TY - JOUR A1 - Wirth, Jonas A1 - Neumann, Rainer A1 - Antonietti, Markus A1 - Saalfrank, Peter T1 - Adsorption and photocatalytic splitting of water on graphitic carbon nitride: a combined first principles and semiempirical study JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - Graphitic carbon nitride, g-C3N4, is a promising organic photo-catalyst for a variety of redox reactions. In order to improve its efficiency in a systematic manner, however, a fundamental understanding of the microscopic interaction between catalyst, reactants and products is crucial. Here we present a systematic study of water adsorption on g-C3N4 by means of density functional theory and the density functional based tight-binding method as a prerequisite for understanding photocatalytic water splitting. We then analyze this prototypical redox reaction on the basis of a thermodynamic model providing an estimate of the overpotential for both water oxidation and H+ reduction. While the latter is found to occur readily upon irradiation with visible light, we derive a prohibitive overpotential of 1.56 eV for the water oxidation half reaction, comparing well with the experimental finding that in contrast to H-2 production O-2 evolution is only possible in the presence of oxidation cocatalysts. Y1 - 2014 U6 - https://doi.org/10.1039/c4cp02021a SN - 1463-9076 SN - 1463-9084 VL - 16 IS - 30 SP - 15917 EP - 15926 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Jeon, Jae-Hyung A1 - Chechkin, Aleksei V. A1 - Metzler, Ralf T1 - Scaled Brownian motion: a paradoxical process with a time dependent diffusivity for the description of anomalous diffusion JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - Anomalous diffusion is frequently described by scaled Brownian motion (SBM), a Gaussian process with a power-law time dependent diffusion coefficient. Its mean squared displacement is < x(2)(t) similar or equal to 2K(t)t with K(t) similar or equal to t(alpha-1) for 0 < alpha < 2. SBM may provide a seemingly adequate description in the case of unbounded diffusion, for which its probability density function coincides with that of fractional Brownian motion. Here we show that free SBM is weakly non-ergodic but does not exhibit a significant amplitude scatter of the time averaged mean squared displacement. More severely, we demonstrate that under confinement, the dynamics encoded by SBM is fundamentally different from both fractional Brownian motion and continuous time random walks. SBM is highly non-stationary and cannot provide a physical description for particles in a thermalised stationary system. Our findings have direct impact on the modelling of single particle tracking experiments, in particular, under confinement inside cellular compartments or when optical tweezers tracking methods are used. Y1 - 2014 U6 - https://doi.org/10.1039/c4cp02019g SN - 1463-9076 SN - 1463-9084 VL - 16 IS - 30 SP - 15811 EP - 15817 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Wessig, Pablo A1 - Gerngross, Maik A1 - Pape, Simon A1 - Bruhns, Philipp A1 - Weber, Jens T1 - Novel porous materials based on oligospiroketals (OSK) JF - RSC Advances N2 - New porous materials based on covalently connected monomers are presented. The key step of the synthesis is an acetalisation reaction. In previous years we used acetalisation reactions extensively to build up various molecular rods. Based on this approach, investigations towards porous polymeric materials were conducted by us. Here we wish to present the results of these studies in the synthesis of 1D polyacetals and porous 3D polyacetals. By scrambling experiments with 1D acetals we could prove that exchange reactions occur between different building blocks (evidenced by MALDI-TOF mass spectrometry). Based on these results we synthesized porous 3D polyacetals under the same mild conditions. Y1 - 2014 U6 - https://doi.org/10.1039/c4ra04437a SN - 2046-2069 VL - 4 IS - 59 SP - 31123 EP - 31129 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Zborowski, Krzysztof Kazimierz A1 - Koch, Andreas A1 - Kleinpeter, Erich A1 - Proniewicz, Leonard Marian T1 - Searching for aromatic celate rings. Oxygen versus Thio and Seleno Ligands JF - Zeitschrift für physikalische Chemie : international journal of research in physical chemistry and chemical physics N2 - As a part of searching for fully aromatic chelate compounds, copper complexes of malondialdehyde as well as its sulfur and selenium derivatives were investigated using the DFT quantum chemical methods. Chelate complexes of both Cu(I) and Cu(II) ions wereconsidered. Aromaticity of the metal complexes studied were analyzed using NICS(0), NICS(1), PDI, I-ring, MCI, ICMCI and I-B aromaticity indices, and by TSNMRS visualizations of the spatial magnetic properties. It seems that partial aromaticityof studied chelates increases when oxygen atoms in malondialdehyde are replaced by sulfur and selenium. KW - Aromaticity KW - Chelatoaromaticity KW - Copper Metal Complexes KW - Quantum Chemical Calculations Y1 - 2014 U6 - https://doi.org/10.1515/zpch-2014-0528 SN - 0942-9352 VL - 228 IS - 8 SP - 869 EP - 878 PB - De Gruyter CY - Berlin ER - TY - JOUR A1 - Xie, Zai-Lai A1 - Huang, Xing A1 - Titirici, Maria-Magdalena A1 - Taubert, Andreas T1 - Mesoporous graphite nanoflakes via ionothermal carbonization of fructose and their use in dye removal JF - RSC Advances N2 - The large-scale green synthesis of graphene-type two-dimensional materials is still challenging. Herein, we describe the ionothermal synthesis of carbon-based composites from fructose in the iron-containing ionic liquid 1-butyl-3-methylimidazolium tetrachloridoferrate(III), [Bmim][FeCl4] serving as solvent, catalyst, and template for product formation. The resulting composites consist of oligo-layer graphite nanoflakes and iron carbide particles. The mesoporosity, strong magnetic moment, and high specific surface area of the composites make them attractive for water purification with facile magnetic separation. Moreover, Fe3Cfree graphite can be obtained via acid etching, providing access to fairly large amounts of graphite material. The current approach is versatile and scalable, and thus opens the door to ionothermal synthesis towards the larger-scale synthesis of materials that are, although not made via a sustainable process, useful for water treatment such as the removal of organic molecules. Y1 - 2014 U6 - https://doi.org/10.1039/c4ra05146g SN - 2046-2069 VL - 4 IS - 70 SP - 37423 EP - 37430 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Schmidt, Christian A1 - Behl, Marc A1 - Lendlein, Andreas A1 - Beuermann, Sabine T1 - Synthesis of high molecular weight polyglycolide in supercritical carbon dioxide JF - RSC Advances N2 - Polyglycolide (PGA) is a biodegradable polymer with multiple applications in the medical sector. Here the synthesis of high molecular weight polyglycolide by ring-opening polymerization of diglycolide is reported. For the first time stabilizer free supercritical carbon dioxide (scCO(2)) was used as a reaction medium. scCO(2) allowed for a reduction in reaction temperature compared to conventional processes. Together with the lowering of monomer concentration and consequently reduced heat generation compared to bulk reactions thermal decomposition of the product occurring already during polymerization is strongly reduced. The reaction temperatures and pressures were varied between 120 and 150 degrees C and 145 to 1400 bar. Tin(II) ethyl hexanoate and 1-dodecanol were used as catalyst and initiator, respectively. The highest number average molecular weight of 31 200 g mol(-1) was obtained in 5 hours from polymerization at 120 degrees C and 530 bar. In all cases the products were obtained as a dry white powder. Remarkably, independent of molecular weight the melting temperatures were always at (219 +/- 2)degrees C. Y1 - 2014 U6 - https://doi.org/10.1039/c4ra06815g SN - 2046-2069 VL - 4 IS - 66 SP - 35099 EP - 35105 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Hildebrand, Viet A1 - Laschewsky, André A1 - Zehm, Daniel T1 - On the hydrophilicity of polyzwitterion poly (N, N-dimethyl-N(3-(methacrylamido)propyl)ammoniopropane sulfonate) in water, deuterated water, and aqueous salt solutions JF - Journal of biomaterials science : Polymer edition KW - polyzwitterion KW - sulfobetaine KW - synthesis KW - fluorescence label KW - upper critical solution temperature KW - isotope effect KW - anti-polyelectrolyte effect Y1 - 2014 U6 - https://doi.org/10.1080/09205063.2014.939918 SN - 0920-5063 SN - 1568-5624 VL - 25 IS - 14-15 SP - 1602 EP - 1618 PB - Routledge, Taylor & Francis Group CY - Abingdon ER - TY - JOUR A1 - Metzler, Ralf A1 - Jeon, Jae-Hyung A1 - Cherstvy, Andrey G. A1 - Barkai, Eli T1 - Anomalous diffusion models and their properties: non-stationarity, non-ergodicity, and ageing at the centenary of single particle tracking JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - Modern microscopic techniques following the stochastic motion of labelled tracer particles have uncovered significant deviations from the laws of Brownian motion in a variety of animate and inanimate systems. Such anomalous diffusion can have different physical origins, which can be identified from careful data analysis. In particular, single particle tracking provides the entire trajectory of the traced particle, which allows one to evaluate different observables to quantify the dynamics of the system under observation. We here provide an extensive overview over different popular anomalous diffusion models and their properties. We pay special attention to their ergodic properties, highlighting the fact that in several of these models the long time averaged mean squared displacement shows a distinct disparity to the regular, ensemble averaged mean squared displacement. In these cases, data obtained from time averages cannot be interpreted by the standard theoretical results for the ensemble averages. Here we therefore provide a comparison of the main properties of the time averaged mean squared displacement and its statistical behaviour in terms of the scatter of the amplitudes between the time averages obtained from different trajectories. We especially demonstrate how anomalous dynamics may be identified for systems, which, on first sight, appear to be Brownian. Moreover, we discuss the ergodicity breaking parameters for the different anomalous stochastic processes and showcase the physical origins for the various behaviours. This Perspective is intended as a guidebook for both experimentalists and theorists working on systems, which exhibit anomalous diffusion. Y1 - 2014 U6 - https://doi.org/10.1039/c4cp03465a SN - 1463-9076 SN - 1463-9084 VL - 16 IS - 44 SP - 24128 EP - 24164 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Braune, Steffen A1 - Walter, M. A1 - Schulze, F. A1 - Lendlein, Andreas A1 - Jung, Friedrich T1 - Changes in platelet morphology and function during 24 hours of storage JF - Clinical hemorheology and microcirculation : blood flow and vessels N2 - For in vitro studies assessing the interaction of platelets with implant materials, common and standardized protocols for the preparation of platelet rich plasma (PRP) are lacking, which may lead to non-matching results due to the diversity of applied protocols. Particularly, the aging of platelets during prolonged preparation and storage times is discussed to lead to an underestimation of the material thrombogenicity. Here, we study the influence of whole blood-and PRP-storage times on changes in platelet morphology and function. Whole blood PFA100 closure times increased after stimulation with collagen/ADP and collagen/epinephrine. Twenty four hours after blood collection, both parameters were prolonged pathologically above the upper limit of the reference range. Numbers of circulating platelets, measured in PRP, decreased after four hours, but no longer after twenty four hours. Mean platelet volumes (MPV) and platelet large cell ratios (P-LCR, 12 fL - 40 fL) decreased over time. Immediately after blood collection, no debris or platelet aggregates could be visualized microscopically. After four hours, first debris and very small aggregates occurred. After 24 hours, platelet aggregates and also debris progressively increased. In accordance to this, the CASY system revealed an increase of platelet aggregates (up to 90 mu m diameter)with increasing storage time. The percentage of CD62P positive platelets and PF4 increased significantly with storage time in resting PRP. When soluble ADP was added to stored PRP samples, the number of activatable platelets decreased significantly over storage time. The present study reveals the importance of a consequent standardization in the preparation of WB and PRP. Platelet morphology and function, particularly platelet reactivity to adherent or soluble agonists in their surrounding milieu, changed rapidly outside the vascular system. This knowledge is of crucial interest, particularly in the field of biomaterial development for cardiovascular applications, and may help to define common standards in the in vitro hemocompatibility testing of biomaterials. KW - Platelet KW - platelet function KW - platelet rich plasma KW - whole blood KW - platelet aging KW - platelet storage KW - hemocompatibility KW - biomaterials Y1 - 2014 U6 - https://doi.org/10.3233/CH-141876 SN - 1386-0291 SN - 1875-8622 VL - 58 IS - 1 SP - 159 EP - 170 PB - IOS Press CY - Amsterdam ER - TY - JOUR A1 - Schwarze, Thomas A1 - Mueller, Holger A1 - Ast, Sandra A1 - Steinbrück, Dorte A1 - Eidner, Sascha A1 - Geißler, Felix A1 - Kumke, Michael Uwe A1 - Holdt, Hans-Jürgen T1 - Fluorescence lifetime-based sensing of sodium by an optode JF - Chemical communications N2 - We report a 1,2,3-triazol fluoroionophore for detecting Na+ that shows in vitro enhancement in the Na+-induced fluorescence intensity and decay time. The Na+-selective molecule 1 was incorporated into a hydrogel as a part of a fiber optical sensor. This sensor allows the direct determination of Na+ in the range of 1-10 mM by measuring reversible fluorescence decay time changes. Y1 - 2014 U6 - https://doi.org/10.1039/c4cc06112h SN - 1359-7345 SN - 1364-548X VL - 50 IS - 91 SP - 14167 EP - 14170 PB - Royal Society of Chemistry CY - Cambridge ER -