Highly sensitive fluorescence sensor for mercury(II) based on boron- and nitrogen-co-doped graphene quantum dots.

In this work, we invented a new method to synthesize boron- and nitrogen-co-doped graphene quantum dots (B, N-GQDs). This synthesis method was more reliable, simple, and environmentally friendly than the bottom-up methods reported in the current literature that use citric acid or other organic materials as the carbon source. Instead, B, N-GQDs were synthesized from graphene oxide (GO) by a top-down method. The obtained B, N-GQDs showed a bright blue luminescence under a UV lamp at 365 nm, and the absolute photoluminescence quantum yield (PLQY) was 5.13%. Because mercury(II) ions (Hg) are highly toxic and can seriously affect the ecological environment and human health, the detection of low-concentration Hg and the establishment of rapid, accurate and sensitive methods for detecting Hg are of great significance to the activities of life, including those of humans. Therefore, using the good luminescence properties of B, N-GQDs, we invented a new type of fluorescence sensor that can detect Hg. The sensor was very sensitive to Hg, had a good linear relationship in the concentration range of 0.2-1 μM, and exhibited a minimum limit of detection of 6.4 nM. Furthermore, this approach was successfully applied to the detection of Hg in real environmental water samples.