A facile and rapid fluorescent sensing system for palladium ion (Pd2+) and iron ion (Fe3+) has been established based on carbon dots (CDs) using fresh Momordica charantia as the sole precursor via a one‐step hydrothermal treatment. The added Pd2+ and Fe3+ lead to the fluorescence quenching of CDs due to the static quenching effect (SQE). Such fluorescence response can be quenched by Pd2+ and Fe3+ in the linear ranges of 0–325 μM and 0–150 μM. Meanwhile, this sensing system exhibits good selectivity and sensitivity toward Pd2+ and Fe3+ over other analytes with low detection limits of 0.348 μM and 0.175 μM, respectively. Furthermore, the proposed sensing system has been successfully used for Pd2+ and Fe3+ in tap and environmental water and the recoveries range from 96.25 % to 107.3 %. The results mentioned above demonstrate its great promise as a practical platform for Pd2+ and Fe3+ sensing in aqueous media.

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The level of Al3+ is an indicator for many diseases of human, so the selective and sensitive detection of Al3+ is critically important for human health. In this study, a simple and sensitive ratiometric fluorescent sensor for the detection of Al3+ in the aqueous solution was developed based on the inner filter effect (IFE) and static quenching effect (SQE) of the carbon dots (CDs) and fluorescein. The preparation of CDs was facile and green by a one‐step hydrothermal method, using the fresh Melia azedarach L. leaves as the raw material. The fluorescence of CDs at 430 nm was quenched owing to the combination of IFE and SQE while the fluorescence of fluorescein at 515 nm was enhanced upon adding fluorescein. Meanwhile, fluorescein interacted with Al3+ resulting in the quenching of the fluorescence of fluorescein at 515 nm and the recovering of the fluorescence of CDs at 430 nm with the addition of Al3+ into the system of CDs‐fluorescein. The linear range of the ratiometric fluorescent sensor (F515/F430) for Al3+ detection was 0–500 μM and the detection limit was 0.216 μM. Importantly, it had been successfully applied in the detection of Al3+ in the drinking and environmental water.