Altering surface charge nonuniformity on individual colloidal particles

Charge nominiformity (sigmaxi) was altered on individual polystyrene latex particles and measured using the novel experimental technique of rotational electrophoresis. It has recently been shown that unaltered sulfated latices often have significant charge nominiformity (sigmaxi = 100 mV) on individual particles. Here it is shown that anionic polyelectrolytes and surfactants reduce the native charge nominiformity on negatively charged particles by 80% (sigmaxi = 20 mV), even while leaving the average surface charge density almost unchanged. Reduction of charge uniformity occurs as large domains of nominiformity are minimized, giving a more random distribution of charge on individual particle surfaces. Targeted reduction of charge nominiformity opens new opportunities for the dispersion of nanoparticles and the oriented assembly of particles.