Use of small-angle neutron scattering to investigate modifications of internal structure in self-assembled grains of nanoparticles synthesized by spray drying

Micrometric spherical grains consisting of self-assembled silica nanoparticles have been synthesized by spray drying of colloidal suspension. Inter-particle correlation and available specific surface area of silica and void interfaces, in the assembled grains, were modified by addition of electrolyte in initial colloidal dispersion prior to self-assembly process but keeping the overall spherical shape of the assembled grains un-altered. While the external morphology of the assembled grains was probed by scanning electron microscopy, small-angle neutron scattering technique has been employed to investigate the modifications in the internal structure and the inter-particle correlation inside the assembled grains. It is revealed that a sticky hard sphere type of inter-particle correlation between the constituent particles gets altered to a fractal type of correlation with addition of electrolyte. Further, the specific surface area of the silica-void interface gets somewhat enhanced by addition of electrolyte and particularly at higher electrolyte concentration due to formation of some hollow and buckled assembled grains. (C) 2010 Elsevier Inc. All rights reserved.