TY - CONF A1 - Resch-Genger, Ute A1 - Tavernaro, Isabella A1 - Abram, Sarah-Luise A1 - Andresen, Elina A1 - Matiushkina, Anna T1 - Quantifying the number of total and accessible functional groups on nanomaterials N2 - Inorganic and organic functional nanomaterials (NM) of different size, shape, chemical composition, and surface chemistry are relevant for many key technologies of the 21st century. Decisive for most applications of NM are their specific surface properties, which are largely controlled by the chemical nature and number of ligands and functional groups (FG on the NM surface. The surface chemistry can strongly affect the physicochemical properties of NM, their charge, hydrophilicity/hydrophobicity, reactivity, stability, and processability and thereby their impact on the environment and biological species as well as their possible risk for human health. Thus, reliable, validated, and eventually standardized analytical methods for the characterization of NM surface chemistry, i.e., the chemical identification, quantification, and accessibility of FG and surface ligands 1,2] flanked by interlaboratory comparisons, control samples, and reference materials, 2 ,3 are of considerable importance for process and quality control of NM production and function. This is also important for the safe use of NM the design of novel NM, and sustainable concepts for NM fabrication. Here, we provide an overview of analytical methods for FG analysis and quantification and highlight method and material related challenges for selected NM. Analytical techniques address ed include electrochemical titration methods, optical assays, nuclear magnetic resonance (NMR) and vibrational (IR) spectroscopy, and X ray based and thermal analysis methods. Criteria for method classification and evaluation include the need for a signal generating label, provision of either the total or derivatizable number of FG, and suitability for process and production control. T2 - AUC - Analytical Ultracentrifugation CY - Nuremberg, Germany DA - 22.07.2024 KW - Nanoparticle KW - Particle KW - Microparticle KW - Silica KW - Quantum dot KW - Polymer KW - Surface group KW - Luminescence KW - Quality assurance KW - Synthesis KW - Surface modification KW - ILC KW - Optical assay KW - Functional group KW - Ligand KW - qNMR KW - Conductometry KW - Potentiometry KW - Standardization KW - Reference product KW - Reference material PY - 2024 AN - OPUS4-60749 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - DeRose, P.C. A1 - Resch-Genger, Ute T1 - Recommendations for fluorescence instrument qualification: the new ASTM standard guide N2 - Aimed at improving quality assurance and quantitation for modern fluorescence techniques, ASTM International (ASTM) is about to release a Standard Guide for Fluorescence, reviewed here. The guide's main focus is on steady state fluorometry, for which available standards and instrument characterization procedures are discussed along with their purpose, suitability, and general instructions for use. These include the most relevant instrument properties needing qualification, such as linearity and spectral responsivity of the detection system, spectral irradiance reaching the sample, wavelength accuracy, sensitivity or limit of detection for an analyte, and day-to-day performance verification. With proper consideration of method-inherent requirements and limitations, many of these procedures and standards can be adapted to other fluorescence techniques. In addition, procedures for the determination of other relevant fluorometric quantities including fluorescence quantum yields and fluorescence lifetimes are briefly introduced. The guide is a clear and concise reference geared for users of fluorescence instrumentation at all levels of experience and is intended to aid in the ongoing standardization of fluorescence measurements. KW - Fluorescence KW - Method KW - Quantum yield KW - Photoluminescence KW - Standard KW - Emission KW - Spectral correction KW - Excitation KW - Anisotropy KW - Recommendation KW - Instrument qualification PY - 2010 DO - https://doi.org/10.1021/ac902507p SN - 0003-2700 SN - 1520-6882 VL - 82 IS - 5 SP - 2129 EP - 2133 PB - American Chemical Society CY - Washington, DC AN - OPUS4-21066 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Resch-Genger, Ute A1 - Hoffmann, Katrin A1 - Pfeifer, Dietmar ED - Chris D. Geddes, T1 - Simple calibration and validation standards for fluorometry KW - Fluorescence KW - Standard KW - Spectral correction KW - Emission KW - Glass KW - Quantum yield KW - Fluorescence intensity KW - Quality assurance PY - 2009 SN - 978-0-387-88721-0 DO - https://doi.org/10.1007/978-0-387-88722-7_1 SN - 1573-8086 N1 - Serientitel: Reviews in Fluorescence – Series title: Reviews in Fluorescence VL - 4 SP - 1 EP - 31 PB - Springer Science + Business Media AN - OPUS4-19830 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Auxillos, J. A1 - Crouigneau, R. A1 - Li, Y.-F. A1 - Dai, Y. A1 - Stigliani, A. A1 - Tavernaro, Isabella A1 - Resch-Genger, Ute A1 - Sandelin, A. A1 - Marie, R. A1 - Pedersen, S. F. T1 - Spatially resolved analysis of microenvironmental gradient impact on cancer cell phenotypes N2 - Despite the physiological and pathophysiological significance of microenvironmental gradients, e.g., for diseases such as cancer, tools for generating such gradients and analyzing their impact are lacking. Here, we present an integrated microfluidic-based workflow that mimics extracellular pH gradients characteristic of solid tumors while enabling high-resolution live imaging of, e.g., cell motility and chemotaxis, and preserving the capacity to capture the spatial transcriptome. Our microfluidic device generates a pH gradient that can be rapidly controlled to mimic spatiotemporal microenvironmental changes over cancer cells embedded in a 3D matrix. The device can be reopened allowing immunofluorescence analysis of selected phenotypes, as well as the transfer of cells and matrix to a Visium slide for spatially resolved analysis of transcriptional changes across the pH gradient. This workflow is easily adaptable to other gradients and multiple cell types and can therefore prove invaluable for integrated analysis of roles of microenvironmental gradients in biology. KW - Bioimaging KW - Fluorescence KW - Cell KW - Cancer KW - Method KW - Microfluids KW - Model KW - Calibration KW - Sensor KW - Ph KW - Probe KW - Workflow PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-604631 DO - https://doi.org/10.1126/sciadv.adn3448 VL - 19 IS - 18 SP - 1 EP - 17 AN - OPUS4-60463 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Würth, Christian A1 - González, M.G. A1 - Niessner, R. A1 - Panne, Ulrich A1 - Haisch, C. A1 - Resch-Genger, Ute T1 - Determination of the absolute fluorescence quantum yield of rhodamine 6G with optical and photoacoustic methods - providing the basis for fluorescence quantum yield standards N2 - To establish the methodical basis for the development and certification of fluorescence quantum yield standards, we determined the fluorescence quantum yield Φf of rhodamine 6G (R6G) with two absolute methods with complementary measurement principles, here optical spectroscopy using an integrating sphere setup and pulsed laser photoacoustic spectroscopy (PAS). For the assessment of aggregation- and reabsorption-induced distortions of measured fluorescence quantum yields and procedures for the reliable consideration of such effects, this systematic comparison was performed in ethanol and in water employing different concentrations of R6G. In addition, the relative and absolute fluorescence quantum yields of these solutions were obtained with a calibrated spectrofluorometer and a commercialized integrating sphere setup. Based upon this systematic comparison, experimental advantages and systematic sources of variation were identified for both methods. KW - Fluorescence KW - Photoluminescence KW - Quantum yield KW - Photoacoustic spectroscopy KW - Absolute quantum yield KW - Integrating sphere KW - Rhodamine 6G KW - Aggregation KW - Reabsorption PY - 2012 DO - https://doi.org/10.1016/j.talanta.2011.12.051 SN - 0039-9140 VL - 90 SP - 30 EP - 37 PB - Elsevier CY - Amsterdam AN - OPUS4-25710 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hoffmann, Katrin A1 - Spieles, Monika A1 - Bremser, Wolfram A1 - Resch-Genger, Ute T1 - Narrow-band emitting solid fluorescence reference standard with certified intensity pattern N2 - The development of a lanthanum-phosphate glass doped with several rare-earth-ions for use as solid fluorescence standard is described. The cuvette-shaped reference material which shows a characteristic emission intensity pattern upon excitation at 365 nm consisting of a multitude of relatively narrow emission bands in the wavelength region between 450 nm and 700 nm is intended for the day-to-day performance validation of fluorescence measuring devices. Evaluation of the fluorescent glass include the determination of all properties which can affect its relative emission intensity profile or contribute to the uncertainty of the certified values like absorption spectra, fluorescence anisotropy, excitation wavelength and temperature dependence of the spectroscopic features, homogeneity of fluorophore distribution, photo- and long-term stability. Moreover, a certification procedure was developed including the normalization of the intensity profile consisting of several narrow emission bands and the calculation of wavelength-dependent uncertainties. Criteria for the design, characterization, and working principle of the new reference material BAM-F012 are presented, and possible applications of this ready-to-use fluorescence standard are discussed. PY - 2015 DO - https://doi.org/10.1021/acs.analchem.5b02209 SN - 0003-2700 SN - 1520-6882 VL - 87 SP - 7204 EP - 7210 PB - American Chemical Society CY - Washington, DC AN - OPUS4-33615 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Oskoei, P. A1 - Nogueira, J. A1 - Keller, Lisa-Marie A1 - Andresen, Elina A1 - Maturi, F. E. A1 - Rühle, Bastian A1 - Resch-Genger, Ute A1 - Daniel-da-Silva, A. L. A1 - Carlos, L. D. A1 - Oliviera, H. T1 - Effects of doxorubicin-loaded UCNP@MSN core-shell particles with a thermoresponsive nanovalve in melanoma cells N2 - Melanoma, one of the most aggressive forms of skin cancer, has an increasingly higher incidence. When detected in advanced stages, tumour eradication is often incomplete, contributing to poor prognosis with conventional treatments. Upconversion nanoparticles (UCNPs) haveunique optical properties that allow their effective use in several biomedical applications. This includes the excitability under near-infrared (NIR) excitation light, which has a relatively high penetration depth in tissue, a multitude of characteristic emission bands in the ultraviolet (UV), visible (Vis), NIR, and short-wave infrared (SWIR), along with long luminescence lifetimes, and high photostability. Mesoporous silica nanoparticles (MSN) with nanovalves or derived coatings have widely been used for triggered and targeted drug delivery in the past. Anticancer drugs can be loaded into the pores of MSN, enabling spatiotemporally controlled drug release. KW - Nano KW - Particle KW - Silica KW - Upconversation KW - Lanthanide KW - Triggered release KW - Temperature KW - Cell studies KW - Drug KW - Toxicity studies PY - 2024 DO - https://doi.org/10.1016/j.toxlet.2024.07.237 SN - 0378-4274 VL - 399 IS - Supplement 2 SP - S89 EP - S90 PB - Elsevier B.V. AN - OPUS4-62571 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kollmannsberger, M. A1 - Rurack, Knut A1 - Resch-Genger, Ute A1 - Daub, J. T1 - Ultrafast charge transfer in amino-substituted boron dipyrromethene dyes and Its inhibition by cation complexation - a new design concept for highly sensitive fluorescent probes N2 - The photophysical behavior of a newly synthesized aza crown-substituted boron-dipyrromethene (BDP) dye and its dimethylamino analogue were investigated with steady-state and time-resolved fluorometry and compared to a reference compound. In solvents more polar than hexane, excitation of the dyes leads to a fast charge transfer from the locally excited (LE) state to a weakly emissive charge-transfer (CT) state. The donor-substituted compounds show dual emission from the LE and CT state, both fluorescence quantum yields being low. The rate constant of excited-state charge separation, calculated from the global analysis of time-resolved emission data, was determined to 1.6 × 1011 s-1 in 1,4-dioxane. The crowned compound forms 1:1-complexes with various alkali and alkaline-earth metal ions, which exist as two conformers in solution. In these complexes, coordination of the cation to the nitrogen donor atom of the crown inhibits the charge-transfer process, leading to a cation-dependent enhancement of the LE emission and the fluorescence lifetimes by factors >103. This efficient "switching on" of the fluorescence renders the crowned BDP dye an extremely sensitive fluorescent probe for metal ions. PY - 1998 DO - https://doi.org/10.1021/jp982701c SN - 1089-5639 SN - 1520-5215 VL - 102 IS - 50 SP - 10211 EP - 10220 PB - Soc. CY - Washington, DC AN - OPUS4-2095 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute A1 - Rurack, Knut A1 - Bricks, J. A1 - Koval'chuk, A. A1 - Slominskii, J. T1 - Synthesis and Photophysical Properties of Cation-sensitive styryl bases derived from substituted Benzothiazole T2 - 1st All-Russian Conference on Heterocyclic Chemistry CY - Suzdal, Russia DA - 2000-09-19 PY - 2000 SP - 1 AN - OPUS4-858 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heckmann, A. A1 - Dümmler, S. A1 - Pauli, Jutta A1 - Margraf, M. A1 - Köhler, J. A1 - Stich, D. A1 - Lambert, C. A1 - Fischer, I. A1 - Resch-Genger, Ute T1 - Highly fluorescent open-shell NIR dyes: the time-dependence of back electron transfer in triarylamine-perchlorotriphenylmethyl radicals KW - Triarylamine-perchlorotriphenylmethyl radical KW - Dono-acceptor compounds KW - CT state KW - Fluorescence quantum KW - Yield KW - Life time PY - 2009 DO - https://doi.org/10.1021/jp908425w SN - 1932-7447 SN - 1089-5639 VL - 113 SP - 20958 EP - 20966 PB - Soc. CY - Washington, DC AN - OPUS4-20757 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Amouroux, B. A1 - Eftekhari, A. A1 - Roux, C. A1 - Micheau, J. A1 - Roblin, P. A1 - Pasturel, M. A1 - Gauffre, F. A1 - Würth, Christian A1 - Resch-Genger, Ute A1 - Sliwa, M. A1 - Bouchet, A. A1 - Coudret, C. T1 - Synthesis and Emission Dynamics of Sub-3 nm Upconversion Nanoparticles N2 - Reducing the size of upconversion nanoparticles (UCNPs) down to a few nm yields luminescent materials containing a very small number of emitters. Considering the bottom limit of one activator per particle ultrasmall UCNPs offer an unprecedented platform to study the contributions of the energy transfers at play in upconversion luminescence. Maintaining detectable emission despite the limited number of emitting ions and the high surface-to-volume ratio requires suitable particle architectures. Na(Gd-Yb)F4:Tm3+ emissive sub-3 nm diameter 𝜷-phase UCNPs are prepared using a gadolinium-rich composition in situ mixing of the precursors and a microwave high-temperature cycling sequence allowing precise control of the particle size and dispersity. These cores are coated with a NaGdF4 inert shell to minimize the deleterious influence of surface quenching (SQ). Time-resolved luminescence measurements combining standard NIR excitation of the Yb3+ sensitizer and direct UV excitation of the Tm3+ activator are performed to quantify cross relaxation and surface quenching processes. The fine tuning of the number of activators per particle via an optimized synthesis pathway along with the use of an appropriate excitation scheme enabled to provide an accurate analysis of the different mechanisms at play in these model nanoparticles and to characterize the structure of the core-shell architecture. KW - Lanthanide KW - Nanoparticle KW - Luminescence KW - Quantitative spectroscopy KW - Quantum yield KW - Energy transfer KW - Quality assurance KW - Synthesis KW - Surface modification KW - Photophysics PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-606877 DO - https://doi.org/10.1002/adom.202303283 SN - 2195-1071 SP - 1 EP - 13 AN - OPUS4-60687 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nirmalananthan-Budau, Nithiya A1 - Budau, J. H. A1 - Moldenhauer, Daniel A1 - Hermann, G. A1 - Kraus, Werner A1 - Hoffmann, Katrin A1 - Paulus, Beate A1 - Resch-Genger, Ute T1 - Substitution pattern controlled aggregation-induced emission in donor-acceptor-donor dyes with one and two propeller-like triphenylamine donors N2 - We present a comparative study of the spectroscopic properties of the donor–acceptor–donor substituted dyes triphenylamine-allylidenemalononitrile-julolidine (TMJ) and triphenylamine-allylidenemalononitriletriphenylamine (TMT), bearing one and two propeller-like triphenylamine donor moieties, in solvents of varying polarity and viscosity and in the aggregated and solid state. Our results reveal control of the aggregation-induced spectroscopic changes and the packing motifs of the dye molecules in the solid state by the chemical nature and structure of the second nitrogen-containing donor, i.e., a planar and a rigid julolidine or a twisted triphenyl group. Assuming that the TMT and TMJ aggregates show a comparable arrangement of the molecules to the respective crystals, these different molecular interactions in the solid state are responsible for aggregation induced emission (AIE) in the case of TMT and its absence for TMJ. Moreover, a versatile strategy for the fluorescence enhancement of only weakly emissive AIE dyes is shown, turning these dyes into bright nanoscale fluorescent reporters by using them as stains for preformed polymer particles. KW - Nano KW - Nanoparticle KW - Photoluminescence KW - Fluorescence KW - Quantum yield KW - Photophysics KW - Lifetime KW - Sensor KW - Dye KW - Enhancement KW - Particle KW - Polarity KW - AIE KW - Aggregation KW - Aggregation-induced emission KW - Solid state emission PY - 2020 DO - https://doi.org/10.1039/d0cp00413h VL - 22 IS - 25 SP - 14142 EP - 14154 AN - OPUS4-50967 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stroyuk, O. A1 - Raievska, O. A1 - Barabash, A. A1 - Batentschuk, M. A1 - Osvet, A. A1 - Fiedler, Saskia A1 - Resch-Genger, Ute A1 - Hauch, J. A1 - Brabec, C. J. T1 - "Green" synthesis of highly luminescent lead-free Cs2AgxNa1-xBiyIn1-yCl6 perovskites N2 - A new “green” and mild synthesis of highly stable microcrystalline Cs2AgxNa1-xBiyIn1-yCl6 (CANBIC) perovskites under ambient conditions was developed that is scalable to the multi-gram production. Under UV illumination, the CANBIC perovskites emit intense broadband photoluminescence (PL) with a quantum yield (QY) of 92% observed for x = 0.35 and y = 0.01-0.02. The combination of strong UV absorbance and broadband visible emission, high PL QY, and long PL lifetimes of up to 1.4 μs, along with an outstanding stability makes these CANBICs a promising material class for many optical applications. KW - Fluorescence KW - Perovskites KW - Solar cell KW - Automated synthesis KW - Green synthesis KW - Quantum yield KW - Integrating sphere spectroscopy KW - Absolute fluorescence KW - Quality assurance KW - Nano KW - Particle KW - Application KW - Semiconductor KW - Quantum dot KW - Renewable energy PY - 2022 DO - https://doi.org/10.1039/d2tc02055f SN - 2050-7526 VL - 10 IS - 27 SP - 9938 EP - 9944 PB - Royal Society of Chemistry AN - OPUS4-55453 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Resch-Genger, Ute A1 - Grabolle, Markus A1 - Nitschke, R. A1 - Nann, T. ED - Demchenko, A.P. T1 - Nanocrystals and nanoparticles versus molecular fluorescent labels as reporters for bioanalysis and the life sciences: a critical comparison N2 - At the core of photoluminescence techniques are suitable fluorescent labels and reporters, the spectroscopic properties of which control the limit of detection, the dynamic range, and the potential for multiplexing. Many applications including recent developments in intracellular labeling rely on well established molecular chromophores such as small organic dyes or fluorescent proteins. However, one of the most exciting – but also controversial – advances in reporter technology, the emerging development and application of luminescent nanoparticles with unique optical properties, yet complicated surface chemistry paves new roads for fluorescence imaging and sensing as well as for in vitro and in vivo labeling. Here, we compare and evaluate the differences in physico-chemical properties of common fluorophores, focusing on traditional organic dyes and luminescent nanocrystals with size-dependent features. The ultimate goal is to provide a better understanding of the advantages and limitations of both classes of chromophores, facilitate fluorophore choice for users of fluorescence techniques, and address future challenges in the rational design and manipulation of nanoparticulate labels and probes. KW - Amplification KW - Fluorescent reporter KW - Fluorophore KW - FRET KW - In vitro KW - In vivo KW - Labeling KW - Lanthanide chelate KW - Multiplexing KW - Nanoparticle KW - Quantum dot KW - Transition metal complex PY - 2010 SN - 978-3-642-04699-5 DO - https://doi.org/10.1007/978-3-642-04701-5_1 N1 - Serientitel: Springer Series on Fluorescence – Series title: Springer Series on Fluorescence VL - 9 IS - 1 SP - 3 EP - 40 PB - Springer AN - OPUS4-22186 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Li, Yanqin A1 - Bricks, J.L. A1 - Resch-Genger, Ute A1 - Spieles, Monika A1 - Rettig, W. T1 - CT-Operated Bifunctional Fluorescent Probe Based on a Pretwisted Donor-Donor-Biphenyl N2 - Taking into account the structural requirements for TICT-type sensor molecules, a general synthetic route to derive pH and cation-responsive pretwisted donor (D)–donor (D) biphenyls (b) equipped with donor receptors is developed and a first model compound containing a mono aza-15-crown-5 and a DMA receptor is synthesized, see Scheme 1. The spectroscopic properties of this new bifunctional D–D biphenyl are studied in the non-polar and polar solvents cyclohexane, acetonitrile, and methanol. Protonation as well as complexation studies are performed with the representative metal ions Na(I), K(I), Ca(II), Ag(I), Zn(II), Cd(II), Hg(II), and Pb(II) to reveal the potential of this molecule for communication of whether none, only one, or both binding sites are engaged in analyte coordination by spectroscopically distinguishable outputs. The results are compared to those obtained with closely related donor (D)–acceptor (A) substituted biphenyl-type sensor molecules and are discussed within the framework of neutral and ionic D – A biphenyls. KW - Fluorescent probe KW - Biphenyl KW - TICT KW - Photophysics KW - Bifunctional PY - 2006 SN - 1053-0509 SN - 1573-4994 VL - 16 IS - 3 SP - 337 EP - 348 PB - Plenum Publ. Corp. CY - New York, NY AN - OPUS4-14198 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Geißler, Daniel A1 - Nirmalananthan-Budau, Nithiya A1 - Scholtz, Lena A1 - Tavernaro, Isabella A1 - Resch-Genger, Ute T1 - Analyzing the surface of functional nanomaterials — how to quantify the total and derivatizable number of functional groups and ligands N2 - Functional nanomaterials (NM) of different size, shape, chemical composition, and surface chemistry are of increasing relevance for many key technologies of the twenty-first century. This includes polymer and silica or silica-coated nanoparticles (NP) with covalently bound surface groups, semiconductor quantum dots (QD), metal and metal oxide NP, and lanthanide-based NP with coordinatively or electrostatically bound ligands, as well as surface-coated nanostructures like micellar encapsulated NP. The surface chemistry can significantly affect the physicochemical properties of NM, their charge, their processability and performance, as well as their impact on human health and the environment. Thus, analytical methods for the characterization of NM surface chemistry regarding chemical identification, quantification, and accessibility of functional groups (FG) and surface ligands bearing such FG are of increasing importance for quality control of NM synthesis up to nanosafety. Here, we provide an overview of analytical methods for FG analysis and quantification with special emphasis on bioanalytically relevant FG broadly utilized for the covalent attachment of biomolecules like proteins, peptides, and oligonucleotides and address methodand material-related challenges and limitations. Analytical techniques reviewed include electrochemical titration methods, optical assays, nuclear magnetic resonance and vibrational spectroscopy, as well as X-ray based and thermal analysis methods, covering the last 5–10 years. Criteria for method classification and evaluation include the need for a signal-generating label, provision of either the total or derivatizable number of FG, need for expensive instrumentation, and suitability for process and production control during NM synthesis and functionalization. KW - Functional group quantification KW - Surface ligand KW - Nanomaterial KW - Optical detection KW - Electrochemical titration KW - Nanosafety (Safe-by-design) PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-533597 DO - https://doi.org/10.1007/s00604-021-04960-5 VL - 188 IS - 10 SP - 1 EP - 28 PB - Springer Nature AN - OPUS4-53359 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wang, Cui A1 - Kitzmann, W.R. A1 - Weigert, Florian A1 - Förster, Ch. A1 - Wang, X. A1 - Heintze, K. A1 - Resch-Genger, Ute T1 - Matrix Effects on Photoluminescence and Oxygen Sensitivity of a Molecular Ruby N2 - The molecular ruby analogue [Cr(ddpd)2]3+ (ddpd=N,N’-dimethyl-N,N’-dipyridine-2-ylpyridine-2,6-diamine) exhibits near infrared (NIR) emission with a high photoluminescence (PL) quantum yield ΦPL of 11 % and a lifetime of 898 μs in deaerated water at room temperature. While ligand-based control of the photophysical properties has received much attention, influences of the counter anions and microenvironment are still underexplored. In this study, the luminescence properties of the molecular ruby were systematically examined for the counter anions Cl−, Br−, [BF4]−, [PF6]−, [BPh4]−, and [BArF24]− in acetonitrile (MeCN) solution, in crystals, and embedded into polystyrene nanoparticles (PSNP). Stern-Volmer analyses of the oxygen quenching studies in the intensity and lifetime domain showed the highest oxygen sensitivity of the complexes with the counter anions of [BF4]− and [BArF24]−, which also revealed the longest luminescence lifetimes. Embedding [Cr(ddpd)2][PF6]3 in PSNPs and shielding with poly(vinyl alcohol) yields a strongly NIR-emissive oxygen-insensitive material with a record ΦPL of 15.2 % under ambient conditions. KW - Fluorescence KW - Sensor KW - Oxygen KW - Quantum yield KW - Quality assurance KW - Complex KW - Cr(III) KW - Lifetime KW - Ligand KW - Solid state KW - X-Ray analysis KW - Structure-property relationship KW - Nano KW - Polymer KW - Particle PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-546057 DO - https://doi.org/10.1002/cptc.202100296 SN - 2367-0932 VL - 6 IS - 6 SP - 1 EP - 9 PB - Wiley-VCH CY - Weinheim AN - OPUS4-54605 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sun, C. A1 - Schäferling, Michael A1 - Resch-Genger, Ute A1 - Gradzielski, M. T1 - Solvothermal Synthesis of Lanthanide-doped NaYF4 Upconversion N2 - Lanthanide-doped NaYF4 upconversion nano- and microcrystals were synthesized via a facile solvothermal approach. Thereby, the influence of volume ratios of ethylene glycol (EG)/H2O, molar ratios of NH4F/RE3+ (RE3+ represents the total amount of Y3+ and rare-earth dopant ions), Gd3+ ion contents, types of activator dopant ions, and different organic co-solvents on the crystal phase, size, and morphology of the resulting particles were studied systematically. A possible formation mechanism for the growth of crystals of different morphology is discussed. Our results show that the transition from the α- to the β-phase mainly depends on the volume ratio of EG/H2O and the molar ratio of NH4F/RE3+, while the morphology and size could be controlled by the type of organic co-solvent and Gd3+ dopant ions. Furthermore, the reaction time has to be long enough to convert α-NaYF4 into β-NaYF4 during the growth process to optimize the upconversion luminescence. The formation of larger β-NaYF4 crystals, which possess a higher upconversion luminescence than smaller particles, proceeds via intermediates of smaller crystals of cubic structure. In summary, our synthetic approach presents a facile route to tailor the size, Crystal phase, morphology, and luminescence features of upconversion materials. KW - Nano KW - Nanomaterial KW - Upconversion nanoparticle KW - Photoluminescence KW - Lanthanide KW - Quantum yield KW - Photophysics KW - Lifetime KW - Surface chemistry KW - Single particle KW - Brightness KW - NIR KW - Synthesis PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-520307 DO - https://doi.org/10.1002/cnma.202000564 VL - 7 IS - 2 SP - 174 EP - 183 PB - Wiley AN - OPUS4-52030 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bastos, V. A1 - Oskoei, P. A1 - Andresen, Elina A1 - Saleh, Maysoon I. A1 - Rühle, Bastian A1 - Resch-Genger, Ute A1 - Oliveira, H. T1 - Stability, dissolution, and cytotoxicity of NaYF4‑upconversion nanoparticles with different coatings N2 - Upconversion nanoparticles (UCNPs) have attracted considerable attention owing to their unique photophysical properties. Their utilization in biomedical applications depends on the understanding of their transformations under physiological conditions and their potential toxicity. In this study, NaYF4: Yb,Er UCNPs, widely used for luminescence and photophysical studies, were modified with a set of four different coordinatively bound surface ligands, i.e., citrate, alendronate (AA), ethylendiamine tetra(methylene phosphonate) (EDTMP), and poly(maleic anhydride-alt-1-octadecene) (PMAO), as well as silica coatings with two different thicknesses. Subsequently, the aging-induced release of fluoride ions in water and cell culture media and their cytotoxic profile to human keratinocytes were assessed in parallel to the cytotoxic evaluation of the ligands, sodium fluoride and the lanthanide ions. The cytotoxicity studies of UCNPs with different surface modifications demonstrated the good biocompatibility of EDTMP-UCNPs and PMAO-UCNPs, which is in line with the low amount of fluoride ions released from these samples. An efficient prevention of UCNP dissolution and release of cytotoxic ions, as well as low cytotoxicity was also observed for UCNPs with a sufficiently thick silica shell. Overall, our results provide new insights into the understanding of the contribution of surface chemistry to the stability, dissolution behavior, and cytotoxicity of UCNPs. Altogether, the results obtained are highly important for future applications of UCNPs in the life sciences and bioimaging studies. KW - Nano KW - Nanomaterial KW - Upconversion nanoparticle KW - Lanthanide KW - Photoluminescence KW - Quantum yield KW - Photophysics KW - Excitation power density KW - Surface chemistry KW - Coating PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-544681 DO - https://doi.org/10.1038/s41598-022-07630-5 SN - 2045-2322 VL - 12 SP - 1 EP - 13 PB - Springer Nature CY - London AN - OPUS4-54468 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Witte, F. A1 - Rietsch, P. A1 - Nirmalananthan-Budau, Nithiya A1 - Weigert, Florian A1 - Götze, J. P. A1 - Resch-Genger, Ute A1 - Eigler, S. A1 - Paulus, B. T1 - Aggregation-induced emission leading to two distinct emissive species in the solid-state structure of high-dipole organic chromophores N2 - The concept of aggregation-induced emission represents a means to rationalise photoluminescence of usually nonfluorescent excimers in solid-state materials. In this publication, we study the photophysical properties of selected diaminodicyanoquinone (DADQ) derivatives in the solid state using a combined approach of experiment and theory. DADQs are a class of high-dipole organic chromophores promising for applications in non-linear optics and light-harvesting devices. Among the compounds investigated, we find both aggregation-induced emission and aggregation-caused quenching effects rationalised by calculated energy transfer rates. Analysis of fluorescence spectra and lifetime measurements provide the interesting result that (at least) two emissive species seem to contribute to the photophysical properties of DADQs. The main emission peak is notably broadened in the long-wavelength limit and exhibits a blue-shifted shoulder. We employ high-level quantum-chemical methods to validate a molecular approach to a solid-state problem and show that the complex emission features of DADQs can be attributed to a combination of H-type aggregates, monomers, and crystal structure defects. KW - Fluorescence KW - Optical probe KW - Dye KW - Photophysics KW - Theory KW - Quantum yield KW - Mechanism KW - Quantum chemistry KW - Modelling KW - Aggregation KW - Lifetime KW - Single particle KW - Microscopy KW - Solid KW - Crystal PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-531138 DO - https://doi.org/10.1039/d1cp02534a SP - 1 EP - 9 PB - Royal Society of Chemistry AN - OPUS4-53113 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Andresen, Elina A1 - Radunz, Sebastian A1 - Resch-Genger, Ute T1 - Novel PET-Operated Rosamine Sensor Dyes with Substitution Pattern-Tunable pKa Values and Temperature Sensitivity N2 - We present the synthesis and characterization of a family of regioisomerically pure pH-sensitive rosamine fluorophores consisting of xanthene fluorophore cores, which determine the dyes’ photophysical properties such as excitation/emission wavelength, fluorescence quantum yield, and fluorescence lifetime, and differently substituted phenol moieties. The hydroxyl substituent of the phenol moiety introduces a pH sensitivity of the dyes’ fluorescence exploiting a photoinduced electron transfer (PET), that leads to a protonation-induced switching ON of the rosamine emission. Rational tuning of the pKa value of the rosamine fluorescence between 4 to 9 is achieved by altering the substitution pattern and degree of bromination of the phenolic subunits. Additionally, a temperature sensitivity of the fluorescence quantum yield is introduced or suppressed based upon the degree of rigidity of the xanthene scaffold. KW - Fluorescence KW - Optical probe KW - Sensor KW - Dye KW - Rosamine KW - Synthesis KW - Photophysics KW - PH KW - Quantum yield KW - Quality assurancemechanism KW - temperature PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-530562 DO - https://doi.org/10.1039/d1nj02505h VL - 45 IS - 31 SP - 13934 EP - 13940 PB - Royal Society of Chemistry AN - OPUS4-53056 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Le Guevel, X. A1 - Wegner, Karl David A1 - Würth, Christian A1 - Baulin, V. A. A1 - Musnier, B. A1 - Josserand, V. A1 - Resch-Genger, Ute A1 - Koll, J-C T1 - Tailoring the SWIR emission of gold nanoclusters by surface ligand rigidification and their application in 3D bioimaging N2 - The influence of solvent polarity and surface ligand rigidification on the SWIR emission profile of gold nanoclusters with an anistropic surface was investigated. A strong enhancement of the SWIR emission band at 1200 nm was observed when measuring in different local environments: in solution, in polymer composites, and in solids. SWIR in vivo imaging of mice assisted by deep learning after intravenous administration of these gold nanoclusters provides high definition pseudo-3D views of vascular blood vessels. KW - Nano KW - Nanomaterial KW - Metal cluster KW - Photoluminescence KW - Quantum yield KW - Photophysics KW - Lifetime KW - Sensor KW - NIR KW - SWIR KW - Ligand KW - Gold KW - Mechanism KW - Charge transfer KW - Enhancement strategy KW - Imaging KW - Application KW - Contrast agent PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543582 DO - https://doi.org/10.1039/D1CC06737K VL - 58 IS - 18 SP - 2967 EP - 2970 PB - RSC AN - OPUS4-54358 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Würth, Christian A1 - Kaiser, Martin A1 - Wilhelm, Stefan A1 - Grauel, Bettina A1 - Hirsch, Th. A1 - Resch-Genger, Ute T1 - Excitation power dependent population pathways and absolute quantum yields of upconversion nanoparticles in different solvents N2 - The rational design of brighter upconversion nanoparticles (UCNPs) requires a better understanding of the radiationless deactivation pathways in these materials. Here, we demonstrate the potential of excitation power density (P)-dependent studies of upconversion (UC) luminescence intensities, slope factors, and absolute quantum yields (ΦUC) of popular β-NaYF4:20% Yb3+,2% Er3+ UCNPs of different surface chemistries in organic solvents, D2O, and water as a tool to gain deeper insight into the UC mechanism including population and deactivation pathways particularly of the red emission. Our measurements, covering a P regime of three orders of magnitude, reveal a strong difference of the P-dependence of the ratio of the green and red luminescence bands (Ig/r) in water and organic solvents and P-dependent population pathways of the different emissive energy levels of Er3+. In summary, we provide experimental evidence for three photon processes in UCNPs, particularly for the red emission. Moreover, we demonstrate changes in the excited population dynamics via bi- and triphotonic processes dependent on the environment, surface chemistry, and P, and validate our findings theoretically KW - Upconverion KW - Quantum Yield KW - Photo physics PY - 2017 UR - http://pubs.rsc.org/en/content/articlepdf/2017/nr/c7nr00092h DO - https://doi.org/10.1039/c7nr00092h SN - 2040-3364 SN - 2040-3372 VL - 9 IS - 12 SP - 4283 EP - 4294 PB - The Royal Society of Chemistry AN - OPUS4-39849 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pauli, Jutta A1 - Wycisk, V. A1 - Welker, P. A1 - Justies, A. A1 - Resch-Genger, Ute A1 - Haag, R. A1 - Licha, K. T1 - Glycerol-Based Contrast Agents: A Novel Series of Dendronized Pentamethine Dyes N2 - The synthesis of water-soluble dyes, which absorb and emit in the range between 650 and 950 nm and display high extinction coefficients (ε) as well as high fluorescence quantum yields (Φf), is still a demand for optical imaging. We now present a synthetic route for the preparation of a new group of glycerol-substituted cyanine dyes from dendronized indole precursors that have been functionalized as Nhydroxysuccinimide (NHS) esters. High Φf values of up to 0.15 and extinction coefficients of up to 189 000 L mol−1 cm−1 were obtained for the pure dyes. Furthermore, conjugates of the new dendronized dyes with the antibody cetuximab (ctx) that were directed against the epidermal growth factor receptor (EGFR) of tumor cells could be prepared with dye to protein ratios between 0.3 and 2.2 to assess their potential as imaging probes. For the first time, ctx conjugates could be achieved without showing a decrease in Φf and with an increasing labeling degree that exceeded the value of the pure dye even at a labeling degree above 2. The incorporation of hydrophilically and sterically demanding dendrimers into cyanines prevented dimer formation after covalent conjugation to the antibody. The binding functionality of the resulting ctx conjugates to the EGFR was successfully demonstrated by cell microscopy studies using EGFR expressing cell lines. In summary, the combination of hydrophilic glycerol dendrons with reactive dye labels has been established for the first time and is a promising Approach toward more powerful fluorescent labels with less dimerization. KW - Dye KW - Quantum yield KW - Fluorescence KW - Contrast agent KW - Extinction coefficient PY - 2015 DO - https://doi.org/10.1021/acs.bioconjchem.5b00097 SN - 1043-1802 VL - 26 SP - 773 EP - 781 PB - ACS Publications CY - Washington AN - OPUS4-38880 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Saleh, Maysoon I. A1 - Kembuan, C A1 - Rühle, Bastian A1 - Graf, C A1 - Resch-Genger, Ute T1 - Gold-shell coated NaYF4:Er3+, Yb3+ nanoparticles for the enhancement of fluorescence emission N2 - In the present work, we aim to explore how far the UCNP emission intensity can be enhanced by the aid of plasmonic interactions using a gold shell. The distance between the UCNP core and the gold shell is varied by adding a silica spacer of different thicknesses. The synthetic conditions for obtaining UCNP@SiO2@Au core-shell nanoparticles with precisely tuneable silica shell thicknesses were investigated. A gold shell on the UCNP@SiO2 nanoparticles is expected to give rise to a noticeable enhancement of particle brightness and fluorescence, given that the thicknesses of the silica shell and the gold coating can be controlled and fine-tuned. First single particle studies revealing shortening of the Er3+ lifetimes suggest that plasmonic enhancement occurs. T2 - 2nd Conference and Spring School on Properties, Design and Applications of Upconversion Nanomaterials CY - Valencia, Spain DA - 02.04.2018 KW - Upconversion nanoparticles KW - Silica coating KW - Plasmonic enhancement PY - 2018 AN - OPUS4-44969 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mathejczyk, J. A1 - Pauli, Jutta A1 - Dullin, C. A1 - Napp, J. A1 - Tietze, L.-F. A1 - Kessler, H. A1 - Resch-Genger, Ute A1 - Alves, F. T1 - Spectroscopically well-characterized RGD optical probe as a prerequisite for lifetime-gated tumor imaging N2 - Labeling of RGD peptides with near-infrared fluorophores yields optical probes for noninvasive imaging of tumors overexpressing ανβ3 integrins. An important prerequisite for optimum detection sensitivity in vivo is strongly absorbing and highly emissive probes with a known fluorescence lifetime. The RGD-Cy5.5 optical probe was derived by coupling Cy5.5 to a cyclic arginine–glycine–aspartic acid–D-phenylalanine–lysine (RGDfK) peptide via an aminohexanoic acid spacer. Spectroscopic properties of the probe were studied in different matrices in comparison to Cy5.5. For in vivo imaging, human glioblastoma cells were subcutaneously implanted into nude mice, and in vivo fluorescence intensity and lifetime were measured. The fluorescence quantum yield and lifetime of Cy5.5 were found to be barely affected on RGD conjugation but dramatically changed in the presence of proteins. By time domain fluorescence imaging, we demonstrated specific binding of RGD-Cy5.5 to glioblastoma xenografts in nude mice. Discrimination of unspecific fluorescence by lifetime-gated analysis further enhanced the detection sensitivity of RGD-Cy5.5-derived signals. We characterized RGD-Cy5.5 as a strongly emissive and stable probe adequate for selective targeting of ανβ3 integrins. The specificity and thus the overall detection sensitivity in vivo were optimized with lifetime gating, based on the previous determination of the probés fluorescence lifetime under application-relevant conditions. KW - Time domain near-infrared fluorescence (NIRF) imaging KW - Fluorescence KW - Lifetime KW - Quantum yield KW - RGD-Cy5.5 KW - Spectroscopic analysis PY - 2011 DO - https://doi.org/10.2310/7290.2011.00018 SN - 1535-3508 SN - 1536-0121 VL - 10 IS - 6 SP - 469 EP - 480 PB - Decker CY - Hamilton, Ont. AN - OPUS4-25711 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pauli, Jutta A1 - Ramírez, A. A1 - Crasselt, C. A1 - Schmidt, W. A1 - Resch-Genger, Ute T1 - Utilizing optical spectroscopy and 2',7'-difluorofluorescein to characterize the early stages of cement hydration N2 - The increasingly sophisticated nature of modern, more environmentally friendly cementitious binders requires a better understanding and control particularly of the complex, dynamic processes involved in the early phase of cement hydration. In-situ monitoring of properties of a constantly changing system over a defined period of time calls for simple, sensitive, fast, and preferably also non-invasive methods like optical spectroscopy KW - Flourescence KW - Optical probe KW - Sensor KW - Dye KW - Flourescin KW - Photophysics KW - PH KW - Quantum yield KW - Quality assurance KW - Mechanism KW - Cement KW - Concrete KW - Building material KW - Hydration KW - Process monitoring PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-537176 DO - https://doi.org/10.1088/2050-6120/ac2da0 SN - 2050-6120 VL - 10 IS - 1 SP - 2 EP - 13 PB - IOP Science AN - OPUS4-53717 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yanbaeva, M. A1 - Soyka, J. A1 - Holthoff, J. M. A1 - Rietsch, P. A1 - Engelage, E. A1 - Ruff, A. A1 - Resch-Genger, Ute A1 - Weiss, R. A1 - Eigler, S. A1 - Huber, S. M. T1 - Dimethylene-Cyclopropanide Units as Building Blocks for Fluorescence Dyes N2 - Many organic dyes are fluorescent in solution. In the solid state, however, quenching processes often dominate, hampering material science applications such as light filters, light-emitting devices, or coding tags. We show that the dimethylene-cyclopropanides caffold can be used to form two structurally different types of chromophores, which feature fluorescence quantum yields up to 0.66 in dimethyl sulfoxide and 0.53 in solids. The increased fluorescence in the solid state for compounds bearing malonate substituents instead of dicyanomethide ones is rationalized by the induced twist between the planes of the cyclopropanide core and a pyridine ligand. KW - Fluorescence KW - Dye KW - Sensor KW - Quantum yield KW - Spectroscopy KW - Photophysics KW - Synthesis KW - Solvatochromism PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-614931 DO - https://doi.org/10.1002/chem.202402476 VL - 30 IS - 56 SP - 1 EP - 7 PB - Chemistry - A European Journal AN - OPUS4-61493 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hoffmann, Katrin A1 - Behnke, Thomas A1 - Drescher, Daniela A1 - Kneipp, Janina A1 - Resch-Genger, Ute T1 - Near-infrared-emitting nanoparticles for lifetime-based multiplexed analysis and imaging of living cells N2 - The increase in information content from bioassays and bioimaging requires robust and efficient strategies for the detection of multiple analytes or targets in a single measurement, thereby addressing current health and security concerns. For fluorescence techniques, an attractive alternative to commonly performed spectral or color multiplexing presents lifetime multiplexing and the discrimination between different fluorophores based on their fluorescence decay kinetics. This strategy relies on fluorescent labels with sufficiently different lifetimes that are excitable at the same wavelength and detectable within the same spectral window. Here, we report on lifetime multiplexing and discrimination with a set of nanometer-sized particles loaded with near-infrared emissive organic fluorophores chosen to display very similar absorption and emission spectra, yet different fluorescence decay kinetics in suspension. Furthermore, as a first proof-of-concept, we describe bioimaging studies with 3T3 fibroblasts and J774 macrophages, incubated with mixtures of these reporters employing fluorescence lifetime imaging microscopy. These proof-of-concept measurements underline the potential of fluorescent nanoparticle reporters in fluorescence lifetime multiplexing, barcoding, and imaging for cellular studies, cell-based assays, and molecular imaging. KW - Fluorescence lifetime imaging microscopy KW - FLIM KW - Lifetime multiplexing KW - Near infrared KW - NIR KW - Cell imaging KW - Nanoparticles PY - 2013 DO - https://doi.org/10.1021/nn4029458 SN - 1936-0851 VL - 7 IS - 8 SP - 6674 EP - 6684 PB - ACS Publ. CY - Washington, DC, USA AN - OPUS4-29031 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Otto, S. A1 - Grabolle, Markus A1 - Förster, C. A1 - Kreitner, C. A1 - Resch-Genger, Ute A1 - Heinze, K. T1 - [Cr(ddpd)2]3+: A molecular, water-soluble, highly NIR-emissive ruby analogue N2 - Bright, long-lived emission from first-row transition-metal complexes is very challenging to achieve. Herein, we present a new strategy relying on the rational tuning of energy levels. With the aid of the large N-Cr-N bite angle of the tridentate ligand ddpd (N,N′-dimethyl-N,N′-dipyridine-2-ylpyridine-2,6-diamine) and its strong σ-donating capabilities, a very large ligand-field splitting could be introduced in the chromium(III) complex [Cr(ddpd)2]3+, that shifts the deactivating and photoreactive 4T2 state well above the emitting 2E state. Prevention of back-intersystem crossing from the 2E to the 4T2 state enables exceptionally high near-infrared phosphorescence quantum yields and lifetimes for this 3d metal complex. The complex [Cr(ddpd)2](BF4)3 is highly water-soluble and very stable towards thermal and photo-induced substitution reactions and can be used for fluorescence intensity- and lifetime-based oxygen sensing in the NIR. KW - Chromium complexes KW - Intersystem crossing KW - Ligand-field splitting KW - NIR luminescence KW - Photophysics PY - 2015 DO - https://doi.org/10.1002/anie.201504894 SN - 1433-7851 SN - 1521-3773 SN - 0570-0833 VL - 54 IS - 39 SP - 11572 EP - 11576 PB - Wiley-VCH CY - Weinheim AN - OPUS4-35084 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Abram, Sarah-Luise A1 - Tavernaro, Isabella A1 - Resch-Genger, Ute A1 - Johnston, L. J. A1 - Zou, S. T1 - Nanoscale reference and test materials for the validation of characterization methods for engineered nanomaterials — current state, limitations, and needs N2 - The rational design of engineered nanomaterials (NMs) with improved functionality and their increasing industrial application requires reliable, validated, and ultimately standardized characterization methods for their application-relevant, physicochemical key properties such as size, size distribution, shape, or surface chemistry. This calls for nanoscale (certified) reference materials (CRMs; RMs) and well-characterized reference test materials (RTMs) termed also quality control (QC) samples, assessed, e.g., in interlaboratory comparisons, for the validation and standardization of commonly used characterization methods. Thereby, increasing concerns regarding potential risks of NMs are also addressed and the road for safe and sustainable-by-design concepts for the development of new functional NMs and their use as nanomedicines is paved. With this respect, we will provide an overview of relevant international standardization and regulatory activities, definitions, and recommendations on characterization methods and review currently available organic or inorganic nanoscale CRMs, RMs, and RTMs, including their characterization or certification. In addition, we will highlight typical applications to streamline the regulatory approval process and improve manufacturability including the special challenges imposed by the colloidal nature and sometimes limited stability of NMs. Subsequently, we will critically assess the limitations of currently available nanoscale RMs and RTMs and address the gaps to be filled in the future such as the availability of NMs that come with reference data on properties other than commonly addressed particle size, such as surface chemistry or particle number concentration, or more closely resemble commercially available formulations or address application-relevant matrices. KW - Nano KW - Particle KW - Silica KW - Quality assurance KW - Reference material KW - Review KW - Surface chemistry KW - Size KW - Shape KW - Particle number concentration KW - Lipid nanoparticles KW - Metal nanoparticles KW - Liposomes PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-625746 DO - https://doi.org/10.1007/s00216-024-05719-6 SN - 1618-2650 SP - 1 EP - 21 PB - Springer AN - OPUS4-62574 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Labrador-Paez, Lucia, L. A1 - Kankare, J. A1 - Hyppanen, I. A1 - Soukka, T. A1 - Andresen, Elina A1 - Resch-Genger, Ute A1 - Widengren, J A1 - Liu, H. T1 - Frequency-Domain Method for Characterization of Upconversion Luminescence Kinetics N2 - The frequency-domain (FD) method provides an alternative to the commonly used time-domain (TD) approach in characterizing the luminescence kinetics of luminophores, with its own strengths, e.g., the capability to decouple multiple lifetime components with higher reliability and accuracy. While extensively explored for characterizing luminophores with down-shifted emission, this method has not been investigated for studying nonlinear luminescent materials such as lanthanide-doped upconversion nanoparticles (UCNPs), featuring more complicated kinetics. In this work, employing a simplified rate-equation model representing a standard two-photon energy-transfer upconversion process, we thoroughly analyzed the response of the luminescence of UCNPs in the FD method. We found that the FD method can potentially obtain from a single experiment the effective decay rates of three critical energy states of the sensitizer/activator ions involved in the upconversion process. The validity of the FD method is demonstrated by experimental data, agreeing reasonably well with the results obtained by TD methods. KW - Quality assurance KW - Luminescence KW - Method KW - Quantitative spectroscopy KW - Nano KW - Particle KW - Lifetime KW - Method development PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-597435 DO - https://doi.org/10.1021/acs.jpclett.3c00269 SP - 3436 EP - 3444 AN - OPUS4-59743 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute A1 - Behnke, Thomas A1 - Brehm, Robert A1 - Grabolle, Markus A1 - Hennig, Andreas A1 - Hoffmann, Angelika A1 - Hoffmann, Katrin A1 - Linck, Lena A1 - Lochmann, Cornelia A1 - Pauli, Jutta A1 - Spieles, Monika A1 - Würth, Christian T1 - Funktionelle Chromophor-Systeme, innovative Validierungskonzepte und rückführbare Standards für die fluoreszenzbasierte multiparametrische Bioanalytik N2 - Unter dem Motto „Innovation und Qualitätssicherung in der (Bio)Analytik“ werden in der Arbeitsgruppe Fluoreszenzspektroskopie der BAM, Bundesanstalt für Materialforschung und -prüfung, funktionelle Chromophor-Systeme, einfache Signalverstärkungs- und Multiplexingstrategien sowie innovative Validierungs- und rückführbare Standardisierungskonzepte für verschiedene fluorometrische Messgrößen und Methoden entwickelt. Im Mittelpunkt stehen dabei molekulare Fluorophore, Nanokristalle mit größenabhängigen optischen Eigenschaften (sogenannte Quantenpunkte, QDs) und fluoreszierende Partikel variabler Größe sowie Sonden und Sensormoleküle für neutrale und ionische Analyte und für die Charakterisierung von funktionellen Gruppen. Dabei erfolgen auch methodische Entwicklungen für die Fluoreszenzspektroskopie, die Fluoreszenzmikroskopie, die Milcrofluorometrie, die Sensorik und die Mikroarraytechnologie. Ziele sind u. a. das Design und die Untersuchung von multiplexfähigen selektiven und sensitiven Sonden für die Biomarkeranalytik, die Entwicklung von Methoden zur Charakterisierung der signalrelevanten Eigenschaften dieser Chromophor-Systeme und zur Charakterisierung von funktionellen Gruppen an Oberflächen und ihre Validierung sowie die Entwicklung und Bereitstellung von formatadaptierbaren, flexibel ersetzbaren Standards für die fluoreszenzbasierte Multiparameteranalytik. T2 - 5. Senftenberger Innovationsforum Multiparameteranalytik CY - Senftenberg, Deutschland DA - 10.03.2011 KW - Multiparametric KW - Multiplexing KW - Fluorescence KW - Nanoparticles KW - NIR dyes KW - Surface analysis KW - Quantum yield KW - Quantum dot KW - Lifetime PY - 2011 SP - 86 EP - 108 CY - Senftenberg AN - OPUS4-23635 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Würth, Christian A1 - Pauli, Jutta A1 - Lochmann, Cornelia A1 - Spieles, Monika A1 - Resch-Genger, Ute T1 - Integrating sphere setup for the traceable measurement of absolute photoluminescence quantum yields in the near infrared N2 - There is an increasing interest in chromophores absorbing and emitting in the near-infrared (NIR) spectral region, e.g., for applications as fluorescent reporters for optical imaging techniques and hence, in reliable methods for the characterization of their signal-relevant properties like the fluorescence quantum yield (Φf) and brightness. The lack of well established Φf standards for the NIR region in conjunction with the need for accurate Φf measurements in transparent and scattering media encouraged us to built up an integrating sphere setup for spectrally resolved measurements of absolute fluorescence traceable to radiometric scales. Here, we present the design of this setup and its characterization and validation including an uncertainty budget for the determination of absolute Φf in the visible and NIR. To provide the basis for better measurements of Φf in the spectral window from ca. 600 to 1000 nm used, e.g., for optical imaging, the absolute Φf of a set of NIR chromophores covering this spectral region are measured and compared to relative values obtained using rhodamine 101 as Φf standard. Additionally, the absolute Φf values of some red dyes that are among the most commonly used labels in the life sciences are presented as well as the absolute quantum yield of an optical probe for tumor imaging. KW - Fluorescence KW - Photoluminescence KW - Quantum yield KW - Dye KW - Uncertainty KW - Absolute quantum yield KW - Method comparison KW - Integrating sphere KW - NIR KW - Standards KW - Quantum yield standards PY - 2012 DO - https://doi.org/10.1021/ac2021954 SN - 0003-2700 SN - 1520-6882 VL - 84 IS - 3 SP - 1345 EP - 1352 PB - American Chemical Society CY - Washington, DC AN - OPUS4-25504 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Introduction to Fluorescence Spectroscopy N2 - A brief introduction to fluorescence spectroscopy will be provided, ranging from typically measured fluorescence quantities over instrument-specific contributions to measured fluorescence signals to selected applications. In this context, an overview of the photoluminescence properties of molecular and nanoscale luminescence reporters will be given including a brief insight into their photophysics and fluorescence standards designed by division Biophotonics for the calibration and instrument performance validation of fluorescence measuring devices will be presented. T2 - Analytical Academy CY - Berlin, Germany DA - 13.01.2020 KW - Linearity KW - Fluorescence KW - Dye KW - Quality assurance KW - Nnano particle KW - Method KW - Measurement uncertainty KW - Quantification PY - 2020 AN - OPUS4-51618 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Absolute Fluorescence Measurements > 800 nm - Setup Design, Challenges, and Characterization of Semiconductor and Lanthanide-based Nanocrystals N2 - There is an increasing interest in optical reporters like semiconductor and lanthanide-based nanocrystals with emission > 800 nm and recently also > 1000 nm for bioanalysis, medical diagnostics, and safety barcodes. Mandatory for the comparison of different emitter classes and the rational design of the next generation of reporters for the short wavelength infrared (SWIR) region are reliable and quantitative photoluminescence measurements in this challenging wavelength region. This is of special relevance for nanocrystalline emitters like semiconductor quantum dots and rods as well as for upconversion and downconversion nanocrystals, where surface states and the accessibility of emissive states by quenchers largely control accomplishable quantum yields and hence, signal sizes and detection sensitivities from the reporter side. Such measurements are currently hampered by the lack of suitable methods and standards for instrument calibration and validation as well as by the lack of quantum yield standards with emission > 800 nm and especially > 1000 nm. In this respect, we present the design of integrating sphere setups for absolute and excitation power densitydependent measurements of emission spectra and quantum yields in the wavelength region of 650 to 1650 nm including calibration strategies and first candidates for potential fluorescence standards. Subsequently, the photoluminescence properties of different types of nanocrystals are presented and discussed including absolute photoluminescence measurements of upconversion and down conversion emission in different solvents. T2 - MRS 2017 CY - Boston, MA, USA DA - 26.11.2017 KW - Upconversion KW - Nanoparticle KW - Absolute fluorometry KW - Integrating sphere spectroscopy KW - NIR KW - IR KW - Fluorescence KW - Surface chemistry KW - Deactivation pathways KW - Semiconductor quantum dot KW - SWIR KW - Quantum yield KW - Energy transfer KW - Size PY - 2017 AN - OPUS4-43202 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Career Options in Public Service N2 - In the following, an overview of possible career options for chemists is presented covering metrology institutes, departmental research institutes of ministries, Federal and state research institutes and options in areas such as Federal or state institutions in charge of occupational safety, the German armed forces, wastewater treatment plants and labs/institutes controlling water quality, and museums. Thereby also examples and personal insights of the daily work routine are provided for some employers. T2 - Career-Workshop ChiÖD CY - Karlsruhe, Germany DA - 02.04.2025 KW - Quality assurance KW - Reference analysis KW - Standardization KW - Metrology KW - Reference products KW - Reference materials KW - Mission PY - 2025 AN - OPUS4-62867 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mayer-Enthart, Elke A1 - Sialelli, Julien A1 - Rurack, Knut A1 - Resch-Genger, Ute A1 - Köster, D. A1 - Seitz, H. T1 - Toward Improved Biochips Based on Rolling Circle Amplification - Influences of the Microenvironment on the Fluorescence Properties of Labeled DNA Oligonucleotides KW - Rolling circle amplification KW - Fluorescence KW - Biochips KW - Microarrays KW - Signal amplification KW - Cy3-labeled oligonucleotides KW - DNA technology PY - 2008 DO - https://doi.org/10.1196/annals.1430.022 SN - 0077-8923 SN - 1749-6632 SN - 0094-8500 VL - 1130 SP - 287 EP - 292 PB - New York Academy of Sciences CY - New York, NY AN - OPUS4-17633 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Neumann, L. A1 - Jakobs, F. A1 - Spelthann, S. A1 - Zaremba, D. A1 - Radunz, Sebastian A1 - Resch-Genger, Ute A1 - Evert, R. A1 - Kielhorn, J. A1 - Kowalsky, W. A1 - Johannes, H.-H. T1 - Integration of β-NaYF4 Upconversion Nanoparticles into Polymers for Polymer Optical Fiber Applications N2 - Producing active polymer optical fibers (POFs) is a key step towards new applications such as fluorescent fiber solar concentrators (FFSCs), sensors, contactless coupling devices, or fiber integrated light sources and lasers. Therefore, integration of fluorescent nanoparticles into the polymer matrix is necessary and becomes accessible via in situ polymerization. For optical applications, the polymer has to fulfill various requirements such as chemical and physical stability, optical transparency in the application-relevant spectral region as well as a good synthetic accessibility. A common material for these is poly(methyl methacrylate) (PMMA). The β-phase NaYF4:Yb3+,Er3+ upconversion nanoparticles (UCNP) were synthesized from the rare earth salts via thermal decomposition method in high-boiling point solvent 1-octadecene and capping agent oleic acid. Current results show hazy samples of the polymer with integrated nanoparticles made from monomer solution of methyl methacrylate. However, further optical tuning such as increasing the transparency of the bulk samples by changing the monomer solution to non-polar n-butyl methacrylate (nButMA) or cyclohexyl methacrylate (CHMA) or further optimization of the UCNP shell could lead to more suitable polymer bulk samples. T2 - PCNSPA 2018 - Photonic Colloidal Nanostructures: Synthesis, Properties, and Applications CY - St. Petersburg, Russia DA - 04.06.2018 KW - Copolymer KW - Active fibers KW - Rare earth nanoparticles KW - Upconversion PY - 2018 SP - 1 EP - 9 AN - OPUS4-45883 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - From molecular and nanoscale chromophores with UV/VIS/NIR/SWIR luminescence to multi method characterization of surface coatings N2 - An overview of the research activities of division Biophotonics is presented covering examples for photophysical studies of different types of molecular and nanocrystalline luminophores, luminescent particles, and sensor systems in solution, in dispersion, and in the solid state and multi-method charactreization workflow for the characterization of surface-functionalized engineered nanomaterials. In addition, the importance of reliable optical measurements, particularly standardized workflows for the determination of the key performance parameter luminescence quantum yield of transparent and scattering luminescent samples with fluorescence and integrating sphere spectroscopy, and validated methods for quantifying surface functional groups and ligands on nanomaterials is highlighted. Thereby, also ongoing standardization activities are presented as well as certified reference materials and reference materials from division Biophotonics. T2 - Chinese-German Chemical Association - Annual Meeting CY - Berlin, Germany DA - 22.08.2025 KW - Quality assurance KW - Fluorescence KW - Nano KW - Particle KW - Synthesis KW - Quantum yield KW - Characterization KW - Advanced material KW - Surface KW - Lifetime KW - Sensor KW - Oxygen KW - Ph KW - Standardization KW - Fluorescent probe KW - Reference material PY - 2025 AN - OPUS4-64181 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scholtz, Lena A1 - Eckert, J. G. A1 - Elahi, T. A1 - Lübkemann, F. A1 - Hübner, Oskar A1 - Bigall, N. C. A1 - Resch-Genger, Ute T1 - Luminescence encoding of polymer microbeads with organic dyes and semiconductor quantum dots during polymerization N2 - Luminescence-encoded microbeads are important tools for many applications in the life and material sciences that utilize luminescence detection as well as multiplexing and barcoding strategies. The preparation of such beads often involves the staining of premanufactured beads with molecular luminophores using simple swelling procedures or surface functionalization with layer-by-layer (LbL) techniques. Alternatively, these luminophores are sterically incorporated during the polymerization reaction yielding the polymer beads. The favorable optical properties of semiconductor quantum dots (QDs), which present broadly excitable, size-tunable, narrow emission bands and low photobleaching sensitivity, triggered the preparation of beads stained with QDs. However, the colloidal nature and the surface chemistry of these QDs, which largely controls their luminescence properties, introduce new challenges to bead encoding that have been barely systematically assessed. To establish a straightforward approach for the bead encoding with QDs with minimized loss in luminescence, we systematically assessed the incorporation of oleic acid/oleylamine-stabilized CdSe/CdS-core/shell-QDs into 0.5–2.5 μm-sized polystyrene (PS) microspheres by a simple dispersion polymerization synthesis that was first optimized with the organic dye Nile Red. Parameters addressed for the preparation of luminophore-encoded beads include the use of a polymer-compatible ligand such as benzyldimethyloctadecylammonium chloride (OBDAC) for the QDs, and crosslinking to prevent luminophore leakage. The physico-chemical and optical properties of the resulting beads were investigated with electron microscopy, dynamic light scattering, optical spectroscopy, and fluorescence microscopy. Particle size distribution, fluorescence quantum yield of the encapsulated QDs, and QD leaking stability were used as measures for bead quality. The derived optimized bead encoding procedure enables the reproducible preparation of bright PS microbeads encoded with organic dyes as well as with CdSe/CdS-QDs. Although these beads show a reduced photoluminescence quantum yield compared to the initially very strongly luminescent QDs, with values of about 35%, their photoluminescence quantum yield is nevertheless still moderate. KW - Polymerization KW - Quantum dots KW - Microbeads KW - Fluorescence PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-553430 DO - https://doi.org/10.1038/s41598-022-16065-x SN - 2045-2322 VL - 12 SP - 1 EP - 16 PB - Nature Publishing Group CY - London AN - OPUS4-55343 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Clark, P.C.J A1 - Andresen, Elina A1 - Sear, M. J. A1 - Favaro, M. A1 - Girardi, L. A1 - van de Krol, R. A1 - Resch-Genger, Ute A1 - Starr, D.E. T1 - Quantification of the Activator and Sensitizer Ion Distributions in NaYF4:Yb3+, Er3+ Upconverting Nanoparticles Via Depth-Profiling with Tender X-Ray Photoemission N2 - The spatial distribution and concentration of lanthanide activator and sensitizer dopant ions are of key importance for the luminescence color and efficiency of upconverting nanoparticles (UCNPs). Quantifying dopant ion distributions and intermixing, and correlating them with synthesis methods require suitable analytical techniques. Here, X-ray photoelectron spectroscopy depth-profiling with tender X-rays (2000–6000 eV), providing probe depths ideally matched to UCNP sizes, is used to measure the depth-dependent concentration ratios of Er3+ to Yb3+, [Er3+]/[Yb3+], in three types of UCNPs prepared using different reagents and synthesis methods. This is combined with data simulations and inductively coupled plasma-optical emission spectroscopy (ICP-OES) measurements of the lanthanide ion concentrations to construct models of the UCNPs’ dopant ion distributions. The UCNP sizes and architectures are chosen to demonstrate the potential of this approach. Core-only UCNPs synthesized with XCl3·6H2O precursors (β-phase) exhibit a homogeneous distribution of lanthanide ions, but a slightly surface-enhanced [Er3+]/[Yb3+] is observed for UCNPs prepared with trifluroacetate precursors (α-phase). Examination of Yb-core@Er-shell UCNPs reveals a co-doped, intermixed region between the single-doped core and shell. The impact of these different dopant ion distributions on the UCNP's optical properties is discussed to highlight their importance for UCNP functionality and the design of efficient UCNPs. KW - Shell KW - Nanomaterial KW - Nano KW - Upconversion nanoparticle KW - Lanthanide KW - Photoluminescence KW - Quantum yield KW - Photophysics KW - Excitation power density KW - Surface KW - Coating KW - Core-shell KW - XPS KW - Intermixing KW - HAXPES KW - Method PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-552075 DO - https://doi.org/10.1002/smll.202107976 SN - 1613-6813 SP - 1 EP - 13 PB - Wiley-VCH-Verlag CY - Weinheim, Germany AN - OPUS4-55207 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kromer, C. A1 - Schwibbert, Karin A1 - Gadicherla, A. K. A1 - Thiele, Dorothea A1 - Nirmalananthan-Budau, Nithiya A1 - Laux, P. A1 - Resch-Genger, Ute A1 - Luch, A. A1 - Tschiche, H. R. T1 - Monitoring and imaging pH in biofilms utilizing a fluorescent polymeric nanosensor N2 - Biofilms are ubiquitous in nature and in the man-made environment. Given their harmful effects on human health, an in-depth understanding of biofilms and the monitoring of their formation and growth are important. Particularly relevant for many metabolic processes and survival strategies of biofilms is their extracellular pH. However, most conventional techniques are not suited for minimally invasive pH measurements of living biofilms. Here, a fluorescent nanosensor is presented for ratiometric measurements of pH in biofilms in the range of pH 4.5–9.5 using confocal laser scanning microscopy. The nanosensor consists of biocompatible polystyrene nanoparticles loaded with pH-inert dye Nile Red and is surface functionalized with a pH-responsive fluorescein dye. Its performance was validated by fluorometrically monitoring the time-dependent changes in pH in E. coli biofilms after glucose inoculation at 37 °C and 4 °C. This revealed a temperature-dependent decrease in pH over a 4-h period caused by the acidifying glucose metabolism of E. coli. These studies demonstrate the applicability of this nanosensor to characterize the chemical microenvironment in biofilms with fluorescence methods. KW - Dye KW - Fluorescence KW - Signal enhancement KW - Sensor KW - Quantum yield KW - Synthesis KW - Nanoparticle KW - Nano KW - Polymer KW - Ph KW - Biofilm KW - MIC KW - Corrosion KW - Microorganism KW - Bacteria PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-550751 DO - https://doi.org/10.1038/s41598-022-13518-1 SN - 2045-2322 VL - 12 IS - 1 SP - 1 EP - 10 PB - Nature Publishing Group CY - London AN - OPUS4-55075 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stein, L. A1 - Wang, Cui A1 - Förster, C. A1 - Resch-Genger, Ute A1 - Heinze, K. T1 - Bulky ligands protect molecular ruby from oxygen quenching N2 - Chromium(III) complexes can show phosphorescence from the spin-flip excited doublet states 2E/2T1 in the near-infrared with high photoluminescence quantum yields and extremely long lifetimes in the absence of dioxygen. The prototype molecular ruby, [Cr(ddpd)2]3+ (ddpd = N,N’-dimethyl-N,N’-dipyridine-2-ylpyridine-2,6-diamine), has a photoluminescence quantum yield and a luminescence lifetime of 13.7% and 1.1 ms in deaerated acetonitrile, respectively. However, its luminescence is strongly quenched by 3O2 via an efficient Dexter-type energy transfer process. To enable luminescence applications of molecular rubies in solution under aerobic conditions, we explored the potential of sterically demanding ddpd ligands to shield the chromium(III) center from O2 using steady state and time-resolved photoluminescence spectroscopy. The structures of the novel complexes with sterically demanding ligands were investigated by single crystal X-ray diffraction and quantum chemically by density functional theory calculations. The O2 sensitivity of the photoluminescence was derived from absolutely measured photoluminescence quantum yields and excited state lifetimes under inert and aerobic conditions and by Stern–Volmer analyses of these data. Optimal sterically shielded chromium(III) complexes revealed photoluminescence quantum yields of up to 5.1% and excited state lifetimes of 518 μs in air-saturated acetonitrile, underlining the large potential of this ligand design approach to broaden the applicability of highly emissive chromium(III) complexes. KW - Fluorescence KW - Synthesis KW - Production KW - Optical spectroscopy KW - Ligand KW - Photophysics KW - Cr(III) KW - Mechanism KW - NIR KW - Sensor KW - Oxygen PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-570807 DO - https://doi.org/10.1039/d2dt02950b VL - 51 IS - 46 SP - 17664 EP - 17670 PB - The Royal Society of Chemistry CY - Berlin AN - OPUS4-57080 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scholtz, Lena A1 - Tavernaro, Isabella A1 - Eckert, J. G. A1 - Lutowski, Marc A1 - Geißler, Daniel A1 - Hertwig, Andreas A1 - Hidde, Gundula A1 - Bigall, N. C. A1 - Resch-Genger, Ute T1 - Influence of nanoparticle encapsulation and encoding on the surface chemistry of polymer carrier beads N2 - Surface-functionalized polymer beads encoded with molecular luminophores and nanocrystalline emitters such as semiconductor nanocrystals, often referred to as quantum dots (QDs), or magnetic nanoparticles are broadly used in the life sciences as reporters and carrier beads. Many of these applications require a profound knowledge of the chemical nature and total number of their surface functional groups (FGs), that control bead charge, colloidal stability, hydrophobicity, and the interaction with the environment and biological systems. For bioanalytical applications, also the number of groups accessible for the subsequent functionalization with, e.g., biomolecules or targeting ligands is relevant. In this study, we explore the influence of QD encoding on the amount of carboxylic acid (COOH) surface FGs of 2 μm polystyrene microparticles (PSMPs). This is done for frequently employed oleic acid and oleylamine stabilized, luminescent core/shell CdSe QDs and two commonly used encoding procedures. This included QD addition during bead formation by a thermally induced polymerization reaction and a post synthetic swelling procedure. The accessible number of COOH groups on the surface of QD-encoded and pristine beads was quantified by two colorimetric assays, utilizing differently sized reporters and electrostatic and covalent interactions. The results were compared to the total number of FGs obtained by a conductometric titration and Fourier transform infrared spectroscopy (FTIR). In addition, a comparison of the impact of QD and dye encoding on the bead surface chemistry was performed. Our results demonstrate the influence of QD encoding and the QD-encoding strategy on the number of surface FG that is ascribed to an interaction of the QDs with the carboxylic acid groups on the bead surface. These findings are of considerable relevance for applications of nanoparticle-encoded beads and safe-by-design concepts for nanomaterials. KW - Optical spectroscopy KW - Particle KW - Optical assay KW - IR spectroscopy KW - Fluorescence KW - Quantum yield KW - Quality assurance KW - Nano KW - Synthesis KW - Surface chemistry KW - Quantification KW - Method KW - Conductometry PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-581502 DO - https://doi.org/10.1038/s41598-023-38518-7 SN - 2045-2322 VL - 13 IS - 1 SP - 1 EP - 15 PB - Springer Nature CY - London AN - OPUS4-58150 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Reiber, T. A1 - Hübner, Oskar A1 - Dose, C. A1 - Yushchenko, D. A. A1 - Resch-Genger, Ute T1 - Fluorophore multimerization on a PEG backbone as a concept for signal amplification and lifetime modulation N2 - Fluorescent labels have strongly contributed to many advancements in bioanalysis, molecular biology, molecular imaging, and medical diagnostics. Despite a large toolbox of molecular and nanoscale fluorophores to choose from, there is still a need for brighter labels, e.g., for flow cytometry and fluorescence microscopy, that are preferably of molecular nature. This requires versatile concepts for fluorophore multimerization, which involves the shielding of dyes from other chromophores and possible quenchers in their neighborhood. In addition, to increase the number of readout parameters for fluorescence microscopy and eventually also flow cytometry, control and tuning of the labels’ fluorescence lifetimes is desired. Searching for bright multi-chromophoric or multimeric labels, we developed PEGylated dyes bearing functional groups for their bioconjugation and explored their spectroscopic properties and photostability in comparison to those of the respective monomeric dyes for two exemplarily chosen fluorophores excitable at 488 nm. Subsequently, these dyes were conjugated with anti-CD4 and anti-CD8 immunoglobulins to obtain fluorescent conjugates suitable for the labeling of cells and beads. Finally, the suitability of these novel labels for fluorescence lifetime imaging and target discrimination based upon lifetime measurements was assessed. Based upon the results of our spectroscopic studies including measurements of fluorescence quantum yields (QY) and fluorescence decay kinetics we could demonstrate the absence of significant dye-dye interactions and self-quenching in these multimeric labels. Moreover, in a first fluorescence lifetime imaging (FLIM) study, we could show the future potential of this multimerization concept for lifetime discrimination and multiplexing. KW - Imaging KW - Quantum yield KW - Quality assurance KW - Antibody KW - Conjugate KW - Cell KW - FLIM KW - PEG KW - Flow cytometry KW - Lifetime KW - Energy transfer KW - Quantitative spectroscopy KW - Nano KW - Particle KW - Fluorescence KW - Dye KW - Amplification KW - Microscopy PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-602197 DO - https://doi.org/10.1038/s41598-024-62548-4 SN - 2045-2322 VL - 14 IS - 1 SP - 1 EP - 11 AN - OPUS4-60219 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wegner, Karl David A1 - Resch-Genger, Ute T1 - The 2023 Nobel Prize in Chemistry: Quantum dots N2 - The 2023 Nobel Prize in Chemistry was awarded to Aleksey I. Ekimov (prize share 1/3), Louis E. Brus (prize share 1/3), and Moungi G. Bawendi (prize share 1/3) for groundbreaking inventions in the field of nanotechnology, i.e., for the discovery and synthesis of semiconductor nanocrystals, also termed quantum dots, that exhibit size-dependent physicochemical properties enabled by quantum size effects. This feature article summarizes the main milestones of the discoveries and developments of quantum dots that paved the road to their versatile applications in solid-state lighting, display technology, energy conversion, medical diagnostics, bioimaging, and image-guided surgery. KW - Quantum dots KW - Semiconductor nanocrystals KW - Luminescence KW - Quantitative spectroscopy KW - Quantum yield KW - Advanced nanomaterials KW - Quality assurance KW - Energy transfer PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-597843 DO - https://doi.org/10.1007/s00216-024-05225-9 VL - 2024 SP - 1 EP - 11 PB - Springer CY - Cham AN - OPUS4-59784 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mohammad, W. A1 - Wegner, Karl David A1 - Comby-Zerbino, C. A1 - Trouillet, V. A1 - Ogayer, M. P. A1 - Coll, J.-L. A1 - Marin, R. A1 - Jaque Garcia, D. A1 - Resch-Genger, Ute A1 - Antoine, R. A1 - Le Guevel, X. T1 - Enhanced brightness of ultra-small gold nanoparticles in the second biological window through thiol ligand shell control N2 - Gold-based nanoparticles below 2 nm in size are promising as luminescent probes for in vivo bioimaging, owing to their brightness and rapid renal clearance. However, their use as contrast agents in the near-infrared II (NIR-II, 1000–1700 nm) range remains challenging due to their low photoluminescence (PL) quantum yield. To address this, PL enhancement can be achieved by either rigidifying the ligand-shell structure or increasing the size of the ligand shell. In this study, we synthesized ultra-small gold nanoparticles stabilized by co-ligands, namely monothiol and short dithiol molecules. By precisely controlling the amount of reducing agent used during particle preparation, we successfully modulated the physicochemical properties of the co-ligand shell, including its size, composition, and structure. Consequently, we achieved a remarkable 60-fold increase in the absorption cross-section at 990 nm while maintaining the small size of the 1.5-nm metal core. The analytical and optical characterization of our thiol-capped gold nanoparticles indicates that the ligand shell size is governed by the quantity of the reducing agent, which, in turn, impacts the balance between radiative and non-radiative processes, thereby influencing the PL quantum yield. KW - Gold nanocluster KW - NIR-II fluorescence KW - SWIR KW - Nanomaterial design KW - Calibrated fluorescence measurements PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-588117 DO - https://doi.org/10.1039/D3TC03021K SN - 2050-7526 VL - 11 IS - 42 SP - 14714 EP - 14724 PB - Royal Society of Chemistry (RSC) AN - OPUS4-58811 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fiedler, Saskia A1 - Frenzel, Florian A1 - Würth, Christian A1 - Tavernaro, Isabella A1 - Grüne, M. A1 - Schweizer, S. A1 - Engel, A. A1 - Resch-Genger, Ute T1 - Interlaboratory Comparison on Absolute Photoluminescence Quantum Yield Measurements of Solid Light Converting Phosphors with Three Commercial Integrating Sphere Setups N2 - Scattering luminescent materials dispersed in liquid and solid matrices and luminescent powders are increasingly relevant for fundamental research and industry. Examples are luminescent nano- and microparticles and phosphors of different compositions in various matrices or incorporated into ceramics with applications in energy conversion, solid-state lighting, medical diagnostics, and security barcoding. The key parameter to characterize the performance of these materials is the photoluminescence/fluorescence quantum yield (Φf), i.e., the number of emitted photons per number of absorbed photons. To identify and quantify the sources of uncertainty of absolute measurements of Φf of scattering samples, the first interlaboratory comparison (ILC) of three laboratories from academia and industry was performed by following identical measurement protocols. Thereby, two types ofcommercial stand-alone integrating sphere setups with different illumination and detection geometries were utilized for measuring the Φf of transparent and scattering dye solutions and solid phosphors, namely, YAG:Ce optoceramics of varying surface roughness, used as converter materials for blue light emitting diodes. Special emphasis was dedicated to the influence of the measurement geometry, the optical properties of the blank utilized to determine the number of photons of the incident excitation light absorbed by the sample, and the sample-specific surface roughness. While the Φf values of the liquid samples matched between instruments, Φf measurements of the optoceramics with different blanks revealed substantial differences. The ILC results underline the importance of the measurement geometry, sample position, and blank for reliable Φf data of scattering the YAG:Ce optoceramics, with the blank’s optical properties accounting for uncertainties exceeding 20%. KW - Nano KW - Fluorescence KW - Reference material KW - Luminescence KW - Quantitative spectroscopy KW - Particle KW - Quantum yield KW - Quality assurance KW - Phosphor KW - Converter material KW - Lifetime KW - Interlaboratory comparison KW - Method KW - Uncertainty PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-600945 DO - https://doi.org/10.1021/acs.analchem.4c00372 SN - 0003-2700 SP - 6730 EP - 6737 PB - ACS Publications AN - OPUS4-60094 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wang, Cui A1 - Ebel, Kenny A1 - Heinze, Katja A1 - Resch-Genger, Ute A1 - Bald, Ilko T1 - Quantum Yield of DNA Strand Breaks under Photoexcitation of a Molecular Ruby N2 - Photodynamic therapy (PDT) used for treating cancer relies on the generation of highly reactive oxygen species, for example, singlet oxygen 1O2, by light-induced excitation of a photosensitizer (PS) in the presence of molecular oxygen, inducing DNA damage in close proximity of the PS. Although many precious metal complexes have been explored as PS for PDT and received clinical approval, only recently, the potential of photoactive complexes of nonnoble metals as PS has been discovered. Using the DNA origami technology that can absolutely quantify DNA strand break cross sections, we assessed the potential of the luminescent transition metal complex [Cr(ddpd)2]3+ (ddpd=N,N’-dimethyl-N,N’-dipyridine-2-ylpyridine-2,6-diamine) to damage DNA in an air-saturated aqueous environment upon UV/Vis illumination. The quantum yield for strand breakage, that is, the ratio of DNA strand breaks to the number of absorbed photons, was determined to 1–4%, indicating efficient transformation of photons into DNA strand breaks by [Cr(ddpd)2]3+. KW - Fluorescence KW - Synthesis KW - Production KW - Optical spectroscopy KW - Ligand KW - Photophysics KW - Cr(III) KW - Mechanism KW - NIR KW - PDT KW - Singlet oxygen KW - DNA KW - Origami KW - Quantum yield PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-573631 DO - https://doi.org/10.1002/chem.202203719 SP - 1 EP - 7 AN - OPUS4-57363 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -