On the effect of nanoparticle size on water-oxide interfacial chemistry

The effect of nanoparticle size of crystalline hydrated transition metal oxides on their surface chemistry in general, and precisely on their PZC was investigated on maghemite ultrafine nanoparticles. The study has also demonstrated the ability to stabilize crystalline metastable oxyhydroxides phases of aluminum and iron in aqueous solutions and the design of nanorods of various metal oxides into polycrystalline substrates. The experiment obtained the spherical maghemite nanoparticles in solution at room temperature, and were prepared by coprecipitation of ferrous and ferric ion in basic solution at 25°C. The result of experiment illustrates the increase in PZC with the decrease in particle size, with the variation of two pH unit for a one-third decrease in nanoparticle size. The variation of the surface curvature on the adsorption at the water-oxide induces a significant change in the surface acidity due to reduction of electrostatic repulsions at the interface.