Fig. 2. (A) Plots showing how the Raman profile from 4-ATP varies in the presence of the 2D-WS₂ surface and without any surface. To remove the E_g and A_1g band contributions from WS₂, we subtracted the Raman spectra of 4-ATP with the heterostructure SERS substrate from the spectrum of the heterostructure SERS substrate on its own. (B) Plots showing how the Raman profile from 4-ATP varies in the presence of the 0D-GNP surface and without any surface. (C) Plots showing how the Raman profile from 4-ATP varies in the presence of a heterostructure and GNP surface. (D) Plots showing how the Raman profile from 4-ATP varies with concentration in the presence of the heterostructure. The inserted plot shows how log(intensity at 1078 cm⁻¹) varies with log(concentration of 4-ATP). (E) Plots showing how the Raman profile from Rh-6G varies in the presence of the heterostructure and the GNP surface. (F) A plot showing how log(Raman sensitivity) for 4-ATP varies between heterostructures made in different batches. (G) FDTD simulation data showing the electric field enhancement square (|E|²) profiles for a 0D-GNP assembly containing four nanoparticles.