Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The present work describes a simple method for preparing highly dispersed spheroidal metallic silver nanoparticles in surfactant-free N,N-dimethylacetamide solution. The optical properties, shape and size of the metallic silver nanoparticles obtained in N,N-dimethylacetamide after different times of reaction were characterized using UV-vis absorption spectroscopy and transmission electron microscopy. The average size of the metallic silver nanoparticles is smaller than that obtained by the well established procedure using N,N-dimethyformamide. Using optimized geometries for N,N-dimethylacetamide and N,N-dimethyformamide, vertical ionization energies and electron affinities were calculated by means of the UHF/DFT calculations of cations and anions, respectively. The difference between ionization energies and electron affinities is higher for N,N-dimethyformamide indicating that it is a harder base than N,N-dimethylacetamide. Therefore, N,N-dimethyformamide probably interacts more weakly with Ag(I) ions than does N,N-dimethylacetamide. The strength of this chemical interaction has implications on the stabilization and dispersion of silver nanoparticles obtained in N,N-dimethylacetamide. The low cost, simple methodology may be used as a platform for further studies in surface-enhanced Raman spectroscopy as well as with other optical properties that depend on the surface plasmon resonance of metallic silver nanoparticles. (C) 2011 Elsevier B.V. All rights reserved.16115-1615171521Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)