Dissolved Organic Matter Adsorption to Model Surfaces: Adlayer Formation, Properties, and Dynamics at the Nanoscale

Adlayers of dissolved organic matter (DOM) form on many surfaces in natural and engineered systems and affect a number of important processes in these systems. Yet, the nanoscalar properties and dynamics of DOM adlayers remain poorly investigated. This work provides a systematic analysis of the prop...

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Bibliographic Details
Published in:Environmental science & technology 2014-08, Vol.48 (16), p.9420-9429
Main Authors: Armanious, Antonius, Aeppli, Meret, Sander, Michael
Format: Article
Language:English
Subjects:
Acids
Adsorption
Aqueous solutions
Benzopyrans - chemistry
Chemical compounds
Contact angle
Gold - chemistry
Humic Substances
Kinetics
Molecules
Nanostructures - chemistry
Osmolar Concentration
Quartz Crystal Microbalance Techniques
Solutions
Static Electricity
Sulfhydryl Compounds - chemistry
Surface Properties
Water - chemistry
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Summary:Adlayers of dissolved organic matter (DOM) form on many surfaces in natural and engineered systems and affect a number of important processes in these systems. Yet, the nanoscalar properties and dynamics of DOM adlayers remain poorly investigated. This work provides a systematic analysis of the properties and dynamics of adlayers formed from a diverse set of eight humic and fulvic acids, used as DOM models, on surfaces of self-assembled monolayers (SAMs) of different alkylthiols covalently bound to gold supports. DOM adsorption to positively charged amine-terminated SAMs resulted in the formation of water-rich adlayers with nanometer thicknesses that were relatively rigid, irreversibly adsorbed, and collapsed upon air drying, as demonstrated by combined quartz crystal microbalance and ellipsometry measurements. DOM adlayer thicknesses varied only slightly with solution pH from 5 to 8 but increased markedly with increasing ionic strength. Contact angle measurements revealed that the DOM adlayers were relatively polar, likely due to the high water contents of the adlayers. Comparing DOM adsorption to SAM-coated sensors that systematically differed in surface charge and polarity characteristics showed that electrostatics dominated DOM–surface interactions. Laccase adsorption to DOM adlayers on amine-terminated SAMs served to demonstrate the applicability of the presented experimental approach to study the interactions of (bio)­macromolecules and (nano)­particles with DOM.
ISSN:0013-936X
1520-5851
DOI:10.1021/es5026917