TY - JOUR A1 - von Klitzing, Regine A1 - Stehl, Dimitrij A1 - Pogrzeba, Tobias A1 - Schomaäcker, Reinhard A1 - Minullina, Renata A1 - Panchal, Abhishek A1 - Konnova, Svetlana A1 - Fakhrullin, Rawil A1 - Koetz, Joachim A1 - Moehwald, Helmuth A1 - Lvov, Yuri T1 - Halloysites Stabilized Emulsions for Hydroformylation of Long Chain Olefins JF - Advanced materials interfaces N2 - Halloysites as tubular alumosilicates are introduced as inexpensive natural nanoparticles to form and stabilize oil-water emulsions. This stabilized emulsion is shown to enable efficient interfacial catalytic reactions. Yield, selectivity, and product separation can be tremendously enhanced, e.g., for the hydroformylation reaction of dodecene to tridecanal. In perspective, this type of formulation may be used for oil spill dispersions. The key elements of the described formulations are clay nanotubes (halloysites) which are highly anisometric, can be filled by helper molecules, and are abundantly available in thousands of tons, making this technology scalable for industrial applications. Y1 - 2016 U6 - https://doi.org/10.1002/admi.201600435 SN - 2196-7350 VL - 4 IS - 1 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Raju, Rajarshi Roy A1 - Koetz, Joachim T1 - Inner rotation of Pickering Janus emulsions JF - Nanomaterials : open access journal N2 - Janus droplets were prepared by vortex mixing of three non-mixable liquids, i.e., olive oil, silicone oil and water, in the presence of gold nanoparticles (AuNPs) in the aqueous phase and magnetite nanoparticles (MNPs) in the olive oil. The resulting Pickering emulsions were stabilized by a red-colored AuNP layer at the olive oil/water interface and MNPs at the oil/oil interface. The core–shell droplets can be stimulated by an external magnetic field. Surprisingly, an inner rotation of the silicon droplet is observed when MNPs are fixed at the inner silicon droplet interface. This is the first example of a controlled movement of the inner parts of complex double emulsions by magnetic manipulation via interfacially confined magnetic nanoparticles. KW - Janus droplets KW - Pickering emulsions KW - magnetic manipulation KW - gold nanoparticles KW - magnetite nanoparticles Y1 - 2021 U6 - https://doi.org/10.3390/nano11123312 SN - 2079-4991 VL - 11 IS - 12 PB - MDPI CY - Basel ER - TY - GEN A1 - Raju, Rajarshi Roy A1 - Koetz, Joachim T1 - Inner Rotation of Pickering Janus Emulsions T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Janus droplets were prepared by vortex mixing of three non-mixable liquids, i.e., olive oil, silicone oil and water, in the presence of gold nanoparticles (AuNPs) in the aqueous phase and magnetite nanoparticles (MNPs) in the olive oil. The resulting Pickering emulsions were stabilized by a red-colored AuNP layer at the olive oil/water interface and MNPs at the oil/oil interface. The core–shell droplets can be stimulated by an external magnetic field. Surprisingly, an inner rotation of the silicon droplet is observed when MNPs are fixed at the inner silicon droplet interface. This is the first example of a controlled movement of the inner parts of complex double emulsions by magnetic manipulation via interfacially confined magnetic nanoparticles. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1249 KW - Janus droplets KW - Pickering emulsions KW - magnetic manipulation KW - gold nanoparticles KW - magnetite nanoparticles Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-553628 SN - 1866-8372 IS - 1249 ER - TY - JOUR A1 - Rumschöttel, Jens A1 - Baus, Susann A1 - Kosmella, Sabine A1 - Appelhans, Dietmar A1 - Koetz, Joachim T1 - Incorporation of DNA/PEI polyplexes into gelatin/chitosan hydrogel scaffolds BT - a mu-DSC study JF - Composite interfaces N2 - Polyplexes between a double-stranded Salmon DNA and hyperbranched poly(ethyleneimine) (PEI) as well as a maltosylated PEI-Mal were incorporated into a gelatin/chitosan hydrogel scaffold. Calorimetric experiments of the polyplexes show a decrease of the melting temperature in presence of PEI and a peak splitting in presence of PEI-Mal, which can be interpreted to a partial compaction of the DNA strands in presence of PEI-Mal. When the polyplexes are incorporated into a gelatin/chitosan scaffold in the swollen state, the DNA melting peaks at 90 and 93 degrees C, respectively, indicate in both cases the release of the DNA at the surface of the hydrogel scaffold in a more compact form. Specific interactions between the PEI-Mal shell and gelatin are responsible for the tuning of the release properties in presence of the maltose units in the hyperbranched PEI. KW - DNA-PEI polyplexes KW - maltosylated poly(ethyleneimine) KW - mu-DSC KW - DNA release KW - gelatin/chitosan hydrogel scaffold Y1 - 2017 U6 - https://doi.org/10.1080/09276440.2017.1302725 SN - 1568-5543 VL - 25 IS - 1 SP - 1 EP - 11 PB - Routledge, Taylor & Francis Group CY - Abingdon ER - TY - JOUR A1 - Liebig, Ferenc A1 - Sarhan, Radwan Mohamed A1 - Prietzel, Claudia Christina A1 - Schmitt, Clemens Nikolaus Zeno A1 - Bargheer, Matias A1 - Koetz, Joachim T1 - Tuned Surface-Enhanced raman scattering performance of undulated Au@Ag triangles JF - ACS applied nano materials N2 - Negatively charged ultraflat gold nanotriangles (AuNTs) stabilized by the anionic surfactant dioctyl sodium sulfosuccinate (AOT) were reloaded with the cationic surfactant benzylhexadecyldimethylammonium chloride (BDAC). Because of the spontaneous formation of a catanionic AOT micelle/BDAC bilayer onto the surface of the reloaded AuNTs, a reduction of Ag+ ions leads to the formation of spherical silver nanoparticles (AgNPs). With increasing concentration of AgNPs on the AuNTs, the localized surface plasmon resonance (LSPR) is shifted stepwise from 1300 to 800 nm. The tunable LSPR enables to shift the extinction maximum to the wavelength of the excitation laser of the Raman microscope at 785 nm. Surface-enhanced Raman scattering (SERS) experiments performed under resonance conditions show an SERS enhancement factor of the analyte molecule rhodamine RG6 of 5.1 X 10(5), which can be related to the silver hot spots at the periphery of the undulated gold nanoplatelets. KW - gold nanotriangles KW - catanionic surfactant bilayer KW - undulated nanoplatelets KW - SERS KW - LSPR Y1 - 2018 U6 - https://doi.org/10.1021/acsanm.8b00570 SN - 2574-0970 VL - 1 IS - 4 SP - 1995 EP - 2003 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Liebig, Ferenc A1 - Sarhan, Radwan Mohamed A1 - Prietzel, Claudia Christina A1 - Thünemann, Andreas F. A1 - Bargheer, Matias A1 - Koetz, Joachim T1 - Undulated Gold Nanoplatelet Superstructures BT - In Situ Growth of Hemispherical Gold Nanoparticles onto the Surface of Gold Nanotriangles JF - Langmuir N2 - Negatively charged flat gold nanotriangles, formed in a vesicular template phase and separated by an AOT-micelle-based depletion flocculation, were reloaded by adding a cationic polyelectrolyte, that is, a hyperbranched polyethylenimine (PEI). Heating the system to 100 degrees C in the presence of a gold chloride solution, the reduction process leads to the formation of gold nanoparticles inside the polymer shell surrounding the nanoplatelets. The gold nanoparticle formation is investigated by UV-vis spectroscopy, small-angle X-ray scattering, and dynamic light scattering measurements in combination with transmission electron microscopy. Spontaneously formed gold clusters in the hyperbranched PEI shell with an absorption maximum at 350 nm grow on the surface of the nanotriangles as hemispherical particles with diameters of similar to 6 nm. High-resolution micrographs show that the hemispherical gold particles are crystallized onto the {111} facets on the bottom and top of the platelet as well as on the edges without a grain boundary. Undulated gold nanoplatelet superstructures with special properties become available, which show a significantly modified performance in SERS-detected photocatalysis regarding both reactivity and enhancement factor. Y1 - 2018 U6 - https://doi.org/10.1021/acs.langmuir.7b02898 SN - 0743-7463 VL - 34 IS - 15 SP - 4584 EP - 4594 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Liebig, Ferenc A1 - Henning, Ricky A1 - Sarhan, Radwan Mohamed A1 - Prietzel, Claudia Christina A1 - Bargheer, Matias A1 - Koetz, Joachim T1 - A new route to gold nanoflowers JF - Nanotechnology N2 - Catanionic vesicles spontaneously formed by mixing the anionic surfactant bis(2-ethylhexyl)sulfosuccinate sodium salt with the cationic surfactant cetyltrimethylammonium bromide were used as a reducing medium to produce gold clusters, which are embedded and well-ordered into the template phase. The gold clusters can be used as seeds in the growth process that follows by adding ascorbic acid as a mild reducing component. When the ascorbic acid was added very slowly in an ice bath round-edged gold nanoflowers were produced. When the same experiments were performed at room temperature in the presence of Ag+ ions, sharp-edged nanoflowers could be synthesized. The mechanism of nanoparticle formation can be understood to be a non-diffusion-limited Ostwald ripening process of preordered gold nanoparticles embedded in catanionic vesicle fragments. Surface-enhanced Raman scattering experiments show an excellent enhancement factor of 1.7 . 10(5) for the nanoflowers deposited on a silicon wafer. KW - catanionic vesicles KW - gold cluster KW - gold nanoflowers KW - crystal growth KW - HRTEM KW - SEM Y1 - 2018 U6 - https://doi.org/10.1088/1361-6528/aaaffd SN - 0957-4484 SN - 1361-6528 VL - 29 IS - 18 PB - IOP Publ. Ltd. CY - Bristol 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 - JOUR A1 - Poghosyan, Armen H. A1 - Shahinyan, A. A. A1 - Koetz, Joachim T1 - Self-assembled monolayer formation of distorted cylindrical AOT micelles on gold surfaces JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - Self-assembling features of sodium dioctyl sulfosuccinate (AOT) molecules and micelle adsorption on gold Au (111) surfaces have been examined using molecular dynamics simulation. We argue that AOT micelles display a strong adsorption on gold surfaces resulting in distorted cylindrical micelles attached to the (111) facets. The well protected Au(111) facets decorated by a dense packed elongated ellipsoidal AOT layer hinder the diffusion of the reactant to the (111) facets and could result in the preferential growth of ultra-thin gold nanoplatelets. KW - Surfactant micelles KW - Adsorption KW - Gold surface KW - Molecular dynamics Y1 - 2018 U6 - https://doi.org/10.1016/j.colsurfa.2018.02.067 SN - 0927-7757 SN - 1873-4359 VL - 546 SP - 20 EP - 27 PB - Elsevier CY - Amsterdam 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 -