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 -hexadecylethylenediamine 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 C 14 - 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.