Nanocomposites and Nanomaterials
Electrosurface properties of magnetic Laponite RD
M.V. Manilo, T.I. Borodinova, N.I. Lebovka
F.D. Ovcharenko Institute of Biocolloidal Chemistry NAS of Ukraine, 
blv. Vernadskoho 42, Kyiv-142, Ukraine 
E-mail: borodinova.t@gmail.com

Hybrid magnetic particles based on Laponite (Lap) can be promising agents for ecology, therapeutics and diagnostic purposes. These materials combine unique magnetic and surface properties (e.g., high surface area, easily adjustable surface charge, relatively high adsorption capacity etc.). Due to its magnetic properties the external magnetic fields can be used for their targeting delivery and separation. The understanding the electrosurface properties of hybrid particles can help to predict their behaviour. 
In this work nanomagnetite (NM) particles have been synthesized using the Elmore method. Hybrid magnetic particles (LapM) were prepared by mixing of NM and Lap (Rockwood Additives Ltd., UK) nanoparticles in aqueous suspensions. The concentration of NM at suspensions was fixed at 0.75 wt.% and concentration of Lap was varied in the range of 0.0375–1.5 wt% (with mass ratio Xm=mNM/mLap varied in the range of 20.0 - 0.5 correspondingly). The obtained particles were characterized by transmission electron microscopy, X-ray diffraction and dynamic light scattering. The mean diameter were ~20 nm and ~24 nm for NM and hybrid LapM (Xm=1.5) particles correspondingly.
The dependence of ζ-potential of individual NM and hybrid LapM particles for the wide pH interval was studied by microelectrophoresis (Zetasizer NS, Malvern, UK). It is seen that hybrid LapM particles with mass ratio Xm<7.7 exhibit high negative ζ-potential in a wide pH interval (pH 2-12) which was practically equal to that for “pure” Lap particles. The NM particles have charged positively and reversed its charge at pH 5.2. The following features can be marked for hybrid LapM particles: 1) at low Lap content (Xm≥20) only small changes in the ζ-potential value were observed in accordance with nanomagnetite particles; 2) a change in the ζ-potential from positive to negative values with increasing the Lap concentration was observed; 3) at Xm~7.7 isoelectric point of hybrid particles were reached. In general, variations in the ζ-potential reflect the hydrophobic and electrostatic interactions between magnetite and Lap. 

We acknowledge funding from the National research foundation of Ukraine, Grant No. 2020.02/0138 and the NAS of Ukraine, Projects No. 0120U102343.