TY - GEN A1 - Meiling, Till Thomas A1 - Cywiński, Piotr J. A1 - Bald, Ilko T1 - White carbon: Fluorescent carbon nanoparticles with tunable quantum yield in a reproducible green synthesis N2 - In this study, a new reliable, economic, and environmentally-friendly one-step synthesis is established to obtain carbon nanodots (CNDs) with well-defined and reproducible photoluminescence (PL) properties via the microwave-assisted hydrothermal treatment of starch and Tris-acetate-EDTA (TAE) buffer as carbon sources. Three kinds of CNDs are prepared using different sets of above mentioned starting materials. The as-synthesized CNDs: C-CND (starch only), N-CND 1 (starch in TAE) and N-CND 2 (TAE only) exhibit highly homogenous PL and are ready to use without need for further purification. The CNDs are stable over a long period of time (>1 year) either in solution or as freeze-dried powder. Depending on starting material, CNDs with PL quantum yield (PLQY) ranging from less than 1% up to 28% are obtained. The influence of the precursor concentration, reaction time and type of additives on the optical properties (UV-Vis absorption, PL emission spectrum and PLQY) is carefully investigated, providing insight into the chemical processes that occur during CND formation. Remarkably, upon freeze-drying the initially brown CND-solution turns into a non-fluorescent white/slightly brown powder which recovers PL in aqueous solution and can potentially be applied as fluorescent marker in bio-imaging, as a reduction agent or as a photocatalyst. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 264 KW - Fluorescence spectroscopy KW - Nanoparticles KW - Synthesis and processing Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-97087 ER - TY - JOUR A1 - Meiling, Till Thomas A1 - Cywiński, Piotr J. A1 - Bald, Ilko T1 - White carbon: Fluorescent carbon nanoparticles with tunable quantum yield in a reproducible green synthesis JF - Scientific reports N2 - In this study, a new reliable, economic, and environmentally-friendly one-step synthesis is established to obtain carbon nanodots (CNDs) with well-defined and reproducible photoluminescence (PL) properties via the microwave-assisted hydrothermal treatment of starch and Tris-acetate-EDTA (TAE) buffer as carbon sources. Three kinds of CNDs are prepared using different sets of above mentioned starting materials. The as-synthesized CNDs: C-CND (starch only), N-CND 1 (starch in TAE) and N-CND 2 (TAE only) exhibit highly homogenous PL and are ready to use without need for further purification. The CNDs are stable over a long period of time (>1 year) either in solution or as freeze-dried powder. Depending on starting material, CNDs with PL quantum yield (PLQY) ranging from less than 1% up to 28% are obtained. The influence of the precursor concentration, reaction time and type of additives on the optical properties (UV-Vis absorption, PL emission spectrum and PLQY) is carefully investigated, providing insight into the chemical processes that occur during CND formation. Remarkably, upon freeze-drying the initially brown CND-solution turns into a non-fluorescent white/slightly brown powder which recovers PL in aqueous solution and can potentially be applied as fluorescent marker in bio-imaging, as a reduction agent or as a photocatalyst. KW - Fluorescence spectroscopy KW - Nanoparticles KW - Synthesis and processing Y1 - 2016 U6 - https://doi.org/10.1038/srep28557 VL - 6 PB - Nature Publishing Group CY - London ER - TY - THES A1 - Kovach, Ildiko T1 - Development, characterization of Janus emulsions, and their usage as a template phase for fabricating biopolymer scaffolds Y1 - 2016 ER - TY - THES A1 - Riebe, Daniel T1 - Experimental and theoretical investigations of molecular ions by spectroscopy as well as ion mobility and mass spectrometry T1 - Experimentelle und theoretische Untersuchungen molekularer Ionen durch Spektroskopie sowie Ionenmobilitäts- und Massenspektrometrie N2 - The aim of this thesis was the elucidation of different ionization methods (resonance-enhanced multiphoton ionization – REMPI, electrospray ionization – ESI, atmospheric pressure chemical ionization – APCI) in ion mobility (IM) spectrometry. In order to gain a better understanding of the ionization processes, several spectroscopic, mass spectrometric and theoretical methods were also used. Another focus was the development of experimental techniques, including a high resolution spectrograph and various combinations of IM and mass spectrometry. The novel high resolution 2D spectrograph facilitates spectroscopic resolutions in the range of commercial echelle spectrographs. The lowest full width at half maximum of a peak achieved was 25 pm. The 2D spectrograph is based on the wavelength separation of light by the combination of a prism and a grating in one dimension, and an etalon in the second dimension. This instrument was successfully employed for the acquisition of Raman and laser-induced breakdown spectra. Different spectroscopic methods (light scattering and fluorescence spectroscopy) permitting a spatial as well as spectral resolution, were used to investigate the release of ions in the electrospray. The investigation is based on the 50 nm shift of the fluorescence band of rhodamine 6G ions of during the transfer from the electrospray droplets to the gas phase. A newly developed ionization chamber operating at reduced pressure (0.5 mbar) was coupled to a time-of-flight mass spectrometer. After REMPI of H2S, an ionization chemistry analogous to H2O was observed with this instrument. Besides H2S+ and its fragments, H3S+ and protonated analyte ions could be observed as a result of proton-transfer reactions. For the elucidation of the peaks in IM spectra, a combination of IM spectrometer and linear quadrupole ion trap mass spectrometer was developed. The instrument can be equipped with various ionization sources (ESI, REMPI, APCI) and was used for the characterization of the peptide bradykinin and the neuroleptic promazine. The ionization of explosive compounds in an APCI source based on soft x-radiation was investigated in a newly developed ionization chamber attached to the ion trap mass spectrometer. The major primary and secondary reactions could be characterized and explosive compound ions could be identified and assigned to the peaks in IM spectra. The assignment is based on the comparison of experimentally determined and calculated IM. The methods of calculation currently available exhibit large deviations, especially in the case of anions. Therefore, on the basis of an assessment of available methods, a novel hybrid method was developed and characterized. N2 - Ziel dieser Arbeit war die Aufklärung unterschiedlicher Ionisationsmethoden (Resonanz-verstärkte Mehrphotonenionisation – REMPI, Elektrosprayionisation – ESI, chemische Ionisation bei Atmosphärendruck – APCI) in der Ionenmobilitäts (IM)-Spektrometrie. Um ein besseres Verständnis der Ionisationsprozesse zu erhalten, wurden zusätzlich ver¬schiedene spektroskopische, massenspektrometrische und theoretische Methoden eingesetzt. Ein weiterer Schwerpunkt war die Entwicklung neuer experimenteller Techniken, darunter ein hochauflösender Spektrograph und verschiedene Kombinationen von IM- und Massenspektrometern. Der neuartige, hochauflösende 2D Spektrograph ermöglicht spektroskopische Auflösungen im Bereich kommerzieller Echelle-Spektrographen. Die geringste erreichte Halbwertsbreite eines Peaks betrug 25 pm. Der 2D Spektrograph beruht auf der Wellenlängenseparation von Licht durch eine Kombination aus einem Prisma und einem Gitter in der einen Dimension und einem Etalon in der zweiten Dimension. Das Instrument wurde erfolgreich zur Aufnahme von Raman- und laserinduzierten Plasmaspektren ein¬gesetzt. Verschiedene spektroskopische Methoden (Lichtstreuung und Fluoreszenzspektroskopie), die sowohl eine räumliche, als auch eine spektrale Auflösung erlauben, wurden zur Untersuchung der Freisetzung der Ionen im Elektrospray angewandt. Die Untersuchung beruht auf der Verschiebung der Fluoreszenzbande von Rhodamin 6G-Ionen um 50 nm beim Übergang aus den Elektrospray-Tropfen in die Gasphase. Eine neuent¬wickelte Ionisationskammer bei reduziertem Druck (0,5 mbar) wurde an ein Flugzeit-Massenspektrometer gekoppelt. Darin wurde nach REMPI von H2S eine zum H2O analoge Ionisationschemie beobachtet. Neben H2S+ und seinen Fragmenten wurden als Ergebnis von Proto-nen-Transferreaktionen H3S+ und protonierte Analytionen beobachtet. Zur Aufklärung der Peaks in IM-Spektren wurde eine Kopplung von IM-Spektrometer und linearem Quadrupol-Ionenfallen-Massenspektrometer entwickelt. Die Kopplung kann mit verschiedenen Ionisationsquellen (ESI, REMPI, APCI) ausgestattet werden und wurde zur Charakterisierung des Peptids Bradykinin und des Neuroleptikums Promazin angewendet. Die Ionisation von Sprengstoffen in einer APCI-Quelle, die auf weicher Röntgenstrahlung beruht, wurde in einer neu entwickelten, an das Ionenfallen-Massenspektrometer gekoppelten Ionisationskammer untersucht. Dabei konnten die wichtigsten Primär- und Sekundärreaktionen charakterisiert, sowie Sprengstoffionen identifiziert und den Peaks in den IM-Spektren zugeordnet werden. Diese Zuordnung beruht auf dem Vergleich von experimentell bestimmten und berechneten IM. Da die aktuell verfügbaren Berechnungsmethoden insbesondere für Anionen zu große Abweichungen zu den experimentell bestimmten IM aufweisen, wurde auf Basis der Bewertung verfügbarer Methoden eine neue Hybridmethode entwickelt und charakterisiert. KW - ion mobility spectrometry KW - mass spectrometry KW - explosives KW - X-ray KW - photoionization KW - ion mobility calculations KW - Ionenmobilitätsspektrometrie KW - Massenspektrometrie KW - Sprengstoffe KW - Röntgenstrahlung KW - Photoionisation KW - Ionenmobilitäts-Berechnungen Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-94632 ER - TY - GEN A1 - Doriti, Afroditi A1 - Brosnan, Sarah M. A1 - Weidner, Steffen M. A1 - Schlaad, Helmut T1 - Synthesis of polysarcosine from air and moisture stable N-phenoxycarbonyl-N-methylglycine assisted by tertiary amine base N2 - Polysarcosine (Mn = 3650–20 000 g mol−1, Đ ∼ 1.1) was synthesized from the air and moisture stable N-phenoxycarbonyl-N-methylglycine. Polymerization was achieved by in situ transformation of the urethane precursor into the corresponding N-methylglycine-N-carboxyanhydride, when in the presence of a non-nucleophilic tertiary amine base and a primary amine initiator. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 255 KW - acids KW - activated urethane derivatives KW - carboxyanhydrides KW - copolymers KW - phosgene-free synthesis KW - polypeptides KW - ring-opening polymerization Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95852 SP - 3067 EP - 3070 ER - TY - JOUR A1 - Doriti, Afroditi A1 - Brosnan, Sarah M. A1 - Weidner, Steffen M. A1 - Schlaad, Helmut T1 - Synthesis of polysarcosine from air and moisture stable N-phenoxycarbonyl-N-methylglycine assisted by tertiary amine base JF - Polymer Chemistry N2 - Polysarcosine (Mn = 3650–20 000 g mol−1, Đ ∼ 1.1) was synthesized from the air and moisture stable N-phenoxycarbonyl-N-methylglycine. Polymerization was achieved by in situ transformation of the urethane precursor into the corresponding N-methylglycine-N-carboxyanhydride, when in the presence of a non-nucleophilic tertiary amine base and a primary amine initiator. KW - ring-opening polymerization KW - activated urethane derivatives KW - phosgene-free synthesis KW - carboxyanhydrides KW - polypeptides KW - acids KW - copolymers Y1 - 2016 U6 - https://doi.org/10.1039/C6PY00221H SN - 1759-9954 SN - 1759-9962 VL - 7 SP - 3067 EP - 3070 PB - RSC Publ. CY - Cambridge ER - TY - GEN A1 - Olejko, Lydia A1 - Cywiński, P. J. A1 - Bald, Ilko T1 - An ion-controlled four-color fluorescent telomeric switch on DNA origami structures N2 - The folding of single-stranded telomeric DNA into guanine (G) quadruplexes is a conformational change that plays a major role in sensing and drug targeting. The telomeric DNA can be placed on DNA origami nanostructures to make the folding process extremely selective for K+ ions even in the presence of high Na+ concentrations. Here, we demonstrate that the K+-selective G-quadruplex formation is reversible when using a cryptand to remove K+ from the G-quadruplex. We present a full characterization of the reversible switching between single-stranded telomeric DNA and G-quadruplex structures using Förster resonance energy transfer (FRET) between the dyes fluorescein (FAM) and cyanine3 (Cy3). When attached to the DNA origami platform, the G-quadruplex switch can be incorporated into more complex photonic networks, which is demonstrated for a three-color and a four-color FRET cascade from FAM over Cy3 and Cy5 to IRDye700 with G-quadruplex-Cy3 acting as a switchable transmitter. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 254 KW - resonance energy-transfer KW - g-quadruplex KW - quantum dots KW - strand breakage KW - photonic wires KW - 3-color fret KW - nanostructures KW - recognition KW - sensitivity KW - assemblies Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95831 SP - 10339 EP - 10347 ER - TY - JOUR A1 - Olejko, Lydia A1 - Cywiński, Piotr J. A1 - Bald, Ilko T1 - An ion-controlled four-color fluorescent telomeric switch on DNA origami structures JF - Nanoscale N2 - The folding of single-stranded telomeric DNA into guanine (G) quadruplexes is a conformational change that plays a major role in sensing and drug targeting. The telomeric DNA can be placed on DNA origami nanostructures to make the folding process extremely selective for K+ ions even in the presence of high Na+ concentrations. Here, we demonstrate that the K+-selective G-quadruplex formation is reversible when using a cryptand to remove K+ from the G-quadruplex. We present a full characterization of the reversible switching between single-stranded telomeric DNA and G-quadruplex structures using Förster resonance energy transfer (FRET) between the dyes fluorescein (FAM) and cyanine3 (Cy3). When attached to the DNA origami platform, the G-quadruplex switch can be incorporated into more complex photonic networks, which is demonstrated for a three-color and a four-color FRET cascade from FAM over Cy3 and Cy5 to IRDye700 with G-quadruplex-Cy3 acting as a switchable transmitter. KW - resonance energy-transfer KW - g-quadruplex KW - quantum dots KW - strand breakage KW - photonic wires KW - 3-color fret KW - nanostructures KW - recognition KW - sensitivity KW - assemblies Y1 - 2016 U6 - https://doi.org/10.1039/C6NR00119J SN - 2040-3372 SN - 2040-3364 VL - 8 SP - 10339 EP - 10347 PB - RSC Publ. CY - Cambridge ER - TY - GEN A1 - Niedl, Robert Raimund A1 - Berenstein, Igal A1 - Beta, Carsten T1 - How imperfect mixing and differential diffusion accelerate the rate of nonlinear reactions in microfluidic channels N2 - In this paper, we show experimentally that inside a microfluidic device, where the reactants are segregated, the reaction rate of an autocatalytic clock reaction is accelerated in comparison to the case where all the reactants are well mixed. We also find that, when mixing is enhanced inside the microfluidic device by introducing obstacles into the flow, the clock reaction becomes slower in comparison to the device where mixing is less efficient. Based on numerical simulations, we show that this effect can be explained by the interplay of nonlinear reaction kinetics (cubic autocatalysis) and differential diffusion, where the autocatalytic species diffuses slower than the substrate. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 253 KW - arsenious acid KW - fronts KW - paper KW - poly(dimethylsiloxane) KW - scale KW - systems Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95810 SP - 6451 EP - 6457 ER - TY - JOUR A1 - Niedl, Robert Raimund A1 - Berenstein, Igal A1 - Beta, Carsten T1 - How imperfect mixing and differential diffusion accelerate the rate of nonlinear reactions in microfluidic channels JF - Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies N2 - In this paper, we show experimentally that inside a microfluidic device, where the reactants are segregated, the reaction rate of an autocatalytic clock reaction is accelerated in comparison to the case where all the reactants are well mixed. We also find that, when mixing is enhanced inside the microfluidic device by introducing obstacles into the flow, the clock reaction becomes slower in comparison to the device where mixing is less efficient. Based on numerical simulations, we show that this effect can be explained by the interplay of nonlinear reaction kinetics (cubic autocatalysis) and differential diffusion, where the autocatalytic species diffuses slower than the substrate. KW - arsenious acid KW - systems KW - poly(dimethylsiloxane) KW - fronts KW - scale KW - paper Y1 - 2016 U6 - https://doi.org/10.1039/c6cp00224b SN - 1463-9076 SN - 1463-9084 VL - 18 SP - 6451 EP - 6457 PB - Royal Society of Chemistry CY - Cambridge ER -