A Facile Controlled Preparation Method of Multifunctional Core-Shell Magnetic Nanoparticles and Their Potential Use in Microfluidic Separations

Organotriethoxysilanes bearing carboxylic acid, ester, and amine functional groups were synthesized via a facile photoinitiated catalyst-free thiol-ene click reaction. We demonstrate these systems to be excellent candidates to make core-shell magnetic nanoparticles composed of a single-core structure and a variety of surface functionalities via a simple synthesis in a reverse microemulsion system. Compared to the most commonly used surface modification strategies, this method avoids complicated multi-step procedures and tedious removal of metal catalysts from the nanoparticle surface. Also, the density of surface functionality is more predictable and tunable. The results show that the morphology, size, and colloidal stability can be well predicted and amply controlled. The organotriethoxysilanes were confirmed by 1 H-NMR and 13 C-NMR spectra. The surface functionalized nanoparticles were characterized by a variety of methods, including TEM, FTIR, UV-Vis. The resulting nanoparticles have been shown to be monodisperse core-shell structures with a chemically active silica coating onto a single magnetic core, a system with great potential for a broad range of applications, such as biomedicine, catalysis, purification and separation. Notably, we have demonstrated the potential applicability of these systems for use in a closed-cycle magnetic purification (CCMP) microfluidic device by studying the reversible and quantitative affinity of resulting IONPs towards ionic compounds.