Reversible thermo-driven solid-state morphological transformation of nanotextured spinel material

Abstract The present study, highlights essentially a phenomenon rarely encountered in NiFe2O4 nanoparticles self-assembled in the presence of organic azo dye (i.e. Methyl orange). To the best of our knowledge, NiFe2O4 nanoparticles with fibrous morphology is unprecedent. Unexpected features of solid-state morphology changes from zero-dimensional to quasi one-dimensional and back again were evaluated by applying a wide range of complementary physico-chemical characterization techniques to unequivocally assess the nature of the self-assembly process. Scanning electron microscopy reveals the reversibility of the above-mentioned process, under various applied conditions. Zero-dimensional nickel ferrite nanoparticles (as-synthesized) are assembled into quasi one-dimensional fibers, uniformly distributed in all three directions by adsorption of Methyl orange (MO) dye, with texture preserved after the photocatalytic process, and finally it returns to the initial appearance (zero dimensional) by applying a thermal treatment. The presented results may contribute to photocatalyst development by in/ex-situ tuning the morphology of the material, which allows active sites to spread over a wide internal surfaces and pores which, in turn, enhance the photodegradation ability of the catalyst.