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Entropy-Driven Aggregation of Titanium Dioxide Nanoparticles in Aquatic Environments.
Yuliia Herchenova1, Hyeon Yeong Park1, Eun-Ju Kim1,2
1Water Cycle Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea.
The Journal of Physical Chemistry. A
|August 14, 2020
Summary
Isothermal titration calorimetry (ITC) reveals entropy-driven aggregation of titanium dioxide nanoparticles (TiO2 NPs). Humic acid and calcium ions promote NP aggregation, aiding environmental fate studies.
Area of Science:
- Environmental Science
- Materials Science
- Physical Chemistry
Background:
- Engineered nanoparticles (ENPs) aggregation influences their environmental fate and transport.
- Understanding ENP interactions with environmental components is crucial for risk assessment.
Purpose of the Study:
- To apply isothermal titration calorimetry (ITC) for studying the thermodynamics of ENPs aggregation.
- To elucidate the interaction mechanisms between ENPs and environmental constituents.
Main Methods:
- Utilized ITC to measure the thermodynamics of engineered nanoparticles (ENPs) aggregation.
- Investigated aggregation in solutions with varying electrolytes (NaCl, CaCl2), natural organic matter, and hematite nanoparticles.
Main Results:
- Free energy of TiO2 nanoparticle aggregation was dominated by favorable entropy, likely due to water molecule expulsion.
- Humic acid and Ca2+ ions facilitated both homo- and hetero-aggregation via bridging mechanisms.
- Formation of more compact aggregates was observed in the presence of humic acid and Ca2+.
Conclusions:
- ITC is a viable strategy for characterizing ENP interactions with environmental components.
- The findings provide insights into the aggregation behavior of ENPs in ambient water systems.
- Entropy plays a key role in the aggregation thermodynamics of TiO2 NPs.
