Ni–bacterial cellulose nanocomposite; a magnetically active inorganic–organic hybrid gel

Abstract

Bacterial cellulose, which is inherently a non-magnetic hydrogel, has been made magnetic by the infiltration of Ni-nanoparticles via a simple aqueous phase salt reduction method. The resulting hydrogel, when converted to the aerogel and xerogel forms, exhibits different magnetic behaviour due to the microstructural changes, with two distinct size distributions varying from 3.2 nm to 140 nm for the Ni-nanoparticles, and the accompanying magnetic interaction between the particles. The dominant interparticle interactions between the smaller nano-sized particles result in spin glass like collective behaviour at low temperatures. The small fraction of larger particles, on the other hand, exhibit a ferromagnetic response at room temperature with a coercivity varying between 60 G and 110 G depending on the state of the gel. The magnetocrystalline anisotropy energy density of the small Ni-particles is found to vary from ∼1.4–6.6 × 105 J m−3 in the xerogels. This type of multiphase magnetic behaviour is unique to these gel structures wherein the magnetic particles are formed due to uninhibited natural growth events.