Ingenieurwissenschaften und zugeordnete Tätigkeiten
Filtern
Erscheinungsjahr
- 2020 (36) (entfernen)
Dokumenttyp
- Zeitschriftenartikel (25)
- Vortrag (9)
- Posterpräsentation (2)
Schlagworte
- Fluorescence (16)
- Quantum yield (14)
- Lifetime (13)
- Dye (11)
- Photoluminescence (10)
- Photophysics (10)
- Sensor (10)
- Nano (9)
- Lanthanide (7)
- Method (7)
- Particle (7)
- Quality assurance (7)
- NIR (6)
- Nanoparticle (6)
- Quantification (6)
- Surface chemistry (6)
- Upconversion (6)
- Crystal (4)
- Measurement uncertainty (4)
- Synthesis (4)
- AIE (3)
- Aggregation (3)
- Aggregation-induced emission (3)
- Electrochemistry (3)
- Electron microscopy (3)
- Enhancement (3)
- Fluorescence standard (3)
- Linearity (3)
- Nano particle (3)
- Nanomaterial (3)
- Nanoparticles (3)
- Polarity (3)
- Reference materials (3)
- Single particle (3)
- Solid state emission (3)
- Upconversion nanoparticle (3)
- Aging (2)
- Assay (2)
- Automatisation (2)
- Bead (2)
- Brightness (2)
- Coating (2)
- Convolutional neural networks (2)
- Cr(III) (2)
- EMPIR 18HLT01 MetVesII (2)
- Extracellular vesicles (EV) (2)
- Flow cytometry (FCM) (2)
- Fluorescent particles (2)
- Fluoride (2)
- ICP-OES (2)
- Image segmentation (2)
- Integrating sphere spectroscopy (2)
- Iron oxide nanoparticles (2)
- Ligand (2)
- Mechanism (2)
- Method development (2)
- Microscopy (2)
- Multiplexing (2)
- SWIR (2)
- Stability (2)
- Switch (2)
- TEM (2)
- XPS (2)
- Yb(III) complex (2)
- A4F (1)
- AIS (1)
- Absolute (1)
- Absorption (1)
- Aqueous quantum dot (1)
- Aza-BODIPY (1)
- BODIPY (1)
- Barcoding (1)
- Bead-based assay (1)
- C-dot (1)
- CUINS2 nanocrystals (1)
- Cancer (1)
- Capillary electrophoresis (1)
- Carbon dot (1)
- Carboxyl group (1)
- Cement (1)
- Characterization (1)
- Colloidal semiconductor nanocrystals (1)
- Core/shell particle (1)
- Decay kinetics (1)
- Design of experiment (1)
- Emission enhancement (1)
- Energy transfer (1)
- Er(III) (1)
- Field sensor (1)
- Flow cytometry (1)
- Fluorescence microscopy (1)
- Fluorescence quantum yield (1)
- Fluorescent glasses (1)
- Fluorescent probe (1)
- Hydration (1)
- IR (1)
- Imaging techniques (1)
- In vivo imaging (1)
- Instrument calibration (1)
- LiYF4 (1)
- Light harvesting (1)
- Luorescence (1)
- MS (1)
- Mass spectrometry (1)
- Merocyanine (1)
- Metal cluster (1)
- Metasurface (1)
- Modelling (1)
- NIR-II Imaging (1)
- Nanoplattform (1)
- Nanosensor (1)
- Nnano particle (1)
- Optical probes (1)
- PDT (1)
- Particle architecture (1)
- Particle size (1)
- Particle, imaging (1)
- Photonic crystal (1)
- Polymer (1)
- Probe (1)
- Protein (1)
- Quantitative spectroscopy (1)
- Quantum dot (1)
- Redox (1)
- Reference material (1)
- Reference nanomaterials (1)
- Reflection spectroscopy (1)
- Reliable characterization (1)
- Risk assessment (1)
- SAXS (1)
- Safety (1)
- Semiconductor (1)
- Semiconductor quantum dot (1)
- Sensitization (1)
- Sensor molecules (1)
- Shell (1)
- Single particle spectroscopy (1)
- Size (1)
- Size and size distribution (1)
- Solar cells (1)
- SrF2 (1)
- Surface group analysis (1)
- Thickness (1)
- Traceability (1)
- Triplet-triplet annihilation (1)
- calibration (1)
- dye (1)
- fluorescence standards (1)
- organic dyes (1)
- pH (1)
- photoluminescence (1)
- surface group analysis (1)
- synthesis (1)
Organisationseinheit der BAM
- 1.2 Biophotonik (36) (entfernen)
Paper des Monats
- ja (2)
Eingeladener Vortrag
- nein (9)
Monodisperse iron oxide nanoparticles as reference material candidate for particle size measurements
(2020)
In order to utilize and rationally design materials at the nanoscale the reliable characterization of their physico-chemical properties is highly important, especially with respect to the assessment of their environmental or biological impact. Furthermore, the European Commission’s REACH Regulations require the registration of nanomaterials traded in quantities of at least 1 ton. Powders or dispersions where 50% (number distribution) of the constituent particles have sizes ≤ 100 nm in at least one dimension are defined as nanomaterials. This creates a need for industrial manufacturers and research or analytical service facilities to reliably characterize potential nanomaterials. Currently, BAM is developing reference nanoparticles, which shall expand the scarce list of worldwide available nano reference materials certified for particle size distribution and will also target other key parameters like shape, structure, porosity or functional properties. In this respect, materials like iron oxide or titanium dioxide are considered as candidates to complement the already available silica, Au, Ag, and polystyrene reference nanoparticles.
The thermal decomposition of iron oleate precursors in high boiling organic solvents can provide large quantities of iron oxide nanoparticles that can be varied in size and shape.[1, 2] The presence of oleic acid or other hydrophobic ligands as capping agents ensures stable dispersion in nonpolar solvents. Such monodisperse, spherical particles were synthesized at BAM and pre-characterized by electron microscopy (TEM, SEM including the transmission mode STEM-in-SEM) and dynamic light scattering comparing cumulants analysis and frequency power spectrum.
1. REACH regulations and nanosafety concerns create a strong need for nano reference materials with diverse properties.
2. Iron oxide nanoparticles are under development as new candidate reference material at BAM.
3. Narrow particle size distribution confirmed by light scattering and electron microscopy.
Merocyanine–triarylamine bichromophores are readily synthesized by sequentially Pd-catalyzed insertion alkynylation–Michael–Suzuki four-component reactions. White-light emissive systems form upon aggregation in 1 : 99 and 0.1 : 99.9 vol% CH2Cl2–cyclohexane mixtures, ascribed to aggregation-induced dual emission (AIDE) in combination with partial energy transfer between both chromophore units as supported by spectroscopic studies.
In this contribution different ways are explored with the aim to generate suitable training data for ‘non-ideal’ samples using various approaches, e.g., computer-generated images or unsupervised learning algorithms such as generative adversarial networks (GANs). We used these data to train simple CNNs to produce segmentation masks of SEM images and tested the trained networks on real SEM images of complex nanoparticle samples. The novel use of CNN for the automated analysis of the size of nanoparticles of complex shape and with a high degree of agglomeration has proved to be a promising tool for the evaluation of particle size distribution on a large number of constituent particles. Further development and validation of the preliminary model, respectively larger training and validation data sets are necessary.
Synthesis of new upconversion (UC) materials that can convert near-infrared excitation light into visible emission light with high efficiency has crucial importance for energy and bio-applications. Herein, SrF2 single crystals with a doping concentration of 2 mol% Er3+ and 2–8 mol% Yb3+ were synthesized and the optical properties were studied. The absorption cross-section of the different doping ions was calculated. To identify the most efficient and brightest material absolute excitation power dependent UC photoluminescence quantum yields (ϕUC) and brightness values were determined. In addition, excitation characteristics and luminescence lifetimes were analysed to understand the changes in population pathways and possible quenching mechanisms. A dominant two-photon population behaviour of the red and green emission bands was observed for all investigated doping concentrations of Yb3+ and Er3+. The ϕUC value of 6.5% measured using 230 W cm−2 of 976 nm excitation for SrF2 crystal co-doped with 2 mol% Er3+ and 3 mol% Yb3+. These findings broaden the scope of efficient UC materials apart from the record UC material β-NaYF4:Yb3+, Er3+ and provide benchmark values for cubic-phase and especially SrF2- nano and micrometer sized materials.
Upconversion photoluminescence in hetero-oligonuclear metal complex architectures featuring organic ligands is an interesting but still rarely observed phenomenon, despite its great potential from a basic research and application perspective. In this context, a new photonic material consisting of molecular chromium(III) and ytterbium(III) complex Ions was developed that exhibits excitation-power density-dependent cooperative sensitization of the chromium-centered 2E/2T1 phosphorescence at approximately 775 nm after excitation of the ytterbium band 2F7/2!2F5/2 at approximately 980 nm in the solid state at ambient temperature. The upconversion process is insensitive to atmospheric oxygen and can be observed in the presence of water molecules in the crystal lattice.
Light-induced NO release based on exogenous NO donors has attracted substantial attention in clinical applications; the induction light source usually converts near-infrared light to blue or ultraviolet light.
However, the low efficiency of near-infrared light-assisted chemical light energy conversion remains a challenge, especially for NaYF4:Yb3+/Tm3+ photoconverting near-infrared light to ultraviolet (UV) and blue light. In this paper, a luminescence-enhanced strategy is reported by doping Ca2+ into NaYF4:Yb3+/Tm3+ and coating it with NaGdF4 through a two-step solvothermal method. Then, UCNPs modified with methyl-b-cyclodextrin (M-b-CD) are loaded on a ruthenium nitrosyl complex [(3)Ru(NO)(Cl)] as nitric oxide release-molecules (NORMs). X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) data demonstrated that Ca2+ was successfully doped into NaYF4:Yb3+/Tm3+ nanoparticles as the core, and a pure hexagonal phase, NaYF4, was obtained from the doping of Ca2+. TEM revealed that the crystallinity was significantly improved after Ca2+ doping, and the core–shell structure was successfully synthesized, with NaGdF4 directionally grown on the NaYF4:Ca/Yb/Tm core. Fluorescence tests showed that, especially in the ultraviolet and blue light excitation wavelength regions, the UC emission intensity of the Ca-doped NaYF4:Yb3+/Tm3+@NaGdF4 core–shell UCNPs increased by 302.95 times vs. NaYF4:Yb3+/Tm3+ UCNPs. Finally, the release of NO was tested by the Griess method. Under 980 nm irradiation, the cell viability distinctly decreased with increasing UCNPs@M-b-CD-NORMs concentration. This study Shows that NORM release of NO is triggered by enhanced up-converted UV and blue light, which can be used for the development of UV photo-sensitive drugs.
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.
N-Benzyl aroyl-S,N-ketene acetals can be readily synthesized by condensation of aroyl chlorides and N-Benzyl 2-methyl benzothiazolium salts in good to excellent yields, yielding a library of 35 chromophores with bright solid-state emission and aggregation-induced emission characteristics.
Varying the substituent from electron-donating to electronwithdrawing enables the tuning of the solid-state emission Color from deep blue to red.
Single particle imaging of upconversion nanoparticles (UCNPs) has typically been realized using hexagonal (β) phase lanthanide-doped sodium yttrium fluoride (NaYF4) materials, the upconversion luminescence (UCL) of which saturates at power densities (P) of several hundred W cm−2 under 980 nm nearinfrared (NIR) excitation. Cubic (α) phase UCNPs have been mostly neglected because of their commonly observed lower UCL efficiency at comparable P in ensemble level studies. Here, we describe a set of sub-15 nm ytterbium-enriched α-NaYbF4:Er3+@CaF2 core/shell UCNPs doped with varying Er3+ concentrations (5–25%), studied over a wide P range of ∼8–105 W cm−2, which emit intense UCL even at a low P of 10 W cm−2 and also saturate at relatively low P. The highest upconversion quantum yield (ΦUC) and the highest particle brightness were obtained for an Er3+ dopant concentration of 12%, reaching the highest ΦUC of 0.77% at a saturation power density (Psat) of 110 W cm−2. These 12%Er3+-doped core/shell UCNPs were also the brightest UCNPs among this series under microscopic conditions at high P of ∼102–105 W cm−2 as demonstrated by imaging studies at the single particle level. Our results underline the potential applicability of the described sub-15 nm cubic-phase core/shell UCNPs for ensemble- and single particle-
level bioimaging.
We present here the design and characterization of a set of spectral calibration beads. These calibration beads are intended for the determination and regular control of the spectral characteristics of fluorescence microscopes and other fluorescence measuring devices for the readout of bead-based assays. This set consists of micrometer-sized polymer beads loaded with dyes from the liquid Calibration Kit Spectral Fluorescence Standards developed and certified by BAM for the wavelength-dependent Determination of the spectral responsivity of fluorescencemeasuring devices like spectrofluorometers. To cover the wavelength Region from 400 to 800 nm, two new near-infrared emissive dyes were included, which were spectroscopically characterized in solution and encapsulated in the beads. The resulting set of beads presents the first step towards a new platform of spectral calibration beads for the determination of the spectral characteristics of fluorescence instruments like fluorescence microscopes, FCM setups, and microtiter plate readers, thereby meeting the increasing demand for reliable and comparable fluorescence data especially in strongly regulated areas, e.g., medical diagnostics. This will eventually provide the basis for standardized calibration procedures for imaging systems as an alternative to microchannel slides containing dye solutions previously reported by us.