• SER(R)S;
  • silver sol by hydrazine reduction;
  • induced particle aggregation;
  • Nile Blue A


SER(R)S spectra with high signal intensity of Nile Blue A sulfate and 1,1′-diethyl-2,2′-cyanine iodide present in low concentration (≤0.05 µM) can be recorded by employing certain silver sols in the absence of any chloride and without highly aggregated particles. The sols have been prepared by reduction of silver nitrate with hydrazine hydrate in a special procedure at a carefully established pH. In the presence of chloride, the maximum SER(R)S signal observed for a ca. 0.5 µM solution of Nile Blue A is of similar magnitude employing either a silver sol according to Lee and Meisel or our sol C, which contains nearly exclusively single silver particles with diameters of about 50 nm. Without added chloride, however, only our sol produces SER(R)S spectra with similar intensity as with chloride. Because the influence of chloride and coagulation on the intensity of the SER(R)S-signal can be controlled by varying the additives to our silver sol, further experiments of this kind can help to elucidate how these two parameters influence the magnitude of the SERS enhancement. Copyright © 2004 John Wiley & Sons, Ltd.