Influence of natural organic matter (NOM) and synthetic polyelectrolytes on colloidal behavior of metal oxide nanoparticles

2010 2010

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Abstract (summary)

The colloidal behavior of engineered nanomaterials exposed in an aquatic environment may significantly influence their bioavailability as well as toxicity to different species. Natural organic matter (NOM) is one of the major colloidal materials ubiquitous in the environment with significant structural heterogeneity. Therefore, role of NOM molecules on environmental fate of these engineered NPs needs to be addressed. Colloidal behavior of aluminum (Al2O 3) and magnetic iron oxide (γFe2O3) NPs was studied in the presence of structurally different HAs and synthetic polyacrylic acids (PAAs). The conformation behavior of the adsorobed NOM/polyelectrolyte under specific solution conditions were determined with dynamic light scattering, atomic force microscopy measurements.

Al2O3 NPs followed the classical DLVO model of colloidal behavior in their pristine state. However, a significant deviation from the classical DLVO model was observed when these NPs were coated with structurally different HAs. Low polar, high molecular weight HA fractions showed much stronger stabilization against Ca2+ induced aggregation. Previously, we observed that these low polar, high molecular weight fractions strongly destabilized the NP suspension when added in a small quantity. A significant transformation in suspension stability was observed possibly due to steric effect of these adsorbed HAs.

The colloidal behavior of PAA/NOM coated ferrimagnetic γFe 2O3 NPs were investigated. Pure γFe2O 3 NPs were extremely unstable in aqueous solution but a significant enhancement in colloidal stability was observed after coating with polyelectrolytes/NOM. The steric as well as electrostatic stabilization introduced by the polyelectrolyte coating strongly dictated the colloidal stability. The alteration of electrosteric stabilization mechanisms by pH-induced conformation change profoundly influences the colloidal stability. Atomic force microscopy (AFM) study revealed a highly stretched conformation of the HA molecular chains adsorbed on γFe 2O3 NP surface with increasing pH from 5 to 9 which enhanced the colloidal stability trough long range electrosteric stabilization. The depletion of the polyelectrolytes during dilution of the suspension in the acidic solution conditions and in the presence of Na+ or Ca 2+ decreased the colloidal stability. The conformation of the polyelectrolytes adsorbed on the NP surface altered significantly as a function of substrate surface charge as viewed from the AFM imaging.

Indexing (details)

Soil sciences;
0481: Soil sciences
0565: Nanoscience
Identifier / keyword
Applied sciences; Biological sciences; Aggregation; Colloids; Humic acid; Nanoparticles; Natural organic matter
Influence of natural organic matter (NOM) and synthetic polyelectrolytes on colloidal behavior of metal oxide nanoparticles
Ghosh, Saikat
Number of pages
Publication year
Degree date
School code
DAI-B 71/07, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Xing, Baoshan
Committee member
Bhowmik, Prasanta C.; Hu, Weiguo; McClements, Julian D.
University of Massachusetts Amherst
Plant & Soil Sciences
University location
United States -- Massachusetts
Source type
Dissertations & Theses
Document type
Dissertation/thesis number
ProQuest document ID
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
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