Nitrogen, boron-doped Ti₃C₂ MXene quantum dot-based ratiometric fluorescence sensing platform for point-of-care...

The Ti₃C₂ MXene quantum dots (Ti₃C₂ MQDs) derived from Ti₃C₂ MXene have received much attention because of their remarkable advantages in biosensing. Nevertheless, the functionalization of Ti₃C₂ MQDs to improve their properties is just in its infant stage. Herein, we firstly synthesized nitrogen and boron co-doped Ti₃C₂ MQDs (N, B-Ti₃C₂ MQDs) with good water solubility, strong stability, and high optical characteristics. The N, B-Ti₃C₂ MQDs exhibit excitation wavelength-dependent blue photoluminescence with optimal excitation/emission peaks at 335/439 nm. Nowadays, the development of fast and real-time detection of tetracycline (TC) in animal derived food is very essential. In this work, a novel point-of-care testing (POCT) platform was established based on ratiometric fluorescence method using N, B-Ti₃C₂ MQDs coupled with Eu³⁺. Upon addition of TC in the Eu³⁺/N, B-MQDs system, blue fluorescence emission of N, B-Ti₃C₂ MQDs was quenched and red fluorescence emission of Eu³⁺ was enhanced gradually, which was ascribed to the synergistic inner filter effect and antenna effect. Moreover, we prepared test papers with N, B-Ti₃C₂ MQDs and Eu³⁺ for TC detection based on the change of fluorescence color, which could be recognized by color recognizer app installed in the smartphone. Therefore, great promise for POCT of TC is given with the merits of simplicity and visible detection possibility. The proposed method demonstrated a low detection limit of 20 nM. Application of the platform for TC quantification in milk samples opened a novel means for the potential use of N, B-Ti₃C₂ MQDs in food safety.