Carbon quantum dots (CQDs) with good biosafety can be doped with metals to construct multimodal imaging probes with a wide range of applications in fluorescence and molecular imaging. However, developing...

This work reports a simple, low cost and eco-friendly one-step hydrothermal method to obtain Si- and N-doped carbon quantum dots (Si-N-CQDs) using only citric acid and (3-aminopropyl) trimethoxysilane. These codoped Si-N-CQDs demonstrated 0D spherical morphology and an average size of [Formula: see text]2.54[Formula: see text]nm as well as good solubility in water and high quantum yield equal to 14.3%. Fluorescence emission of these Si-N-CQDs was quenched selectively under the presence of Fe[Formula: see text]. Based on this property, we developed a very sensitive sensor capable of detecting Fe[Formula: see text] up to 400[Formula: see text][Formula: see text]M concentration with a 3.14[Formula: see text][Formula: see text]M detection limit. This sensor was used for Fe[Formula: see text] detection in real tap and lake water and demonstrated satisfactory recovery equal to 102.3–108.0% and 103.5–108.5%, respectively. Photocatalytic activity of our Si-N-CQDs was demonstrated using methylene blue (MB) organic dye. The degradation rate of MB under visible light irradiation increased 2.7 times under the presence of Si-N-CQDs within 60[Formula: see text]min. Such excellent performance was attributed to very efficient light absorption of Si-N-CQDs as well as excellent electron transfer and separation of photogenerated charge carriers.