TY - JOUR A1 - Tiseanu, Carmen A1 - Geßner, Andre A1 - Kumke, Michael Uwe A1 - Parvulescu, V. T1 - Dehydration and rehydration effects on the photoluminescence properties of terbium-exchanged MFI type materials Y1 - 2008 U6 - https://doi.org/10.1016/j.jnoncrysol.2007.11.017 ER - TY - JOUR A1 - Tiseanu, Carmen A1 - Geßner, Andre A1 - Kumke, Michael Uwe A1 - Gagea, Bogdan A1 - Parvulescu, Vasile Ion A1 - Martens, Johan T1 - Photoluminescence spectra and dynamics of lanthanide-doped microporous materials N2 - A series of terbium- and europium-exchanged microporous-mesoporous zeolite Socony Mobil Five (MFI)-type materials such as Zeotile-1 and Zeogrid with varying Si/Al ratios was investigated using FTIR, PXRD, adsorption- desorption isotherms of N-2 at 77 K and time-resolved luminescence spectroscopy. Silylation of the lanthanides-exchanged Zeotile-1 and Zeogrid with hexadecyl trimethoxysilanes via post-synthesis grafting was also studied. The results showed that the lanthanide's photoluminescence spectra and decays were modified due to silylation. The different silylation effects in Zeotile-1 and Zeogrid were correlated with the textural properties of the investigated materials. (C) 2007 Elsevier B.V. All rights reserved. Y1 - 2008 UR - http://www.sciencedirect.com/science/article/pii/S0022231307003262 U6 - https://doi.org/10.1016/j.jlumin.2007.10.018 ER - TY - THES A1 - Geßner, André T1 - Neuartige Lanthanoid-dotierte mikro- und mesoporöse Feststoffe : Charakterisierung von Ion-Wirt-Wechselwirkungen, Speziesverteilung und Lumineszenzeigenschaften mittels zeitaufgelöster Lumineszenzspektroskopie T1 - Novel lanthanide doped micro- and mesoporous solids : characterization of ion-host-interactions, species distribution and luminescence properties using time-resolved luminescence spectroscopy N2 - Poröse Sol-Gel-Materialien finden in vielen Bereichen Anwendung bzw. sind Gegenstand der aktuellen Forschung. Zu diesen Bereichen zählen sowohl klassische Anwendungen, wie z. B. die Verwendung als Katalysator, Molekularsieb oder Trockenmittel, als auch nichtklassische Anwendungen, wie z. B. der Einsatz als Kontrastmittel in der Magnet-Resonanz-Tomographie oder in Form von dünnen Zeolithfilmen als Isolatoren in Mikrochips. Auch für den Einsatz in der Photonik werden poröse Materialien in Betracht gezogen, wie die Entwicklung des Zeolith-Farbstoff-Lasers zeigt. Mikroporöse Zeolithe können generell über einfache Ionenaustauschreaktionen mit Lanthanoidionen in lumineszente Materialien umgewandelt werden. Neben der Erzeugung eines lumineszenten Materials, dessen Lumineszenzeigenschaften charakterisiert werden müssen, bietet die Nutzung von Lanthanoidionen die Möglichkeit diese Ionen als Sonde zur Charakterisierung der Ion-Wirt-Wechselwirkungen zu funktionalisieren, was z. B. in Bezug auf die Anwendung als Katalysator von großer Bedeutung ist. Dabei werden die einzigartigen Lumineszenzeigenschaften der Lanthanoidionen, in diesem Fall von Europium(III) und Terbium(III), genutzt. In dieser Arbeit wurden Lanthanoid-dotierte mikroporöse Zeolithe, mikroporös-mesoporöse Hybridmaterialien und mesoporöse Silikate hinsichtlich ihrer Lumineszenzeigenschaften und ihrer Wechselwirkung des Wirtsmaterials mit den Lanthanoidionen mittels zeitaufgelöster Lumineszenzspektroskopie untersucht. Zeitaufgelöste Emissionsspektren (TRES) liefern dabei sowohl Informationen in der Wellenlängen- als auch in der Zeitdomäne. Erstmalig wurden die TRES mittels einer umfangreichen Auswertemethodik behandelt. Neben der Anpassung des Abklingverhaltens mit einer diskreten Zahl von Exponentialfunktionen, wurden unterstützend auch Abklingzeitverteilungsanalysen durchgeführt. Zeitaufgelöste flächennormierte Emissionsspektren (TRANES), eine Erweiterung der normalen TRES, konnten erstmals zur Bestimmung der Zahl der emittierenden Lanthanoidspezies in porösen Materialien genutzt werden. Durch die Berechnung der Decayassoziierten Spektren (DAS) konnten den Lanthanoidspezies die entsprechenden Lumineszenzspektren zugeordnet werden. Zusätzlich konnte, speziell im Fall der Europium-Lumineszenz, durch Kombination von zeitlicher und spektraler Information das zeitabhängige Asymmetrieverhältnis R und die spektrale Evolution des 5D0-7F0-Übergangs mit der Zeit t untersucht und somit wesentliche Informationen über die Verteilung der Europiumionen im Wirtsmaterial erhalten werden. Über die Abklingzeit und das Asymmetrieverhältnis R konnten Rückschlüsse auf die Zahl der OH-Oszillatoren in der ersten Koordinationssphäre und die Symmetrie der Koordinationsumgebung gezogen werden. Für die mikroporösen und mikroporös-mesoporösen Materialien wurden verschiedene Lanthanoidspezies, im Regelfall zwei, gefunden, welche entsprechend der beschriebenen Methoden charakterisiert wurden. Diese Lanthanoidspezies konnten Positionen in den Materialien zugeordnet werden, die sich im tief Inneren des Porensystems oder auf bzw. nahe der äußeren Oberfläche oder in den Mesoporen befinden. Erstere Spezies ist aufgrund ihrer Position im Material gut vor Feuchtigkeitseinflüssen geschützt, was sich deutlich in entsprechend langen Lumineszenzabklingzeiten äußert. Zusätzlich ist diese Europiumspezies durch unsymmetrische Koordinationsumgebung charakterisiert, was auf einen signifikanten Anteil an Koordination der Lanthanoidionen durch die Sauerstoffatome im Wirtsgitter zurückzuführen ist. Ionen, die sich nahe oder auf der äußeren Oberfläche befinden, sind dagegen für Feuchtigkeit zugänglicher, was in kürzeren Lumineszenzabklingzeiten und einer symmetrischeren Koordinationsumgebung resultiert. Der Anteil von Wassermolekülen in der ersten Koordinationssphäre ist hier deutlich größer, als bei den Ionen, die sich tiefer im Porensystem befinden und entspricht in vielen Fällen der Koordinationszahl eines vollständig hydratisierten Lanthanoidions. Auch der Einfluss von Oberflächenmodifikationen auf die Speziesverteilung und das Verhalten der Materialien gegenüber Feuchtigkeit wurde untersucht. Dabei gelang es den Einfluss der Feuchtigkeit auf die Lumineszenzeigenschaften und die Speziesverteilung durch die Oberflächenmodifikation zu verringern und die Lumineszenzeigenschaften teilweise zu konservieren. Im Fall der mesoporösen Silikamonolithe wurde auch eine heterogene Verteilung der Lanthanoidionen im Porensystem gefunden. Hier wechselwirkt ein Teil der Ionen mit der Porenwand, während sich die restlichen Ionen in der wäßrigen Phase innerhalb des Porensystems aufhalten. Das Aufbringen von Oberflächenmodifikationen führte zu einer Wechselwirkung der Ionen mit diesen Oberflächenmodifikationen, was sich in Abhängigkeit von der Oberflächenbeladung in den enstprechenden Lumineszenzeigenschaften niederschlug. N2 - Porous sol-gel materials are suitable for many applications and subject to ongoing research activities. This includes classical applications, e.g. as catalyst, molecular sieve or drying agent, as well as non-classical applications, e.g. as contrast agent in magnetic resonance tomography or in the form of thin zeolite films as isolators in microchips. The interest in porous materials also covers photonic applications as shown by the development of the zeolite-dye-microlaser. Zeolites, which belong to the subfamily of microporous materials, can be converted into luminescent materials using simple ion-exchange procedures. In addition to the creation of a luminescent material, which luminescence properties have to be characterized, the incorporation of lanthanide ions offers the possibility to use these ions as a luminescent probe for the characterization of the ion-host interactions. This is particularly interesting concerning the application of porous materials as catalysts. Therefor, the unique luminescence properties of the lanthanide ions europium(III) and terbium(III) are used. In this work lanthanide-doped microporous zeolites, microporous-mesoporous hybrid materials and mesoporous silicates were investigeted regarding their luminescence properties and the ion-host-interactions using time-resolved luminescence spectroscopy. Thereby, time-resolved emission spectra (TRES) provide information in the wavelength and time domain. For the analysis of the TRES a broad set of analytic methods was applied and thus a corresponding “toolbox“ developed. Fitting of the luminescence decays was performed with a discrete number of exponentials and supported by luminescence decay times distributions. Time-resolved area normalized emission spectra (TRANES), an advancement of TRES, could be used for the determination of the number of emissive lanthanide species in porous materials for the first time. Calculation of the decay-associated spectra (DAS) allowed the correlation of spectral information with luminescence decay times and thus delivered the luminescence spectra of the different europium species. For europium(III) we could use in addition the time-dependent asymmetry ratio and spectral evolution of the 5D0-7F0-transition with time to obtain further information about the distribution of the lanthanide ions in the host material. Luminescence decay times and spectra allowed conclusions on the number of OH-oscillators in and the symmetry of the first coordination sphere. For the microporous and microporous-mesoporous materials were found different lanthanide species, which were characterized by the above mentioned methods. These lanthanide species can be found on different positions in the host material. One position is located deep in the pore system. Here, lanthanide ions are hardly accessible for water and mainly coordinated by framework oxygens. This results in long luminescence decay times and distorted coordination spheres. The second position can be found near or on the outer surface or in the mesopores. Lanthanide ions located here, are easily accessible for water and thus show shorter luminescence decay times and a more symmetrical coordination sphere, which is mostly made up by water molecules. Another investigated aspect was the influence of surface modifications on the luminescence behavior of the lanthanide ions inside the material. Here we could show, that surface modifications hydrophobize the material and thus are able to protect the lanthanide ions from water, which is important for the conservation of the luminescence properties. Concerning the mesoporous silicates, again a heterogeneous distribution of the lanthanide ions in the pore system was found. A part of the lanthanide ions interacts with the pore wall, while the other part is located in the aqueous phase inside the pores. Surface modification led to a interaction of the lanthanide ions with the modification. This was reflected in the luminescence properties depending on the structure of the modification and the surface loading. KW - Lanthanoide KW - Lumineszenz KW - Zeolithe KW - TRES KW - TRANES KW - Lanthanides KW - Luminescence KW - Zeolites KW - TRES KW - TRANES Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-52371 ER - TY - JOUR A1 - Morgner, Frank A1 - Bennemann, Mark A1 - Cywiński, Piotr J. A1 - Kollosche, Matthias A1 - Górski, Krzysztof A1 - Pietraszkiewicz, Marek A1 - Geßner, André A1 - Löhmannsröben, Hans-Gerd T1 - Elastic FRET sensors for contactless pressure measurement JF - RSC Advances : an international journal to further the chemical sciences N2 - Contactless pressure monitoring based on Forster resonance energy transfer between donor/acceptor pairs immobilized within elastomers is demonstrated. The donor/acceptor energy transfer is employed by dispersing terbium(III) tris[(2-hydroxybenzoyl)-2-aminoethyl] amine complex (LLC, donor) and CdSe/ZnS quantum dots (QD655, acceptor) in styrene-ethylene/buthylene-styrene (SEBS) and poly(dimethylsiloxane) (PDMS). The continuous monitoring of QD luminescence showed a reversible intensity change as the pressure signal is alternated between two stable states indicating a pressure sensitivity of 6350 cps kPa(-1). Time-resolved measurements show the pressure impact on the FRET signal due to an increase of decay time (270 ms up to 420 ms) for the donor signal and parallel drop of decay time (170 mu s to 155 mu s) for the acceptor signal as the net pressure applied. The LLC/QD655 sensors enable a contactless readout as well as space resolved monitoring to enable miniaturization towards smaller integrated stretchable opto-electronics. Elastic FRET sensors can potentially lead to developing profitable analysis systems capable to outdo conventional wired electronic systems (inductive, capacitive, ultrasonic and photoelectric sensors) especially for point-of-care diagnostics, biological monitoring required for wearable electronics. Y1 - 2017 U6 - https://doi.org/10.1039/c7ra06379b SN - 2046-2069 VL - 7 SP - 50578 EP - 50583 PB - RSC Publishing CY - Cambridge ER - TY - JOUR A1 - Tiseanu, Carmen A1 - Parvulescu, Vasile A1 - Parvulescu, Victoria A1 - Cotoi, Elena A1 - Gessner, Andre A1 - Kumke, Michael Uwe A1 - Simon, Simion A1 - Vasiliu, Florin T1 - Structural and photoluminescence characterization of mesoporous silicon-phosphates N2 - Two different types of mesoporous silicon-phosphate supports using different surfactants (a mixture of (CH3)(3)C13H27NBr with an organophosphorus coupling molecule (HO-PO(i-C3H7)(2)) and with a co-surfactant ((C2H5)(3)(C6H5)PCl), respectively) were synthesized. Trivalent europium (Eu) ions were immobilized via ion-exchange on these supports. The resulting materials were characterized using nitrogen adsorption isotherms at -196 degrees C, thermogravimetric analysis, SEM, TEM, FT-IR, PXRD, CP/MAS. (HSi)-H-1-Si-29 and P-31 NMR, DR-UV-vis as well as steady- state and time-resolved photoluminescence spectroscopy. The results evidenced that the co-polymerization of silicon and phosphorous yielded a unique morphology in these materials. Following calcination at 450 and 900 degrees C europium- exchanged silicon-phosphates with great surface area (BET=600-705 m(2) g(-1)) and 3.4 nm sized mesopores were obtained. The differences among the optical properties of the non-calcined europium materials such as the emission lifetimes, local environment at the europium sites or the relative contribution of the upper excited levels to the total photoluminescence were assigned to the surfactants used in the synthesis. Calcination of the silicon-phosphates at higher temperatures than 450 degrees C did not induce major changes in the structural properties: in contrast, photoluminescence properties of europium were markedly improved in terms of intensity and average lifetime. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/10106030 U6 - https://doi.org/10.1016/j.jphotochem.2010.07.015 SN - 1010-6030 ER - TY - JOUR A1 - Tiseanu, Carmen A1 - Parvulescu, Vasile Ion A1 - Cojocaru, Bogdan A1 - Lorenz-Fonfria, Victor A. A1 - Kumke, Michael Uwe A1 - Gessner, Andre A1 - Enculescu, Ion T1 - Polymer-microporous host interactions probed by photoluminescence spectroscopy N2 - Zeolites NaY and ZSM-5 were used as hosts for styrene polymerization after ion-exchange with europium ions. The parent and hybrid, polystyrene coated Eu-NaY (Eu-NaY/PS) and Eu-ZSM-5 (Eu-ZSM-5/PS) zeolites were investigated by using thermal analysis, SEM, PXRD, FT-IR, DR-UV/Vis, steady state and time-resolved photoluminescence spectroscopy. FT-IR spectra evidenced for the interaction between the zeolitic hosts and polystyrene while the PXRD spectra supported for the presence of the polymer inside the channels/pores of Eu-NaY/PS and Eu-ZSM-5/PS materials. The optical properties of Eu-NaY/PS and Eu-ZSM-5/PS were significantly changed relative to those of the parent zeolites, giving further evidence for the presence of polymer inside zeolites. An interesting case is presented by NaY zeolite: following styrene polymerization, the polymer interacted selectively with one of the two main species co-existing inside zeolite while for ZSM-5 a similar effect was not observed. Y1 - 2010 UR - http://www.rsc.org/Publishing/Journals/CP/index.asp U6 - https://doi.org/10.1039/B922591a SN - 1463-9076 ER - TY - JOUR A1 - Tiseanu, Carmen A1 - Kumke, Michael Uwe A1 - Parvulescu, Vasile Ion A1 - Geßner, Andre A1 - Gagea, Bogdan A1 - Martens, Johan T1 - Europium(3+) : an efficient luminescence probe for the Si to Al ratio and silylation effect in the microporous- mesoporous Zeogrid materials Y1 - 2008 UR - http://pubs.acs.org/doi/pdf/10.1021/jp711337h U6 - https://doi.org/10.1021/Jp711337h ER - TY - JOUR A1 - Tiseanu, Carmen A1 - Lorenz-Fonfria, Victor A. A1 - Parvulescu, Vasile Ion A1 - Geßner, Andre A1 - Kumke, Michael Uwe T1 - Photoluminescence study of terbium-exchanged ultrastable Y zeolites: Number of species, photoluminescence decays and decay-associated spectra Y1 - 2008 UR - http://scitation.aip.org/getpdf/servlet/ GetPDFServlet?filetype=pdf&id=JAPIAU000104000003033530000001&idtype=cvips&doi=10.1063/1.2966304&prog=normal U6 - https://doi.org/10.1063/1.2966304 ER - TY - JOUR A1 - Tiseanu, Carmen A1 - Pârvulescu, Victor I. A1 - Kumke, Michael Uwe A1 - Dobroiu, Svako A1 - Geßner, André A1 - Simon, Simion T1 - Effects of support and ligand on the photoluminescence properties of siliceous grafted europium complexes N2 - Europium ions were introduced in SiO2 and MCM-41 via two different pathways: (1) grafting the europium complexes with two alkoxide structures, 3-(2-imidazolin-1-yl)-propyl-triethoxysilane (IPTES) and aminopropyltrimethoxysilane (APTMS), and (2) functionalization of the SiO2 support with silicon 4- carboxylbutyltriethoxide followed by subsequent addition of the europium ions. The new materials were characterized using nitrogen adsorption isotherms at -196 degrees C, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared, NMR, DR-UV-vis, steady-state emission and excitation, and time-resolved photoluminescence spectroscopy. Spectral changes found in the time-resolved photoluminscence spectra strongly point to the distribution of europium ions on a range of environments in both SiO2 and MCM-41 supports. The average europium photoluminescence lifetimes decrease within the order: Eu3+-IPTES/SiO2 (550 mu s) > Eu3+-APTMS/SiO2 (425 mu s) > Eu3+-APTMS/MCM-41 (370 mu s) > Eu3+-IPTES/MCM-41 (320 mu s) > Eu3+-CABES/SiO2 (240 mu s). The photoluminescence quantum efficiency has the largest value, of 22%, for Eu3+-IPTES/SiO2, while the most reduced value, of 9%, was measured for Eu3+-CABES/SiO2. Y1 - 2009 UR - http://pubs.acs.org/journal/jpccck U6 - https://doi.org/10.1021/Jp808411e SN - 1932-7447 ER - TY - JOUR A1 - Tiseanu, Carmen A1 - Lorenz-Fonfria, Victor A. A1 - Geßner, André A1 - Kumke, Michael Uwe A1 - Gagea, Bogdan T1 - Comparative luminescence study of terbium-exchanged zeolites silylated with alkoxysilanes N2 - Terbium-exchanged ZSM-5, MOR and (H)BEA zeolites were silylated with phenyl-, vinyl- and hexadecyl trimethoxysilanes via a post-synthesis grafting. All samples were investigated by means of PXRD, FT-IR, TGA, physical adsorption, DR-UV-Vis and time-resolved photoluminescence spectroscopy. From the comparison of the photoluminescence decays of terbium-exchanged in parent (non-silylated) and silylated zeolites, it resulted that the silylation efficiency of the various alkoxysilanes is determined by the type of zeolite and follows the sequences: phenyl > vinyl > hexadecyl > parent for ZSM-5, hexadecyl a parts per thousand phenyl a parts per thousand vinyl > parent for MOR and hexadecyl > phenyl a parts per thousand vinyl > a parts per thousand parent for BEA zeolites, respectively. Y1 - 2009 UR - http://www.springerlink.com/content/100190 U6 - https://doi.org/10.1007/s10854-008-9597-1 SN - 0957-4522 ER - TY - JOUR A1 - Antoniou, Stella A1 - Pashalidis, Ioannis A1 - Gessner, Andre A1 - Kumke, Michael Uwe T1 - Spectroscopic investigations on the effect of humic acid on the formation and solubility of secondary solid phases of Ln(2)(CO3)(3) JF - Journal of rare earths N2 - The formation of secondary Ln(III) solid phases (e.g., Nd-2(CO3)(3) and Sm-2(CO3)(3)) was studied as a function of the humic acid concentration in 0.1 mol/L NaClO4 aqueous solution in the neutral pH range (5-6.5). The solid phases under investigation were prepared by alkaline precipitation under 100% CO2 atmosphere and characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), time-resolved laser fluorescence spectroscopy (TRLFS), diffuse reflectance ultraviolet-visible (DR-UV-Vis), Raman spectroscopy, and solubility measurements. The spectroscopic data obtained indicated that Nd-2(CO3)(3) and Sm-2(CO3)(3) were stable and remained the solubility limiting solid phases even in the presence of increased humic acid concentration (0.5 g/L) in solution. Upon base addition in the Ln(III)-HA system, decomplexation of the previously formed Ln(III)-humate complexes and precipitation of two distinct phases occurred, the inorganic (Ln(2)(CO3)(3)) and the organic phase (HA), which was adsorbed on the particle surface of the former. Nevertheless, humic acid affected the particle size of the solid phases. Increasing humic acid concentration resulted in decreasing crystallite size of the Nd-2(CO3)(3) and increasing crystallite size of the Sm-2(CO3)(3) solid phase, and affected inversely the solubility of the solid phases. However, this impact on the solid phase properties was expected to be of minor relevance regarding the chemical behavior and migration of trivalent lanthanides and actinides in the geosphere. KW - lanthanide ions KW - humic acid KW - solid phase KW - solubility KW - Raman KW - TRLFS KW - DR-UV-Vis KW - rare earths Y1 - 2011 U6 - https://doi.org/10.1016/S1002-0721(10)60490-5 SN - 1002-0721 VL - 29 IS - 6 SP - 516 EP - 521 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Radziuk, Darya A1 - Skirtach, Andre A1 - Gessner, Andre A1 - Kumke, Michael Uwe A1 - Zhang, Wei A1 - Möhwald, Helmuth A1 - Shchukin, Dmitry T1 - Ultrasonic Approach for Formation of Erbium Oxide Nanoparticles with Variable Geometries JF - Langmuir N2 - Ultrasound (20 kHz, 29 W. cm(-2)) is employed to form three types of erbium oxide nanoparticles in the presence of multiwalled carbon nanotubes as a template material in water. The nanoparticles are (i) erbium carboxioxide nanoparticles deposited on the external walls of multiwalled carbon nanotubes and Er(2)O(3) in the bulk with (ii) hexagonal and (iii) spherical geometries. Each type of ultrasonically formed nanoparticle reveals Er(3+) photoluminescence from crystal lattice. The main advantage of the erbium carboxioxide nanoparticles on the carbon nanotubes is the electromagnetic emission in the visible region, which is new and not examined up to the present date. On the other hand, the photoluminescence of hexagonal erbium oxide nanoparticles is long-lived (mu s) and enables the higher energy transition ((4)S(3/2)-(4)I(15/2)), which is not observed for spherical nanoparticles. Our work is unique because it combines for the first time spectroscopy of Er(3+) electronic transitions in the host crystal lattices of nanoparticles with the geometry established by ultrasound in aqueous solution of carbon nanotubes employed as a template material. The work can be of great interest for "green" chemistry synthesis of photoluminescent nanoparticles in water. Y1 - 2011 U6 - https://doi.org/10.1021/la203622u SN - 0743-7463 VL - 27 IS - 23 SP - 14472 EP - 14480 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Antoniou, Stella A1 - Pashalidis, I. A1 - Gessner, Andre A1 - Kumke, Michael Uwe T1 - The effect of humic acid on the formation and solubility of secondary solid phases (Nd(OH)CO3 and Sm(OH)CO3) JF - Radiochimica acta : international journal for chemical aspects of nuclear science and technology N2 - The formation of secondary Ln(III) solid phases (e.g. Nd(OH)CO3 and Sm(OH)CO3) has been studied as a function of the humic acid (HA) concentration in 0.1 M NaClO4 aqueous solution and their solubility has been investigated in the neutral pH range (6.5-8) under normal atmospheric conditions. Nd(III) and Sm(III) were selected as analogues for trivalent lanthanide and actinide ions. The solid phases under investigation have been prepared by alkaline precipitation and characterized by TGA, ATR-FTIR, XRD, TRLFS, DR-UV-Vis and Raman spectroscopy, and solubility measurements. The spectroscopic data obtained indicate that Nd(OH)CO3 and Sm(OH)CO3 are stable and remain the solubility limiting solid phases even in the presence of increased HA concentration (0.5 g/L) in solution. Upon base addition in the Ln(III)-HA system decomplexation of the previously formed Ln(III)-humate complexes and precipitation of two distinct phases occurs, the inorganic (Ln(OH)CO3) and the organic phase (HA), which is adsorbed on the particle surface of the former. Nevertheless, HA affects the particle size of the solid phases. Increasing HA concentration results in decreasing crystallite size of the Nd(OH)CO3 and increasing crystallite size of the Sm(OH)CO3 solid phase, and affects inversely the solubility of the solid phases. However, this impact on the solid phase properties is expected to be of minor relevance regarding the chemical behavior and migration of trivalent lanthanides and actinides in the geosphere. KW - Lanthanide ions KW - Humic acid KW - Solid phase KW - Solubility KW - Raman KW - TRLFS KW - DR-UV-Vis Y1 - 2011 U6 - https://doi.org/10.1524/ract.2011.1812 SN - 0033-8230 VL - 99 IS - 4 SP - 217 EP - 223 PB - De Gruyter CY - Berlin ER - TY - GEN A1 - Heyne, Benjamin A1 - Arlt, Kristin A1 - Geßner, André A1 - Richter, Alexander F. A1 - Döblinger, Markus A1 - Feldmann, Jochen A1 - Taubert, Andreas A1 - Wedel, Armin T1 - Mixed Mercaptocarboxylic Acid Shells Provide Stable Dispersions of InPZnS/ZnSe/ZnS Multishell Quantum Dots in Aqueous Media T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Highly luminescent indium phosphide zinc sulfide (InPZnS) quantum dots (QDs), with zinc selenide/zinc sulfide (ZnSe/ZnS) shells, were synthesized. The QDs were modified via a post-synthetic ligand exchange reaction with 3-mercaptopropionic acid (MPA) and 11-mercaptoundecanoic acid (MUA) in different MPA:MUA ratios, making this study the first investigation into the effects of mixed ligand shells on InPZnS QDs. Moreover, this article also describes an optimized method for the correlation of the QD size vs. optical absorption of the QDs. Upon ligand exchange, the QDs can be dispersed in water. Longer ligands (MUA) provide more stable dispersions than short-chain ligands. Thicker ZnSe/ZnS shells provide a better photoluminescence quantum yield (PLQY) and higher emission stability upon ligand exchange. Both the ligand exchange and the optical properties are highly reproducible between different QD batches. Before dialysis, QDs with a ZnS shell thickness of ~4.9 monolayers (ML), stabilized with a mixed MPA:MUA (mixing ratio of 1:10), showed the highest PLQY, at ~45%. After dialysis, QDs with a ZnS shell thickness of ~4.9 ML, stabilized with a mixed MPA:MUA and a ratio of 1:10 and 1:100, showed the highest PLQYs, of ~41%. The dispersions were stable up to 44 days at ambient conditions and in the dark. After 44 days, QDs with a ZnS shell thickness of ~4.9 ML, stabilized with only MUA, showed the highest PLQY, of ~34%. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1026 KW - quantum dots KW - cadmium-free KW - Cd-free KW - InP KW - InPZnS KW - multishell KW - mercaptocarboxylic acids KW - 3-mercaptopropionic acid KW - 11-mercaptoundecanoic acid KW - phase transfer KW - ligand exchange KW - aqueous dispersion KW - QDs Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-486032 SN - 1866-8372 IS - 1026 ER - TY - JOUR A1 - Xie, Zai-Lai A1 - Xu, Hai-Bing A1 - Gessner, Andre A1 - Kumke, Michael Uwe A1 - Priebe, Magdalena A1 - Fromm, Katharina M. A1 - Taubert, Andreas T1 - A transparent, flexible, ion conductive, and luminescent PMMA ionogel based on a Pt/Eu bimetallic complex and the ionic liquid [Bmim][N(Tf)(2)] JF - Journal of materials chemistry N2 - Transparent, ion-conducting, luminescent, and flexible ionogels based on the room temperature ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl) imide [Bmim][N(Tf)(2)], a PtEu2 chromophore, and poly(methylmethacrylate) (PMMA) have been prepared. The thermal stability of the PMMA significantly increases with IL incorporation. In particular, the onset weight loss observed at ca. 229 degrees C for pure PMMA increases to 305 degrees C with IL addition. The ionogel has a high ionic conductivity of 10(-3) S cm(-1) at 373 K and exhibits a strong emission in the red with a long average luminescence decay time of tau = 890 mu s. The resulting material is a new type of soft hybrid material featuring useful thermal, optical, and ion transport properties. Y1 - 2012 U6 - https://doi.org/10.1039/c2jm15862k SN - 0959-9428 VL - 22 IS - 16 SP - 8110 EP - 8116 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Heyne, Benjamin A1 - Arlt, Kristin A1 - Geßner, André A1 - Richter, Alexander F. A1 - Döblinger, Markus A1 - Feldmann, Jochen A1 - Taubert, Andreas A1 - Wedel, Armin T1 - Mixed Mercaptocarboxylic Acid Shells Provide Stable Dispersions of InPZnS/ZnSe/ZnS Multishell Quantum Dots in Aqueous Media JF - Nanomaterials N2 - Highly luminescent indium phosphide zinc sulfide (InPZnS) quantum dots (QDs), with zinc selenide/zinc sulfide (ZnSe/ZnS) shells, were synthesized. The QDs were modified via a post-synthetic ligand exchange reaction with 3-mercaptopropionic acid (MPA) and 11-mercaptoundecanoic acid (MUA) in different MPA:MUA ratios, making this study the first investigation into the effects of mixed ligand shells on InPZnS QDs. Moreover, this article also describes an optimized method for the correlation of the QD size vs. optical absorption of the QDs. Upon ligand exchange, the QDs can be dispersed in water. Longer ligands (MUA) provide more stable dispersions than short-chain ligands. Thicker ZnSe/ZnS shells provide a better photoluminescence quantum yield (PLQY) and higher emission stability upon ligand exchange. Both the ligand exchange and the optical properties are highly reproducible between different QD batches. Before dialysis, QDs with a ZnS shell thickness of ~4.9 monolayers (ML), stabilized with a mixed MPA:MUA (mixing ratio of 1:10), showed the highest PLQY, at ~45%. After dialysis, QDs with a ZnS shell thickness of ~4.9 ML, stabilized with a mixed MPA:MUA and a ratio of 1:10 and 1:100, showed the highest PLQYs, of ~41%. The dispersions were stable up to 44 days at ambient conditions and in the dark. After 44 days, QDs with a ZnS shell thickness of ~4.9 ML, stabilized with only MUA, showed the highest PLQY, of ~34%. KW - quantum dots KW - cadmium-free KW - Cd-free KW - InP KW - InPZnS KW - multishell KW - mercaptocarboxylic acids KW - 3-mercaptopropionic acid KW - 11-mercaptoundecanoic acid KW - phase transfer KW - ligand exchange KW - aqueous dispersion KW - QDs Y1 - 2020 U6 - https://doi.org/10.3390/nano10091858 SN - 2079-4991 VL - 10 IS - 9 PB - MDPI CY - Basel ER - TY - JOUR A1 - Balischewski, Christian A1 - Choi, Hyung-Seok A1 - Behrens, Karsten A1 - Beqiraj, Alkit A1 - Körzdörfer, Thomas A1 - Gessner, Andre A1 - Wedel, Armin A1 - Taubert, Andreas T1 - Metal sulfide nanoparticle synthesis with ionic liquids state of the art and future perspectives JF - ChemistryOpen N2 - Metal sulfides are among the most promising materials for a wide variety of technologically relevant applications ranging from energy to environment and beyond. Incidentally, ionic liquids (ILs) have been among the top research subjects for the same applications and also for inorganic materials synthesis. As a result, the exploitation of the peculiar properties of ILs for metal sulfide synthesis could provide attractive new avenues for the generation of new, highly specific metal sulfides for numerous applications. This article therefore describes current developments in metal sulfide nano-particle synthesis as exemplified by a number of highlight examples. Moreover, the article demonstrates how ILs have been used in metal sulfide synthesis and discusses the benefits of using ILs over more traditional approaches. Finally, the article demonstrates some technological challenges and how ILs could be used to further advance the production and specific property engineering of metal sulfide nanomaterials, again based on a number of selected examples. KW - Ionic liquids KW - ionic liquid crystals KW - ionic liquid precursors KW - metal KW - sulfides KW - catalysis KW - electrochemistry KW - energy materials KW - LED KW - solar KW - cells Y1 - 2021 U6 - https://doi.org/10.1002/open.202000357 SN - 2191-1363 VL - 10 IS - 2 SP - 272 EP - 295 PB - Wiley-VCH CY - Weinheim ER -