TY - CONF A1 - Würth, Christian T1 - Time resolved spectroscopy of upconverting lanthanide based upconversion nanocrystals N2 - The optical properties of these materials strongly depend on the excitation power density, i.e., the number of photons absorbed per time interval. The upconversion quantum efficiencies (ΦUC) of these materials, the excitation power dependent population i.e. the emission characteristics, and the deactivation dynamics are influenced by nanoparticle architecture, doping concentration, and the microenvironment. We will discuss how time resolved measurements can help to understand the fundamental photophysical mechanisms and discuss differences to other nanocrystals like quantum dots. T2 - 19th International Course on “Principles and Applications of Time-resolved Fluorescence Spectroscopy” CY - Berlin, Germany DA - 16.11.2022 KW - Nanoparticle KW - Lanthanide KW - Upconversion KW - Energy transfer PY - 2022 AN - OPUS4-57000 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Quantitation of luminescent properties of Yb and Ho co-doped NaYF4 colloidal nanoparticles - novel active-core-active-shell materials and novel characterization methods N2 - 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, we present here a series of core@shell NaYF4 UCNPs doped with Yb3+ and Ho3+ ions, where the same dopant concentrations were 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. As revealed by quantitative steady state and time-resolved luminescence studies, the relative spatial distribution of the A and S ions in the UCNPs and their protection from surface quenching has critical impact on their luminescent characteristics. Interestingly, although the increased amount of Yb3+ ions boosts UCNP performance by increasing the absorption, the Yb3+ ions can also dissipate the energy stored in the material through energy migration to surface, thereby reducing the overall energy transfer efficiency to the activator ions. T2 - COST Workshop CY - Aveiro, Portugal DA - 30.06.2017 KW - Upconversion KW - Nanoparticle KW - Flourescence KW - Core-shell architecture KW - NIR KW - Absolute flourometry KW - Integrating sphere spectroscopy KW - Ho(III) KW - Yb(III) PY - 2017 AN - OPUS4-41161 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Research and development in material and life sciences and quality assurance at BAM N2 - Research and development activities at BAM are presented with Special Focus on bioanalysis and biophotonics. This includes Topics from the Focus Areas Material, Environment, and Analytical Sciences. Also, Job opportunities at BAM are emphasized. T2 - MPI CY - Göttingen, Germany DA - 26.10.2017 KW - Analytics KW - Materials KW - Fluorometry KW - Sensors KW - Biophotonics KW - Microbiology KW - Reference material KW - Standard KW - Calibration KW - Nanoparticle PY - 2017 AN - OPUS4-43132 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 - Getting it right with photoluminescence quantum yields of molecular and nanoscale luminophores and luminescent particles N2 - Photophysical and mechanistic studies, the comparison of different emitter classes, and the rational design of the next generation of molecular and nanoscale reporters require quantitative photoluminescence measurements and the reliable determination of the key performance parameter photoluminescence quantum yield (QY), i.e., the number of emitted per absorbed photons. This is of special importance for all photoluminescence applications in the life and material sciences in the UV/vis/NIR/SWIR. To improve the reliability and comparability of photoluminescence and QY measurements across laboratories, pitfalls, achievable uncertainties, and material-specific effects related to certain emitter classes must be explored. Also, suitable protocols and reference materials are needed which have been validated in interlaboratory comparisons for different wavelength regions and transparent and scattering luminophores.[1] Based on absolute and relative photoluminescence measurements of functional dyes and nanomaterials like semiconductor quantum dots and rods, spectrally shifting lanthanide upconversion nanocrystals, perovskites, and YAG:Cer converter materials, reliable methods for determining QY of transparent and scattering luminophores, nonlinear emitters, and solid luminescent nanomaterials have been developed.[2,3] Thereby, material- and method-related uncertainties of relative and absolute QY measurements and achievable uncertainties could be quantified for linear and nonlinear UV/vis/NIR/SWIR emitters and lately for also luminescent and scattering materials and solid phoshors, here in an interlaboratory comparison of three labs utilizing integrating sphere spectroscopy.[4,5] In addition, to provide simple tools for a better comparability of QY measurements, recently, a first set of UV/vis/NIR quantum yield standards has been developed and certified with complete uncertainty budgets.[6] In the following, the outcome of these studies will be presented, thereby addressing common pitfalls and providing recommendations on the performance of reliable QY measurements of linear and non-linear emitters in transparent, scattering, and solid samples. T2 - 29th Lecture Conference on Photochemistry (LCP 2024) GDCh CY - Mainz, Germany DA - 16.09.2024 KW - Nanoparticle KW - Nano KW - Luminescence KW - Quality assurance KW - Synthesis KW - Standardization KW - Reference material KW - Quantum yield KW - Fluorescence KW - Reference data KW - Integrating sphere spectroscopy KW - ILC KW - Converter material KW - YAG:Ce KW - Optoceramic PY - 2024 AN - OPUS4-61075 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Optical spectroscopy – Techniques, instrumentation, and typical molecular and nanoscale reporters N2 - Different types of optical spectroscopies are introduced with special emphasis on method-inherent limitations and reliable instrument calibration and performance validation. In addition, different classes of molecular and nanocrystalline emitters are presented and the underlying photophysical processes are briefly described. T2 - Fakultät der University of Ottawa CY - Ottawa, Canada DA - 11.12.2018 KW - quality assurcance KW - Optical spectroscopy KW - Method comparison KW - Photoluminescence KW - Calibration KW - Performance validation KW - Dye KW - Nanoparticle KW - Quantum dots KW - Quantum yields KW - Uncertainty KW - Method validation PY - 2018 AN - OPUS4-47631 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Würth, Christian T1 - Setup for the power-dependent absolute quantum yield measurements: example of upconversion nanoparticles N2 - Lanthanide-doped up-converting nanoparticles (UCNPs), are promising reporters for bioanalysis and theranostics, which are excitable in the near infrared (NIR) by multiphoton absorption processes, and show multiple narrow emission bands in the visible (vis) and NIR, excellent photostability, and long luminescence lifetimes in the µs range. The rational design of brighter UCNP requires an improved understanding of the radiationless deactivation pathways in UCNP, that are affected by size, surface chemistry, and microenvironment. In this respect, we discuss the experimental requirements on absolute measurements of the upconversion quantum yield and its excitation radiant power density dependence and present the design and characterization of unique integrating sphere setup for such measurements in the vis to IR spectral region including its calibration, the influence of the excitation beam profile and solutions to perform such measurements in aqueous media. T2 - Upcon2016 CY - Breslau, Poland DA - 23.05.2016 KW - Upconversion KW - Quantum yield KW - Nanoparticle PY - 2016 AN - OPUS4-38409 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Functional Nanomaterials with VIS/NIR Emission-Spectroscopic Properties And Surface Group Analysis N2 - Optical-spectroscopic methods for the quantitative characterization of the optical properties of different types of vis/NIR-emissive nanomaterials like semiconductor quantum dots and upconversion nanocrystals will be presented and their relevance for the mechanistic understanding of nonradiative decay channels and the rational design of new nanomaterials will be underpinned. In this respect, also validation concepts for such measurements and absolute fluorometry will be introduced. In addition, the potential of optical spectroscopy for surface group and ligand analysis surface chemistry will be demonstrated exemplarily for semiconductor quantum dots. T2 - Universität Mainz, AK Professor K. Heinze CY - Mainz, Germany DA - 24.07.2017 KW - Upconversion KW - Nanoparticle KW - Flourescence KW - Surface group analysis KW - NIR KW - Absolute flourometry KW - Integrating sphere spectroscopy KW - Optical probe KW - Assay KW - Thiol ligand PY - 2017 N1 - Geburtsname von Nirmalananthan-Budau, Nithiya: Nirmalananthan, N. - Birth name of Nirmalananthan-Budau, Nithiya: Nirmalananthan, N. AN - OPUS4-41115 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Absolute spectroscopic characterization of the optical properties of semiconductor and upconversion nanocrystals in the vis and IR N2 - Nanocrystalline fluorophores like semiconductor quantum dots and rods and recently also lanthanide-based upconversion phosphors with emission in the visible (vis), near-infrared (NIR), and IR (infrared) region are increasingly being used in bioimaging studies and fluorescence assays as well as in photovoltaics and solid state lighting. The assessment and comparison of material performance as well as the development of rational design strategies for improved systems require spectroscopic tools, which enable the determination of the signal-relevant optical properties like photoluminescence quantum yields and brightness values. In the case of nonlinear fluorescence as shown by upconversion materials, such measurements must be also performed as function of excitation power density. In this work, we report on methods for the absolute determination of the photoluminescence quantum yield and brightness of fluorescent particles in dispersion and as powders based on integrating sphere spectroscopy and underline the importance of such measurements for the understanding of the photophysics of such nanocrystals. T2 - International Conference on Fundamental Processes in Semiconductor Nanocrystals (FQDots16) CY - Berlin, Germany DA - 05.09.2016 KW - Fluorescence KW - Nanoparticle KW - Semiconductor quantum dot KW - Upconversion nanocrystal KW - NIR KW - Integrating sphere spectroscopy KW - Fluorescence quantum yield KW - Method PY - 2016 AN - OPUS4-38695 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Effect of Particle Size and Excitation Power Density on the Luminescence Efficiency of Upconversion Nanocrystals in Different Dispersion Media N2 - Upconversion nanoparticles (UCNPs) offer new strategies for luminescence-based sensing and imaging. One of the best studied materials are ..-NaYF4 UCNPs doped with 20 % Yb3+ and 2 % Er3+, which efficiently convert 976 nm light to photons emitted at 540 nm, 655 nm, and 845 nm, respectively, reveal long luminescence lifetimes (> 100 µs), are photostable and chemically inert. Their upconversion (UC) luminescence (UCL) properties are, however, strongly influenced by particle size, surface chemistry, and microenvironment. In addition, the multiphotonic absorption processes responsible for UCL render UCL excitation power density (..) dependent. This makes quantitative UCL measurements as well as the determination of UC quantum yields (.UC) very challenging. The rational design of brighter UCNPs particle architectures and the interest in identifying optimum particle architectures for FRET-based sensing and imaging schemes, which often rely on core-only UCNPs to minimize donor-acceptor distances, encouraged us to assess the influence of particle size and P on UCL. Here, we present the photophysical properties of a series of hexagonal NaYF4 UCNPs with sizes from 10 to 43 nm with different surface ligands dispersed in organic solvents and water studied by steady state and time-resolved fluorometry as well as quantitatively by integrating sphere spectrometry with P varied over about three orders of magnitude. Our results underline the need for really quantitative luminescence studies for mechanistic insights and the potential of high P to compensate for UCL quenching due to high energy phonons and surface effects. T2 - 15th Conference on Methods and Applications in Fluorescence CY - Bruges, Belgium DA - 10.09.2017 KW - Upconversion KW - Nanoparticle KW - Absolute fluorometry KW - Integrating sphere spectroscopy KW - NIR KW - IR KW - Fluorescence KW - Surface chemistry KW - Deactivation pathways KW - Photophysics KW - Quantum yield PY - 2017 AN - OPUS4-43181 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Scholtz, Lena T1 - Luminescent, Semiconductor Nanoparticle-loaded Polymer Microbeads - Comparing Particle Architectures N2 - The synthesis of luminescent polymer microparticles stained with different, including non-spherical, semiconductor nanoparticles (NPs) was developed and optimized while ensuring a good preservation of the particle photoluminescence. The aplicability of the different semiconductor NPs was determined to depend on their surface chemistry and shape. Thus, a first correlation of semiconductor NP architecture and applicability could be deduced, which has not been reported before. T2 - 821. WE-Heraeus-Seminar CY - Bad Honnef, Germany DA - 12.11.2024 KW - Nanoparticle KW - Surface chemistry KW - Synthesis KW - Fluorescence KW - Luminescence PY - 2024 AN - OPUS4-61732 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Suitable geometries for the measurement of photoluminescence quantum yields of luminescent and scattering samples – The DIN TNS project N2 - The characterization of the optical properties of photoluminescent systems, that scatter, like dispersions of nanoparticles with sizes exceeding about 25 nm or solid nanophosphors is of increasing importance for many applications in the life and material sciences. Examples present nanoscale optical reporters and dye-doped microparticles for bioimaging, fluorescence assays or DNA sequencing as well as nanocrystalline emitters like semiconductor quantum dots and rods or lanthanide-based nanophosphors embedded into solid matrices for solid state lighting, display technologies, or barcoding/security applications. The assessment and comparison of material performance as well as the development of rational design strategies for improved systems require spectroscopic tools, which enable the determination of the signal-relevant optical properties like photoluminescence quantum yields and brightness values. This encouraged us to built up an integrating sphere setup enabling absolute measurements of photoluminescence spectra and quantum yields of transparent and scattering photoluminescent dispersions and solid samples in different measurement geometries, i.e., direct and indirect illumination and the combination of both geometries and perform first measurements with selected emitters. Here, the design of this setup is presented and first recommendations concerning suitable measurement geometries are given. T2 - DKE-Sitzung CY - Frankfurt am Main, Germany DA - 31.08.2016 KW - Nanoparticle KW - Integrating sphere KW - Fluorescence KW - Quantum yield KW - Method KW - Standardization KW - Calibration KW - Reference material PY - 2016 AN - OPUS4-38643 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Simple methods, validation concepts, and reference materials for the characterization of functional nanomaterials and microparticles N2 - The surface chemistry / functionalization of nanomaterials and microparticles largely controls the stability of these materials as well as their solubility and subsequent biofunctionalization and their interactions with biological systems. Moreover, in the case of some nanomaterials like semiconductor quantum dots or lanthanide-based upconversion nanocrystals, the ligand shell strongly affects their optical properties, e.g., via passivation of surface states and traps that favor luminescence quenching or the protection of surface atoms from quenching water molecules. This renders analytical methods for the quantification of surface groups like functionalities very important. Targets of broad interest are here amino, carboxyl, alkine and maleimide groups used for common bioconjugation reactions and typical ligands like thiols and polyethylene glycol (PEG) molecules of varying length, used for the tuning of material hydrophilicity and biocompatibility, minimization of unspecific interactions, prevention of biofouling, and enhancement of blood circulation times as well as surface-bound biomolecules like streptavidin or other biomolecules relevant e.g., for diagnostic assays. Here, we focus on simple optical methods relying on standard laboratory instrumentation, validated by method comparison and/or mass balances and present examples for their use for the characterization of different types of nanomaterials and microparticles. T2 - Innovationsforum Senftenberg CY - Senftenberg, Germany DA - 01.06.2016 KW - Surface chemistry KW - Functional group analysis KW - Thiol assay KW - Fluorescence KW - Nanomaterial KW - Nanoparticle KW - PEG KW - Ligand KW - Semiconductor quantum dot KW - Quantum yield KW - Quantification KW - Method validation KW - Integrating sphere spectroscopy KW - Fluorescence standard PY - 2016 N1 - Geburtsname von Nirmalananthan-Budau, Nithiya: Nirmalananthan, N. - Birth name of Nirmalananthan-Budau, Nithiya: Nirmalananthan, N. AN - OPUS4-37111 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Semiconductor nanocrystals with VIS and NIR/IR emission - spectroscopy properties and surface chemistry N2 - Semiconductor nanocrystals with a spherical (QDs) core and a spherical or a rod-shaped Shell, u.a., so-called Quantum dot-Quantum rods (QDQRs) are increasingly used as fluorescent Reporters or optically active components in the life and material science, e.g., in solid state lightening including Plasma Displays. (1,2) Morever, there is an increasing interest in materials with emission >800 nm for bioanalysis, medical diagnostics, and safety barcodes. Prerequisites for the mechanistic understanding of nonradiativ decay channels needed for the rational design of improved nanomaterials and the comparison of material Performance are reliable fluorescence measurements and validated methods for the assessment of their surface chemistry. (3,4) The latter is of particular importance for nanocrystalline Emitters, where surface states and the accessibility of emissive states by quenchers largely control photoluminescence properties. (5) Here, we present results from systematic spectroscopic studies including absolutely measured photolumunescence Quantum yields of different vissible and NIR emisisve QD and QDQRs Systems of varying particle architecture size and surface chemistries in Dispersion and embedded in salt crystals. (6,7) T2 - MCare 2017 CY - Jeju, South Korea DA - 20.02.2017 KW - Semiconductor quantum dot KW - Nanoparticle KW - Absolute fluorometry KW - Integrating sphere spectroscopy KW - NIR KW - IR KW - Fluorescence KW - Surface chemistry KW - Photophysics KW - Quantum yield KW - Single particle PY - 2017 AN - OPUS4-43133 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Quantitative Characterization of Functional Nanomaterials with vis/NIR Emission N2 - The rational design of functional nanomaterials for optical applications in the material and life sciences requires optical-spectroscopic methods for the quantitative characterization of their signal-relevant optical properties. Additionally, methods for the simple and quantitative analysis of the surface chemistry are desired as the chemical nature and number of the surface groups and ligands can affect the optical features and controls the interaction of these nanomaterials with their environment. Here, we present quantitative photoluminescenvce studies of different types of vis/NIR-emissive nanomaterials like semiconductor quantum dots and upconversion nanocrystals will be presented and their relevance for the mechanistic understanding of nonradiative decay channels and the rational design of new nanomaterials will be underpinned. In this respect, also validation concepts for such measurements and absolute fluorometry will be introduced. In addition, the potential of optical spectroscopy for surface group and ligand analysis surface chemistry will be demonstrated exemplarily for semiconductor quantum dots T2 - AK Prof. Voss CY - Uni Brunswick, Germany DA - 03.08.2017 KW - Semiconductor KW - Upconversion KW - Nanoparticle KW - Fluorescence KW - Surface group analysis KW - NIR KW - Absolute fluoreometry KW - Integrating sphare spectroscopy KW - Optical probe KW - Assay KW - Thiol ligand PY - 2017 N1 - Geburtsname von Nirmalananthan-Budau, Nithiya: Nirmalananthan, N. - Birth name of Nirmalananthan-Budau, Nithiya: Nirmalananthan, N. AN - OPUS4-41366 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Photoluminescence quantum yields of molecular & nanoscale luminophores in the UV/VIS/NIR/SWIR in dispersion and in the solid state N2 - Photophysical and mechanistic studies, the comparison of different emitter classes, and the rational design of the next generation of molecular and nanoscale reporters require quantitative photoluminescence measurements and the reliable determination of the key performance parameter photoluminescence quantum yield (QY), i.e., the number of emitted per absorbed photons. This is of special importance for all photoluminescence applications in the life and material sciences in the UV/vis/NIR/SWIR. T2 - MAF 2024 Conference CY - Valencia, Spain DA - 08.09.2024 KW - Nanoparticle KW - Nano KW - Luminescence KW - Quality assurance KW - Synthesis KW - Standardization KW - Reference material KW - Quantum yield KW - Fluorescence KW - Reference data KW - Integrating sphere spectroscopy KW - ILC KW - Converter material PY - 2024 AN - OPUS4-61072 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Challenges and examples for quantitative fluorescence measurements > 800 nm with semiconductor and lanthanide-doped nanocrystals N2 - There is an increasing interest in molecular and nanoscale with emission > 800 nm and recently also > 1000 nm for bioanalysis, medical diagnostics, bioimaging, 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 lanthanide-based upconversion and downconversion nanocrystals, where surface states and the accessibility of emissive states by quenchers largely control accomplishable photoluminescence 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 and 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 density-dependent measurements of emission spectra and photoluminescence 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 including the upconversion and downconversion emission of differently sized and surface functionalized lanthanide-doped nanoparticles and photoluminescence quenching effects are quantified. T2 - SHIFT 2017 CY - Teneriffa, Spain DA - 13.11.2017 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 PY - 2017 AN - OPUS4-43203 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Spectroscopic characterization of semiconductor and lanthanide-based nanocrystals with vis and NIR emission N2 - The increasing interest in molecular and nanoscale emitters with photoluminescence > 800 nm and recently also > 1000 nm for bioanalysis, medical diagnostics, bioimaging, and safety Barcodes requires quantitative spectroscopic studies, which are, however still challenging in this long wavelength region. This is of special relevance for nanocrystalline emitters like semiconductor quantum dots and rods as well as lanthanide-based upconversion and downconversion nanocrystals, where surface states and the accessibility of emissive states by quenchers largely control accomplishable photoluminescence quantum yields and hence, signal sizes and detection sensitivities from the reporter side. Moreover, nonlinear emitters like lanthanide-based upconversion nanocrystals require also power density-dependent studies of their luminescence spectra, quantum yields, and decay kinetics. Here, we present suitable absolute methods and underline the impact of such measurements on a profound mechanistic understanding of the nonradiative deactivation pathways in semiconductor and upconversion nanocrystals of different chemical composition and particle architecture. T2 - PCNSPA 2018 - Photonic Colloidal Nanostructures: Synthesis, Properties, and Applications CY - St. Petersburg, Russia DA - 04.06.2018 KW - Semiconductor KW - Nanoparticle KW - Quantum dot KW - Absolute fluorometry KW - Integrating sphere spectroscopy KW - NIR KW - IR KW - Fluorescence KW - Surface chemistry KW - Deactivation pathways KW - Photophysics KW - Modeling PY - 2018 AN - OPUS4-45796 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - The European Upconversion Network: From the Design of Photon-upconverting Nanomaterials to (Biomedical) Applications (CM1403) WG1 Materials Research & Photophysical Characterization N2 - Lanthanide-doped photon-upconversion nanoparticles (UCNPs) have been in the focus of many research activities in the material and life sciences over the last 15 years because of their potential to convert light between different spectral regions and their unique photophysical properties. In order to fully exploit the application potential of these fascinating nanomaterials, a number of challenges has to be overcome such as the low brightness particularly of small UCNPs and the reliable quantification of the excitation power density (P)-dependent upconversion luminescence (UCL). Here, the need and requirements on the characterization of the optical properties of UCNPs are discussed with special focus on the reliabiliy and comparability of relative and quantitative luminescence measurements and prerequisites for their standardization. T2 - COST Treffen CY - Aveiro, Portugal DA - 26.06.2017 KW - Upconversion KW - Nanoparticle KW - Fluorescence KW - NIR KW - Absolute fluorometry KW - Integrating sphere spectroscopy KW - Reference maerial KW - Standardization KW - Quantum yield PY - 2017 AN - OPUS4-41367 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute T1 - Effect of particle architecture, dopant concentration, size, and excitation power density on the luminescence efficiency of upconversion nanocrystals N2 - Lanthanide-based upconversion nanoparticles (UCNPs) offer new strategies for luminescence-based sensing and imaging. One of the best studied materials are hexagonal ß-NaYF4 UCNPs doped with 20% Yb3+ and 2% Er3+, which efficiently convert 976 nm light to photons emitted at 540 nm, 655 nm, and 845 nm, respectively, reveal Long luminescence lifetimes (> 100 µs), and are very photostable and chemically inters.[1,2] The properties of their upconversion (UC) luminescence (UCL) are, however, strongly influenced by particle size, concentration and spatial arrangement of dopant Ions, surface chemistry, and microenvironment.[3,4] In addition, the multiphotonic absorption processes responsible for UCL render UCL dependent on excitation power density (P). The rational design of brighter UCNPs particle architectures encouraged us to assess systematically the influence of these parameters on UCL for differently doped UCNPs relying on the commonly used ß-NaYf4 matrix using steady state and time resolved fluorometry as well as integrating sphere spectroscopy for P varied over almost three orders of magnitude. This includes comprehensive studies of the influence of size and shell, Yb3+ and Er3+ dopand concentrations, and energy Transfer processes from UCNPs to surface-bound organic dyes or vice versa [5]. Our results underline the need for really quantitative luminescence studies for mechanistic insights, the potential of high p to compensate for UCL surface quenching, and the matrix- and P-dependence of the optimum dopand concentration. T2 - BIOSPIE 2018 CY - San Francisco, USA DA - 27.01.2018 KW - Upconversion KW - Nanoparticle KW - Absolute fluorometry KW - Integrating sphere spectroscopy KW - NIR KW - IR KW - Fluorescence KW - Surface chemistry KW - Deactivation pathways KW - Modeling KW - Size PY - 2018 AN - OPUS4-43939 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -