Superparamagnetic iron oxide nanoparticles (SPIONs) are used for a wide range of biomedical applications requiring precise control over their physical and magnetic properties, which are dependent on their size and crystallographic phase. Here we present a comprehensive template for the design and synthesis of iron oxide nanoparticles with control over size, size distribution, phase, and resulting magnetic properties. We investigate critical parameters for synthesis of monodisperse SPIONs by organic thermal decomposition. Three different, commonly used, iron containing precursors (iron oleate, iron pentacarbonyl, and iron oxyhydroxide) are evaluated under a variety of synthetic conditions. We compare the suitability of these three kinetically controlled synthesis protocols, which have in common the use of iron oleate as a starting precursor or reaction intermediate, for producing nanoparticles with specific size and magnetic properties. Monodisperse particles were produced over a tunable range of sizes from approximately 2–30 nm. Reaction parameters such as precursor concentration, addition of surfactant, temperature, ramp rate, and time were adjusted to kinetically control size and size-distribution, phase, and magnetic properties. In particular, large quantities of excess surfactant (up to 25:1 molar ratio) alter reaction kinetics and result in larger particles with uniform size; however, there is often a trade-off between large particles and a narrow size distribution. Iron oxide phase, in addition to nanoparticle size and shape, is critical for establishing magnetic properties such as differential susceptibility (dm/dH) and anisotropy. As an example, we show the importance of obtaining the required size and iron oxide phase for application to Magnetic Particle Imaging (MPI), and describe how phase purity can be controlled. These results provide much of the information necessary to determine which iron oxide synthesis protocol is best suited to a particular application.

A new law for the thinning of surfactant-free lamellae (applicable to metallic and ceramic foams with mobile interfaces) in a cross-section of an arid gas–liquid foam is derived using matched asymptotic analysis. Two limiting cases are identified at small capillary number: the well-known semi-arid foam having unit-order liquid fraction and the arid foam in which it is small. The lamellar thinning rates in both cases exhibit $t^{-2}$ power-law behaviour at long times even though the foam liquid area fractions have different orders of magnitude in capillary number. At early times, arid foam thinning is slowed because the curvature of the capillary quasi-static interfacial region must decrease in order to accommodate the flow from the films. Therefore, the thinning of lamellae feeding into a given Plateau border is coupled and the dynamics is distinct from that of the semi-arid foam.Approximations of rupture times in arid and semi-arid foams are found by calculating the times for lamellae to thin to a pre-specified thickness. For given initial lamellar thicknesses, and for arid and semi-arid foams that have identical initial lamellar liquid areas, the arid foam ruptures more quickly than the semi-arid foam. On the other hand the rupture of lamellae is significantly delayed in arid foam compared to semi-arid foam if the initial lamellar thickness and capillary number are the same.

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