TY - JOUR A1 - Raju, Rajarshi Roy A1 - Liebig, Ferenc A1 - Klemke, Bastian A1 - Koetz, Joachim T1 - Ultralight magnetic aerogels from Janus emulsions JF - RSC Advances N2 - Magnetite containing aerogels were synthesized by freeze-drying olive oil/silicone oil-based Janus emulsion gels containing gelatin and sodium carboxymethylcellulose (NaCMC). The magnetite nanoparticles dispersed in olive oil are processed into the gel and remain in the macroporous aerogel after removing the oil components. The coexistence of macropores from the Janus droplets and mesopores from freeze-drying of the hydrogels in combination with the magnetic properties offer a special hierarchical pore structure, which is of relevance for smart supercapacitors, biosensors, and spilled oil sorption and separation. The morphology of the final structure was investigated in dependence on initial compositions. More hydrophobic aerogels with magnetic responsiveness were synthesized by bisacrylamide-crosslinking of the hydrogel. The crosslinked aerogels can be successfully used in magnetically responsive clean up experiments of the cationic dye methylene blue. Y1 - 2019 U6 - https://doi.org/10.1039/c9ra10247g SN - 2046-2069 VL - 10 IS - 13 SP - 7492 EP - 7499 PB - RSC Publishing CY - London ER - TY - JOUR A1 - Raju, Rajarshi Roy A1 - Liebig, Ferenc A1 - Klemke, Bastian A1 - Koetz, Joachim T1 - pH-responsive magnetic Pickering Janus emulsions JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - We report ultrasonically generated pH-responsive Pickering Janus emulsions of olive oil and silicone oil with controllable droplet size and engulfment. Chitosan was used as a pH-responsive emulsifier. The increase of pH from 2 to 6 leads to a transition from completely engulfed double emulsion droplets to dumbbell-shaped Janus droplets accompanied by a significant decrease of droplet diameter and a more homogeneous size distribution. The results can be elucidated by the conformational change of chitosan from a more extended form at pH 2 to a more flexible form at pH 4-5. Magnetic responsiveness to the emulsion was attributed by dispersing superparamagnetic nanoparticles (Fe3O4 with diameter of 13 +/- 2 nm) in the olive oil phase before preparing the Janus emulsion. Incorporation of magnetic nanoparticles leads to superior emulsion stability, drastically reduced droplet diameters, and opened the way to control movement and orientation of the Janus droplets according to an external magnetic field. KW - Janus emulsion KW - Chitosan KW - pH-responsive KW - Magnetic-responsive KW - Cryo-SEM KW - TEM Y1 - 2018 U6 - https://doi.org/10.1007/s00396-018-4321-z SN - 0303-402X SN - 1435-1536 VL - 296 IS - 6 SP - 1039 EP - 1046 PB - Springer CY - New York ER - TY - GEN A1 - Raju, Rajarshi Roy A1 - Liebig, Ferenc A1 - Klemke, Bastian A1 - Koetz, Joachim T1 - Ultralight magnetic aerogels from Janus emulsions T2 - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe N2 - Magnetite containing aerogels were synthesized by freeze-drying olive oil/silicone oil-based Janus emulsion gels containing gelatin and sodium carboxymethylcellulose (NaCMC). The magnetite nanoparticles dispersed in olive oil are processed into the gel and remain in the macroporous aerogel after removing the oil components. The coexistence of macropores from the Janus droplets and mesopores from freeze-drying of the hydrogels in combination with the magnetic properties offer a special hierarchical pore structure, which is of relevance for smart supercapacitors, biosensors, and spilled oil sorption and separation. The morphology of the final structure was investigated in dependence on initial compositions. More hydrophobic aerogels with magnetic responsiveness were synthesized by bisacrylamide-crosslinking of the hydrogel. The crosslinked aerogels can be successfully used in magnetically responsive clean up experiments of the cationic dye methylene blue. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 828 Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-445522 IS - 828 ER - TY - JOUR A1 - Liebig, Ferenc A1 - Moreno, Silvia A1 - Thuenemann, Andreas F. A1 - Temme, Achim A1 - Appelhans, Dietmar A1 - Koetz, Joachim T1 - Toxicological investigations of "naked" and polymer-entrapped AOT-based gold nanotriangles JF - Colloids and surfaces : an international journal devoted to fundamental and applied research on colloid and interfacial phenomena in relation to systems of biological origin ; B, Biointerfaces N2 - Negatively charged ultrathin gold nanotriangles (AuNTs) were synthesized in a vesicular dioctyl sodium sulfosuccinate (AOT)/phospholipid-based template phase. These "naked" AuNTs with localized surface plasmon resonances in the NIR region at about 1300 nm and special photothermal properties are of particular interest for imaging and hyperthermia of cancerous tissues. For these kinds of applications the toxicity and the cellular uptake of the AuNTs is of outstanding importance. Therefore, this study focuses on the toxicity of "naked" AOT-stabilized AuNTs compared to polymer-coated AuNTs. Polymeric coating consisted of non-modified hyperbranched poly(ethyleneimine) (PEI), maltose-modified poly(ethyleneimine) (PEI-Mal) and heparin. The toxicological experiments were carried out with two different cell lines (embryonic kidney carcinoma cell line HEK293T and NK-cell leukemia cell line YTS). This study revealed that the heparin-coating of AuNTs improved biocompatibility by a factor of 50 when compared to naked AuNTs. Of note, the highest nontoxic concentration of the AuNTs coated with PEI and PEI-Mal is drastically decreased. Overall, this is mainly triggered by the different surface charges of polymeric coatings. Therefore, AuNTs coated with heparin were selected to carry out uptake studies. Their promising high biocompatibility and cellular uptake may open future studies in the field of biomedical applications. (C) 2018 Elsevier B.V. All rights reserved. KW - Gold nanotriangles KW - Polymer-coating KW - Toxicity KW - Heparin KW - Cellular uptake Y1 - 2018 U6 - https://doi.org/10.1016/j.colsurfb.2018.04.059 SN - 0927-7765 SN - 1873-4367 VL - 167 SP - 560 EP - 567 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Henning, Ricky A1 - Liebig, Ferenc A1 - Prietzel, Claudia Christina A1 - Klemke, Bastian A1 - Koetz, Joachim T1 - Gold nanotriangles with magnetite satellites JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - This work describes the synthesis of hybrid particles of gold nanotriangles (AuNTs) with magnetite nanoparticles (MNPs) by using 1-mercaptopropyl-3-trimethoxysilan (MPTMS) and L-cysteine as linker molecules. Due to the combination of superparamagnetic properties of MNPs with optical properties of the AuNTs, nanoplatelet-satellite hybrid nanostructures with combined features become available. By using MPTMS with silan groups as linker molecule a magnetic "cloud" with embedded AuNTs can be separated. In presence of L-cysteine as linker molecule at pH > pH(iso) a more unordered aggregate structure of MNPs is obtained due to the dimerization of the L-cysteine. At pH < pH(iso) water soluble positively charged AuNTs with satellite MNPs can be synthesized. The time-dependent loading with MNP satellites under release of the extinction and magnetization offer a hybrid material, which is of special relevance for biomedical applications and plasmonic catalysis. KW - nanotriangles KW - Superparamagnetic magnetite KW - Satellite hybrid KW - nanostructures KW - L-Cysteine KW - UV-Vis-NIR KW - HRTEM Y1 - 2020 U6 - https://doi.org/10.1016/j.colsurfa.2020.124913 SN - 0927-7757 SN - 1873-4359 VL - 600 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Liebig, Ferenc A1 - Thünemann, Andreas F. A1 - Koetz, Joachim T1 - Ostwald Ripening Growth Mechanism of Gold Nanotriangles in Vesicular Template Phases JF - Langmuir N2 - The mechanism of nanotriangle formation in multivesicular vesicles (MMV) is investigated by using time-dependent SAXS measurements in combination with UV-vis spectroscopy, light, and transmission electron microscopy. In the first time period 6.5 nm sized spherical gold nanoparticles are formed inside of the vesicles, which build up soft nanoparticle aggregates. a) In situ SAXS experiments show a linear increase of the volume and molar mass of nanotriangles in the second time period. The volume growth rate of the triangles is 16.1 nm(3)/min, and the growth rate in the vertical direction is only 0.02 nm/min. Therefore, flat nanotriangles with a thickness of 7 nm and a diameter of 23 nm are formed. This process can be described by a diffusion limited Ostwald ripening growth mechanism. TEM micrographs visualize soft coral-like structures with thin nanoplatelets at the periphery of the aggregates, which disaggregate in the third time period into nanotriangles and spherical particles. The 16 times faster growth of nanotriangles in the lateral than that in the vertical direction is related to the adsorption of symmetry breaking components, i.e., AOT and the polyampholyte PalPhBisCarb, on the {111} facets of the gold nanoplatelets in combination with confinement effects of the vesicular template phase. Y1 - 2016 U6 - https://doi.org/10.1021/acs.langmuir.6b02662 SN - 0743-7463 VL - 32 SP - 10928 EP - 10935 PB - American Chemical Society CY - Washington ER - TY - GEN A1 - Raju, Rajarshi Roy A1 - Liebig, Ferenc A1 - Hess, Andreas A1 - Schlaad, Helmut A1 - Koetz, Joachim T1 - Temperature-triggered reversible breakdown of polymer-stabilized olive BT - silicone oil Janus emulsions T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - A one-step moderate energy vibrational emulsification method was successfully employed to produce thermo-responsive olive/silicone-based Janus emulsions stabilized by poly(N,N-diethylacrylamide) carrying 0.7 mol% oleoyl side chains. Completely engulfed emulsion droplets remained stable at room temperature and could be destabilized on demand upon heating to the transition temperature of the polymeric stabilizer. Time-dependent light micrographs demonstrate the temperature-induced breakdown of the Janus droplets, which opens new aspects of application, for instance in biocatalysis. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 751 KW - microgels KW - step Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-436461 SN - 1866-8372 IS - 751 SP - 19271 EP - 19277 ER - TY - THES A1 - Liebig, Ferenc T1 - Synthesis and characterization of superstructures based on gold nanotriangles Y1 - 2018 ER - TY - JOUR A1 - Raju, Rajarshi Roy A1 - Liebig, Ferenc A1 - Hess, Andreas A1 - Schlaad, Helmut A1 - Koetz, Joachim T1 - Temperature-triggered reversible breakdown of polymer-stabilized olive BT - silicone oil Janus emulsions JF - RSC Advances N2 - A one-step moderate energy vibrational emulsification method was successfully employed to produce thermo-responsive olive/silicone-based Janus emulsions stabilized by poly(N,N-diethylacrylamide) carrying 0.7 mol% oleoyl side chains. Completely engulfed emulsion droplets remained stable at room temperature and could be destabilized on demand upon heating to the transition temperature of the polymeric stabilizer. Time-dependent light micrographs demonstrate the temperature-induced breakdown of the Janus droplets, which opens new aspects of application, for instance in biocatalysis. KW - microgels KW - step Y1 - 2019 U6 - https://doi.org/10.1039/c9ra03463c SN - 2046-2069 VL - 9 IS - 35 SP - 19271 EP - 19277 PB - RSC Publishing CY - London ER - TY - JOUR 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 JF - RSC Advances 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. Y1 - 2016 U6 - https://doi.org/10.1039/c6ra04808k SN - 2046-2069 VL - 6 SP - 33561 EP - 33568 PB - Royal Society of Chemistry CY - Cambridge ER -