One step synthesis of SERS active colloidal gold nanoparticles by reduction with polyethylene glycol

• A simple synthesis of colloidal gold nanoparticles by reduction with PEG is proposed.
• The particles are covered with a 2–3 nm PEG layer conferring high stability in time.
• Shape and size of gold nanoparticles can be controlled during synthesis.
• An excellent SERS substrate, comparable to conventional colloids, is introduced.

The utility of polyethylene glycol (PEG) modified gold nanoparticles (GNPs) as novel drug carriers was comprehensively described in the last decade. We report a very effective, simple, one step and rapid synthesis method for stable, highly surface-enhanced Raman scattering (SERS) active gold colloids, by reduction and stabilization with short and long chain polyethylene glycol, PEG200 and PEG8000, respectively. Depending on the mixing rate during the synthesis, the mean size of the GNPs can be controlled between 15 and 60 nm. The obtained colloids have been characterized by UV–vis spectroscopy, transmission electron microscopy (TEM), and SERS. TEM micrographs reveal spherical nanoparticles with an average diameter of 15 nm, and polygonal particles with a mean size of 60 nm for the gold colloid with the absorption maximum at 520 nm and 562 nm, respectively. The SERS activity of these new gold colloids is comparable to that of the conventional gold colloid obtained by citrate reduction, as shown by the SERS spectra of various analytes, using the 633 laser line.

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