Electron dynamics in charge-transfer-to-solvent states of aqueous chloride revealed by Cl- 2p resonant Auger-electron spectroscopy

Charge-transfer-to-solvent (CTTS) excited states of aqueous chloride are studied by a novel experimental approach based on resonant inner-shell photoexcitation, Cl(-)aq 2p --> e(i), i = 1-4, which denotes a series of excitations to lowest and higher CTTS states. These states are clearly identified through the occurrence of characteristic spectator Auger decays to double Cl 3p valence-hole states, where the CTTS states can be more stabilized as compared to single Cl(-)aq 2p core excitations and optical valence excitations. Furthermore, we have found for the first time that the CTTS electron e(i) bound by a single Cl 2p hole not only behaves as a spectator e(i) --> e'(i), bound by a double valence-hole state before relaxation of the excited electron (i) itself, but also shows electron dynamics to the relaxed lowest state, e(i) --> e'(1*). This interpretation is supported by ab initio calculations. The key to performing photoelectron and Auger-electron spectroscopy studies from aqueous solutions is the use of a liquid microjet in ultrahigh vacuum in conjunction with synchrotron radiation.     

Application of digital holographic microscopy to investigate the sedimentation of intact red blood cells and their interaction with artificial surfaces

Red blood cells are able to undergo shape change from the "normal" discocyte to either echinocytes or stomatocytes depending on a large variety of membrane and cytoplasmic parameters. Such shape changes can be relatively fast (within seconds) during the sedimentation of the cells in suspension or after the cells are getting in contact with artificial surfaces. High resolution digital holographic microscopy has been applied to study these processes. This method represents a new set-up allowing a contact-less and marker-free quantitative phase-contrast imaging of living cells under conventional laboratory conditions. With the applied technique we were able to detect and analyse fast shape changes of red blood cells.     

Surface characterisation of oxygen plasma treated electrospun polyurethane fibres and their interaction with red blood cells

In this work, the effects of oxygen plasma surface modification have been studied on electrospun polyether-based polyurethane in order to investigate the imposed limitations and possibilities to improve surface characteristics on fibrous assemblies. The evolution of induced changes in surface morphology, chemistry and wettability by the plasma treatment has been characterised for increasing plasma exposure time using scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Significant reduction in fibre diameter concomitant with progressing rough surface textures are found on the fibres in surface layers during early treatment phases while extended exposure eventually causes the fibre structure to deteriorate. Surface oxygen content and functionalities such as carbonyl and carboxyl increase slightly with longer treatments until loss of material integrity occurs. The results have also shown that oxygen plasma rapidly alters the initially strong hydrophobic character of the non-woven fibres to hydrophilic behaviour, allowing water penetration into the network, but without significant changes for increased exposure time. In addition, the response of red blood cell shape to pristine and oxygen plasma treated fibres were found to be similar. In both cases, a population of cells having fibre contact displayed protrusions while measurements showed that the cell function remain intact and indicated that the adhesion was non-specific. The reported findings yield useful process knowledge that can support the formation of well-defined fibre architectures and are valuable in the designs of electrospun polyurethane material systems utilising oxygen plasma surface modification.