Recently, many attempts have been made to develop processes and techniques that would yield ‘monodispersed colloids’ consisting of uniform nanoparticles both in size and shape. In these systems, the entire uniform physicochemical properties directly reflect the properties of each constituent particle. Monodispersed colloids have been exploited in fundamental research and as models in the quantitative assessment of properties that depend on the particle size and shape. In addition, it has become evident that the quality and reproducibility of commercial products can be more readily achieved by starting with well-defined powders of known properties. In this way, these powders have found application in photography, inks in high-speed printing, ceramic, catalysis, and especially in medicine.
For each application, the concept of “ideal” nanoparticles (i.e. the ones that exhibit the best performance) is different. Therefore, the ideal nanoparticle needs to be tailored mainly by their size and shape. In general, a synthetic route that leads to nanoparticles with an accurate control on their size and shape, low size distribution, controlled aggregation state, high crystallinity and chemical purity is the best one. The resulting particles would be ideal candidates for the intended applications since all of them will contribute to the desire effect. In this sense, colloidal routes developed in liquid media render nanoparticles accomplishing these properties, with low-cost production and large-scalability. Moreover, the preparation of nanoparticles in liquid media enables an easier manipulation and post-processing procedures when used in the form of colloids (e.g. surface modification, deposition forming self-assembly, dispersion in different media).
During the latest years, the synthesis of anisotropic magnetic iron oxide nanoparticles, i.e. nanoparticles with non-spherical shape, has received a great attention. The anisometry leads to new functionalities such as enhanced magnetic properties due to the increase in the magnetic effective anisotropy, a higher surface to volume ratio and different particle facets exposed modulating the reactivity with molecules, particles or other entities. These properties are very advantageous in widespread applications such as biomedicine as theranostic agents (MRI and magnetic/optical hyperthermia) and others such as magnetic recording media, environmental remediation, Li-ion batteries, spintronics or microwave absorption [Design strategies for shape-controlled magnetic iron oxide nanoparticles].
Our group is focussed on magnetic iron oxide colloids, which can be easily synthesized at low cost, are biocompatible and present a well-developed surface chemistry.