SERS spectra. (a) SERS spectrum of 10−6 M CuTMpyP4 adsorbed on the top side of porous copper membrane. (b, c) Raman spectra of 10−6 M CuTMpyP4 deposited from water and solution on bottom side of Cu membrane and porous silicon substrate, respectively. Laser plasma bands are marked by asterisks. Excitation wavelength was 441.6 nm.