Growth of silver colloidal particles obtained by citrate reduction to increase the Raman enhancement factor

A method is reported for obtaining silver colloids with a large particle si ze. It is based on the growth of seed colloidal particles obtained by chemi cal reduction of silver nitrate with citrate. These colloids were character ized by means of UV-visible spectroscopy and transmission electron microsco py. The nucleation mechanism is discussed on the basis of the morphology an d size of the resulting particles. Moreover, the surface-enhanced Raman sca ttering activity of the resulting colloids was evaluated in the near-infrar ed region by using 1,5-dimethylcytosine as adsorbate.