SERS Detected Adsorption of Guanine on Small Particles of Colloidal Silver

Abstract

Intense Raman scattering by guanine molecules adsorbed on silver aqueous sol particles of dimensions comparable to the wavelength of the laser excitation line is reported. Surface enhanced Raman scattering (SERS) spectra of guanine, 7-methylguanine and deutero guanine in pH 4.5 solution at rather low concentrations (~10⁻⁶M) were recorded in the spectral range of 100 to 1800 cm⁻¹. Prominent SERS bands for these bic molecules are the ring breath-ing modes at 653 cm ⁻¹ in guanine, 635 cm⁻¹ in deutero-guanine and 651 cm⁻¹ in 7-methylguanine. The alkylation of guanine leads to a specific change in the SERS spectrum. The strong enhanced ring modes at 1386 cm⁻¹ and 1467 cm⁻¹ in guanine disappear in the 7-methylguanine spectrum and new enhanced bands appear at 703 cm⁻¹ and 1354 cm⁻¹.