Dual “Turn-On” Fluorescent and Colorimetric Sensing of Permanganate Based on Yellow Carbon Dots

Existing permanganates (MnO₄⁻) sensing methods suffered from the poor selectivity, restricted solubility, and/or less desirable signaling mechanisms (e.g., “turn-off” processes), resulting in the false positive result. In this work, an effective “turn-on” fluorescence method for MnO₄⁻ detection in aqueous media was proposed via yellow fluorescence carbon dots (Y-CDs) with the maximum emission peak of 553 nm. Upon the introduction of MnO₄⁻, the fluorescence of Y-CDs increased significantly due to the enhanced surface passivation degree and intramolecular charge transfer. In the range of 0.1–10 μM, the fluorescence ratio (F/F₀) is proportional to the MnO₄⁻ ions concentration, realizing the “turn-on” fluorescence sensing of MnO₄⁻. On the other hand, utilizing the significant color change of Y-CDs by MnO₄⁻ ions, the colorimetric analysis can also be established for MnO₄⁻ assay. Compared with other probes, the analysis results obtained by bimodal sensing tactics of fluorescent and colorimetric can be mutually verified to improve the reliability and meet the sensing needs of targets in complex environments.