Formation of silver nanoparticles from a N-hexadecylethylenediamine silver nitrate complex

We report the capability for forming silver nanoparticles from a single source of N-hexadecylethyl-enediamine silver nitrate complex that acts as both a metal ion provider and a particle protector. The formation of the metal-ligand complex and nanocomposite is evident from the similarity of a Fourier transform infrared spectrum of free N-hexadecylethylenediamine to those of the complex and the composite.. The formation and size of particles have been determined from the UV-vis plasmon absorption spectroscopic and transmission electron microscopic (TEM) analyses, respectively. The average particle size is 7.0 +/- 1.0 to 12.1 +/- 2.9 nm depending on the complex concentration. The TEM photograph shows a two-dimensional array of these particles with an average edge-edge spacing between silver cores of 3.8-3.9 nm (close to double the N-hexadecylethylenediamine chain length) after drying the solution. The small-angle X-ray scattering (SAXS) spectrum supports the array of the nanoparticles. The closest center-to-center distance (calculated from the first scattering peak of the SAXS spectrum) between neighboring particles is in agreement with the TEM result. The large edge-edge spacing between cores, in comparison with those of C14-18 alkanethiol- and fatty acid-protected nanoparticles which are usually shorter than the alkyl chain length, is due to the dense packing of the diamine monolayer on a metal core and induces a weak interaction force between neighboring particles. Such weak interaction is very important in designing the nanotechnology based on nanoparticles. The colloidal solution of diamine-protected silver nanoparticles is free from flocculation or aggregation for several months.