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Reversible or not? Distinguishing agglomeration and aggregation at the nanoscale
Stanislav V Sokolov1, Kristina Tschulik1, Christopher Batchelor-McAuley1
1Department of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University , South Parks Road, Oxford OX1 3QZ, U.K.
Analytical Chemistry
|September 10, 2015
Summary
Distinguishing nanoparticle aggregation from agglomeration is challenging. Electrochemical nanoimpacts reveal small nanoparticles in high ionic strength, indicating reversible agglomeration, not irreversible aggregation, for colloids.
Area of Science:
- Colloid and Surface Science
- Nanomaterials Characterization
- Electrochemistry
Background:
- Nanoparticles in solution can undergo aggregation (irreversible) or agglomeration (reversible) clustering.
- Conventional techniques like DLS, NTA, and electron microscopy struggle to differentiate these processes, only confirming particle clusters.
- Distinguishing between aggregation and agglomeration is crucial for understanding nanoparticle behavior and stability.
Purpose of the Study:
- To develop and apply a joint approach to differentiate between nanoparticle aggregation and agglomeration.
- To characterize a colloidal system of silver nanoparticles (Ag NPs) using multiple techniques.
- To demonstrate the utility of electrochemical nanoimpacts in analyzing nanoparticle clustering.
Main Methods:
- Dynamic Light Scattering (DLS)
- Nanoparticle Tracking Analysis (NTA)
- Scanning Electron Microscopy (SEM)
- Transmission Electron Microscopy (TEM)
- Electrochemical Nanoimpacts
Main Results:
- Conventional techniques (DLS, NTA, SEM, TEM) confirmed the presence of large nanoparticle clusters.
- Electrochemical nanoimpacts detected small nanoparticles (<30 nm) even in high ionic strength media (>0.5 M KCl).
- The detection of small nanoparticles in high ionic strength solutions indicated a reversible clustering process.
Conclusions:
- The observed clustering of Ag NPs was identified as reversible agglomeration, not irreversible aggregation.
- Electrochemical nanoimpacts provide a feasible method for analyzing colloids and distinguishing between aggregation and agglomeration.
- This approach has broad applicability for characterizing various colloidal systems and understanding subtle process differences.
