I have tried to separate the chemical mode from electromagnetic mode using a spacer layer of polyvinylpyridine, but found that intensity of all the peaks are reduced equally in case of a Surface Enhanced Raman Scattering (SERS) spectra. The metal was functionalized by aromatic thiol. In another try, I have used halides before functionalization by thiol to increase the intensity of chemical modes, but the intensity reduced for all the peaks which is contrary to my expectation. The nanosubstrate is on the solid surface. SERS spectrum was recorded in solid state. Please suggest me to explain this behavior. Or suggest where I can find out the way to separate the CM from EM.