Some physicochemical aspects of photochemical synthesis of alginate-stabilized silver nanoparticles

In this work, colloids of alginate-stabilized silver nanoparticles are photochemically synthesized and characterized using transmission electron microscopy and ultraviolet-visible absorption spectroscopy. The colloid stability of the synthesized nanoparticles toward 1:1 electrolytes is estimated, and formation of the cohesive silver halide layer is considered as the main reason of their coagulation by halide solutions. A correlation matrix for several physicochemical parameters of the colloids is calculated, and explanation of the strong correlations found is given. Effects of implementation of different protocols of the reaction mixture preparation are discussed in terms of the non-equilibrium behavior of alginate compositions. In addition to the conventional nanoparticle coarsening by means of the adsorptive reduction of silver ions, which negatively correlates with temperature, a mechanism of thermally activated aggregation of alginate-stabilized nanoparticles through the adsorbed silver-carboxyl complex exchange is proposed. The activation energy of this process is found to be 77.4 +/- 54.4 kJ mol(-1), which is comparable with other estimates of the activation energy of silver desorption from silver surface. Encompassing a rather broad area of physicochemical processes associated with the photochemical synthesis of alginate-stabilized silver nanoparticles, this work paves the way for more thorough and detailed studies for controlling composition and size distribution in the nanoparticle colloids.