Dual-channel Fe3+ detection based on carbon dots and a pH-driven “on–off–on” fluorescent sensor

To achieve highly sensitive and selective detection of ferric ions (Fe 3+ ), a dual-channel fluorescent sensing platform based on carbon dots (BV-CDs) was developed, enabling both quantitative fluorescence analysis and visual recognition. The BV-CDs prepared via a one-step hydrothermal method exhibited excellent optical properties, with a quantum yield of 25.6% in N , N -dimethylformamide (DMF). Fe 3+ can specifically quench the fluorescence of BV-CDs, and the response is not disturbed in the presence of a variety of coexisting metal ions and amino acids. At the same time, the system can realize Fe 3+ visual recognition through color change, and a smart phone sensor platform is constructed. In addition, the fluorescence response of the system is stable in the range of pH 2–11, and the fluorescence is restored at pH 12, forming an ‘on-off-on ‘regulation mode. Quantitative analysis showed a good linear correlation between the fluorescence intensity ratio and Fe 3+ concentration within the range of 0–150 μM, with a detection limit of 0.17 μM. For real water samples, the method achieved recoveries of 93.9–104.3% with relative standard deviations (RSDs) below 2.04%, confirming its accuracy and reliability. This study provides a simple and efficient strategy for rapid and sensitive Fe 3+ detection.