TY - JOUR A1 - Neumann, Bernhard A1 - Horstkemper, Marianne A1 - Krüger, Wolfgang A1 - Wilkens, Martin A1 - Bohlen, Andreas A1 - Frübing, Peter A1 - Wegener, Michael A1 - Scheff, Ullrich A1 - Neher, Dieter A1 - Brehmer, Ludwig A1 - Kleinpeter, Erich A1 - Wolf, Gunter A1 - Koetz, Joachim A1 - Peter, Martin G. A1 - Senkbeil, Sigrid A1 - Meyer, Till T1 - Portal = Im Trend: Physiker und Chemiker erforschen "Soft Matter" BT - Die Potsdamer Universitätszeitung N2 - Aus dem Inhalt: Im Trend: Physiker und Chemiker erforschen „Soft Matter“ -Brandenburger Netzwerk für Existenzgründer erhält Förderung -Universität leistet Beitrag zum Romantik-Jahr -Musiksender MTV und Bryan Adams auf dem Campus T3 - Portal: Das Potsdamer Universitätsmagazin - 06/2002 Y1 - 2002 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-501441 SN - 1618-6893 VL - 2002 ER - TY - JOUR A1 - Grott, Saskia A1 - Peter, Martin G. A1 - Linker, Torsten A1 - Sefkow, Michael A1 - Kroll, Jürgen A1 - Koetz, Joachim A1 - Laschewsky, André A1 - Lokatis, Siegfried A1 - Rheinberg, Falko A1 - Manig, Yvette T1 - Portal = Chemie: Werkstoffe, Wirkstoffe, Lebensvorgänge BT - Die Potsdamer Universitätszeitung N2 - Aus dem Inhalt: - Chemie: Werkstoffe, Wirkstoffe, Lebensvorgänge - Institut für Kirchenrecht gegründet - Computerlinguisten erstellen digitales Wörterbuch - Vom Spaß am Graffiti-Sprayen T3 - Portal: Das Potsdamer Universitätsmagazin - 01-02/2003 Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-439713 SN - 1618-6893 IS - 01-02/2003 ER - TY - GEN A1 - Thete, Aniket A1 - Rojas, Oscar A1 - Neumeyer, David A1 - Koetz, Joachim A1 - Dujardin, Erik T1 - Ionic liquid-assisted morphosynthesis of gold nanorods using polyethyleneimine-capped seeds N2 - Seed-mediated gold nanorods with tunable lengths are prepared using new polyethyleneimine-capped gold nanoparticles synthesized in ionic liquid. The effect of polyethyleneimine and ionic liquid during nanorod growth is investigated and shows a marked effect on their final aspect ratio. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 245 KW - aqueous-solution KW - aspect-ratio KW - cationic surfactants KW - chemical-synthesis KW - delivery KW - metal nanoparticles KW - mixtures KW - shape KW - silver nanowires KW - surface-plasmon resonance Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95196 SP - 14294 EP - 14298 ER - TY - GEN A1 - Ermeydan, Mahmut Ali A1 - Cabane, Etienne A1 - Hass, Philipp A1 - Koetz, Joachim A1 - Burgert, Ingo T1 - Fully biodegradable modification of wood for improvement of dimensional stability and water absorption properties by poly(ε-caprolactone) grafting into the cell walls N2 - Materials derived from renewable resources are highly desirable in view of more sustainable manufacturing. Among the available natural materials, wood is one of the key candidates, because of its excellent mechanical properties. However, wood and wood-based materials in engineering applications suffer from various restraints, such as dimensional instability upon humidity changes. Several wood modification treatments increase water repellence, but the insertion of hydrophobic polymers can result in a composite material which cannot be considered as renewable anymore. In this study, we report on the grafting of the fully biodegradable poly(ε-caprolactone) (PCL) inside the wood cell walls by Sn(Oct)2 catalysed ring-opening polymerization (ROP). The presence of polyester chains within the wood cell wall structure is monitored by confocal Raman imaging and spectroscopy as well as scanning electron microscopy. Physical tests reveal that the modified wood is more hydrophobic due to the bulking of the cell wall structure with the polyester chains, which results in a novel fully biodegradable wood material with improved dimensional stability. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 270 KW - ring-opening polymerization KW - confocal raman microscopy KW - epsilon-caprolactone KW - mechanical-properties KW - structural-characterization KW - stannous octoate KW - copolymers KW - degradation KW - composites KW - cellulose Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-97265 SP - 3313 EP - 3321 ER - TY - GEN A1 - Ermeydan, Mahmut Ali A1 - Cabane, Etienne A1 - Gierlinger, Notburga A1 - Koetz, Joachim A1 - Burgert, Ingo T1 - Improvement of wood material properties via in situ polymerization of styrene into tosylated cell walls N2 - As an engineering material derived from renewable resources, wood possesses excellent mechanical properties in view of its light weight but also has some disadvantages such as low dimensional stability upon moisture changes and low durability against biological attack. Polymerization of hydrophobic monomers in the cell wall is one of the potential approaches to improve the dimensional stability of wood. A major challenge is to insert hydrophobic monomers into the hydrophilic environment of the cell walls, without increasing the bulk density of the material due to lumen filling. Here, we report on an innovative and simple method to insert styrene monomers into tosylated cell walls (i.e. –OH groups from natural wood polymers are reacted with tosyl chloride) and carry out free radical polymerization under relatively mild conditions, generating low wood weight gains. In-depth SEM and confocal Raman microscopy analysis are applied to reveal the distribution of the polystyrene in the cell walls and the lumen. The embedding of polystyrene in wood results in reduced water uptake by the wood cell walls, a significant increase in dimensional stability, as well as slightly improved mechanical properties measured by nanoindentation. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 274 Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98736 ER - TY - GEN A1 - Liebig, Ferenc A1 - Sarhan, Radwan Mohamed A1 - Prietzel, Claudia Christina A1 - Reinecke, Antje A1 - Koetz, Joachim T1 - “Green” gold nanotriangles: synthesis, purification by polyelectrolyte/micelle depletion flocculation and performance in surface-enhanced Raman scattering N2 - The aim of this study was to develop a one-step synthesis of gold nanotriangles (NTs) in the presence of mixed phospholipid vesicles followed by a separation process to isolate purified NTs. Negatively charged vesicles containing AOT and phospholipids, in the absence and presence of additional reducing agents (polyampholytes, polyanions or low molecular weight compounds), were used as a template phase to form anisotropic gold nanoparticles. Upon addition of the gold chloride solution, the nucleation process is initiated and both types of particles, i.e., isotropic spherical and anisotropic gold nanotriangles, are formed simultaneously. As it was not possible to produce monodisperse nanotriangles with such a one-step procedure, the anisotropic nanoparticles needed to be separated from the spherical ones. Therefore, a new type of separation procedure using combined polyelectrolyte/micelle depletion flocculation was successfully applied. As a result of the different purification steps, a green colored aqueous dispersion was obtained containing highly purified, well-defined negatively charged flat nanocrystals with a platelet thickness of 10 nm and an edge length of about 175 nm. The NTs produce promising results in surface-enhanced Raman scattering. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 317 KW - morphological transformation KW - halide-ions KW - nanoparticles KW - shape KW - size KW - nanoprisms KW - vesicles KW - nanorods KW - silver KW - poly(ethyleneimine) Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394430 SP - 33561 EP - 33568 ER - TY - GEN A1 - Schulze, Nicole A1 - Koetz, Joachim T1 - Kinetically Controlled Growth of Gold Nanotriangles in a Vesicular Template Phase by Adding a Strongly Alternating Polyampholyte N2 - This paper is focused on the temperature dependent synthesis of gold nanotriangles in a vesicular template phase, containing phosphatidylcholin and AOT, by adding the strongly alternating polyampholyte PalPhBisCarb. UV-vis absorption spectra in combination with TEM micrographs show that flat gold nanoplatelets are formed predominantly in presence of the polyampholyte at 45 °C. The formation of triangular and hexagonal nanoplatelets can be directly influenced by the kinetic approach, i.e., by varying the polyampholyte dosage rate at 45 °C. Corresponding zeta potential measurements indicate that a temperature dependent adsorption of the polyampholyte on the {111} faces will induce the symmetry breaking effect, which is responsible for the kinetically controlled hindered vertical and preferred lateral growth of the nanoplatelets. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 271 KW - Polyampholytes KW - Nanotriangles KW - Kinetically controlled nanocrystal growth Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98380 ER - TY - GEN A1 - Sarhan, Radwan Mohamed A1 - Koopman, Wouter-Willem Adriaan A1 - Schuetz, Roman A1 - Schmid, Thomas A1 - Liebig, Ferenc A1 - Koetz, Joachim A1 - Bargheer, Matias T1 - The importance of plasmonic heating for the plasmondriven photodimerization of 4-nitrothiophenol T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - Metal nanoparticles form potent nanoreactors, driven by the optical generation of energetic electrons and nanoscale heat. The relative influence of these two factors on nanoscale chemistry is strongly debated. This article discusses the temperature dependence of the dimerization of 4-nitrothiophenol (4-NTP) into 4,4′-dimercaptoazobenzene (DMAB) adsorbed on gold nanoflowers by Surface-Enhanced Raman Scattering (SERS). Raman thermometry shows a significant optical heating of the particles. The ratio of the Stokes and the anti-Stokes Raman signal moreover demonstrates that the molecular temperature during the reaction rises beyond the average crystal lattice temperature of the plasmonic particles. The product bands have an even higher temperature than reactant bands, which suggests that the reaction proceeds preferentially at thermal hot spots. In addition, kinetic measurements of the reaction during external heating of the reaction environment yield a considerable rise of the reaction rate with temperature. Despite this significant heating effects, a comparison of SERS spectra recorded after heating the sample by an external heater to spectra recorded after prolonged illumination shows that the reaction is strictly photo-driven. While in both cases the temperature increase is comparable, the dimerization occurs only in the presence of light. Intensity dependent measurements at fixed temperatures confirm this finding. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 698 KW - enhanced raman-scattering KW - charge-transfer KW - metal KW - nanoparticles KW - catalysis KW - AU KW - 4-nitrobenzenethiol KW - aminothiophenol KW - photocatalysis KW - wavelength Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-427197 SN - 1866-8372 IS - 698 ER - TY - GEN A1 - Broeker, Nina K. A1 - Kiele, Franziska A1 - Casjens, Sherwood R. A1 - Gilcrease, Eddie B. A1 - Thalhammer, Anja A1 - Koetz, Joachim T1 - In Vitro Studies of Lipopolysaccharide-Mediated DNA Release of Podovirus HK620 T2 - Viruses N2 - Gram-negative bacteria protect themselves with an outermost layer containing lipopolysaccharide (LPS). O-antigen-specific bacteriophages use tailspike proteins (TSP) to recognize and cleave the O-polysaccharide part of LPS. However, O-antigen composition and structure can be highly variable depending on the environmental conditions. It is important to understand how these changes may influence the early steps of the bacteriophage infection cycle because they can be linked to changes in host range or the occurrence of phage resistance. In this work, we have analyzed how LPS preparations in vitro trigger particle opening and DNA ejection from the E. coli podovirus HK620. Fluorescence-based monitoring of DNA release showed that HK620 phage particles in vitro ejected their genome at velocities comparable to those found for other podoviruses. Moreover, we found that HK620 irreversibly adsorbed to the LPS receptor via its TSP at restrictive low temperatures, without opening the particle but could eject its DNA at permissive temperatures. DNA ejection was solely stimulated by LPS, however, the composition of the O-antigen dictated whether the LPS receptor could start the DNA release from E. coli phage HK620 in vitro. This finding can be significant when optimizing bacteriophage mixtures for therapy, where in natural environments O-antigen structures may rapidly change. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 469 KW - O-antigen specific phage KW - podovirus KW - HK620 KW - lipopolysaccharide KW - in vitro particle opening KW - tailspike protein Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-417493 ER - TY - GEN A1 - Liebig, Ferenc A1 - Henning, Ricky A1 - Sarhan, Radwan Mohamed A1 - Prietzel, Claudia Christina A1 - Schmitt, Clemens Nikolaus Zeno A1 - Bargheer, Matias A1 - Koetz, Joachim T1 - A simple one-step procedure to synthesise gold nanostars in concentrated aqueous surfactant solutions T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - Due to the enhanced electromagnetic field at the tips of metal nanoparticles, the spiked structure of gold nanostars (AuNSs) is promising for surface-enhanced Raman scattering (SERS). Therefore, the challenge is the synthesis of well designed particles with sharp tips. The influence of different surfactants, i.e., dioctyl sodium sulfosuccinate (AOT), sodium dodecyl sulfate (SDS), and benzylhexadecyldimethylammonium chloride (BDAC), as well as the combination of surfactant mixtures on the formation of nanostars in the presence of Ag⁺ ions and ascorbic acid was investigated. By varying the amount of BDAC in mixed micelles the core/spike-shell morphology of the resulting AuNSs can be tuned from small cores to large ones with sharp and large spikes. The concomitant red-shift in the absorption toward the NIR region without losing the SERS enhancement enables their use for biological applications and for time-resolved spectroscopic studies of chemical reactions, which require a permanent supply with a fresh and homogeneous solution. HRTEM micrographs and energy-dispersive X-ray (EDX) experiments allow us to verify the mechanism of nanostar formation according to the silver underpotential deposition on the spike surface in combination with micelle adsorption. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 769 KW - optical-properties KW - nanoparticles KW - sers KW - ultrafast KW - size KW - nanotriangles KW - nanoflowers KW - wavelength Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-438743 SN - 1866-8372 IS - 769 SP - 23633 EP - 23641 ER -