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Christian Homann, Lisa Krukewitt, Florian Frenzel, Bettina Grauel, Christian Würth, Ute Resch-Genger, Markus Haase
Upconversion core/shell nanocrystals with different mean sizes ranging from 15 to 45 nm were prepared via a modified synthesis procedure based on anhydrous rare earth acetates. All particles consist of a core of NaYF4:Yb,Er, doped with 18% Yb3+ and 2% Er3+, and an inert shell of NaYF4, with the shell thickness being equal to the radius of the core particle. Absolute measurements of the photoluminescence quantum yield at a series of different excitation power densities show that the quantum yield of 45 nm core/shell particles is already very close to the quantum yield of microcrystalline upconversion phosphor powder...
May 6, 2018: Angewandte Chemie
Oleksandr Zavoiura, Ute Resch-Genger, Oliver Seitz
Detection of pathogenic nucleic acids remains one of the most reliable approaches for the diagnosis of a broad range of diseases. Current PCR-based methods require experienced personnel and cannot be easily used for point-of-care diagnostics, making alternative strategies for the sensitive, reliable, and cost-efficient detection of pathogenic nucleic acids highly desirable. Here, we report an enzyme-free method for the fluorometric detection of RNA that relies on a target-induced fluorophore transfer onto a semiconductor quantum dot (QD), uses PNA probes as selective recognition elements and can be readout with simple and inexpensive equipment...
April 25, 2018: Bioconjugate Chemistry
Gerardo Abbandonato, Katrin Hoffmann, Ute Resch-Genger
Comparing the photoluminescence (PL) properties of ensembles of nanocrystals like semiconductor quantum dots (QDs) with single particle studies is of increasing interest for many applications of these materials as reporters in bioimaging studies performed under very dilute conditions or even at the single particle level. Particularly relevant is here the PL quantum yield (ΦF), which determines the signal size together with the reporter's molar extinction coefficient and is a direct measure for nanocrystal quality, especially for the inorganic surface passivation shell and its tightness, which can be correlated also with nanocrystal stability and the possible release of heavy metal ions...
April 4, 2018: Nanoscale
Christian Würth, Stefan Fischer, Bettina Grauel, A Paul Alivisatos, Ute Resch-Genger
We synthesized and characterized a set of ultra-small hexagonal-phase NaGdF4: 20% Yb3+ , 2% Er3+ upconversion nanopar-ticles with core diameters of 3.7 ± 0.5 nm. In order to assess passivation effects and the influence of possible core-shell intermixing to identify optimum particle structures for combined imaging in the visible and near infrared (VIS-NIR; 410-850 nm) and short-wave infrared (SWIR;1520 nm), NaYF4 shells of varying thicknesses (monolayer to 10 nm) were introduced and the influence of this parameter on the upconversion and downshifting photoluminescence of these particles was studied at different excitation power densities...
March 23, 2018: Journal of the American Chemical Society
Marijana Tadic, Martin Genger, Ana Baudisch, Sebastian Kelle, Cesare Cuspidi, Evgeny Belyavskiy, Franziska Burkhardt, Lucia Venneri, Philipp Attanasio, Burkert Pieske
BACKGROUND: We sought to investigate left ventricular (LV) function and mechanics in patients with cancer before they received chemotherapy or radiotherapy, as well as the relationship between cancer and reduced LV multidirectional strain in the whole study population. METHODS: The retrospective study involved 122 chemotherapy- and radiotherapy-naive patients with cancer and 45 age- and sex-matched controls with a cardiovascular risk profile similar to that of the patients with cancer...
March 2018: Canadian Journal of Cardiology
Norman Scholz, Thomas Behnke, Ute Resch-Genger
Micelles are of increasing importance as versatile carriers for hydrophobic substances and nanoprobes for a wide range of pharmaceutical, diagnostic, medical, and therapeutic applications. A key parameter indicating the formation and stability of micelles is the critical micelle concentration (CMC). In this respect, we determined the CMC of common anionic, cationic, and non-ionic surfactants fluorometrically using different fluorescent probes and fluorescence parameters for signal detection and compared the results with conductometric and surface tension measurements...
January 2018: Journal of Fluorescence
Cui Wang, Sven Otto, Matthias Dorn, Elisabeth Kreidt, Jakob Lebon, Laura Sršan, Patrick Di Martino-Fumo, Markus Gerhards, Ute Resch-Genger, Michael Seitz, Katja Heinze
The recently reported luminescent chromium(III) complex 13+ ([Cr(ddpd)2 ]3+ ; ddpd=N,N'-dimethyl-N,N'-dipyridine-2-yl-pyridine-2,6-diamine) shows exceptionally strong near-IR emission at 775 nm in water under ambient conditions (Φ=11 %) with a microsecond lifetime as the ligand design in 13+ effectively eliminates non-radiative decay pathways, such as photosubstitution, back-intersystem crossing, and trigonal twists. In the absence of energy acceptors, such as dioxygen, the remaining decay pathways are energy transfer to high energy solvent and ligand oscillators, namely OH and CH stretching vibrations...
January 22, 2018: Angewandte Chemie
Kai Huang, Haichun Liu, Marco Kraft, Swati Shikha, Xiang Zheng, Hans Ågren, Christian Würth, Ute Resch-Genger, Yong Zhang
Lanthanide-doped upconversion nanoparticles (UCNPs) are of great interest for biomedical applications. Currently, the applicability of UCNP bionanotechnology is hampered by the generally low luminescence intensity of UCNPs and inefficient energy transfer from UCNPs to surface-bound chromophores used e.g. for photodynamic therapy or analyte sensing. In this work, we address the low-efficiency issue by developing versatile core-shell nanostructures, where high-concentration sensitizers and activators are confined in the core and shell region of representative hexagonal NaYF4 :Yb,Er UCNPs...
December 21, 2017: Nanoscale
Aleksandra Pilch, Christian Würth, Martin Kaiser, Dominika Wawrzyńczyk, Michalina Kurnatowska, Sebastian Arabasz, Katarzyna Prorok, Marek Samoć, Wiesław Strek, Ute Resch-Genger, Artur Bednarkiewicz
At the core of luminescence color and lifetime tuning of rare earth doped upconverting nanoparticles (UCNPs), is the understanding of the impact of the particle architecture for commonly used sensitizer (S) and activator (A) ions. In this respect, a series of core@shell NaYF4 UCNPs doped with Yb(3+) and Ho(3+) ions are presented here, where the same dopant concentrations are distributed in different particle architectures following the scheme: YbHo core and YbHo@…, …@YbHo, Yb@Ho, Ho@Yb, YbHo@Yb, and Yb@YbHo core-shell NPs...
November 8, 2017: Small
Chris Guhrenz, Vladimir Sayevich, Florian Weigert, Eileen Hollinger, Annett Reichhelm, Ute Resch-Genger, Nikolai Gaponik, Alexander Eychmüller
We report on a novel and simple approach to surface ligand design of CdSe-based nanocrystals (NCs) with biocompatible, heterobifunctional polyethylene glycol (PEG) molecules. This method provides high transfer yields of the NCs into aqueous media with preservation of the narrow and symmetric emission bands of the initial organic-capped NCs regardless of their interior crystal structure and surface chemistry. The PEG-functionalized NCs show small sizes, high photoluminescence quantum yields of up to 75%, as well as impressive optical and colloidal stability...
November 16, 2017: Journal of Physical Chemistry Letters
Marijana Tadic, Sabine Haßfeld, Burket Pieske, Martin Genger
No abstract text is available yet for this article.
October 5, 2017: Chinese Medical Journal
Seiche C Genger, Keijiro Mizukami, Michael P Martin, Jeffrey R Applegate, H John Barnes, Urs Giger
Clinicopathological diagnosis of mucopolysaccharidosis type IIIB (MPS IIIB; Sanfilippo syndrome B), an inherited autosomal recessive lysosomal storage disease, as a cause of losses in a commercial emu flock and screening breeders using a mutation-specific DNA test are described. Between 2012 and 2015, ∼5-10 juvenile emus from a few weeks to several months of age developed progressive neurological signs and died while others in the flock remained healthy. Necropsy of two affected siblings revealed multiple sites of haemorrhage, cytoplasmic periodic acid-Schiff and Luxol fast blue-positive inclusions in neurons, and aggregates of foamy macrophages in visceral organs...
February 2018: Avian Pathology: Journal of the W.V.P.A
Norman Scholz, Amol Jadhav, Milind Shreykar, Thomas Behnke, Nithiya Nirmalananthan, Ute Resch-Genger, Nagaiyan Sekar
A comprehensive systematic study of absorption and fluorescence properties in solvents of varying viscosity and polarity of three novel and red-emitting coumarin-rhodamine hybrid derivatives with differences in the rigidity of their substituents is presented. This includes ethanol-polyethylene glycol, toluene-polyethylene glycol, and toluene-paraffin mixtures. Moreover, protonation-induced effects on the spectroscopic properties are studied. A viscosity-induced emission enhancement was observed for all coumarin-rhodamine hybrid derivatives...
November 2017: Journal of Fluorescence
Monirehalsadat Mousavi, Björn Thomasson, Meng Li, Marco Kraft, Christian Würth, Ute Resch-Genger, Stefan Andersson-Engels
The quantum yield is a critically important parameter in the development of lanthanide-based upconverting nanoparticles (UCNPs) for use as novel contrast agents in biological imaging and optical reporters in assays. The present work focuses on the influence of the beam profile in measuring the quantum yield (ϕ) of nonscattering dispersions of nonlinear upconverting probes, by establishing a relation between ϕ and excitation light power density from a rate equation analysis. A resulting 60% correction in the measured ϕ due to the beam profile utilized for excitation underlines the significance of the beam profile in such measurements, and its impact when comparing results from different setups and groups across the world...
August 23, 2017: Physical Chemistry Chemical Physics: PCCP
Ute Resch-Genger, Hans H Gorris
Lanthanide-doped photon-upconversion nanoparticles (UCNPs) have been the focus of many research activities in materials and life sciences in the last 15 years because of their potential to convert light between different spectral regions and their unique photophysical properties. To fully exploit the application potential of these fascinating nanomaterials, a number of challenges have to be overcome, such as the low brightness, particularly of small UCNPs, and the reliable quantification of the excitation-power-density-dependent upconversion luminescence...
October 2017: Analytical and Bioanalytical Chemistry
Hans H Gorris, Ute Resch-Genger
In Part II of this review series on lanthanide-doped photon-upconversion nanoparticles (UCNPs), we present and critically discuss the performance and suitability of UCNPs as background-free luminescent reporters in bioimaging and bioanalytical applications. The preparation of a biocompatible nanoparticle surface is an integral step for all life - science-related applications. UCNPs have found their way into a large number of diagnostic platforms, homogeneous and heterogeneous assay formats, and sensor applications...
October 2017: Analytical and Bioanalytical Chemistry
Martin Kaiser, Christian Würth, Marco Kraft, Iko Hyppänen, Tero Soukka, Ute Resch-Genger
Photophysical studies of nonlinear lanthanide-doped photon upconverting nanoparticles (UCNPs) increasingly used in biophotonics and photovoltaics require absolute measurements of the excitation power density (P)-dependent upconversion luminescence (UCL) and luminescence quantum yields (ΦUC) for quantifying the material performance, UCL deactivation pathways, and possible enhancement factors. We present here the P-dependence of the UCL spectra, ΦUC, and slope factors of the different emission bands of representative 25 nm-sized oleate-capped β-NaYF4:17% Yb(3+), 3% Er(3+) UCNPs dispersed in toluene and as powder as well as ΦUC of 3 μm-sized upconversion particles (UCμP), all measured with a newly designed integrating sphere setup, enabling controlled variation of P over four orders of magnitude...
July 20, 2017: Nanoscale
Mario Kasner, Aleksandar Aleksandrov, Felicitas Escher, Nidal Al-Saadi, Markus Makowski, Frank Spillmann, Martin Genger, Heinz-Peter Schultheiss, Uwe Kühl, Burkert Pieske, Daniel A Morris, Michel Noutsias, Carsten Tschöpe
BACKGROUND: Up to one third of patients with chronic myocarditis (MC) have preserved left ventricular (LV) ejection fraction (MCpEF). The purpose of this study was to evaluate the role of adding 2D speckle-tracking echocardiography (STE) to cardiac magnetic resonance imaging (cMRI) in the diagnosis of patients with MCpEF. METHODS AND RESULTS: We analyzed 67 patients with suspected MCpEF who underwent endomyocardial biopsy (EMB). Thirty-two patients with confirmed chronic myocardial inflammation by EMB served as study group (MCpEF) and the remaining patients (n=35) served as control group...
September 15, 2017: International Journal of Cardiology
D Geißler, C Würth, C Wolter, H Weller, U Resch-Genger
The excitation wavelength (λexc ) dependence of the photoluminescence (PL) quantum yield (ΦPL ) and decay behavior (τPL ) of a series of CdSe/CdS quantum dot/quantum rods (QDQRs), consisting of the same spherical CdSe core and rod-shaped CdS shells, with aspect ratios ranging from 2 to 20 was characterized. λexc between 400-565 nm were chosen to cover the first excitonic absorption band of the CdSe core material, the onset of absorption of the CdS shell, and the region of predominant shell absorption. A strong λexc dependence of relative and absolutely measured ΦPL and τPL was found particularly for the longer QDQRs with higher aspect ratios...
May 17, 2017: Physical Chemistry Chemical Physics: PCCP
Sven Otto, Norman Scholz, Thomas Behnke, Ute Resch-Genger, Katja Heinze
The unparalleled excited-state potential-energy landscape of the chromium(III)-based dye [1]3+ ([Cr(ddpd)2 ]3+ ; ddpd=N,N'-dimethyl-N,N'-dipyridin-2-yl-pyridin-2,6-diamine) enables a strong dual emission in the near infrared region. The temperature dependence of this dual emission allows the use of [1]3+ as an unprecedented molecular ratiometric thermometer in the 210-373 K temperature range in organic and in aqueous media. Incorporation of [1]3+ in biocompatible nanocarriers, such as 100 nm-sized polystyrene nanoparticles and solutol micelles, provides nanodimensional thermometers operating under physiological conditions...
September 7, 2017: Chemistry: a European Journal
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