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Aggregation kinetics of colloidal particles measured by gas-phase differential mobility analysis
D-H Tsai1, L F Pease, R A Zangmeister
1Department of Chemistry and Biochemistry and Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, USA.
Langmuir : the ACS Journal of Surfaces and Colloids
|December 10, 2008
Summary
Electrospray gas-phase ion-mobility analysis effectively tracks nanoparticle aggregation. This method quantifies gold nanoparticle clusters, revealing aggregation rates and surface potential for colloidal stability studies.
Area of Science:
- Nanotechnology
- Colloid Science
- Physical Chemistry
Background:
- Nanoparticle aggregation (flocculation) impacts material properties and stability.
- Quantifying early-stage aggregation is crucial for understanding colloidal systems.
- Existing methods may have limitations in characterizing dynamic aggregation processes.
Purpose of the Study:
- To introduce and validate electrospray gas-phase ion-mobility analysis (ES-DMA) for investigating nanoparticle aggregation.
- To quantitatively characterize the formation and evolution of gold nanoparticle (Au-NP) aggregates.
- To determine key aggregation parameters like rate and stability ratio, and extract surface properties.
Main Methods:
- Utilized electrospray (ES) to introduce Au-NP solutions into the gas phase.
- Employed differential ion-mobility analysis (DMA) to separate and detect Au-NP monomers and aggregates (dimers, trimers, tetramers).
- Analyzed multimodal size distributions over time to quantify aggregation kinetics and ionic strength effects.
Main Results:
- ES-DMA successfully resolved distinct size distributions for Au-NP monomers and various aggregate sizes.
- Quantitative characterization of aggregate fractions allowed determination of aggregation degree, rate, and stability ratio.
- Extracted a surface potential of 64 ± 2 mV for 10 nm Au-NPs, consistent with other techniques.
Conclusions:
- ES-DMA is a powerful and validated technique for real-time, quantitative analysis of early-stage colloidal aggregation.
- The method provides insights into nanoparticle surface properties and colloidal stability.
- ES-DMA can serve as a preparatory tool for size-selective isolation of nanoparticle aggregates.
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