Fluorescent carbon dots from Shewanella oneidensis MR–1 for Hg2+ and tetracycline detection and selective fluorescence imaging of Gram–positive bacteria

Mercury ion (Hg2+) and tetracycline are environmental pollutants that endanger the ecological environment and human health. In this work, fluorescent carbon dots (denoted [email protected]–1) were synthesized via a one–step hydrothermal process using Shewanella oneidensis MR–1. The prepared [email protected]–1 detected Hg2+ and tetracycline in real water samples. The fluorescence quenching efficiency showed a good linear relationship between the range of 0–9.38 μg·mL–1 (R2 = 0.997) and 0–7.5 μg·mL–1 (R2 = 0.995), and the limits of detection were 0.43 μg·mL−1 and 0.21 μg·mL−1 for Hg2+ and tetracycline, respectively. The mechanism of fluorescence quenching can be attributed to the internal filtration effect (IFE) for tetracycline, whereas dynamic quenching (DQ), static quenching (SQ), and the IFE contribute to the Hg2+ detection. Additionally, the obtained [email protected]–1 has been shown to selectively interact with Gram–positive bacteria and distinguish Gram–positive bacteria from Gram–negative bacteria. The multifunctionality of [email protected]–1 can be useful in various applications.