Simple Size Tuning of Magnetic Nanoparticles using a Microwave Solvothermal Method and their Application to Facilitate Solid Phase Synthesis of Smart Polymers.

Abstract

We demonstrate a simple, economical, rapid and scalable microwave method to produce magnetite-based magnetic nanoparticles (MNPs) at a desired size and their application to facile synthesis of high value polymer products. One solvothermal method gaining traction is the use of microwave synthesis as it offers a rapid and green method to MNP production. In this work, we report a previously unreported simple and reliable method where adjusting the microwave temperature ramp time (between 2-15 minutes) during synthesis produces size control of superparamagnetic MNP@CHO nanoparticles. Nanoparticles size distributions measured using dynamic light scattering range from for 14 nm ±8 nm (at 2-minute ramp time) and 122 nm ± 49 nm (at 10-minute ramp time) and are produced within 20-30 minutes. Magnetic sizing analysis using the method of Chantrell confirmed iron-oxide core size increases as a function of ramp time over the range 7.91 to 11.25 nm in terms of median diameter and with lognormal σ values within (0.22 ≤ σ ≤ 0.33). Particle cluster size increase with increasing ramp time measured using transmission electron microscopy was found to be a function of particle agglomeration. Further, we demonstrate that the MNP@CHO functionalised with a protein of interest can then be applied to the rational solid phase synthesis of molecularly imprinted polymer nanoparticles (nanoMIPs) with high affinity for protein biomarkers. We demonstrate that there is an optimal MNP size for highly efficient MNP-based nanoMIP production which is key to mass production and commercialisation of low-cost and sustainable bespoke size-tuned MNPs and artificial antibodies.