Fig. 1. Schematic representation of a Hg²⁺ sensor based on A15-ssDNA AuNCs

Fig. 2. (a) TEM images of DNA-AuNCs; (b) The Fluorescence excitation and emission spectra of AuNCs;(c) Fluorescence emission spectra of AuNCs under different conditions
a: AuNCs; b: AuNCs+Hg²⁺

Fig. 3. (a) Effects of the pH in the absence (a) and presence of Hg²⁺ (b); (b) Effects of the reaction time

Fig. 4. (a) Fluorescence spectra with different concentration of Hg²⁺ (the concentration from up to down were 0, 0.01, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 2, 5, 10, 20, 50 μmol·L^-1); (b) Plot of fluorescence intensity of the AuNCs versus Hg²⁺ concentration. Inset: relative fluorescence intensity versus Hg²⁺ concentration; (c) Selectivity analysis of the sensor for Hg²⁺. The concentration of Hg²⁺ and other interferences are 20 and 50 μmol·L^-1, respectively

Table 1. Recovery of the biosensor for determination of Hg²⁺ in tap water samples