Continuous synthesis of iron and aluminium-based nanoparticles

Abstract

Nanoparticles exhibit exceptional properties (enhanced catalytic activity, magnetic or plasmonic properties) compared to their bulk counterparts, owing to their small dimensions. Thus, plenty of new and exciting applications leveraging these properties have been proposed, such as drug delivery, MRI contrast agents, plasmonic catalysis, etc. However, large scale production of nanomaterials remains problematic because of their extreme sensitivity to small changes in the reaction conditions such as concentration and temperature. This thesis employs continuous flow processes as an alternative to standard batch processes to address the challenge raised by nanomaterial synthesis scale-up. Continuous processes are more reproducible because they provide accurate control over fluid dynamics, heat and mass transfer. Several promising materials are selected, and their continuous synthesis is investigated along with the design of suitable microreactor assemblies. Herein, synthesis of metallic iron nanoparticles through thermal decomposition of Fe(CO)5 is studied and the effects of the reaction parameters such as surfactant type and concentration, temperature and mixing are assessed, unravelling the particle formation mechanism. Optimizing the reaction conditions by tuning the mixing through the flow rate allowed for monodisperse nanoparticles to be obtained in high yields. The continuous synthesis of metallic aluminium nanoparticles by decomposition of alane and alkylaluminium precursors is evaluated, demonstrating strategies to operate with highly reactive systems and highlighting limitations such as reactor fouling. Furthermore, continuous synthesis of iron oxide nanoparticles through precipitation methods is examined. A strategy integrating the synthesis and functionalization of iron oxide nanoparticles into a single green process and set-up is developed, enabling the low cost, reproducible, large scale production of application-ready nanoparticles. These functionalized iron oxide nanoparticles are demonstrated to be highly stable, fully biocompatible and suitable T2 MRI contrast agents. Moreover, simple further derivatization enables the nanoparticles to act as a platform for biomedical applications. This thesis serves as a significant step towards the upscaling of nanoparticle technology and its implementation into real world applications.