Physical Trace Gas Identification with the Photo Electron Ionization Spectrometer (PEIS).

Chemosensor technology for trace gases in the air always aims to identify these compounds and then measure their concentrations. For identification, traceable methods are sparse and relate to large appliances such as mass spectrometers. We present a new method that uses the alternative traceable measurement of the ionization energies of trace gases in a way that can be miniaturized and energetically tuned. We investigate the achievable performance. Since tunable UV sources are not available for photoionization, we take a detour via impact ionization with electrons, which we generate using the photoelectric effect and bring to sharp, defined energies on a nanoscale in the air. Electron impact ionization is thus possible at air pressures of up to 900 hPa. The sensitivity of the process reaches 1 ppm and is equivalent to that of classic PID. With sharpened energy settings, substance identification is currently possible with an accuracy of 30 meV. We can largely explain the experimental observations with the known quantum mechanical models.

Electroactive 3D Printed Scaffolds Based on Percolated Composites of Polycaprolactone With Thermally Reduced Graphene Oxide for Antibacterial and Tissue Engineering Applications.

Applying electrical stimulation (ES) could affect different cellular mechanisms, thereby producing a bactericidal effect and an increase in human cell viability. Despite its relevance, this bioelectric effect has been barely reported in percolated conductive biopolymers. In this context, electroactive polycaprolactone (PCL) scaffolds with conductive Thermally Reduced Graphene Oxide (TrGO) nanoparticles were obtained by a 3D printing method. Under direct current (DC) along the percolated scaffolds, a strong antibacterial effect was observed, which completely eradicated S. aureus on the surface of scaffolds. Notably, the same ES regime also produced a four-fold increase in the viability of human mesenchymal stem cells attached to the 3D conductive PCL/TrGO scaffold compared with the pure PCL scaffold. These results have widened the design of novel electroactive composite polymers that could both eliminate the bacteria adhered to the scaffold and increase human cell viability, which have great potential in tissue engineering applications.

Nanostructured manganese oxide particles from coordination complex decomposition and their catalytic properties for ethanol oxidation.

Novel manganese oxide particles with complex morphologies and different nanostructures (i.e., spherical/lamellar) were synthesized by initial preparation of a coordination complex of manganese with 1,4,7,10-tetraazacyclododecane (cyclen), followed by characterization of the nanostructured oxide as a catalytic material for ethanol oxidation. The samples present a bulk gamma-MnO2 structure although X-ray photoelectron spectroscopy analysis reveals that their surfaces have different chemical compositions. Some of these nanostructured particles show high catalytic activities for ethanol oxidation enabling a decrease of the reaction temperature by more than 80 degrees C as compared with traditional MnO2 particles. The high catalytic activity of the particles depends on their morphology and a relationship between morphology and specific area was established. It is proposed that these novel nanostructured manganese oxide particles may be highly active in the catalytic oxidation of other volatile organic compounds (VOCs) opening up their further development for environmental applications.

Microstructure and crystallographic-texture of giant barnacle (Austromegabalanus psittacus) shell.

Barnacle shell is a very complex and strong composite bioceramic composed of different structural units which consist of calcite 15 microcrystals of very uniform size. In the study reported herein, the microstructural organization of these units has been examinated in detail with optical and scanning electron microscopy, and X-ray diffraction techniques. These analyses showed that the external part of the shell has a massive microstructure consisting of randomly oriented crystals. Toward the interior, the shell became organized in mineral layers separated by thin organic sheets. Each of these mineral layers has a massive microstructure constituted by highly oriented calcite microcrystals with their c-axes aligned [(001) fibre texture] perpendicular to the organic sheets and the shell surface. Interestingly, in another structural unit, the shell shield, the orientation of the c-axis calcite crystals shifts from being perpendicular to being parallel to the shell surface across its thickness. This study provides evidence that the organic matrix is responsible for the organization of the shell mineral and exterts strong a strict control on the polymorphic type, size and orientation of shell-forming crystals.