Figure 3.

SERS analysis of Cu(PAR)₂ and methylene blue. SERS spectra (employing the 532-nm laser line) of methylene blue adsorbed on (curve A) the rapid PEG-reduced (peg_r), (curve B) the hydroxylamine-reduced (hya), and (curve C) the citrate-reduced (cit) silver sol and of Cu(PAR)₂ adsorbed on (curve D) the rapid PEG-reduced (peg_r), (curve E) the dropwise PEG-reduced (peg_s), (curve F) the hydroxylamine-reduced (hya), and (curve G) the citrate-reduced (cit) silver sol. The spectra were shifted for clarity. Specific vibrational peaks of analyte molecules are clearly visible for all three classes of silver colloids.