Research Article Ultra-Small Fatty Acid-Stabilized Magnetite Nanocolloids Synthesized by In Situ Hydrolytic Precipitation Kheireddine El-Boubbou, 1,2 Rabih O. Al-Kaysi, 1,2 Muhanna K. Al-Muhanna, 3 Hassan M. Bahhari, 2 Abdulaziz I. Al-Romaeh, 3 Nadim Darwish, 4 Khaled O. Al-Saad, 2 and Salem D. Al-Suwaidan 2 1 King Saud bin Abdulaziz University for Health Sciences (KSAU-HS), King Abdulaziz Medical City, National Guard Health Afairs, Riyadh 11481, Saudi Arabia 2 King Abdullah International Medical Research Center (KAIMRC), King Abdulaziz Medical City, National Guard Hospital, Riyadh 11426, Saudi Arabia 3 King Abdulaziz City for Science and Technology (KACST), Riyadh 11442, Saudi Arabia 4 Departament de Qu´ ımica F´ ısica & Institut de Bioenginyeria de Catalunya (IBEC), Universitat de Barcelona, 08028 Barcelona, Spain Correspondence should be addressed to Kheireddine El-Boubbou; elboubboukh@ngha.med.sa Received 6 March 2015; Revised 31 July 2015; Accepted 3 August 2015 Academic Editor: Mohmmad A. Malik Copyright © 2015 Kheireddine El-Boubbou et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Simple, fast, large-scale, and cost-efective preparation of uniform controlled magnetic nanoparticles remains a major hurdle on the way towards magnetically targeted applications at realistic technical conditions. Herein, we present a unique one-pot approach that relies on simple basic hydrolytic in situ coprecipitation of inexpensive metal salts (Fe 2+ and Fe 3+ ) compartmentalized by stabilizing fatty acids and aided by the presence of alkylamines. Te synthesis was performed at relatively low temperatures (∼80 ∘ C) without the use of high-boiling point solvents and elevated temperatures. Tis method allowed for the production of ultra-small, colloidal, and hydrophobically stabilized magnetite metal oxide nanoparticles readily dispersed in organic solvents. Te results reveal that the obtained magnetite nanoparticles exhibit narrow size distributions, good monodispersities, high saturation magnetizations, and excellent colloidal stabilities. When the [fatty acid] : [Fe] ratio was varied, control over nanoparticle diameters within the range of 2–10 nm was achieved. Te amount of fatty acid and alkylamine used during the reaction proved critical in governing morphology, dispersity, uniformity, and colloidal stability. Upon exchange with water-soluble polymers, the ultra-small sized particles become biologically relevant, with great promise for theranostic applications as imaging and magnetically targeted delivery vehicles. 1. Introduction Lately, the continuous trials to produce controlled monodis- perse magnetic metal oxide nanoparticles (M 3 NPs) for both in vitro and in vivo endpoints have sky-rocketed [1]. In particular, the use of iron oxide (Fe 2 O 3 /Fe 3 O 4 ) NPs in a variety of physioelectronic and biomedical applications ofered M 3 NPs a remarkable glow [2]. In fact, it has been shown that M 3 NPs based on ferrites were applied to record storage devices, energy storage, catalysis, labeling cells, mag- netically targeted imaging, drug delivery, and medical thera- nostics [1–3]. Various synthetic methods have been reported to produce M 3 NPs, which include nonaqueous and aque- ous sol-gel, microemulsion, sonochemical, and the most popular hydrothermal/solvothermal techniques [3]. Of the many available approaches, two main synthetic solution- based routes [4] have been popularized: (a) basic aqueous coprecipitation [5] of iron salts (as demonstrated by Massart) in the presence or absence of surfactants/polymers [6], (b) high-temperature thermal decomposition [7] of organometal- lic precursors (Fe(acac) 3 [8], Fe-oleate [9], Fe-carboxylate [10], Fe-pivalate [11], or heterodoped ferrite pivalate [12, 13]) in high-boiling solvents at elevated temperatures (∼200– 360 ∘ C). Despite the popularity of the conventional basic Hindawi Publishing Corporation Journal of Nanomaterials Volume 2015, Article ID 620672, 11 pages http://dx.doi.org/10.1155/2015/620672