By complexation with starch, Co2+ ions have been preferentially bound to starch, resulting in clathrate cages. A controlled preparative methodology which involves initial drying at a temperature of 80-90 degrees C, removed a large number of water molecules to provide for a solid rigid network, in which the metal ions remained segregated. Subsequent calcination and sacrifice of the template resulted in monodispersed nanoparticles of around 20 nm. The nanoparticles were characterized by a coercivity value of 893 Oe. M-r value of 0.1128 emu/g and M-s value of 0.6353 emu/g. The nanoparticles also possessed above 80% reflectance in near infrared region, with potential applications as cool green-black pigment which had sufficient covering properties for surface coating applications. (c) 2011 Elsevier BM. All rights reserved.