Ratiometric Fluorescence Sensor for On-Off Detection Vitamin B2 and Hexavalent Chromium Based on Silicon Quantum Dots

Silicon quantum dots (SiQDs) function as ratiometric fluorescent sensors for detecting Vitamin B₂ (VB₂) and Cr⁶⁺, exhibiting an on-off response. Upon introducing VB₂ to the SiQDs solution, the blue emission peak of SiQDs at 445 nm gradually decreases, while the yellow emission peak at 520 nm, associated with VB₂, increases gradually. In the presence of Cr⁶⁺, both the blue and yellow fluorescence diminish. Through the utilization of Fluorescence Resonance Energy Transfer (FRET), we developed ratiometric fluorescent sensors that displayed specificity and sensitivity in detecting VB₂ and Cr⁶⁺. The linear detection ranges for VB₂ and Cr⁶⁺ were found to be 0.2 µM to 0.8 µM and 2 µM to 18 µM, respectively. Limit of detection (LOD) was determined to be 1.43 nM for VB₂ and 0.75 µM for Cr⁶⁺ (based on 3 s/k, LOD). With a short response time, good selectivity, and resistance to interference, the recovery rate in lake water ranges from 84.8 to 98.0%.