Magnetic composites obtained by H2 treatment of (Mg,Ni)3Si2O5(OH)4 phyllosilicate nanoscrolls

Among various layered silicate minerals, 1:1 phyllosilicates attract increased attention due to a possibility of spontaneous curling yielding nanotubes and nanoscrolls. Chemical conjunction of metal hydroxide and silica sheets opens wide perspectives for phyllosilicate application as reinforcing fillers, adsorbents, catalysts, and catalyst supports. However, magnetic behavior of both transition metal phyllosilicates and their modification products remains poorly studied. Here, we report on magnetic properties alterations of H${}_2$-treated (Mg${}_{1-x}$Ni${}_x$)₃Si₂O₅(OH)₄ $(x=2/3,1)$ phyllosilicate nanoscrolls, studied by means of direct current magnetization (in the 4–300 K range) and electron spin resonance (in the 5–720 K range). Before the reduction, the nanoscrolls become predominantly ferromagnetic below 10 and 24 K for $x=2/3$ and 1, respectively. Heat treatment induces Ni reduction in the form of 5–15 nm metal nanoparticle networks encapsulated in highly anisotropic initial phyllosilicate precursor. The resulting Ni-phyllosilicate composites are superparamagnetic near the room temperature, and transition to paramagnetic state occurs at 650 and 473 K, respectively. We believe that these composites may be perspective in the fields of targeted delivery, advanced water remediation, and local magnetic structure diagnostics.