Binary
Short-Range Colloidal Assembly of Magnetic
Iron Oxides Nanoparticles and Fullerene (nC<sub>60</sub>) in Environmental
Media
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Abstract
Colloidal
assembly of nC<sub>60</sub> fullerene with naturally
abundant magnetic iron oxide NPs will affect their fate and transformation
in environmental media. In solution, fullerene association to aggregating
iron oxide NPs/clusters greatly enhanced the overall colloidal stability.
Development of depletion-mediated structured fullerene layers between
pure and surface modified γFe<sub>2</sub>O<sub>3</sub> NPs possibly
resulted in such stabilization. Here, we also report that on air–water
interface, association of fullerene to pure and humic acid (HA7) coated
γFe<sub>2</sub>O<sub>3</sub> NPs led to the formation of ordered
assemblies, e.g., binary wires and closed-packed “crystalline”
and “glassy” structures in the presence and absence
of electrolytes suggesting immobilization of the former. The interaction
of fullerene to Fe<sub>3</sub>O<sub>4</sub> NPs and clusters also
produced ordered assemblies along with amorphous aggregates. Fullerene
interaction with Fe<sub>3</sub>O<sub>4</sub> NPs in low concentration
of HA1 and Na<sup>+</sup> at pH 6 formed dendritic growth and polycrystalline
circular assemblies on air–water interface. HRTEM study further
revealed that the monolayer circular assemblies were highly ordered
but structural degeneracy was evident in multilayers. Therefore, interfacial
assemblies of fullerene with iron oxide NPs resulted in short-range
periodic structures with concomitant immobilization and reduction
in availability of the former, especially in soils or sediments rich
in the latter