of dopamine based on carbon dots/copper nanoclusters dual-emitting nanohybrids

In this article, blue-emitting carbon dots (CDs) were prepared via hydrothermal treatment of sodium citrate and NH 4 HCO 3 , and then combined with 3-aminophenylboronic acid (APBA) to prepare APBA modified-CDs. APBA acted as the receptor of dopamine (DA). Using bovine serum albumin (BSA) as a stabilizer and N 2 H 4 ·H 2 O as a reducing reagent, BSA-stabilized and red-emitting copper nanoclusters (CuNCs) were prepared. By carbodiimide-activated coupling, novel nanohybrids consisting of CDs and CuNCs were constructed and exhibited dual-emitting fluorescence (FL). In the presence of DA, marked FL (at 440   nm) quenching of nanohybrids was detected. Specific coupling interactions between boric acid of APBA and cis-glycol of DA induced the combination of DA and APBA on the surface of CDs. As a superior electron receptor, DA triggered the electron transfer from CDs to DA, resulting in the FL quenching of CDs in nanohybrids. The FL (at 640   nm) of CuNCs in nanohybrids was almost unchanged after the addition of DA, and so further used for a reference FL to develop a novel ratiometric FL probe for DA detection. In addition to high sensitivity and selectivity, superior analytical performances of this probe were confirmed in applications, including dual-signal FL sensing of DA and naked-eye visual FL imaging of DA in aqueous solution and on filter paper.