Microbial synthesis of Pd/Fe3O4, Au/Fe3O4 and PdAu/Fe3O4 nanocomposites for catalytic reduction of nitroaromatic compounds

Abstract

Magnetically recoverable noble metal nanoparticles are promising catalysts for chemical reactions. However, the chemical synthesis of these nanocatalysts generally causes environmental concern due to usage of toxic chemicals under extreme conditions. Here, Pd/Fe3O4, Au/Fe3O4 and PdAu/Fe3O4 nanocomposites are biosynthesized under ambient and physiological conditions by Shewanella oneidensis MR-1. Microbial cells firstly transform akaganeite into magnetite, which then serves as support for the further synthesis of Pd, Au and PdAu nanoparticles from respective precursor salts. Surface-bound cellular components and exopolysaccharides not only function as shape-directing agent to convert some Fe3O4 nanoparticles to nanorods, but also participate in the formation of PdAu alloy nanoparticles on magnetite. All these three kinds of magnetic nanocomposites can catalyze the reduction of 4-nitrophenol and some other nitroaromatic compounds by NaBH4. PdAu/Fe3O4 demonstrates higher catalytic activity than Pd/Fe3O4 and Au/Fe3O4. Moreover, the magnetic nanocomposites can be easily recovered through magnetic decantation after catalysis reaction. PdAu/Fe3O4 can be reused in at least eight successive cycles of 4-nitrophenol reduction. The biosynthesis approach presented here does not require harmful agents or rigorous conditions and thus provides facile and environmentally benign choice for the preparation of magnetic noble metal nanocatalysts.

Environmental implications and applications of engineered nanoscale magnetite and its hybrid nanocomposites: A review of recent literature

“…Pd/Fe3O4, Au/Fe3O4, and PdAu/Fe3O4 nanocomposites are biosynthesized by S. oneidensis MR-1. Microbial cells firstly transform akaganeite into magnetite, which then serves as support for the further synthesis of Pd, Au and PdAu NPs from respective precursor salts [49]. Compared with engineered MNPs synthesized by chemical approaches, bacterial MMPs have the properties of large production, monodispersity, high crystallinity, and close-to-bulk magnetization, which enable them to be the highly promising MNPs for use in nanobiotechnology [50].…”

Gd3+-Doped Magnetic Nanoparticles for Biomedical Applications

“…Let us brie y discuss the possible reasons without entering into matters of detail. e aforementioned di culty for the larger Gd 3+ ion to accommodate in the iron oxide lattice implies a fraction of gadolinium being preserved in the reaction mixture in either a form of unreacted salt or, more likely, as a hydroxide (Gd(OH) 3 ). At the end of synthesis, it would not be recovered with a magnet and will not remain in the nal material.…”

“…ey have possible applications in catalysis [2,3], biomedicine [4], water purification from heavy metals [5,7], magnetic data recording devices [8], and so on. MNPs can be obtained by a variety of wet chemical methods, including a sol-gel method with the use of NaCl and NaH 2 PO 4 to control initial aggregation [9], a hydrothermal synthesis with polyethyleneimine as a capping ligand [10], and a solvothermal synthesis in ethylene glycol (EG) with oleylamine and 1,3-diaminopropane as surfactants and sodium acetate as a steric stabilizer [11].…”

Palladized cells as suspension catalyst and electrochemical catalyst for reductively degrading aromatics contaminants: Roles of Pd size and distribution

“…Accordingly, the biological inspired methods have been developed as an efficient and ecofriendly approach. The topic regarding to biogenic Pd (bioPd) NPs has received extensive interests recently (Narayanan and Sakthivel, 2010;Wu et al, 2011;Hennebel et al, 2012;Pat-Espadas et al, 2014;Tuo et al, 2015;Hou et al, 2016;Windt et al, 2005).…”

“…The palladized cell (Pd-cell) is capable of being as an efficient catalyst without further treatment. For environmental purpose, the catalysis of Pd-cell has been realized in the reductive dehalogenation of chlorinated compounds, nitroaromatic compounds and chromate reduction, etc (Hosseinkhani et al, 2013;Tuo et al 2013Tuo et al , 2015Martins et al, 2017).…”