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Surface Characterization of TiO2 Polymorphic Nanocrystals through 1H-TD-NMR
Massimo Tawfilas1, Michele Mauri1, Luca De Trizio2
1Department of Materials Science , University of Milano-Bicocca , via R. Cozzi 55 , 20125 Milan , Italy.
Langmuir : the ACS Journal of Surfaces and Colloids
|July 18, 2018
Summary
Proton transverse relaxation times (T2) of water near titanium dioxide nanocrystals (NCs) can differentiate crystal phases and surface areas. This TD-NMR method offers insights into NC surface chemistry and interactions.
Area of Science:
- Materials Science
- Nanotechnology
- Physical Chemistry
Background:
- Nanocrystal (NC) surface characterization is crucial for understanding nanoscale phenomena.
- Surface properties dictate NC interactions, stability, and nanocomposite feasibility.
- Titanium dioxide (TiO2) nanocrystals exist in various polymorphs (rutile, anatase, brookite) with distinct surface characteristics.
Purpose of the Study:
- To extract detailed surface information from different titanium dioxide (TiO2) nanocrystal (NC) polymorphs.
- To utilize 1H-TD-NMR of water as a tool for surface characterization of TiO2 NCs.
- To correlate proton transverse relaxation times (T2) with specific surface area and crystal phase.
Main Methods:
- Proton transverse relaxation time (T2) measurements of water interacting with TiO2 NCs.
- Time-Domain Nuclear Magnetic Resonance (TD-NMR) spectroscopy was employed.
- Analysis of relaxivity (R2) as a function of NC concentration (Cm) and specific surface area (δp·Cm).
Main Results:
- A linear correlation was observed between relaxivity (R2) and TiO2 NC concentration (Cm).
- Normalized slopes of this correlation indicate surface/water interaction, varying by crystal phase and size.
- Distinct surface/water interaction values were obtained for rutile, anatase, and brookite TiO2 NCs, correlating with surface energy trends.
Conclusions:
- Proton relaxation phenomena at the NC surface enable differentiation of TiO2 polymorphs.
- TD-NMR of water provides a method to determine the specific surface area of TiO2 NCs in solution.
- This technique offers valuable insights into the surface chemistry and interactions of nanomaterials.
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