Ternary cobalt-iron phosphide nanocrystals with controlled compositions, properties, and morphologies from nanorods and nanorice to split nanostructures

Abstract

Structural phase-controlled formation of binary Co2P and CoP nanocrystals is achieved by reacting cobalt(II) oleate with trioctylphosphine. In the absence of oleylamine, Co2P nanowires are formed at both 290 and 320°C. In the presence of oleylamine, Co2P nanorods are formed at 290°C, and CoP nanorods are formed at 320°C. With the simultaneous reaction of iron(III) oleate and cobalt(II) oleate with trioctylphosphine in the presence of oleylamine, ternary Co2P-type cobalt-iron phosphide nanostructures are produced at both 290 and 320°C, corresponding to rice-shaped Co1.5Fe0.5P nanorods and split Co1.7Fe0.3P nanostructures, respectively. The controlled incorporation of iron into cobalt phosphide can alter the magnetic properties from paramagnetic binary Co2P to ferromagnetic Co 2P-type ternary cobalt-iron phosphide nanostructures. Meanwhile, the time-dependent morphological evolution from small nanodots/nanorods, through seeded growth to unique split nanostructures is demonstrated in one-pot reaction at 320°C. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.