Fig. 3: Aligned-unaligned excitation-detection experiments in monolayer MoS2.
From: Spatially resolved photocatalytic active sites and quantum efficiency in a 2D semiconductor
Illustrations depicting the measurements performed with the nanoprobe when the excitation – detection was unaligned (a), or aligned (b). Photoactivity (ΔI) measured far from the light excitation spot (c), and aligned with the light excitation spot (d), while the ML-MoS2 was excited under chopped light (5 s; increased light power at every pulse; transition C, 455 nm, purple; exciton B, 595 nm, yellow; exciton A, 660 nm, dark red). The probe positions correspond to the respective inset image, showing the monolayer (ML-) MoS2 flake (white dashed triangle), the position of the light excitation spot (black dashed circle), and the ultramicroelectrode (UME) position (red dashed circle). e Scheme representing the spatial distribution of the photo-redox processes detected at the UME in ML-MoS2 when excited at a fixed position, with the corresponding photogenerated charge carriers (oxidation: holes, blue region; reduction: electrons, red region). Conditions: rT = 0.1 µm, RG = 25, rlight = 5 µm and Z = 5 µm for (c), (d). The experiments were performed in aqueous solutions containing 1 mM FcDM and 0.1 M KCl. FcDM+ is present in low concentration due to the redox couple equilibrium in water (Fig. S7). UME: ultra-microelectrode.
