Fig. 6. Surface activities between semiconductors and probe molecules. (a) Total electron density distributions of probe molecules chemically adsorbed onto the surface of amorphous ZnO (a-ZnO) and crystalline ZnO (c-ZnO). Reproduced with permission from ref. 65. Copyright 2017, John Wiley and Sons. (b) Brønsted and Lewis acid sites present on the H₂SO₄-treated TiO₂ surface. Reproduced with permission from ref. 98. Copyright 2015, the Royal Society of Chemistry. (c) Optical and SERS mapping image of R6G (1362 cm⁻¹) on Li-exfoliated MoS₂. Adapted with permission from ref. 101. Copyright 2017, the Royal Society of Chemistry. (d) Raman spectrum of monolayer Janus MoSSe exhibiting a strong out-of-plane vibration. Reproduced with permission from ref. 102. Copyright 2020, the Royal Society of Chemistry.