Gadolinium (III) doped carbon dots as dual-mode sensor for the recognition of dopamine hydrochloride and glutamate enantiomers with logic gate operation.

Dopamine hydrochloride (DH) and D-Glutamic acid (D-Glu) are important excitatory neurotransmitters, which are closely relative to central nervous system diseases. Therefore, it is critical to develop the sensitive and facile sensor to precisely monitor the changes of these neurotransmitters. Herein, the gadolinium-doped carbon dots (Gd-CDs) were synthesized by a low-cost and effortless one-pot solvothermal method. These CDs exhibited rapid and reliable fluorescent and colorimetric response signals towards DH and D-Glu. Interestingly, the fluorescence of Gd-CDs could be selectively quenched by DH owing to the fact that the Gd-CDs could coordinate with phenolic hydroxyl groups of DH. Moreover, the quench process was effectively inhibited because the D-Glu competitively coordinated with Gd-CDs-DH system to form a more stable complex. In fluorescence mode, the designed fluorescence sensor possessed an excellent linear relationship for DH in the range from 1 to 10 μM with a low detection limit of 1.26 nM, and the fluorescence could be selectively recovered by D-Glu. In colorimetric manner, DH and D-Glu could be detected by UV-Vis absorption spectrum in the range of 1-15 μM and 1-1.50 mM, respectively. Moreover, the proposed method could not only easily monitor the DH and D-Glu in aqueous solutions as well as mouse serum and human urine samples, but also be employed for detecting DH and D-Glu in cells. Fortunately, the fluorescent and colorimetric dual readout AND logic operation was successfully demonstrated in all-aqueous media. Accordingly, the prepared Gd-CDs hold the potential to become a promising nano-sensor for DH and D-Glu sensing in disease diagnosis areas.