Fabricating mono-dispersed Fe3O4-SiO2 core-shell particles with help of triboelectrification

For years, it has been widely held that triboelectrification is not the sought-after technique to develop innovative materials with enhanced functionalities. In this study, we tried to break such a traditional concept and find its ever-expanding roles in material science. In our strategy, triboelectrification brought adequate charge to particles, so as to achieve their mono-dispersity in solutions. Following this strategy, the synthesis of mono-dispersed Fe3O4-SiO2 core-shell particles involved two-stage triboelectrification treatment. In the first-stage treatment, positive triboelectric charges on Fe3O4 cores ensured their uniform SiO2 coating and well-defined core-shell structure. In the second-stage treatment, positive triboelectric charges on Fe3O4-SiO2 core-shell particles guaranteed their mono-dispersity for further biological use. The Zeta potential of these triboelectrically-treated Fe3O4-SiO2 core-shell particles still maintained at ca. +55 mV after standing for two months, and their conglomeration was negligible owing to their limited increase in hydrodynamic size. Besides, their excellent linearity between relaxivities and iron concentration, and their virtually unchanged r(2)/r(1) ratio within two months manifested that triboelectrification can be a promising technique in fabricating advanced materials. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.