X-Ray Absorption Spectroscopy of TiO2 Nanoparticles in Water Using a Holey Membrane-Based Flow Cell

Many applications of TiO2 nanoparticles, such as photocatalytic water splitting
or water remediation, occur in aqueous environment. However, the
impact of solvation on TiO2 electronic structure remains unclear because
only few experimental methods are currently available to probe nanoparticle–
water interface. Soft X-ray absorption spectroscopy has been extensively
used to characterize the electronic structure of TiO2 materials, but so far
only in vacuum conditions. Here, oxygen K edge and titanium L edge X-ray
absorption spectroscopy characterization of TiO2 nanoparticles measured
directly in aqueous dispersion is presented. For this purpose, a new method
to probe nanomaterials in liquid using a holey membrane-based flow cell is
introduced. With this approach, the X-ray transmission of the membrane is
increased, especially in the water window, compared to solid membranes.