Polarimetric Angle-Resolved Second Harmonic Scattering of Colloidal TiO2 Nanoparticles in Aqueous Environments
Marie Bischoff a, Arianna Marchioro a, Sylvie Roke a
a Laboratory for fundamental BioPhotonics, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
nanoGe Fall Meeting
Proceedings of nanoGe Fall Meeting19 (NGFM19)
#CharDy19. Charge Carrier Dynamics
Berlin, Germany, 2019 November 3rd - 8th
Organizers: Marcus Scheele and Maksym Yarema
Poster, Marie Bischoff, 345
Publication date: 16th July 2019

Titanium dioxide (TiO2) is strongly investigated for the use in environmental and energy applications, such as photocatalytic waste water treatment and solar water splitting. Those operations require a high physical and chemical stability of the material in aqueous environments. TiO2 is a resistant semiconductor oxide with relevant optical and electronical properties to perform photocatalytic reactions and therefore a promising candidate in this area of application. Understanding the microscopic structure of the TiO2/liquid interface is key to enhance the performance of the material in photocatalytic devices.

In this work, we investigate colloidal TiO2 nanoparticles in different aqueous environments. We use polarimetric angle-resolved second harmonic scattering (AR-SHS) to access the surface potential of the TiO2 colloids with respect to the bulk electrolyte solution and the nonlinear surface susceptibility as a measure of molecular ordering of the water molecules at the interface. Those are important parameters in order to better understand surface‑mediated processes happening at the interface. Here we first demonstrate the independence of surface potential and surface molecular water orientation on particle concentration, and show how the surface molecular orientation of the water at the TiO2 interface and the surface potential change with pH and in the presence of different salts.

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