  Silver nanocrystals have been prepared by reacting silver nitrate with
ascorbic acid in aqueous solution containing a low concentration of a
commercial polynaphtalene sulphonate polymer (Daxad 19). Various crystalline
morphologies have been obtained simply by tuning the reaction temperature. We
have investigated the nanoparticle formation mechanism at three different
temperatures by in situ and time resolved Small Angle X ray Scattering
measurements. By modeling the scattering intensity with interacting spherical
particles in a fractal-like polymer-Ag matrix, we found signatures of
nucleation, growth and assembly of primary particles of about 15-20 nm. We
observed how the time evolution of both spatial correlations between primary
particles and the dynamic fractal geometry of the polymer-Ag matrix could
influence and determine both the aggregation mechanism and the morphology of
forming nanostructures in solution.
