Electronic Structure of Individual Hybrid Colloid Particles Studied by Near-Edge X‑ray Absorption Fine Structure (NEXAFS) Spectroscopy in the X‑ray Microscope

The electronic structure of individual hybrid particles was studied by nanoscale near-edge X-ray absorption spectromicroscopy. The colloidal particles consist of a solid polystyrene core and a cross-linked poly-N-(isopropylacrylamide) shell with embedded crystalline titanium dioxide (TiO₂) nanoparticles (d = 6 ± 3 nm). The TiO₂ particles are generated in the carrier network by a sol–gel process at room temperature. The hybrid particles were imaged with photon energy steps of 0.1 eV in their hydrated environment with a cryo transmission X-ray microscope (TXM) at the Ti L_2,3-edge. By analyzing the image stacks, the obtained near-edge X-ray absorption fine structure (NEXAFS) spectra of our individual hybrid particles show clearly that our synthesis generates TiO₂ in the anastase phase. Additionally, our spectromicroscopy method permits the determination of the density distribution of TiO₂ in single carrier particles. Therefore, NEXAFS spectroscopy combined with TXM presents a unique method to get in-depth insight into the electronic structure of hybrid materials.