Hybridized electronic states in potassium-doped picene probed by soft x-ray spectroscopies

The electronic structure of the unoccupied and occupied states of potassium (K)-doped and undoped picene crystalline films has been investigated by using the element-selective and bulk-sensitive photon-detection methods of X-ray absorption and emission spectroscopies. We observed the formation of the doping-induced unoccupied and occupied electronic states in K-doped picene. By applying the inner-shell resonant-excitation experiments, we observed the evidence for the orbital hybridization between K and picene near the Fermi energy. Furthermore, the resonant X-ray emission experiment suggests the presence of the Raman-active vibronic interaction in K-doped picene. These experimental evidences play a crucial role in the superconductivity of K-doped picene.Comment: 12 pages, 3 figure

Structures of small mixed krypton-xenon clusters

Structures of small mixed krypton-xenon clusters of different compositions with an average size of 30–37 atoms are investigated. The Kr 3d 5/2 and Xe 4d 5/2surface core level shifts and photoelectron intensities originating from corner, edge, and face/bulk sites are analyzed by using soft x-ray photoelectron spectroscopy. Structural models are derived from these experiments, which are confirmed by theoretical simulation taking induced dipole interactions into account. It is found that one or two small Xe cores are partly embedded in the surface of the Kr clusters. These may grow and merge leading to a phase separation between the two rare gas moieties in mixed clusters with increasing the Xe content

Structures of mixed argon-nitrogen clusters

The structures of mixed argon-nitrogen clusters of different compositions are investigated by analyzing core level shifts and relative intensities of surface and bulk sites in the Ar 2p 3/2 regime in soft X-ray photoelectron spectroscopy. These structures are confirmed by core level shift calculations taking induced dipole interactions into account, in which several model structures of the mixed clusters are considered by Monte Carlo simulations. These results suggest that the mixed argon-nitrogen clusters show partial core-shell structures, where an argon core is partially covered by nitrogen molecules

Probing the Penetration of Rapamycin by Scanning Transmission X-ray Microscopy

Drug penetration in human skin ex vivo following a modification of skin barrier permeability is systematically investigated by scanning transmission X-ray microscopy. Element-selective excitation is used in the O 1s regime for probing quantitatively the penetration of topically applied rapamycin in different formulations with a spatial resolution reaching <75 nm. The data were analyzed by a comparison of two methods: (i) two-photon energies employing the Beer–Lambert law and (ii) a singular value decomposition approach making use of the full spectral information in each pixel of the X-ray micrographs. The latter approach yields local drug concentrations more reliably and sensitively probed than the former. The present results from both approaches indicate that rapamycin is not observed within the stratum corneum of nontreated skin ex vivo, providing evidence for the observation that this high-molecular-weight drug inefficiently penetrates intact skin. However, rapamycin is observed to penetrate more efficiently the stratum corneum when modifications of the skin barrier are induced by the topical pretreatment with the serine protease trypsin for variable time periods ranging from 2 to 16 h. After the longest exposure time to serine protease, the drug is even found in the viable epidermis. High-resolution micrographs indicate that the lipophilic drug preferably associates with corneocytes, while signals found in the intercellular lipid compartment were less pronounced. This result is discussed in comparison to previous work obtained from low-molecular-weight lipophilic drugs as well as polymer nanocarriers, which were found to penetrate the intact stratum corneum exclusively via the lipid layers between the corneocytes. Also, the role of the tight junction barrier in the stratum granulosum is briefly discussed with respect to modifications of the skin barrier induced by enhanced serine protease activity, a phenomenon of clinical relevance in a range of inflammatory skin disorders