Green synthesis of rock salt CoO nanoparticles for coating applications by complexation and surface passivation with starch

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 °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, Mr value of 0.1128 emu/g and Ms 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.

Graphical abstractRocksalt CoO nanoparticles can be synthesized on starch templates through calcination route. Synthesized nanoparticles are monodisperse and have applications as cool pigments.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Rocksalt CoO can be synthesized without use of harmful reagents. ► Starch serves as template and passivating agent for synthesis of CoO. ► Nanoparticles have good covering power and high near infra-red reflectance. ► Synthesized nanoparticles can find applications as cool pigments.