Synthesis and characterization of porous metal oxides and core-shell nanoparticles

Abstract

Surface atoM.S. have lesser number of neighbours than atoms in the bulk. The smaller particle, the larger fraction of atoM.S. at the surface compared to volume. The surface-to-volume ratio increases with decreasing in size and therefore there exist a numerous properties like melting point, other phase transition temperature etc which are completely different from their bulk.[20-23] Edge and corner atoM.S. have a lower co-ordination and bind foreign atoM.S. or molecules more tightly and therefore, small clusters behave like molecules than as bulk and showing completely different properties.[21] The fraction of atoM.S. at the surface with respect to its volume called dispersion F, varies with surface to volume ratio (shown in the equation below). The size dependence of dispersion for cubes of n atoM.S. along an edge and a total of N=n3 atoM.S. is shown in Figure-2.[