Simple hydrothermal preparation of carbon nanodots and their application in colorimetric and fluorimetric detection of mercury ions

Abstract

The present article reports on the one-step rapid green synthesis of water-soluble, fluorescent carbon nanodots (C-dots) with a quantum yield of 8.9%. Compared with previous hydrothermal methods, the proposed method is performed at lower temperature and results in larger size (20–30 nm) C-dots. We observed that UV-Vis absorbance at 302 nm of C-dots shows a significant linear correlation with the concentration of Hg²⁺ added, which indicates that the as-prepared carbon dots could act as a colorimetric probe for Hg²⁺. The linear range of this colorimetric probe is 1.0 × 10⁻⁹–7.0 × 10⁻⁷ mol L⁻¹ and the detection limit is 5.7 × 10⁻¹⁰ mol L⁻¹. Simultaneously, the fluorescence of the C-dots in pH 5.0 phosphate buffer solution can be dramatically quenched by Hg²⁺, whereas it is nearly unaffected by other metal ions. A good linear relationship exists between the quenching efficiency (F₀/F) and the concentration of Hg²⁺ in the range of 7.0 × 10⁻⁹–7.0 × 10⁻⁷ mol L⁻¹ with a detection limit (3σ) of 5.5 × 10⁻¹⁰ mol L⁻¹. This dual probe for Hg²⁺ exhibits excellent performance in polluted tap water samples analysis, suggesting its promising application in the future.