@misc{HeyneArltGessneretal.2020,
  author    = {Heyne, Benjamin and Arlt, Kristin and Geßner, Andr{\´e} and Richter, Alexander F. and D{\"o}blinger, Markus and Feldmann, Jochen and Taubert, Andreas and Wedel, Armin},
  title     = {Mixed Mercaptocarboxylic Acid Shells Provide Stable Dispersions of InPZnS/ZnSe/ZnS Multishell Quantum Dots in Aqueous Media},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1026},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-48603},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-486032},
  pages     = {26},
  year      = {2020},
  abstract  = {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\%.},
  language  = {en}
}
@article{HeyneArltGessneretal.2020,
  author    = {Heyne, Benjamin and Arlt, Kristin and Geßner, Andr{\´e} and Richter, Alexander F. and D{\"o}blinger, Markus and Feldmann, Jochen and Taubert, Andreas and Wedel, Armin},
  title     = {Mixed Mercaptocarboxylic Acid Shells Provide Stable Dispersions of InPZnS/ZnSe/ZnS Multishell Quantum Dots in Aqueous Media},
  series = {Nanomaterials},
  volume    = {10},
  journal   = {Nanomaterials},
  number    = {9},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2079-4991},
  doi       = {10.3390/nano10091858},
  pages     = {24},
  year      = {2020},
  abstract  = {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\%.},
  language  = {en}
}
@article{CywinskiHammannHuehnetal.2014,
  author    = {Cywinski, Piotr J. and Hammann, Tommy and Huehn, Dominik and Parak, Wolfgang J. and Hildebrandt, Niko and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {Europium-quantum dot nanobioconjugates as luminescent probes for time-gated biosensing},
  series = {Journal of biomedical optics},
  volume    = {19},
  journal   = {Journal of biomedical optics},
  number    = {10},
  publisher = {SPIE},
  address   = {Bellingham},
  issn      = {1083-3668},
  doi       = {10.1117/1.JBO.19.10.101506},
  pages     = {8},
  year      = {2014},
  abstract  = {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)},
  language  = {en}
}
@misc{CywińskiNonoCharbonniereetal.2014,
  author    = {Cywiński, Piotr J. and Nono, Katia Nchimi and Charbonni{\`e}re, Lo{\"i}c J. and Hammann, Tommy and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {Photophysical evaluation of a new functional terbium complex in FRET-based time-resolved homogenous fluoroassays},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-95390},
  pages     = {6060 -- 6067},
  year      = {2014},
  abstract  = {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 F{\"o}rster 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 F{\"o}rster theory, F{\"o}rster-radii (R0) were found to be around 60 {\AA} for organic dyes and around 105 {\AA} 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 {\AA} for organic dye acceptors, while for acceptor QDs between 120 {\AA} and 145 {\AA}. 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.},
  language  = {en}
}
@misc{OlejkoCywińskiBald2016,
  author    = {Olejko, Lydia and Cywiński, P. J. and Bald, Ilko},
  title     = {An ion-controlled four-color fluorescent telomeric switch on DNA origami structures},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-95831},
  pages     = {10339 -- 10347},
  year      = {2016},
  abstract  = {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 F{\"o}rster 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.},
  language  = {en}
}
@article{OlejkoCywińskiBald2016,
  author    = {Olejko, Lydia and Cywiński, Piotr J. and Bald, Ilko},
  title     = {An ion-controlled four-color fluorescent telomeric switch on DNA origami structures},
  series = {Nanoscale},
  volume    = {8},
  journal   = {Nanoscale},
  publisher = {RSC Publ.},
  address   = {Cambridge},
  issn      = {2040-3372},
  doi       = {10.1039/C6NR00119J},
  pages     = {10339 -- 10347},
  year      = {2016},
  abstract  = {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 F{\"o}rster 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.},
  language  = {en}
}