Magnetically responsive bacterial cellulose: Synthesis and magnetic studies

Abstract

Bacterial cellulose with its porous network structure was used as a support to precipitate Ni nanoparticles by room temperature chemical reduction of Ni-chloride hexahydrate. The room temperature reduction in an aqueous environment results in the formation of crystalline Ni nanoparticles of size 10 to 60 nm inside the bacterial cellulose along with Ni(OH)2. The nanocrystals have an equiaxed shape and are found both as individual particles as well as small aggregates depending on the porous network structure of cellulose matrix. The bacterial cellulose does not undergo any change and retains its crystal structure even after chemical reduction reaction. The Ni loaded bacterial cellulose is found to be ferromagnetic at room temperature with a saturation magnetization of 2.81 emu g−1 which increases by an order of magnitude to 21.8 emu g−1 at 1.8 K. The coercive field also increases by two orders of magnitude from 28 G at 300 K to 2900 G at 1.8 K. The zero field cooled magnetization however exhibits a superparamagnetic behavior with a peak at 20 K, the blocking temperature and this behavior is observed even in ac magnetization. The magnetization decrease with increasing temperature up to 400 K, when extrapolated to high temperatures using a power law indicates a Curie transition at 500 K, much lower than the Curie temperature of bulk Ni. The fraction of isolated superparamagnetic nanoparticles present in the composite was estimated from the saturation magnetization and is found to be ∼88%. These results clearly highlight the presence of two separate magnetic phases, superparamagnetic, and ferromagnetic, and the role of various magnetic interactions in the collective magnetic behavior of Ni nanoparticles in the composite structure.

Review of nanocellulose for sustainable future materials

“…16). 110 The coercive field also increases by two orders of magnitude from 28 G at 300 K to 2900 G at 1.8 K. The magnetization decrease with increasing temperature up to 400 K, when extrapolated to high temperatures using a power law indicates a Curie transition at 500 K, much lower than the Curie temperature of bulk Ni.…”

Magnetic Responsive Cellulose Nanocomposites and Their Applications

“…The Co loaded cellulose is found to be ferromagnetic at room temperature with obvious coercivity (Pirkkalainen et al, 2007(Pirkkalainen et al, , 2008. The room temperature reduction in an aqueous environment is also an effective method for the controlling synthesis of magnetic nanoparticle with small particle size (Vitta et al, 2010). The formation of crystalline Ni nanoparticles with controlled particle size inside the bacterial cellulose along with Ni(OH)2 has been performed.…”

Cellulose Nanofibrils

“…For example, as discussed earlier, embedding magnetic domains into a cellulose aerogel can be used to prepare super-adsorbent structures that can be triggered with applied magnetic fi elds [40]. In the case of cellulose matrix structured as BC the hybrid material can be deployed as a magnetic scaffold [133]. The most effi cient way to increase a high loading in the cellulosic matrix appears to be by precipitation of the particles using precursor salts.…”