Fig. 4. Surface diffusion dynamics of fluorescein on 2D layered InSe.
(A) Single-molecular tracks over InSe (Fig. 1) during a short imaging period under 1 μM APF in 1× phosphate-buffered saline (PBS) buffer. The interval between the two data points is 0.1 s. Inset: The zoom-in single-molecular tracks marked by the dash square in (A). Three types of tracks on InSe, showing immobile, mobile, and hybrid trajectories. (B) Apparent diffusion coefficients of fluorescein at different structural features under 1 μM APF in 1× PBS buffer. The error bars are means ± SD (basal plane > 250, edge > 80, wrinkle > 30, and vacancy > 10). (C) Dissociation rate (vd) of direct desorption pathway and desorption-mediated diffusion pathway at different structural features derived from the traces of immobile and mobile fluorescein, respectively. The error bars were calculated as the uncertainty of Gaussian fitting the distribution of dissociation rates from immobile and mobile tracks (Immobile tracks: basal plane, ~100; edge, ~48; wrinkle, ~72; and vacancy, ~290; mobile tracks: basal plane, ~131; edge, ~143; wrinkle, ~54; and vacancy, ~47).