Chitosan nanoparticles synthesis caught in action using microdroplet reactions.

The ionic gelation process for the synthesis of chitosan nanoparticles was carried out in microdroplet reactions. The synthesis could be stopped instantaneously at different time points by fast dilution of the reaction mixture with DI water. Using this simple technique, the effect of temperature and reactant concentrations on the size and distribution of the nanoparticles formed, as a function of time, could be investigated by DLS and SEM. Results obtained indicated very early (1-5 s) nucleation of the particles followed by growth. The concentration of reactants, reaction temperature as well as time, were found to (severally and collectively) determine the size of nanoparticles and their distribution. Nanoparticles obtained at 4 °C were smaller (60-80 nm) with narrower size distribution. Simulation experiments using Comsol software showed that at 4 °C 'droplet synthesis' of nanoparticles gets miniaturised to 'droplet-core synthesis', which is being reported for the first time.