Spacer-free SERRS spectra of unperturbed porphyrin detected at 100 fM concentration in Ag hydrosols prepared by modified Tollens method

Surface-enhanced resonance Raman scattering (SERRS) spectroscopy is a powerful tool for the selective and sensitive detection of porphyrins. We report a repeatable detection of unperturbed free base 5,10,15,20-tetrakis(1-methyl-4-pyridyl)21H,23H-porphine in concentrations as low as 1 x 10(13)?M in the final system when Ag nanoparticles prepared by modified Tollens method are employed as Raman scattering amplifiers, i.e. without any further post-modifications of their surface. Most probably the residues of sugar oxidation present on Ag nanoparticle surface are responsible for the effective protection of 5,10,15,20-tetrakis(1-methyl-4-pyridyl)21H,23H-porphine molecules against the metalation by silver. Copyright (C) 2011 John Wiley & Sons, Ltd.