Sustainable red beetroot-derived synthesis of n-doped carbon dots for ratiometric detection of doxorubicin and portable visual sensing platform based on 3D microfluidics paper-based analytical device

It is of great significance to develop fluorescence sensors that are both high-performance and environmentally friendly for on-site monitoring of doxorubicin (DXR), which plays a crucial role in protecting the ecological environment and human health. In this work, a rapid and ultrasensitive fluorescence sensing strategy based on red beetroot-derived carbon dots (N-CDs) is proposed for the determination of DXR. N-CDs are successfully prepared through facile hydrothermal treatment using red beetroot as the sole raw material, which have a cyan emission at 496 nm under the 416 nm excitation. Further, the proposed N-CDs serve as a sensitive fluorescent probe for the ratiometric determination of DXR owing to the occurrence of fluorescence resonance energy transfer effect (FRET). The detection limit (LOD) of DXR is calculated as 78.3 nM within the good linear range of 3-35 μM. Simultaneously, to achieve precise on-site analysis, a real-time fluorescent assay platform is proposed, which combines the portability of 3D microfluidics paper-based analytical device (3D-µPAD) with the analysis capability of smartphone. This platform enables the real-time monitoring of DXR in real samples with acceptable recoveries (98.9 %-103.2 %), presenting the promising application for CDs in on-site detection and drug safety supervision.