Fig. 2. Hg²⁺ detection of SPR sensor based on GB-rich 1L WS₂ film and 1L WS₂ single crystal.

a SPR spectra at Hg²⁺ concentrations ranging from 10⁻¹⁸ M to 10⁻¹¹ M. b Corresponding extracted resonance angle shifts of ∆θ. For the prepared 10⁻¹⁸ M Hg²⁺ concentration, the x-axis error bar was estimated to be ±0.1 × 10⁻¹⁸ M (“Methods”). At each Hg²⁺ concentration, the collection of data was performed for 5 times, from which the average value of Δθ and y-error bar were determined.