A combination of synchrotron radiation photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy has been used to study the adsorption of phenylphosphonic acid (PPA) on anatase TiO₂(101) single crystal at coverages of 0.15 monolayer (ML) and 0.85 ML. The photoelectron spectroscopy data suggests that at 0.15 ML coverage PPA adsorbs in a bidentate geometry following deprotonation of both phosphonate hydroxyl groups, leaving the P=O group unbound. At 0.85 ML there is a shift to a mixed bidentate/monodentate binding mode. The carbon K-edge NEXAFS spectra was recorded at two azimuths. Our calculations show that for PPA on anatase TiO₂(101) the phenyl ring is oriented 65◦ ± 4◦ away from the surface plane with an azimuthal twist of 57◦ ± 11◦ away from the [10-1] azimuth.

The adsorption of p-aminobenzoic acid (pABA) on the anatase TiO₂(101) surface has been investigated using synchrotron radiation photoelectron spectroscopy, near edge X-ray absorption fine structure (NEXAFS) spectroscopy, and density functional theory (DFT). Photoelectron spectroscopy indicates that the molecule is adsorbed in a bidentate mode through the carboxyl group following deprotonation. NEXAFS spectroscopy and DFT calculations of the adsorption structures indicate the ordering of a monolayer of the amino acid on the surface with the plane of the ring in an almost upright orientation. The adsorption of pABA on nanoparticulate TiO₂ leads to a red shift of the optical absorption relative to bare TiO₂ nanoparticles. DFT and valence band photoelectron spectroscopy suggest that the shift is attributed to the presence of the highest occupied molecular orbitals in the TiO₂ band gap region and the presence of new molecularly derived states near the foot of the TiO₂ conduction band.

The photocatalytic activity of anatase TiO₂ decorated with metal clusters has been widely documented, but the nature of the metal–metal oxide interface and reaction intermediates in catalytic processes are still not well understood. This in part is due to the fact that use of photoelectron spectroscopy to deduce the surface chemistry of catalytic systems has long been hampered by the huge pressure difference between real-world operation and the requirement of high vacuum for electron detection. Here, the in situ growth of silver nanoparticles on a model metal-oxide catalyst support and their reactivity with a CO/H₂O gas mixture has been investigated in detail. Using synchrotron X-ray photoelectron spectroscopy, near-ambient pressure X-ray photoelectron spectroscopy, and scanning tunneling microscopy, the interaction of Ag with the anatase TiO₂ surface leads to metal-surface charge transfer and low mobility of Ag on the surface. Upon exposure to a 1.5 mbar CO/1.5 mbar H₂O gas mixture, partial oxidation of the Ag clusters is observed. There is also evidence suggesting that a Ag–carbonyl species is formed during exposure of the Ag/TiO₂ surface to a CO/H₂O gas mixture.

Supercrystalline nanocomposite materials with micromechanical properties approaching those of nacre or similar structural biomaterials can be produced by self-assembly of organically modified nanoparticles, and further strengthened by crosslinking. The strengthening of these nanocomposites is controlled via thermal treatment, which promotes the formation of covalent bonds between interdigitated ligands on the nanoparticles’ surface. In this work it is shown how the extent of the mechanical properties’ enhancement can be controlled by the solvent used during the self-assembly step. We find that the resulting mechanical properties correlate with the Hansen solubility parameters of the solvents and ligands used for the supercrystal assembly: hardness and elastic modulus decrease as the Hansen solubility parameter of the solvent approaches the Hansen solubility parameter of the ligands that stabilize the nanoparticles. Moreover, it is shown that self-assembled supercrystals that are subsequently uniaxially pressed can deform up to 6 %. The extent of this deformation is also closely related to the solvent used during the self-assembly step. These results indicate that the conformation and arrangement of the organic ligands on the nanoparticle surface not only control the self-assembly itself, but also influence the mechanical properties of the resulting supercrystalline material. The Hansen solubility parameter may therefore serve as tool to predict what solvents and ligands should be used to obtain supercrystalline materials with good mechanical properties.