One-Pot Hydrothermal Synthesis of Carbon Dots as Fluorescent Probes for the Determination of Mercuric and Hypochlorite Ions

• Main Authors: Hsin Lee, Yen-Chang Su, Hsiang-Hao Tang, Yu-Sheng Lee, Jan-Yee Lee, Cho-Chun Hu, Tai-Chia Chiu
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Nanomaterials
• Subjects: carbon dots; fluorescence quenching; hydrothermal; hypochlorite ion; mercuric ion; water samples
• Online Access: https://www.mdpi.com/2079-4991/11/7/1831

Nitrogen and sulfur codoped carbon dots (NSCDs) were synthesized via a one-pot hydrothermal method, and citric acid, ethylenediamine, and methyl blue were used as precursors. The obtained NSCDs were spherical with an average size of 1.86 nm. The fluorescence emission spectra of the NSCDs were excitation independent and emitted blue fluorescence at 440 nm with an excitation wavelength at 350 nm. The quantum yield of the NSCDs was calculated to be 68.0%. The NSCDs could be constructed as fluorescent probes for highly selective and sensitive sensing mercuric (Hg²⁺) and hypochlorite (ClO⁻) ions. As the addition of Hg²⁺ or ClO⁻ ions to the NSCDs, the fluorescence intensity was effectively quenched due to dynamic quenching. Under the optimal conditions, the linear response of the fluorescence intensity ranged from 0.7 μM to 15 μM with a detection limit of 0.54 μM and from 0.3 μM to 5.0 μM with a limit of detection of 0.29 μM for Hg²⁺ and ClO⁻ ions, respectively. Finally, the proposed method was successfully used for quantifying Hg²⁺ and ClO⁻ ions in spiked tap water samples.