Counter Anion-Directed Growth of Iron Oxide Nanorods in a Polyol Medium with Efficient Peroxidase-Mimicking Activity for Degradation of Dyes in Contaminated Water

Abstract

Development of nanozymes, which are nanomaterials with intrinsic enzymatic properties, has emerged as an appealing alternative to the natural enzymes with tremendous application potential from the chemical industry to biomedicine. The self-assembled growth of micrometer-sized oxide materials with controlled nonspherical shapes can be an important tool for enhancing activity as artificial enzymes, as the formation of these superstructures often results in high surface area with favorable impact on catalytic activity. Herein, the growth of rod-shaped Fe 3 O 4 microstructures via a one-pot microwave-based method and using a water–poly(ethylene glycol) mixture as a solvent is reported, without the involvement of external shape-directing agents. The precursor metal salt played a key role in the size, shape, and phase selective evolution of iron oxide micro/nanomaterials. Whereas self-assembled microrod superstructures were obtained using Fe(NO 3 ) 3 as the metal salt precursor, use of FeCl 3 or Fe-acetate as precursors afforded hollow Fe 2 O 3 microparticles and Fe 3 O 4 nanoparticles, respectively. A graphitic layer was deposited on the Fe 3 O 4 surface, imparting a negative surface charge as a result of a high-temperature treatment of poly(ethylene glycol). The rod-shaped Fe 3 O 4 microcrystals show efficient peroxidase-mimicking activity toward 3,3,5,5′-tetramethylbenzidine and pyrogallol as peroxidase substrates with a Michaelis–Menten rate constant ( K m ) value of 0.05 and 0.52 mM, respectively. The proficient enzyme mimicking behavior of these magnetic superstructures was further explored for the degradation of organic dyes that includes rhodamine B, methylene blue, and methyl orange with a rate constant ( k ) of 0.038, 0.011, and 0.007 min –1 respectively, using H 2 O 2 . This fast and simple method could help to develop a new pathway for differently shaped oxide nanoparticles in a sustainable and economical manner that can be harnessed as nanozymes for industrial as well as biological applications.

Facile strategy for the synthesis of silver nanoparticles on magnetic Fe3O4@C core–shell nanocomposites and their application in catalytic reduction

“…The apparent decrease can be attributed to the occupation of Ag nanoparticles. 33,34 Upon further increases in the ratio to 1 : 3, the surface area increases to 99.24 m 2 g −1 . It is not clear why there is a significant increase in surface area, but we speculate that some small carbon nanotubes that appeared at higher concentrations of AgNO 3 might have opened additional pores in the carbon shell, making them available for N 2 adsorption.…”

Self‐assembled CoSe2 Microspheres with Intrinsic Peroxidase Mimicking Activity for Efficient Degradation of Variety of Dyes

“…In another case, CoFe 2 O 4 fails to achieve time economy even with a higher catalyst dose. PEG‐assisted synthesized Fe 2 O 3 microrods have comparable results with the present catalyst with low catalyst economy and dye degradation rate [58] . The overall scenario introduces CoSe 2 MS as a new efficient candidate with peroxidase mimicking property to degrade high concentration of anionic dyes and almost complete removal of cationic dye with good recyclability which makes it suitable for pollutant degradation in acidic effluent.…”

Role of Anions in the Synthesis and Crystal Growth of Selected Semiconductors

“…The shape-selectivity of a semiconductor is usually achieved by additional shape-directing agents. These agents absorb preferentially on specific crystallographic planes leading to the change of direction and rate of crystal growth ( Jain et al, 2019 ). Moreover, synthesis methods also play a role in the shape-selectivity of a semiconductor ( Figure 2 ).…”