Ingenieurwissenschaften und zugeordnete Tätigkeiten
Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (124)
- Vortrag (62)
- Beitrag zu einem Tagungsband (5)
- Posterpräsentation (3)
- Sonstiges (2)
- Buchkapitel (1)
- Corrigendum (1)
Schlagworte
- Quantum yield (98)
- Fluorescence (89)
- Nano (55)
- NIR (54)
- Lifetime (53)
- Dye (49)
- Nanoparticle (47)
- Photophysics (45)
- Quality assurance (43)
- Sensor (41)
- Lanthanide (37)
- Photoluminescence (36)
- Upconversion (35)
- Particle (34)
- Integrating sphere spectroscopy (31)
- Surface chemistry (30)
- Method (27)
- Nanomaterial (26)
- Mechanism (21)
- IR (19)
- SWIR (19)
- Quantification (18)
- Synthesis (18)
- Upconversion nanoparticle (18)
- Reference material (17)
- Energy transfer (16)
- Brightness (14)
- Luminescence (13)
- Quantum dot (13)
- Semiconductor quantum dot (13)
- Absolute fluorometry (12)
- Calibration (12)
- Quantitative spectroscopy (12)
- Single particle (11)
- Imaging (10)
- Optical spectroscopy (10)
- Size (10)
- Aggregation (9)
- Ligand (9)
- Multiplexing (9)
- Standard (9)
- Uncertainty (9)
- Assay (8)
- Fluorescence standard (8)
- Nanocrystal (8)
- Optical probe (8)
- Polymer (8)
- Semiconductor (8)
- Surface analysis (7)
- Temperature (7)
- Absolute fluorescence quantum yield (6)
- Application (6)
- Coating (6)
- Crystal (6)
- Deactivation pathways (6)
- Excitation power density (6)
- Flourescence (6)
- Microscopy (6)
- Nanoparticles (6)
- Optical assay (6)
- Quantum dots (6)
- Surface group analysis (6)
- Bead (5)
- Cell (5)
- Life sciences (5)
- Measurement uncertainty (5)
- Modeling (5)
- Signal enhancement (5)
- Silica (5)
- Single particle spectroscopy (5)
- Stability (5)
- Switch (5)
- Upconverting nanoparticles (5)
- BODIPY (4)
- Electrochemistry (4)
- Environment (4)
- FRET (4)
- Fluorescence decay kinetics (4)
- Instrument calibration (4)
- PDT (4)
- Probe (4)
- Rare earth nanoparticles (4)
- SAXS (4)
- Standardization (4)
- Traceability (4)
- Upconversion nanocrystal (4)
- pH (4)
- AIE (3)
- AIS (3)
- Absolute flourometry (3)
- Active fibers (3)
- Aggregation-induced emission (3)
- Aging (3)
- Antibody (3)
- Barcoding (3)
- Bioimaging (3)
- Certification (3)
- Cleavable probe (3)
- Conductometry (3)
- Cr(III) (3)
- Encoding (3)
- Enhancement (3)
- Flow cytometry (3)
- Fluorescence quantum yield (3)
- Fluoride (3)
- ICP-OES (3)
- Interlaboratory comparison (3)
- Label (3)
- Linearity (3)
- Method development (3)
- Method validation (3)
- Modelling (3)
- NMR (3)
- Nano particle (3)
- Nanomaterials (3)
- PEG (3)
- Polarity (3)
- Power density dependence (3)
- Reference data (3)
- Reference product (3)
- Reporter (3)
- Sensitization (3)
- Sensors (3)
- Shell (3)
- Solid state emission (3)
- Surface (3)
- TEM (3)
- XPS (3)
- Yb(III) complex (3)
- Absolute fluoreometry (2)
- Absolute fluorescence (2)
- Aggregation induced emission (2)
- Analytics (2)
- Bead-based assay (2)
- Cancer (2)
- Cell studies (2)
- Characterization (2)
- Comparison (2)
- Conjugate (2)
- Contrast agent (2)
- Copolymer (2)
- Cyanine (2)
- DNA (2)
- Electron microscopy (2)
- Enhancement strategy (2)
- Excitation (2)
- FLIM (2)
- Fluorescent glasses (2)
- Functional group analysis (2)
- Gold (2)
- Ho(III) (2)
- Hydration (2)
- Integrating sphere (2)
- Iron oxide (2)
- Liftetime (2)
- Ligand analysis (2)
- Limit of detection (2)
- Llifetime (2)
- Mass spectrometry (2)
- Metal cluster (2)
- Method comparison (2)
- Microfluidics (2)
- Microparticle (2)
- Monitoring (2)
- Monomer (2)
- Nanosensor (2)
- Nile Red (2)
- Particle architecture (2)
- Performance validation (2)
- Phosphor (2)
- Photonic crystal (2)
- Polymer particle (2)
- Power density (2)
- Protein (2)
- Quantum Yield (2)
- Quantum rod (2)
- Quantum yields (2)
- Quenching (2)
- Reliability (2)
- Safety (2)
- Semiconducor nanocrystals (2)
- Semiconductor nanocrystal (2)
- Semiconductor nanocrystals (2)
- Sensing (2)
- Sensor molecules (2)
- Simulation (2)
- Singlet oxygen (2)
- Spectroscopy (2)
- Surface group quantification (2)
- Surface modification (2)
- Sythesis (2)
- Ternary quantum dots (2)
- Theory (2)
- Thiol ligand (2)
- Triplet-triplet annihilation (2)
- Upconverion (2)
- Upconversion nanoparticles (2)
- Yb(III) (2)
- fluorescence (2)
- pH probe (2)
- 150th anniversary (1)
- A4F (1)
- ABC (1)
- AIS QD (1)
- Ab initio calculation (1)
- Absolute (1)
- Absolute flourescence (1)
- Absolute measurement (1)
- Absorption (1)
- Activatable probe (1)
- Adsorption (1)
- Advanced Materials (1)
- Advanced material (1)
- Advanced materials (1)
- Advanced nanomaterials (1)
- Aldrithiol (1)
- Amplification (1)
- Analysis (1)
- Analytical sciences (1)
- Analytical services (1)
- Artificial weathering (1)
- Automated synthesis (1)
- Automation (1)
- Aza-BODIPY (1)
- BAM (1)
- Bacteria (1)
- Bioconjugate (1)
- Biofilm (1)
- Biomarker (1)
- Biophotonics (1)
- Biosensing (1)
- Boron Neutron Capture Therapy (BNCT) (1)
- Brithtness (1)
- Bundesanstalt für Materialforschung und -prüfung (1)
- C-dot (1)
- COSMO (1)
- CRP (1)
- Calibrated fluorescence measurements (1)
- Capillary electrophoresis (1)
- Carbon (1)
- Carbon dot (1)
- Carboxyl group (1)
- Catalogue of services (1)
- Catch and release assay (1)
- CdSe (1)
- Cellular uptake (1)
- Cement (1)
- Cement hydration (1)
- Certified reference material (1)
- Charge transfer (1)
- Chiral (1)
- Circular dichroism (1)
- Cleavable linker (1)
- Cleavable probes (1)
- Cluster (1)
- Collection (1)
- Color (1)
- Color tuning (1)
- Complex (1)
- Conductor-like screening model (1)
- Converter marterial (1)
- Converter material (1)
- Core shell structure (1)
- Core-shell architecture (1)
- Core-shell nanoparticles (1)
- Core/shell particle (1)
- Corrosion (1)
- Cr complex (1)
- Critical micelle concentration (CMC) (1)
- Crosslinking (1)
- Cubical shape (1)
- Cysteine (1)
- DNA origami (1)
- DPA (1)
- Decay kinetics (1)
- Decay time (1)
- Degradation (1)
- Density functional theory (DFT) (1)
- Design of experiment (1)
- Dipole moment (1)
- Dodecanethiol (1)
- Dual emission (1)
- Dual sensing (1)
- Dye labeling (1)
- Dyes (1)
- EC4SafeNano (1)
- Editorial (1)
- Electrochemical titration (1)
- Ellman (1)
- Emission enhancement (1)
- Emission standards (1)
- Er(III) (1)
- European Centre (1)
- Excitation energy dependence (1)
- Excitation power density dependence (1)
- Excitation spectra (1)
- Exciton (1)
- Field sensor (1)
- Film (1)
- Fluoranthene (1)
- Fluorescence intensity ratio (1)
- Fluorescence lifetime (1)
- Fluorescence microscopy (1)
- Fluorescence probe (1)
- Fluorescence spectroscopy (1)
- Fluorescent label (1)
- Fluorescent probe (1)
- Fluorometry (1)
- Fluorophore (1)
- Fully aromatic frameworks (1)
- Functional group quantification (1)
- Funtional Groups (1)
- Giant carbon dot (1)
- Glass (1)
- Gold nanocluster (1)
- Gold nanoclusters (1)
- Green synthesis (1)
- Heory (1)
- Homogeneity (1)
- IR fluorescence (1)
- IR spectroscopy (1)
- Immunoassay (1)
- In vivo imaging (1)
- Infrastructure (1)
- Instrument qualification (1)
- Integrating sphare spectroscopy (1)
- Integrating sphere spectroscopy, (1)
- Interlaboratory (1)
- Interlabority comparison (1)
- Jahrestag (1)
- K+ doped (1)
- LT-FCM (1)
- Lanthanide-doped nayf-4 (1)
- Lanthanides (1)
- Legionella (1)
- LiYF4 (1)
- Lifetime analysis (1)
- Ligand exchange (1)
- Ligand quantification (1)
- Ligands (1)
- Light harvesting (1)
- Luorescence (1)
- MIC (1)
- MOF (1)
- MS (1)
- Magic-sized cluster (1)
- Magnetic (1)
- Material sciences (1)
- Materials (1)
- Medicine (1)
- Merocyanine (1)
- Metal (1)
- Metasurface (1)
- Method evaluation (1)
- Methods (1)
- Methos comparision (1)
- Micelle (1)
- Microbiology (1)
- Microorganism (1)
- Miniaturization (1)
- Moisture (1)
- Molecular beacon (1)
- Molecular diagnostics (1)
- NIR dyes (1)
- NIR-II Imaging (1)
- NIR-II fluorescence (1)
- NIRII (1)
- NMR spectroscopy (1)
- Nanaoparticle (1)
- Nano CRM (1)
- Nano-safety (1)
- Nanocrystals (1)
- Nanomaterial design (1)
- Nanopartikel (1)
- Nanophosphor (1)
- Nanoplatelet (1)
- Nanosafety (Safe-by-design) (1)
- Nanoscale luminescent reporters (1)
- Nanotoxicity (1)
- Nd excitation (1)
- Near infrared (1)
- Near-infrared light (1)
- Nicht lineare Prozesse (1)
- Nnano particle (1)
- Non lienear processes (1)
- Non-thermally coupled levels (1)
- Nonlinear (1)
- One-pot synthesis (1)
- Optical Spectroscopy (1)
- Optical detection (1)
- Optical probes (1)
- Optical spectroscopie (1)
- Optical temperature sensing (1)
- Organic–inorganic nanostructures (1)
- Origami (1)
- Oxygen (1)
- Oxygen sensitive (1)
- PEG ligands (1)
- PET (1)
- PH (1)
- Particle Synthesis (1)
- Particle sensors (1)
- Particle synthesis (1)
- Particle, imaging (1)
- Pd(II) (1)
- Perovskite (1)
- Perovskites (1)
- Ph (1)
- Phosphinine (1)
- Photo physics (1)
- Photocatalytic activity (1)
- Photoluminescence quantum yield (1)
- Photophysic (1)
- Photosensitizer (1)
- Pitfalls (1)
- Pollutant (1)
- Poloxazolines (1)
- Polycarboxylate ether (1)
- Polymer particles (1)
- Polymers (1)
- Polyurethane (1)
- Porphyrin (1)
- Pphotophysics (1)
- Production (1)
- Protein corona (1)
- Pt(II) (1)
- QNMR (1)
- Qantum yield (1)
- Quality assurcance (1)
- Quantenausbeute (1)
- Quantitative Analysis (1)
- Quantum chemistry (1)
- Quantum do (1)
- Quantum yield standard (1)
- Quinones (1)
- Ratiometric (1)
- Ratiometric sensing (1)
- Redox (1)
- Reference maerial (1)
- Reference materials (1)
- Reference nanoparticles (1)
- Reflection spectroscopy (1)
- Release (1)
- Renewable energy (1)
- Reproducibility (1)
- Reverse microemulsion (1)
- Rheology (1)
- Risk assessment (1)
- Rreference material (1)
- SWIR photoluminescence (1)
- Safe-by-Design (1)
- Scattering (1)
- Self-assembly (1)
- Semiconductur (1)
- Shape (1)
- Signal amplification (1)
- Silanization (1)
- Silica and Polystyrene Particles (1)
- Silica and polystyrene nanoparticles (1)
- Silica coating (1)
- Single emitter (1)
- Single enhancement (1)
- Single molecule (1)
- Small-angle scattering (1)
- Solar cell (1)
- Solar concentrator (1)
- Solar energy (1)
- Solid (1)
- Special issue (1)
- Spectral correction (1)
- Spectroscopy / Instrumentation (1)
- Spectroscopy / Theory (1)
- SrF2 (1)
- Standards (1)
- Stepwise growth (1)
- Surface Chemistry (1)
- Surface coating (1)
- Surface group (1)
- Surface groups (1)
- Surface ligand (1)
- Suzuki-Miyaura coupling (1)
- Syntheseis (1)
- Tag (1)
- Therapy (1)
- Thermal coupling energy level (1)
- Thermally coupled levels (1)
- Thick shells (1)
- Thickness (1)
- Thiol (1)
- Thiol assay (1)
- Thiols (1)
- Time-gated emission (1)
- Time-resolved flow cytometry (1)
- Toxicity (1)
- Triggered (1)
- UV Vis (1)
- UV/Vis and emission spectroscopy (1)
- Upconversion luminescence (1)
- Upconversion nanocrystals (1)
- Upconverstion (1)
- VAMAS (1)
- X-ray (1)
- X-ray diffractometry (XRD) (1)
- X-ray spectroscopy (1)
- Zinc(II) complexes (1)
- ZnSe (1)
- antibody (1)
- bacteria (1)
- bacteria detection (1)
- biotechnological (1)
- calibration (1)
- carrier system (1)
- dye (1)
- flow cytometry (1)
- fluorescence microscopy (1)
- fluorescence standards (1)
- fluorescent reporter (1)
- immunoseparation (1)
- laponite (1)
- lifetime (1)
- magnetic nanoparticle (1)
- method (1)
- nanoclay (1)
- nanocrystals (1)
- nanoparticle (1)
- organic dye (1)
- organic dyes (1)
- particle (1)
- pharmaceutical (1)
- photoluminescence (1)
- photoluminescence quantum yield (1)
- photophysics (1)
- photovoltaics (1)
- quality assurcance (1)
- quantum dot (1)
- quantum yield (1)
- screening (1)
- screening tes (1)
- solar cell (1)
- surface group analysis (1)
- synthesis (1)
Organisationseinheit der BAM
- 1 Analytische Chemie; Referenzmaterialien (151)
- 1.2 Biophotonik (151)
- 6 Materialchemie (14)
- 6.1 Oberflächen- und Dünnschichtanalyse (11)
- 6.3 Strukturanalytik (4)
- 1.0 Abteilungsleitung und andere (3)
- 1.7 Organische Spuren- und Lebensmittelanalytik (3)
- 5 Werkstofftechnik (3)
- 7 Bauwerkssicherheit (3)
- 4 Material und Umwelt (2)
Paper des Monats
- ja (5)
Eingeladener Vortrag
- nein (62)
Luminophore stained micro- and nanobeads made from organic polymers like polystyrene (PS) are broadly used in the life and material sciences as luminescent reporters, for bead-based assays, sensor arrays, printable barcodes, security inks, and the calibration of fluorescence microscopes and flow cytometers. Initially mostly prepared with organic dyes, meanwhile luminescent core/shell nanoparticles (NPs) like spherical semiconductor quantum dots (QDs) are increasingly employed for bead encoding. This is related to their narrower emission spectra, tuneability of emission color, broad wavelength excitability, and better photostability. However, correlations between particle architecture, morphology, and photoluminescence (PL) of the luminescent nanocrystals used for encoding and the optical properties of the NP-stained beads have been rarely explored. This encouraged us to perform a screening study on the incorporation of different types of luminescent core/shell semiconductor nanocrystals into polymer microparticles (PMPs) by a radical-induced polymerization reaction. Nanocrystals explored include CdSe/CdS QDs of varying CdS shell thickness, a CdSe/ZnS core/shell QD, CdSe/CdS quantum rods (QRs), and CdSe/CdS nanoplatelets (NPLs).
Thereby, we focused on the applicability of these NPs for the polymerization synthesis approach used and quantified the preservation of the initial NP luminescence. The spectroscopic characterization of the resulting PMPs revealed the successful staining of the PMPs with luminescent CdSe/CdS QDs and CdSe/CdS NPLs. In contrast, usage of CdSe/CdS QRs and CdSe QDs with a ZnS shell did not yield luminescent PMPs. The results of this study provide new insights into structure–property relationships between NP stained PMPs and the initial luminescent NPs applied for staining and underline the importance of such studies for the performance optimization of NP-stained beads.
Core–shell nanoparticles have attracted much attention in recent years due to their unique properties and their increasing importance in many technological and consumer products. However, the chemistry of nanoparticles is still rarely investigated in comparison to their size and morphology. In this review, the possibilities, limits, and challenges of X-ray photoelectron spectroscopy (XPS) for obtaining more insights into the composition, thickness, and homogeneity of nanoparticle coatings are discussed with four examples: CdSe/CdS quantum dots with a thick coating and a small core; NaYF4-based upconverting nanoparticles with a large Yb-doped core and a thin Er-doped coating; and two types of polymer nanoparticles with a poly(tetrafluoroethylene) core with either a poly(methyl methacrylate) or polystyrene coating. Different approaches for calculating the thickness of the coating are presented, like a simple numerical modelling or a more complex simulation of the photoelectron peaks. Additionally, modelling of the XPS background for the investigation of coating is discussed. Furthermore, the new possibilities to measure with varying excitation energies or with hard-energy X-ray sources (hard-energy X-ray photoelectron spectroscopy) are described. A discussion about the sources of uncertainty for the determination of the thickness of the coating completes this review.
Aroyl-S,N-ketene acetal-based bichromophores can be readily synthesized in a consecutive three-component synthesis in good to excellent yields by condensation of aroyl chlorides and an N-(p-bromobenzyl) 2-methyl benzothiazolium salt followed by a Suzuki coupling, yielding a library of 31 bichromophoric fluorophores with substitution patterntunable emission properties. Varying both chromophores enables different communication pathways between the chromophores, exploiting aggregation-induced emission (AIE) and energy transfer (ET) properties, and thus, furnishing aggregation-based fluorescence switches. Possible applications range from fluorometric analysis of alcoholic beverages to pH sensors.
Controlling thickness and tightness of surface passivation shells is crucial for many applications of core–shell nanoparticles (NP). Usually, to determine shell thickness, core and core/shell particle are measured individually requiring the availability of both nanoobjects. This is often not fulfilled for functional nanomaterials such as many photoluminescent semiconductor quantum dots (QD) used for bioimaging, solid state lighting, and display technologies as the core does not show the applicationrelevant functionality like a high photoluminescence (PL) quantum yield, calling for a whole nanoobject approach. By combining high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS), a novel whole nanoobject approach is developed representatively for an ultrabright oleic acid-stabilized, thick shell CdSe/CdS QD with a PL quantum yield close to unity. The size of this spectroscopically assessed QD, is in the range of the information depth of usual laboratory XPS. Information on particle size and monodispersity were validated with dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) and compared to data derived from optical measurements. In addition to demonstrating the potential of this novel whole nanoobject approach for determining architectures of small nanoparticles, the presented results also highlight challenges faced by different sizing and structural analysis methods and method-inherent uncertainties.
Wepresent here a systematic analysis of the influence of Tm3+ Doping concentrations (xTm) on the excitation power (P)-dependent upconversion luminescence and -performance of hexagonal-Phase NaYF4: 20% Yb3+, xTm%Tm3+ upconversion nanoparticles (UCNPs) for xTm of 0.2, 0.5, 0.8, 1.2, and 2.0, respectively. Our results reveal the influence of these differentTm3+ doping concentrations with respect to optimized upconversion quantum yield (ΦUC) values of the variousTm3+ upconversion emission bands, with the highestΦUC values of theTm3+ emission bands above 700 nmresulting for different xTm values as theTm3+ emission bands below 700 nm. This underlines the potential ofTm3+ dopant concentration for colour tuning. Special emphasis was dedicated to the spectroscopic parameters that can be linked to the (de)population pathways of the variousTm3+ energy levels, like the P- and xTm-dependent slope factors and the intensity ratios of selected emission bands. The evaluation of all parameters indicates that not only energy transfer upconversion-, but also crossrelaxation processes between neighbouringTm3+ ions play a vital role in the (de)population of the excited energy levels of Yb3+, Tm3+ codoped nanocrystals.
A concept for the growth of silica shells with a thickness of 5–250 nm onto oleate-coated NaYF4:Yb3+/Er3+ upconversion nanoparticles (UCNP) is presented. The concept enables the precise adjustment of shell thicknesses for the preparation of thick-shelled nanoparticles for applications in plasmonics and sensing. First, an initial 5–11 nm thick shell is grown onto the UCNPs in a reverse microemulsion. This is followed by a stepwise growth of these particles without a purification step, where in each step equal volumes of tetraethyl orthosilicate and ammonia water are added, while the volumes of cyclohexane and the surfactant Igepal® CO-520 are increased so that the ammonia water and surfactant concentrations remain constant. Hence, the number of micelles stays constant, and their size is increased to accommodate the growing core–shell particles. Consequently, the formation of core-free silica particles is suppressed. When the negative zeta potential of the particles, which continuously decreased during the stepwise growth, falls below −40 mV, the particles can be dispersed in an ammoniacal ethanol solution and grown further by the continuous addition of tetraethyl orthosilicate to a diameter larger than 500 nm. Due to the high colloidal stability, a coalescence of the particles can be suppressed, and single-core particles are obtained. This strategy can be easily transferred to other nanomaterials for the design of plasmonic nanoconstructs and sensor systems.
Dye-stained micrometer-sized polymer beads are important tools in the life sciences with applications in biomedical, biochemical, and clinical research. Here, bead-based assays are increasingly used, for example, in DNA sequencing and the detection of autoimmune diseases or pathogenic microorganisms. Moreover, stained beads are employed as calibration tools for fluorescence microscopy and flow cytometry methods with increasing complexity. To address the requirements concerning the relevant fluorescence features, the spectroscopic properties of representative polymer beads with diameters ranging from about 1 to 10 μm stained with varying concentrations of rhodamine 6G were systematically assessed. The observed dependence of the spectral properties, fluorescence decay kinetics, and fluorescence quantum yields on bead size and dye loading concentration is attributed to different fluorescence characteristics of fluorophores located in the particle core and near-surface dye molecules. Supported by the fluorescence anisotropy measurements, the origin of the observed alteration of fluorescence features is ascribed to a combination of excitation energy transfer and polarity-related effects that are especially pronounced at the interface of the bead and the surrounding medium. The results of our studies underline the need to carefully control and optimize all Parameters that can affect the fluorescence properties of the dye-stained beads.
Surface functionalization of 2D- and 3D-supports and nanomaterials are nowadays at the core of many applications of functional materials in the life and material sciences. Examples range from membranes and microarrays over bead-based assays, immunoseparation, and next generation sequencing to nanometer-sized optical reporters, nanosensors, and magnetic and optical contrast agents. Typically performed functionalization procedures include silanization and grafting reactions with reactive monomers to introduce functional groups like amino or carboxylic acid groups and the attachment of ligands like polyethylene glycol (PEG) molecules and biomolecules such as peptides, proteins, and DNA.[1-3]
We present here a versatile concept to quantify the number of bioanalytically relevant functional groups like carboxyl, amino, and aldehyde moieties through the specific binding and subsequent release of small reporter molecules such as fluorescent dyes and non-fluorescent chromophores utilizing cleavable linkers or the formation of cleavable bonds as a reversible covalent labeling strategy. This is representatively demonstrated for different types of nano- and microparticles with different labeling densities of carboxyl, amino, and aldehyde groups. This strategy enables to separate the signal-generating molecule from the bead surface, thereby circumventing uncertainties associated with light scattering, binding-induced changes in reporter fluorescence, and fluorescence quenching dye-dye interactions on crowded material surfaces.[1-3] Moreover, the reporters are chosen to be detectable with different analytical methods as prerequisite for straightforward validation via method compari-sons and mass balances. Applications of these assays and multimodal cleavable probes range from a quantitative comparison of bead batches and process control to a qualitative prediction of the coupling efficiencies in bioconjugation reactions.
We report the synthesis and spectroscopic characteristics of two different sets of carbon dots (CDs) formed by hydrothermal reaction between citric acid and polyethylenimine (PEI) or 2,3-diaminopyridine (DAP). Although the formation of amide-based species and the presence of citrazinic acid type derivates assumed to be responsible for a blue emission is confirmed for both CDs by elemental analysis, infrared spectroscopy, and mass spectrometry, a higher abundance of sp2-hybridized nitrogen is observed for DAP-based CDs, which causes a red-shift of the n-π* absorption band relative to the one of PEI-based CDs. These CD Systems possess high photoluminescence quantum yields (QY) of ∼40% and ∼48% at neutral pH, demonstrating a possible tuning of the optical properties by the amine precursor. pH-Dependent spectroscopic studies revealed a drop in QY to < 9% (pH ∼ 1) and < 21% (pH ∼ 12) for both types of CDs under acidic and basic conditions. In contrast, significant differences in the pHdependency of the n-π* transitions are found for both CD types which are ascribed to different (de)protonation sequences of the CD-specific fluorophores and functional groups using Zeta potential analysis.
Enzyme-activatable optical probes are important for future advances in cancer imaging, but may easily suffer from low signal-to-background ratios unless not optimized. To address this shortcoming, numerous mechanisms to modulate the fluorescence signal have been explored.
We report herein newly synthesized probes based on selfimmolative linkers containing chiral J-aggregate-forming dyes.
Signal modulation by formation of chiral J-aggregates is yet unexplored in optical enzyme probe design. The comprehensive characterization of the probes by absorption, CD, fluorescence, and time-resolved fluorescence spectroscopy revealed dye−dye interactions not observed for the free dyes in solution as well as dye−protein interactions with the enzyme. This suggested
that J-aggregate formation is challenging to achieve with current probe design and that interactions of the dyes with the Enzyme may interfere with achieving high signal-to-background ratios. The detailed understanding of the interactions provided herein provides valuable guidelines for the future design of similar probes.
There is an increasing interest in optical reporters like semiconductor quantum dots and upconversion nanocrystals with emission > 800 nm for bioanalysis, medical diagnostics, and safety barcodes. Prerequisites for the comparison of material performance, the mechanistic understanding of nonradiative decay channels, and the rational design of new nanomaterials with improved properties are reliable fluorescence measurements and validated methods for the assessment of their surface chemistry. The latter is of special relevance for nanocrystalline emitters, 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. Here, we present the design of integrating sphere setups for the excitation power density-dependent absolute measurement of emission spectra and photoluminescence quantum yields in the wavelength region of 350 to 1600 nm and results from spectroscopic studies of semiconductor quantum dots and upconversion nanocrystals of different size and surface chemistries in various environments. Subsequently, examples for simple approaches to surface group and ligand analysis are presented.
Characterization and quantification of functional groups and coatings on nanoobjects an overview
(2024)
Characterization of Nanoparticles – Questions to Ask, Functional Nanoparticles (NPs) – Organic, Inorganic, and Hybrid Nanoparticles Nanomaterial Characterization Standardization – Addressing Remaining Gaps Surface FGs Particle Surface Chemistry - Why is it Important? Particle Surface Chemistry - A Key Driver for Performance, Applications, and Safety Aspects Method Development for Quantifying FGs and Ligands on Particle Surfaces FG Quantification – Method Choice & Criteria Relevant for Data Interpretation Quantifying the Amount of Total and Accessible FGs on Aminated Silica Nanoparticles (SiO2-NH2) Comparing the Total and Accessible –NH2 Content on Aminated Silica NPs of Different Size Characterization of Nanoparticles Standardization Standardized Measurements of Surface FGs on Nanoparticles EMP Project SMURFnano EMP Project SMURFnano Work Packages & Goals Certified Reference Materials from BAM
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.
A set of highly fluorescent, pH-responsive boron dipyrromethene dyes covering the pH range of 5-12 is presented for broad range pH measurements in mixed aqueous-organic median and polymer matrices. Readout in the intensity Domain with low cost and miniaturized Instrumentation utilizes reversible protonation induced switching ON of their initially completely quenched flourescence mediated by photoinduced electron Transfer. All dyes, rationally designed to reveal closely matching Absorption and Emission properties, are accessible via facile two-step reactions in Overall yields of up to 20%. By modifying the Substitution pattern of the meso-Aryl substiuent, the pKa values could be fine-tuned from 6 to 11. Integration of these molecules into polymeric films by a simple mixing procedure yielded reversible and longterm stable pH sensors for naked eye detection.
Optical spectroscopic studies of the influence of size, particle architecture, and surface chemistry of different types of photoluminescent nanocrystals with emission in the vis/NIR will be presented including semiconductor quantum dots and lanthanide-based upconversion nanoparticles. This will include the photophysics of these materials assessed with steady state and time-resolved fluorometry on the ensemble and single particle level and concepts for the quantification of surface groups at nanomaterials with optical methods using cleavable probes and catch-and-release assays.
An increasing number of (bio)analytical techniques rely on multiparametric analyses and the measurement of a very small number of emitters. While the former implies encoding or labeling by means of easily distinguishable properties like luminescence color or lifetime in conjunction with high-throughput optical-spectroscopic methods such as flow cytometry, the latter requires methods suitable for the characterization of the optical properties of single emitters. Here, we present the use of fluorescence correlation spectroscopy (FCS) for the relative determination of the key parameter photoluminescence quantum yield [5] and first results from flow cytometry measurements in the time-domain with a custom-designed instrument with luminescence lifetime analysis capability.
Between Aromatic and Quinoid Structure: A Symmetrical UV to Vis/NIR Benzothiadiazole Redox Switch
(2020)
Reversibly switching the light absorption of organic molecules by redox processes is of interest for applications in sensors, light harvesting, smart materials, and medical diagnostics. This work presents a symmetrical benzothiadiazole (BTD) derivative with a high fluorescence quantum yield in solution and in the crystalline state and shows by spectroelectrochemical analysis that reversible switching of UV absorption in the neutral state, to broadband Vis/NIR absorption in the 1st oxidized state, to sharp band Vis absorption in the 2nd oxidized state, is possible.
For the one-electron oxidized species, formation of a delocalized radical is confirmed by electron paramagnetic resonance spectroelectrochemistry. Furthermore, our results reveal an increasing quinoidal distortion upon the 1st and 2nd oxidation, which can be used as the leitmotif for the development of BTD based redox switches.
The quantum yield is a critically important parameter in the development of lanthanide-based upconverting nanoparticles (UCNPs) for use as novel contrast agents in biological imaging and optical reporters in assays. The present work focuses on the influence of the beam Profile in measuring the quantum yield (f) of nonscattering dispersions of nonlinear upconverting probes, by establishing a relation between f and excitation light power density from a rate equation analysis. A resulting 60% correction in the measured f due to the beam profile utilized for excitation underlines the significance of the beam profile in such measurements, and its impact when comparing results from different Setups and groups across the world.
The overall interest in nanotoxicity, triggered by the increasing use of nanomaterials in the material and life sciences, and the synthesis of an ever increasing number of new functional nanoparticles calls for standardized test procedures1,2 and for efficient approaches to screen the potential genotoxicity of these materials. Aiming at the development of fast and easy to use, automated microscopic methods for the determination of the genotoxicity of different types of nanoparticles, we assess the potential of the fluorometric γH2AX assay for this purpose. This assay, which can be run on an automated microscopic detection system, relies on the detection of DNA double strand breaks as a sign for genotoxicity3. Here, we provide first results obtained with broadly used nanomaterials like CdSe/CdS and InP/ZnS quantum dots as well as iron oxide, gold, and polymer particles of different surface chemistry with previously tested colloidal stability and different cell lines like Hep-2 and 8E11 cells, which reveal a dependence of the genotoxicity on the chemical composition as well as the surface chemistry of these nanomaterials. These studies will be also used to establish nanomaterials as positive and negative genotoxicity controls or standards for assay performance validation for users of this fluorometric genotoxicity assay. In the future, after proper validation, this microscopic platform technology will be expanded to other typical toxicity assays.