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Isoelectric Point of Metal Oxide Films Formed by Anodization
Aydan Yadigarli1, Patrick Hartwich1, Gabriel Onyenso1
1Chemistry and Structure of novel Materials, University of Siegen, Paul-Bonatz Strasse 9-11, 57068 Siegen, Germany.
Langmuir : the ACS Journal of Surfaces and Colloids
|January 23, 2025
Summary
The isoelectric point (IEP) of metal oxide films, crucial for surface charge prediction, was determined. IEP varies based on film properties like composition and phase, differing from nanoparticle counterparts.
Area of Science:
- Materials Science
- Surface Chemistry
- Electrochemistry
Background:
- Surface charge of metal oxides impacts adsorption, catalysis, and material science.
- Isoelectric point (IEP) and solution pH predict surface charge.
- Limited IEP data exists for metal oxide films compared to nanoparticles.
Purpose of the Study:
- Determine the IEP of various compact metal oxide films.
- Compare the IEP of nanostructured oxides with compact films.
- Investigate factors influencing the IEP of metal oxides.
Main Methods:
- Streaming potential technique for IEP determination.
- Electrochemical anodization for film formation.
- Scanning electron microscopy, contact angle, XRD, and XPS for characterization.
Main Results:
- IEP values were determined for compact TiO2, Nb2O5, WO3, ZrO2, NiO, and Al2O3 films.
- Nanostructured TiO2 and NiO IEPs were compared to compact films.
- IEP of compact anodic oxides differed from nanoparticle and ALD counterparts.
Conclusions:
- The IEP of metal oxides is sensitive to chemical composition, hydroxylation, and crystallographic phases.
- Film formation method significantly influences the IEP.
- Understanding IEP is key for controlling surface properties in applications.
