This paper describes a new method for the preparation of silver colloids with a narrow range of particle size to be used in surface‐enhanced Raman spectroscopy. Using malachite green as a strongly adsorbing dye, it can be shown that colloids from different preparation batches exhibit the same enhancement factor within an error margin of about 15%. By varying the number of nucleation centers, the particle size can be determined at will. An increase in particle diameter from about 38 to about 76 nm leads to an estimated five‐fold increase in surface enhancement.

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After adding cationic dyes like oxazine 170, malachite green, and crystal violet to a solution of colloidal silver sometimes an absorption band appears at wavelengths > 750 nm which is neither caused by the monomeric dye nor by a coagulation of the colloid. Based on electrochemical measurements this new absorption band is assigned to a chinhydron‐like adsorption geometry of the dye. Usually this band is only observed at low concentration of the dye, whereas at higher concentration the formation of H‐aggregates occurs. There seems to be a relationship between the intensity of this band and the SERS activity.

Using a recently published procedure, silver colloids with uniform particle size were prepared and stabilized by nine different anions. Although the UV–visible extinction spectra of the colloids showed only small variations with the nature of the stabilizing ions, dramatic differences were observed in the SERS spectra of seven dyes studied. It was demonstrated that each family of dyes experiences a large enhancement factor only with certain stabilizing ions. The adsorption geometry of oxazine dyes changes with the nature of the stabilizing anion and with the concentration of the dye. By comparison of observed and calculated normal modes, conclusions about the adsorption geometry are drawn. The results are discussed in the framework of the ‘adatom model’.