Figure 4.

The proposed SERS enhancement mechanisms of capillary effect, lattice strain, and sulfur vacancies for SnS₂ microspheres

(A) Schematic diagram of combining nano-canyon morphology and hydrophilicity to induce the capillary effect.

(B) Raman mapping image with 72 × 48 μm² region of 10⁻¹⁰ M MeB on SnS₂ microspheres.

(C) Schematic diagram of immersing and dropping MeB molecules to explore physical enrichment.

(D) Raman spectra and SERS intensity of immersing and dropping 10⁻⁷ M MeB on SnS₂ microspheres.

(E) Schematic diagram of hexagonal SnS₂ crystal with the tensile strain in three periodic directions (x, y, and z axis).

(F) Bandgap of hexagonal SnS₂ crystal with 0%–20% tensile strain.

(G) Schematic diagram of charge transfers between MeB molecules and the hexagonal SnS₂ crystal with 0%–20% tensile strain.

(H) Band structure of SnS₂ crystal with sulfur vacancies.

(I) Density of states of Sn p orbitals in the perfect SnS₂ crystal and SnS₂ crystal with sulfur vacancies.

(J) Schematic diagram of charge transfers between MeB molecules and the hexagonal SnS₂ crystal with S vacancies.