TY - JOUR A1 - Lapresta-Fernández, Alejandro A1 - Cywinski, Piotr J. A1 - Moro, Artur J. A1 - Mohr, Gerhard J. T1 - Fluorescent polyacrylamide nanoparticles for naproxen recognition N2 - We present the synthesis of fluorescent acrylamide nanoparticles (FANs) capable of recognizing non-steroidal anti-inflammatory drugs (NSAIDs) in buffered aqueous solutions. Within this important group, we selected naproxen, one of the 2-arylpropionic acids (profens), due to its use for the treatment of moderate pain, fever, and inflammation. The nanosensors were prepared under mild conditions of inverse microemulsion polymerization using aqueous acrylamide as the monomer and N,N'-methylenebisacrylamide as the crosslinker, employing the surfactants polyoxyethylene-4-lauryl ether (Brij (R) 30) and sodium bis(2-ethylhexyl) sulfosuccinate in hexane. Furthermore, a fluorescent monomer, (E)-4-[4- (dimethylamino)styryl]-1-[4-(methacryloyloxymethyl)benzyl]pyridinium chloride (mDMASP) has been synthesized and incorporated into the nanoparticles. The nanosensors exhibit a broad absorbance at around 460 nm and a structureless fluorescence band with maximum at 590 nm in 0.5 M phosphate buffer (pH=7.2). The recognition process is performed on the basis of ionic interactions which are monitored by the fluorescence increase at 590 nm upon addition of different concentrations of naproxen. The FANs show a size distribution in the range of 20-80 nm, with a hydrodynamic diameter of 34 nm. In order to assess the selectivity of the FANs, a systematic study was conducted on the effect produced by drugs and biomolecules that could interfere with the analysis of naproxen. Y1 - 2009 UR - http://www.springerlink.com/content/100417 U6 - https://doi.org/10.1007/s00216-009-3007-2 SN - 1618-2642 ER - TY - JOUR A1 - Suriyanarayanan, Subramanian A1 - Cywinski, Piotr J. A1 - Moro, Artur J. A1 - Mohr, Gerhard J. A1 - Kutner, Wlodzimierz ED - Haupt, K T1 - Chemosensors based on molecularly imprinted polymers JF - Topics in current chemistry JF - Topics in Current Chemistry Y1 - 2012 SN - 978-3-642-28421-2 U6 - https://doi.org/10.1007/128_2010_92 SN - 0340-1022 VL - 325 IS - 4 SP - 165 EP - 265 PB - Springer CY - Berlin ER - TY - GEN A1 - Cywiński, Piotr J. A1 - Nono, Katia Nchimi A1 - Charbonnière, Loïc J. A1 - Hammann, Tommy A1 - Löhmannsröben, Hans-Gerd T1 - Photophysical evaluation of a new functional terbium complex in FRET-based time-resolved homogenous fluoroassays N2 - A new functional luminescent lanthanide complex (LLC) has been synthesized with terbium as a central lanthanide ion and biotin as a functional moiety. Unlike in typical lanthanide complexes assembled via carboxylic moieties, in the presented complex, four phosphate groups are chelating the central lanthanide ion. This special chemical assembly enhances the complex stability in phosphate buffers conventionally used in biochemistry. The complex synthesis strategy and photophysical properties are described as well as the performance in time-resolved Förster Resonance Energy Transfer (FRET) assays. In those assays, this biotin-LLC transferred energy either to acceptor organic dyes (Cy5 or AF680) labelled on streptavidin or to quantum dots (QD655 or QD705) surface-functionalised with streptavidins. The permanent spatial donor–acceptor proximity is assured through strong and stable biotin–streptavidin binding. The energy transfer is evidenced from the quenching observed in donor emission and from a decrease in donor luminescence decay, both associated with simultaneous increase in acceptor intensity and in the decay time. The dye-based assays are realised in TRIS and in PBS, whereas QD-based systems are studied in borate buffer. The delayed emission analysis allows for quantifying the recognition process and for auto-fluorescence-free detection, which is particularly relevant for application in bioanalysis. In accordance with Förster theory, Förster-radii (R0) were found to be around 60 Å for organic dyes and around 105 Å for QDs. The FRET efficiency (η) reached 80% and 25% for dye and QD acceptors, respectively. Physical donor–acceptor distances (r) have been determined in the range 45–60 Å for organic dye acceptors, while for acceptor QDs between 120 Å and 145 Å. This newly synthesised biotin-LLC extends the class of highly sensitive analytical tools to be applied in the bioanalytical methods such as time-resolved fluoroimmunoassays (TR-FIA), luminescent imaging and biosensing. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 252 KW - acceptors KW - bioanalysis KW - contrast agents KW - europium KW - fluoroimmunoassay KW - labels KW - lanthanide luminescence KW - quantum dots KW - resonance energy-transfer Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95390 SP - 6060 EP - 6067 ER - TY - GEN A1 - Idzik, Krzysztof Ryszard A1 - Cywinski, Piotr J. A1 - Cranfield, Charles G. A1 - Mohr, Gerhard J. A1 - Beckert, Rainer T1 - Molecular recognition of the antiretroviral drug Abacavir BT - towards the development of a novel carbazole-based fluorosensor T2 - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe N2 - Due to their optical and electro-conductive attributes, carbazole derivatives are interesting materials for a large range of biosensor applications. In this study, we present the synthesis routes and fluorescence evaluation of newly designed carbazole fluorosensors that, by modification with uracil, have a special affinity for antiretroviral drugs via either Watson–Crick or Hoogsteen base pairing. To an N-octylcarbazole-uracil compound, four different groups were attached, namely thiophene, furane, ethylenedioxythiophene, and another uracil; yielding four different derivatives. Photophysical properties of these newly obtained derivatives are described, as are their interactions with the reverse transcriptase inhibitors such as abacavir, zidovudine, lamivudine and didanosine. The influence of each analyte on biosensor fluorescence was assessed on the basis of the Stern–Volmer equation and represented by Stern–Volmer constants. Consequently we have demonstrated that these structures based on carbazole, with a uracil group, may be successfully incorporated into alternative carbazole derivatives to form biosensors for the molecular recognition of antiretroviral drugs. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 847 KW - HIV KW - HAART KW - antiretroviral drugs KW - carbazole KW - base pairing KW - fluorescence spectroscopy Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-430372 SN - 1866-8372 IS - 847 SP - 1195 EP - 1204 ER - TY - JOUR A1 - Cywinski, Piotr J. A1 - Idzik, Krzysztof R. A1 - Cranfield, Charles G. A1 - Beckert, Rainer A1 - Mohr, Gerhard J. T1 - Synthesis and sensing properties of a new carbazole fluorosensor for detection of abacavir N2 - An abacavir-targeted fluorosensor based on the carbazole moiety has been synthesised and characterised. Recognition of abacavir is by base pairing between a uracil moiety present in the fluorosensor and the guanine moiety of abacavir. The fluorosensor exhibits five-fold quenching in the presence of 50M abacavir. Its sensitivity to abacavir is superior to that of other reverse transcriptase inhibitors: zidovudine, lamivudine and didanosine. Due to its high sensitivity, this fluorosensor has the potential to be used in multi-analyte array-based detection platforms as well as in microfluidics systems. Y1 - 2010 UR - http://www.informaworld.com/openurl?genre=journal&issn=1061-0278 U6 - https://doi.org/10.1080/10610278.2010.506541 SN - 1061-0278 ER - TY - JOUR A1 - Cywinski, Piotr J. A1 - Nono, Katia Nchimi A1 - Charbonniere, Loic J. A1 - Hammann, Tommy A1 - Löhmannsröben, Hans-Gerd T1 - Photophysical evaluation of a new functional terbium complex in FRET-based time-resolved homogenous fluoroassays JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - A new functional luminescent lanthanide complex (LLC) has been synthesized with terbium as a central lanthanide ion and biotin as a functional moiety. Unlike in typical lanthanide complexes assembled via carboxylic moieties, in the presented complex, four phosphate groups are chelating the central lanthanide ion. This special chemical assembly enhances the complex stability in phosphate buffers conventionally used in biochemistry. The complex synthesis strategy and photophysical properties are described as well as the performance in time-resolved Forster Resonance Energy Transfer (FRET) assays. In those assays, this biotin-LLC transferred energy either to acceptor organic dyes (Cy5 or AF680) labelled on streptavidin or to quantum dots (QD655 or QD705) surfacefunctionalised with streptavidins. The permanent spatial donor-acceptor proximity is assured through strong and stable biotin-streptavidin binding. The energy transfer is evidenced from the quenching observed in donor emission and from a decrease in donor luminescence decay, both associated with simultaneous increase in acceptor intensity and in the decay time. The dye-based assays are realised in TRIS and in PBS, whereas QD-based systems are studied in borate buffer. The delayed emission analysis allows for quantifying the recognition process and for auto-fluorescence-free detection, which is particularly relevant for application in bioanalysis. In accordance with Forster theory, Forsterradii (R0) were found to be around 60 angstrom for organic dyes and around 105 angstrom for QDs. The FRET efficiency (Z) reached 80% and 25% for dye and QD acceptors, respectively. Physical donor-acceptor distances (r) have been determined in the range 45-60 angstrom for organic dye acceptors, while for acceptor QDs between 120 angstrom and 145 angstrom. This newly synthesised biotin-LLC extends the class of highly sensitive analytical tools to be applied in the bioanalytical methods such as time-resolved fluoroimmunoassays (TR-FIA), luminescent imaging and biosensing. Y1 - 2014 U6 - https://doi.org/10.1039/c3cp54883j SN - 1463-9076 SN - 1463-9084 VL - 16 IS - 13 SP - 6060 EP - 6067 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Cywinski, Piotr J. A1 - Hammann, Tommy A1 - Huehn, Dominik A1 - Parak, Wolfgang J. A1 - Hildebrandt, Niko A1 - Löhmannsröben, Hans-Gerd T1 - Europium-quantum dot nanobioconjugates as luminescent probes for time-gated biosensing JF - Journal of biomedical optics N2 - Nanobioconjugates have been synthesized using cadmium selenide quantum dots (QDs), europium complexes (EuCs), and biotin. In those conjugates, long-lived photoluminescence (PL) is provided by the europium complexes, which efficiently transfer energy via Forster resonance energy transfer (FRET) to the QDs in close spatial proximity. As a result, the conjugates have a PL emission spectrum characteristic for QDs combined with the long PL decay time characteristic for EuCs. The nanobioconjugates synthesis strategy and photo-physical properties are described as well as their performance in a time-resolved streptavidin-biotin PL assay. In order to prepare the QD-EuC-biotin conjugates, first an amphiphilic polymer has been functionalized with the EuC and biotin. Then, the polymer has been brought onto the surface of the QDs (either QD655 or QD705) to provide functionality and to make the QDs water dispersible. Due to a short distance between EuC and QD, an efficient FRET can be observed. Additionally, the QD-EuC-biotin conjugates' functionality has been demonstrated in a PL assay yielding good signal discrimination, both from autofluorescence and directly excited QDs. These newly designed QD-EuC-biotin conjugates expand the class of highly sensitive tools for bioanalytical optical detection methods for diagnostic and imaging applications. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE) KW - quantum dots KW - europium complex KW - amphiphilic polymer assembly KW - nanobioconjugate KW - biosensor KW - time-resolved fluorescence Y1 - 2014 U6 - https://doi.org/10.1117/1.JBO.19.10.101506 SN - 1083-3668 SN - 1560-2281 VL - 19 IS - 10 PB - SPIE CY - Bellingham ER - TY - JOUR A1 - Cywinski, Piotr J. A1 - Moro, Artur J. A1 - Löhmannsröben, Hans-Gerd T1 - Cyclic GMP recognition using ratiometric QD-fluorophore conjugate nanosensors JF - Biosensors and bioelectronics : the principal international journal devoted to research, design development and application of biosensors and bioelectronics KW - Quantum dots KW - Naphthyridines KW - Cyclic GMP KW - Base pairing KW - Fluorescent nanoconjugate KW - Nanosensor Y1 - 2014 U6 - https://doi.org/10.1016/j.bios.2013.09.002 SN - 0956-5663 SN - 1873-4235 VL - 52 SP - 288 EP - 292 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Idzik, Krzysztof Ryszard A1 - Cywinski, Piotr J. A1 - Cranfield, Charles G. A1 - Mohr, Gerhard J. A1 - Beckert, Rainer T1 - Molecular recognition of the antiretroviral drug abacavir towards the development of a novel carbazole-based fluorosensor JF - Journal of fluorescence N2 - Due to their optical and electro-conductive attributes, carbazole derivatives are interesting materials for a large range of biosensor applications. In this study, we present the synthesis routes and fluorescence evaluation of newly designed carbazole fluorosensors that, by modification with uracil, have a special affinity for antiretroviral drugs via either Watson-Crick or Hoogsteen base pairing. To an N-octylcarbazole-uracil compound, four different groups were attached, namely thiophene, furane, ethylenedioxythiophene, and another uracil; yielding four different derivatives. Photophysical properties of these newly obtained derivatives are described, as are their interactions with the reverse transcriptase inhibitors such as abacavir, zidovudine, lamivudine and didanosine. The influence of each analyte on biosensor fluorescence was assessed on the basis of the Stern-Volmer equation and represented by Stern-Volmer constants. Consequently we have demonstrated that these structures based on carbazole, with a uracil group, may be successfully incorporated into alternative carbazole derivatives to form biosensors for the molecular recognition of antiretroviral drugs. KW - HIV KW - HAART KW - Antiretroviral drugs KW - Carbazole KW - Base pairing KW - Fluorescence spectroscopy Y1 - 2011 U6 - https://doi.org/10.1007/s10895-010-0798-7 SN - 1053-0509 SN - 1573-4994 VL - 21 IS - 3 SP - 1195 EP - 1204 PB - Springer CY - New York ER - TY - JOUR A1 - Cywinski, Piotr J. A1 - Moro, Artur J. A1 - Ritschel, Thomas A1 - Hildebrandt, Niko A1 - Löhmannsröben, Hans-Gerd T1 - Sensitive and selective fluorescence detection of guanosine nucleotides by nanoparticles conjugated with a naphthyridine receptor JF - Analytical & bioanalytical chemistry N2 - Novel fluorescent nanosensors, based on a naphthyridine receptor, have been developed for the detection of guanosine nucleotides, and both their sensitivity and selectivity to various nucleotides were evaluated. The nanosensors were constructed from polystyrene nanoparticles functionalized by (N-(7-((3-aminophenyl) ethynyl)-1,8-naphthyridin- 2-yl) acetamide) via carbodiimide ester activation. We show that this naphthyridine nanosensor binds guanosine nucleotides preferentially over adenine, cytosine, and thymidine nucleotides. Upon interaction with nucleotides, the fluorescence of the nanosensor is gradually quenched yielding Stern-Volmer constants in the range of 2.1 to 35.9mM(-1). For all the studied quenchers, limits of detection (LOD) and tolerance levels for the nanosensors were also determined. The lowest (3 sigma) LOD was found for guanosine 3',5'-cyclic monophosphate (cGMP) and it was as low as 150 ng/ml. In addition, we demonstrated that the spatial arrangement of bound analytes on the nanosensors' surfaces is what is responsible for their selectivity to different guanosine nucleotides. We found a correlation between the changes of the fluorescence signal and the number of phosphate groups of a nucleotide. Results of molecular modeling and zeta-potential measurements confirm that the arrangement of analytes on the surface provides for the selectivity of the nanosensors. These fluorescent nanosensors have the potential to be applied in multi-analyte, array-based detection platforms, as well as in multiplexed microfluidic systems. KW - Naphthyridine receptor KW - cGMP KW - Base pairing KW - Nucleotide nanosensor KW - Fluorescence spectroscopy Y1 - 2011 U6 - https://doi.org/10.1007/s00216-010-4420-2 SN - 1618-2642 VL - 399 IS - 3 SP - 1215 EP - 1222 PB - Springer CY - Heidelberg ER - TY - GEN A1 - Węcławski, Marek K. A1 - Tasior, Mariusz A1 - Hammann, Tommy A1 - Cywiński, Piotr J. A1 - Gryko, Daniel T. T1 - From π-expanded coumarins to π-expanded pentacenes N2 - The synthesis of two novel types of π-expanded coumarins has been developed. Modified Knoevenagel bis-condensation afforded 3,9-dioxa-perylene-2,8-diones. Subsequent oxidative aromatic coupling or light driven electrocyclization reaction led to dibenzo-1,7-dioxacoronene-2,8-dione. Unparalleled synthetic simplicity, straightforward purification and superb optical properties have the potential to bring these perylene and coronene analogs towards various applications. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 280 Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98822 ER - TY - GEN A1 - Ciuciu, Adina I. A1 - Cywiński, Piotr J. T1 - Two-photon polymerization of hydrogels – versatile solutions to fabricate well-defined 3D structures N2 - Hydrogels are cross-linked water-containing polymer networks that are formed by physical, ionic or covalent interactions. In recent years, they have attracted significant attention because of their unique physical properties, which make them promising materials for numerous applications in food and cosmetic processing, as well as in drug delivery and tissue engineering. Hydrogels are highly water-swellable materials, which can considerably increase in volume without losing cohesion, are biocompatible and possess excellent tissue-like physical properties, which can mimic in vivo conditions. When combined with highly precise manufacturing technologies, such as two-photon polymerization (2PP), well-defined three-dimensional structures can be obtained. These structures can become scaffolds for selective cell-entrapping, cell/drug delivery, sensing and prosthetic implants in regenerative medicine. 2PP has been distinguished from other rapid prototyping methods because it is a non-invasive and efficient approach for hydrogel cross-linking. This review discusses the 2PP-based fabrication of 3D hydrogel structures and their potential applications in biotechnology. A brief overview regarding the 2PP methodology and hydrogel properties relevant to biomedical applications is given together with a review of the most important recent achievements in the field. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 286 Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-99450 ER - TY - JOUR A1 - Meiling, Till Thomas A1 - Cywinski, Piotr J. A1 - Löhmannsröben, Hans-Gerd T1 - Two-Photon excitation fluorescence spectroscopy of quantum dots BT - photophysical properties and application in bioassays JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - The applications of quantum dots (QDs) in two-photon (2P) excitation applications demand reliable data about their 2P absorption (2PA) cross sections (sigma(2PA)). In the present study, sigma(2PA) values have been determined for a series of commercial colloidal CdSe/ZnS QDs and CdSeTe/ZnS QDs in aqueous media. For the first time for these QDs, the sigma(2PA) values have been determined over a wide spectral range, that is, between 720 and 900 nm, and are compared to the extinction coefficient (epsilon) values obtained under one-photon (1P) excitation. Furthermore, we present a QD in combination with an organic dye in a biotin-streptavidin Forster resonance energy transfer bioassay under 1P and 2P excitation. The results for the bioassay under 2P excitation are compared to those obtained under 1P excitation. The results demonstrate that in the case of the 2P excitation, higher sensitivity can be achieved because of an improved signal-to-noise ratio. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jpcc.7b12345 SN - 1932-7447 SN - 1932-7455 VL - 122 IS - 17 SP - 9641 EP - 9647 PB - American Chemical Society CY - Washington 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 - 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 - GEN A1 - Tasior, Mariusz A1 - Bald, Ilko A1 - Deperasińska, Irena A1 - Cywiński, Piotr J. A1 - Gryko, Daniel T. T1 - An internal charge transfer-dependent solvent effect in V-shaped azacyanines N2 - New V-shaped non-centrosymmetric dyes, possessing a strongly electron-deficient azacyanine core, have been synthesized based on a straightforward two-step approach. The key step in this synthesis involves palladium-catalysed cross-coupling of dibromo-N,N′-methylene-2,2′-azapyridinocyanines with arylacetylenes. The resulting strongly polarized π-expanded heterocycles exhibit green to orange fluorescence and they strongly respond to changes in solvent polarity. We demonstrate that differently electron-donating peripheral groups have a significant influence on the internal charge transfer, hence on the solvent effect and fluorescence quantum yield. TD-DFT calculations confirm that, in contrast to the previously studied bis(styryl)azacyanines, the proximity of S1 and T2 states calculated for compounds bearing two 4-N,N-dimethylaminophenylethynyl moieties establishes good conditions for efficient intersystem crossing and is responsible for its low fluorescence quantum yield. Non-linear properties have also been determined for new azacyanines and the results show that depending on peripheral groups, the synthesized dyes exhibit small to large two-photon absorption cross sections reaching 4000 GM. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 306 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-102704 SP - 11714 EP - 11720 ER - TY - JOUR A1 - Olejko, Lydia A1 - Cywinski, Piotr J. A1 - Bald, Ilko T1 - Ion-Selective formation of a guanine quadruplex on DNA origami structures JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - DNA origami nanostructures are a versatile tool that can be used to arrange functionalities with high local control to study molecular processes at a single-molecule level. Here, we demonstrate that DNA origami substrates can be used to suppress the formation of specific guanine (G) quadruplex structures from telomeric DNA. The folding of telomeres into G-quadruplex structures in the presence of monovalent cations (e.g. Na+ and K+) is currently used for the detection of K+ ions, however, with insufficient selectivity towards Na+. By means of FRET between two suitable dyes attached to the 3- and 5-ends of telomeric DNA we demonstrate that the formation of G-quadruplexes on DNA origami templates in the presence of sodium ions is suppressed due to steric hindrance. Hence, telomeric DNA attached to DNA origami structures represents a highly sensitive and selective detection tool for potassium ions even in the presence of high concentrations of sodium ions. KW - DNA nanotechnology KW - FRET KW - G-quadruplexes KW - nanostructures KW - self-assembly Y1 - 2015 U6 - https://doi.org/10.1002/anie.201409278 SN - 1433-7851 SN - 1521-3773 VL - 54 IS - 2 SP - 673 EP - 677 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Tasior, Mariusz A1 - Bald, Ilko A1 - Deperasinska, Irena A1 - Cywinski, Piotr J. A1 - Gryko, Daniel T. T1 - An internal charge transfer-dependent solvent effect in V-shaped azacyanines JF - Organic & biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry Y1 - 2015 U6 - https://doi.org/10.1039/c5ob01633a SN - 1477-0520 SN - 1477-0539 VL - 13 IS - 48 SP - 11714 EP - 11720 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Meiling, Till T. A1 - Cywinski, 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. Y1 - 2016 U6 - https://doi.org/10.1038/srep28557 SN - 2045-2322 VL - 6 PB - Nature Publ. Group CY - London 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 -