Effect of the oxygen content in the reaction environment on size and shape of CoFe2O4 nanoparticles: morphological analysis by aspect maps.

Advanced synthesis approaches, necessary to achieve a strict control of the structural, morphological and chemical properties of nanomaterials, are at the basis of a reproducible manipulation of their unique physical behaviour. Nowadays, this is one of the most difficult problems faced by nanotechnology. In fact, any advanced application that takes advantage of nanoparticle (NP) systems will also rely on the achievement of such a control. This is particularly true for magnetic nanoparticles since they are unique and complex physical objects whose properties, being particularly sensitive to the particle size [1], greatly differ from the parent massive material. Within this context, the synthesis of spinel ferrite nanoparticles (MeFe2O4, Me = Fe2+, Co2+, Ni2+, Zn2+, ...) with controlled morpho-structural features represents an important issue due to the strong interest in these materials from both a fundamental and a technological point of view (e.g. MRI, hyperthermia, drug delivery, catalysis, microwave applications). Crystalline cobalt ferrite nanoparticles were prepared by a modified high thermal decomposition (HTD) synthesis of acetylacetonates precursors [1,2]. This widely employed synthetic approach has been improved introducing a strict control on the residual oxygen in the reaction environment. A detailed analysis of the effect of the oxygen content was carried out analyzing TEM images through a statistical approach and using aspect maps [3]. Aspect maps allowed us to follow the nanoparticles' growth process and to select the optimal value of O2 pressure to produce particles size of ~ 19 nm with a sharp size distribution (polydispersity 0.4 %). The magnetic properties were analyzed, showing an improvement of NANO 2016, Québec, Canada the switching field distribution, which is a key parameter for technological applications. In addition, our results suggested that particles with larger sizes can be also stabilized. References [1] D. Peddis, C. Cannas, A. Musinu, A. Ardu, F. Orruì, D. Fiorani,. S. Laureti, D. Rinaldi, G. Muscas, G. Concas, G. Piccaluga, Chem. Mater. 2013, 25, 2 [2] S. Sun, H. Zeng, D.B. Robinson, S. Raoux, P.M. Rice, S.X. Wang, G. Li, J. Am. Chem. Soc. 2004, 4, 126 [3] G. Muscas, G. Singh, W.R. Glomm, R. Mathieu, P.A. Kumar G. Concas, E. Agostinelli, D. Peddis, Chem mater. 2015, 27, 1982