Selective detection of mercury ions via single and dual signals by silicon-doped carbon quantum dots

Si-CQDs with uniform particle size and good water solubility were synthesised using low-cost citric acid (CA) and aminopropyltriethoxysilane (APTEOS) as precursors. Si-CQDs were used as a novel fluorescent probe for sensitive and selective detection of mercury ions (Hg2+) by fluorescence quenching. Following the optimisation of the experimental conditions, the fluorescence intensity of Si-CQDs was found to be linearly dependent on the Hg2+ concentration ranging from 0.02 to 5.0 & mu;M with the limit of detection as low as 0.015 & mu;M. A fluorescence resonance energy transfer (FRET) effect between Si-CQDs and Rhodamine B (RhB) was also observed, and it was found that Si-CQDs can be used as fluorescence donors and RhB as fluorescence receptors. On this basis, a ratiometric fluorescent probe (Si-CQDs/RhB) was constructed for Hg2+ detection. When the Hg2+ concentration was 1.0-80.0 & mu;M, the fluorescence intensity ratio (I-540nm/I-440nm) of Si-CQDs/RhB exhibited a good linear relationship with Hg2+ concentration and the detection limit was 0.6 & mu;M. A wide range of Hg2+ detection was ultimately achieved in real samples.