Gadolinium-doped carbon dots as a ratiometric fluorometry and colorimetry dual-mode nano-sensor based on specific chelation for morin detection

Ratiometric fluorometry is an effective method for the quick and sensitive detection of the target objects by reducing the background interference. Carbon dots (Cdots), especially metal-doped carbon dots (M-Cdots), have been extensively developed as ratiometric fluorescence sensors and widely used in materials, chemistry, biomedicine, etc. Herein, we reported a simple and economical one-step hydrothermal method for the synthesis of gadolinium-doped carbon dots (Gd-Cdots) by treating Gd(NO3)3.6H2O and 3-aminothiophenol. The Gd-Cdots afford good fluorescence properties, high T1 relaxivity, and excellent biocompatibility, making them an intrinsical nano-sensor and dual-mode imaging reagent. Based on the unique chelation between Gd and morin, a ratiometric fluorescence nano-sensor for the detection of morin was constructed with the linear range of 0.04–80.0 µM and the detection limit of 25.0 nM. Meanwhile, the color of the Gd-Cdots varied from colorless to deep-yellow, so a colorimetric nano-sensor was developed for morin detection with the linear ranges and the detection limits of 0.04–15.0 µM and 10.5 nM and 15.0–93.0 µM and 21.2 nM, respectively. Compared with the reported fluorescent or colorimetric sensors for the detection of morin, the constructed ratiometric fluorometry and colorimetry nano-sensor based on the Gd-Cdots owns higher sensitivity, lower detection limit, wider linear range, and less background interference. More importantly, the nano-sensor based on the Gd-Cdots was successfully applied to detect morin in human urine and living cells. Overall, the present study shows that the Gd-Cdots possess distinct optical and toxicological properties and are outstanding nanomaterials for the construction of nano-sensors and cellular imaging.