Portable smartphone platform based on Ti₃C₂ MQDs/CDs assembly for ratiometric fluorescence quantitative monitoring of crystal violet

Recent years have witnessed ever-increasing achievements using Ti3C2 MXene quantum dots (Ti3C2 MQDs) and their vital contributions to fluorescent biosensing. However, the applicability and flexibility of most Ti(3)C(2 )MQD-based sensors are limited by their emission of a single blue wavelength. To address this issue, we present a facile strategy to utilize carbon dots as a model to construct a ratiometric fluorescent sensor based on fluorescence resonance energy transfer to quantitatively monitor crystal violet. The fabricated probe exhibited dual emission at 440 and 565 nm, respectively; when introducing crystal violet, the peak at 565 nm was quenched but that at 440 nm remained constant. Further aiming for portable, convenient, and on-site analysis, an innovative smartphone-assisted platform provides promising prospects for future in situ quantitation. This work creates a general strategy for constructing Ti3C2 MQD-based composite fluorescent systems, as well as suggesting great application potential in food security monitoring.