Formation and shape-control of hierarchical cobalt nanostructures using quaternary ammonium salts in aqueous media

Abstract

Aggregation and self-assembly are influenced by molecular interactions. With precise control of molecular interactions, in this study, a wide range of nanostructures ranging from zero-dimensional nanospheres to hierarchical nanoplates and spindles have been successfully synthesized at ambient temperature in aqueous solution. The nanostructures reported here are formed by aggregation of spherical seed particles (monomers) in presence of quaternary ammonium salts. Hydroxide ions and a magnetic moment of the monomers are essential to induce shape anisotropy in the nanostructures. The cobalt nanoplates are studied in detail, and a growth mechanism based on collision, aggregation, and crystal consolidation is proposed based on a electron microscopy studies. The growth mechanism is generalized for rods, spindles, and nearly spherical nanostructures, obtained by varying the cation group in the quaternary ammonium hydroxides. Electron diffraction shows different predominant lattice planes on the edge and on the surface of a nanoplate. The study explains, hereto unaddressed, the temporal evolution of complex magnetic nanostructures. These ferromagnetic nanostructures represent an interesting combination of shape anisotropy and magnetic characteristics.

Formation of Gold Nanorods by Seeded Growth: Mechanisms and Modeling

“…In the past two decades, producing nonspherical nanoparticles has been a subject of comprehensive research − as these particles exhibit novel properties that depend strongly on size and shape of the nanoparticles . For example, gold nanorods depict a split in the plasmon band, with a tunable band gap that is sensitive to the aspect ratio of nanorods .…”

Interaksi Molekuler Amonium Hidroksida

“…b) Bentuk Molekul Amonium Hidroksida (NH4OH) terdiri dari atom N, H dan O. Nitrogen termasuk golongan VA yang mempunyai 5 elektron di kulit terluarnya dan Hidrogen merupan golongan IA yang mempunyai 1 elektron di kulit terluarnya, serta Oksigen dari golongan VIA yang mempunyai 6 elektron di kulit terluarnya. Sehingga bentul molekul NH4OH adalah tetrahedral (18,(126)(127)(128)(129) .…”

Binding modes of carboxylic acids on cobalt nanoparticles

“…When considering the morphology of nanostructures, attractive possibilities of improving the catalytic power by increasing the area of reactive metal surfaces have led to intensive research in synthesis methods, ranging from nanospheres, nanodiscs, and nanosheets, over hollow structures or pellets, to unusual and less ordered geometries, such as snowflakes and leaf-shapes. [17][18][19][20][21][22] Similarly, the shape and size of the nanoparticles can strongly affect the material uptake and biodistribution as well as their reactivity. Since the main interest in hyperthermia is to maximise magnetisation and mobility while minimising oxidation, small spherical nanoparticles are preferred, as after ligand functionalisation the overall diameter should be enough to circulate throughout the blood vessel network for a sustained period of time with minimal surface-to-volume ratio to avoid reacting with the surroundings.…”