Colloidal aggregation and structural assembly of aspect ratio variant goethite (α-FeOOH) with nC60 fullerene in environmental media. (December 2016)

• Record Type: Journal Article
• Authors: Ghosh, Saikat; Pradhan, Nihar R.; Mashayekhi, Hamid; Zhang, Qiu; Pan, Bo; Xing, Baoshan
• Is Part Of: Environmental pollution. Volume 219(2016)
• Page Start: 1049
• Page End: 1059
• Publication Date: 2016-12
• Subjects: Fullerene -- α-FeOOH -- Aggregation -- Assembly -- Magneto-static; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2016.09.005
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Environmental mobility of C60 fullerene can be significantly affected in the presence of naturally abundant α-FeOOH. However, α-FeOOH vary significantly in sizes, shapes and associated properties that can greatly influence the fate and transport of C60 fullerene in environmental media. Therefore, colloidal hetero-association between well crystallized low aspect (LAsp ) α-FeOOH and nC60 fullerene may differ substantially to weakly crystallized high-aspect (HAsp ) counterpart. In contrast to LAsp α-FeOOH, inherent crystal defects and surface charge generation in HAsp α-FeOOH facilitated strong Coulombic attraction and aggregation with fullerene in acidic pH. However, LAsp α-FeOOH demonstrated subtle entropic depletion mediated interaction with fullerene prevalent in hard rods. Humic acid (HA) encapsulation of HAsp α-FeOOH substantially blocked fullerene attachment. Minute enhancement in colloidal stability was detected for HA-coated HAsp α-FeOOH and fullerene mixture to HA-coated HAsp α-FeOOH alone. To investigate the interfacial assembly of α-FeOOH with fullerene " in situ" differential interference contrast (DIC) microscopic investigations were employed. This study showed significantly different interface behavior of the binary mixtures of fullerene and HAsp α-FeOOH NPs, and LAsp particles. On air-water interface, bare HAsp α-FeOOH displayed liquid crystalline packing. However, addition of fullerene to HAsp α-FeOOH suspension at pH5 produced closed-loop polygonal and circular ring structures. Head-to-tail alignment of magnetic dipoles as well as fullerene hydrophobicity facilitated such assembly formation. " Ex situ " AFM investigation revealed further the presence of magnetically derived ring structure which asserts that the formed " in situ " ensembles were not transient, hence, may abate fullerene transport through environmental interfaces. Barring hydrophobicity assisted attachment of fullerene to LAsp α-FeOOHs, the absence of any close-packed structures may unlikely abate fullerene transport as envisaged in case of HAsp α-FeOOH. Thus, aspect ratio variation and associated material properties of naturally abundant α-FeOOH may significantly impact fullerene transport through environmental media. Graphical abstract: Highlights: Lattice defects in HAsp α-FeOOH facilitated Coulombic attraction with fullerene. Humic acid coating on HAsp α-FeOOH prevented fullerene attachment. Interfacial attachment of fullerene to HAsp α-FeOOH produced circular assemblies. Magneto-static energy of HAsp α-FeOOH was attributed to assembly formation. LAsp α-FeOOH formed capillary driven linear assembly upon fullerene adhesion. Abstract : Hetero-association and flux-closed assemblies between HAsp α-FeOOH and fullerene with minimized magneto-static energy can significantly abate the transport of the latter.