Electron-hole correlation effects in core-level spectroscopy probed by the resonant inelastic soft x-ray scattering map of C60

Metastable Brominated Nanodiamond Surface Enables Room Temperature and Catalysis-Free Amine Chemistry

Bromination of high-pressure, high-temperature (HPHT) nanodiamond (ND) surfaces has not been explored and can open new avenues for increased chemical reactivity and diamond lattice covalent bond formation. The large bond dissociation energy of the diamond lattice-oxygen bond is a challenge that prevents new bonds from forming, and most researchers simply use oxygen-terminated NDs (alcohols and acids) as reactive species. In this work, we transformed a tertiary-alcohol-rich ND surface to an amine surface with ∼50% surface coverage and was limited by the initial rate of bromination. We observed that alkyl bromide moieties are highly labile on HPHT NDs and are metastable as previously found using density functional theory. The strong leaving group properties of the alkyl bromide intermediate were found to form diamond-nitrogen bonds at room temperature and without catalysts. This robust pathway to activate a chemically inert ND surface broadens the modalities for surface termination, and the unique surface properties of brominated and aminated NDs are impactful to researchers for chemically tuning diamond for quantum sensing or biolabeling applications.

Dynamic Effects and Hydrogen Bonding in Mixed-Halide Perovskite Solar Cell Absorbers

The organic component (methylammonium) of CH₃NH₃PbI_3-xCl_x-based perovskites shows electronic hybridization with the inorganic framework via H-bonding between N and I sites. Femtosecond dynamics induced by core excitation are shown to strongly influence the measured X-ray emission spectra and the resonant inelastic soft X-ray scattering of the organic components. The N K core excitation leads to a greatly increased N-H bond length that modifies and strengthens the interaction with the inorganic framework compared to that in the ground state. The study indicates that excited-state dynamics must be accounted for in spectroscopic studies of this perovskite solar cell material, and the organic-inorganic hybridization interaction suggests new avenues for probing the electronic structure of this class of materials. It is incidentally shown that beam damage to the methylamine component can be avoided by moving the sample under the soft X-ray beam to minimize exposure and that this procedure is necessary to prevent the creation of experimental artifacts.

Site-specific electronic structure of imidazole and imidazolium in aqueous solutions

The electronic structures of aqueous imidazole and imidazolium solutions are studied in an atom- and site-specific fashion using soft X-ray spectroscopy.

Probing hydrogen bonding orbitals: resonant inelastic soft X-ray scattering of aqueous NH3

Resonant inelastic soft X-ray scattering was used to probe the hydrogen bonding orbitals in aqueous ammonia.