Controlled Fabrication of Polyethylenimine-Functionalized Magnetic Nanoparticles for the Sequestration and Quantification of Free Cu²⁺

Abstract

Presented herein is a detailed study into the controlled adsorption of polyethylenimine (PEI) onto 50 nm crystalline magnetite nanoparticles (Fe(3)O(4) NPs) and how these PEI-coated Fe(3)O(4) NPs can be used for the magnetic capture and quantification of ultratrace levels of free cupric ions. We show the ability to systematically control the amount of PEI adsorbed onto the Fe(3)O(4) magnetic nanoparticle surfaces by varying the concentration of polymer during the adsorption process. This in turn allows for the tailoring of important colloidal properties such as the electrophoretic mobility and aggregation stability. Copper adsorption tests were carried out to investigate the effectiveness of PEI-coated Fe(3)O(4) NPs in copper remediation and detection. The study demonstrated that the NPs ability to bind with copper is highly dependent on the amount of PEI adsorbed on the NP surface. It was found that PEI-coated Fe(3)O(4) NPs were able to capture trace levels (approximately 2 ppb) of free cupric ions and concentrate the ions to allow for detection via ICP-OES. More importantly, it was found that due to the amine-rich structure of PEI, the PEI-coated Fe(3)O(4) NPs selectively adsorb toxic free cupric ions but not the less toxic EDTA complexed copper. This unique property makes PEI-coated Fe(3)O(4) NPs a novel solution for the challenge of separating and quantifying toxic cupric ions as opposed to the total copper concentration of a sample.

Reduction of hexavalent chromium by Pannonibacter phragmitetus LSSE-09 coated with polyethylenimine-functionalized magnetic nanoparticles under alkaline conditions

“…The result reveals that the PEI-modified Fe 3 O 4 NPs exhibited positive zeta potential at pH < 11.5, which can be attributed to the protonation of amine groups in PEI molecules on the particle surface [29]. Goon and his co-workers also reported that the PEI-modified Fe 3 O 4 NPs exhibited positive zeta potential under alkaline conditions, and the pI shifted toward a higher pH as more PEI was attached [31]. It is known that the highly charged nature of lipopolysaccharides confers an overall negative charge on the Gram-negative cell wall [33].…”

“…The hydroxyl groups on the surface of Fe 3 O 4 NPs were exchanged with citrate ligands to provide excess carboxylate groups, which bring negative charges on particle surface to prevent their aggregation [40,41] and induce the formation of surface complexes between Fe 3 O 4 and compounds [42]. PEI molecules were conjugated to the anionic surface of magnetite nanoparticles through strong ionic interactions [38], leading to a significantly enhanced stable suspension [31]. Fig.…”

“…PEI is a water-soluble polycation consisting of primary, secondary, and tertiary amine functional groups [26]. It has been used for the design of DNA delivery vehicles [27,28] and as a functional coating to enhance the performance of heavy metals adsorption [29][30][31][32]. It is known that electrostatic interaction between adsorbent and adsorbate plays an important role in the process of adsorption [29].…”

Applications of Magnetite Nanoparticles for Heavy Metal Removal from Wastewater

“…Goon et al [40] studied the controlled adsorption of polyethylenimine (PEI) onto 50 nm crystalline magnetite nanoparticles (Fe 3 O 4 NPs) and how these PEI-coated Fe 3 O 4 NPs can be used for the magnetic capture and quantification of ultratrace levels of free cupric ions. The authors were able to systematically control the amount of PEI adsorbed onto the Fe 3 O 4 mag-netic nanoparticle surfaces by varying the concentration of polymer during the adsorption process.…”

Preparation of a chelating sorbent based on pyridylethylated polyethylenimine for recovering transition metal ions

“…PEI as a polyamine is highly active in sorption of Hg(II) (3.3 mmol g -1 [3]), Cu(II), Ni(II), Co(II), and Zn(II) ions (no less than 2 mmol g -1 [6]) and, in combination with chitosan, in sorption of Hg(II) [4], Pt(IV), and Pd(II) ions [5]. Such complexing properties of PEI allow preparation of structure-forming [13,14] and metal-containing catalytic [15] materials based on it. Additional N-functionalization of PEI, primarily occurring at the most reactive primary amino groups [10], signifi cantly alters the sorption characteristics.…”