Final Activity Report Summary - NANOMAGMOLS (Nanostructured magnetic molecular systems) Metallic nanoparticles are attracting considerable attention for their intriguing properties and potential applications. Because of their small size the nanoparticles exhibit magnetic, electrical, optical and chemical properties that cannot be achieved by the bulk material. The size and properties of nanoparticles confer them potential technological applications in a wide range of fields, such as data storage and quantum computing, or biomedical applications like magnetic resonance imaging, sensors or immunomagnetic labels. From a synthetic point of view, one of the main challenges in nanoscience is to seek for new procedures that allow for the preparation of nanoparticles in a controlled manner. It aims to produce non-aggregated nanoparticles with a narrow size distribution. In this sense, the main achievement we made was to develop simple and versatile methods to prepare size-selected metallic nanoparticles. The methods we developed were based on the use of the apomolecules and ferritin molecules as chemically and spatially confined environments for building up metallic nanoparticles. Part of the executed work was devoted to the knowledge of the chemical and physical properties of ferritin. This knowledge allowed us to explore and develop a series of new methods for the production of a great variety of metallic nanoparticles. It should be noted that ferritin was used to produce metallic nanoparticles, however the methods we developed had an additional advantage with respect to those previously reported, namely the great flexibility in the chemical composition of the nanoparticles. Thus, we succeeded in obtaining three kinds of encapsulated apoferritin metallic nanoparticles: 1. apoferritin encapsulated zero valent metal nanoparticles, such as copper, nickel and cobalt. Copper nanoparticles were of interest, especially because the high electrical conductivity of copper made their use suitable for future generations of electronic nanodevices. Nanoparticles of the ferromagnets cobalt and nickel were of significant importance because of their applications in magnetic storage devices. 2. apoferritin encapsulated Prussian blue derivatives (PB) nanoparticles, more concretely the FeCu, FeNi and FeCo derivatives. PB represented a unique family of compounds with interesting magnetic properties and their preparation at nanoscale level also emerged as a promising possibility for applications in magnetic nanodevices. 3. metal-shell ferritin core nanoparticles. More precisely, we prepared nanoparticles of gold-coated ferritin. Because of the optical activity due to the gold shell and the magnetic properties due to the ferritin core, the ferritin-gold nanoparticles could be useful in biomedical applications as sensor separators of specific biological material. All the nanoparticles we prepared were water soluble because of the presence of the apoferritin coat. This solubility allowed for the manipulation of their solutions to make films and nanocrystals composed by these nanomaterials, which was a promising step in the search for possible applications. In this sense, we succeeded in obtaining, in collaboration with the group of E. Coronado of the ICMol, Universidad de Valencia, Spain, Langmuir-Blodgett films (LBF) of ferritins with different iron loading. The magnetic study of these systems pointed out the existence of superparamagnetism below a blocking temperature, which correlated with the nanoparticle size. Works were in progress, by the time of the project completion in order to prepare, by using a similar experimental procedure, LBF of other ferritin derivatives. Finally, we recently obtained magnetic data about the apoferritin-encapsulated 5 nm sized Co nanoparticles in collaboration with the group of E. Coronado. These preliminary results were very encouraging because they showed that the particles exhibited superparamagnetic behaviour.
