Ingenieurwissenschaften und zugeordnete Tätigkeiten
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Bioanalytical, diagnostic, and security applications require the fast and sensitive determination of a steadily increasing number of analytes or events in parallel in a broad variety of detection formats.[1,2] Ideal candidates for spectral encoding and multiplexing schemes are luminescent nanocrystals like semiconductor quantum dots (QDs), particularly Cd-containing II/VI QDs with their narrow and symmetric emission bands. With the availability of relatively simple and inexpensive instrumentation for time-resolved fluorescence measurements, similar strategies utilizing the compound-specific parameter fluorescence lifetime or fluorescence decay kinetics become increasingly attractive.[3-5] The potential of different types of QDs like II/VI, III/V and Cd-free ternary QDs such as AgInS (AIS) QDs for lifetime-based encoding and multiplexing has been, however, barely utilized, although the lifetimes of these nanocrystals cover a time windows which is barely accessible with other fluorophores. Here we present a brief insight into the photophysics of AIS QDs and show the potential of dye- and QD-encoded beads for lifetime-based encoding and detection schemes in conjunction with flow cytometry and fluorescence lifetime imaging microscopy
The efficient and sensitive detection of pathogenic microorganisms in aqueous environments, such as water used in medical applications, drinking water, and cooling water of industrial plants, requires simple and fast methods suitable for multiplexed detection such as flow cytometry (FCM) with optically encoded carrier beads. For this purpose, we combine fluorescent Cd-free Ag−In−S ternary quantum dots (t-QDs) with fluorescence Lifetimes (LTs) of several hundred nanoseconds and superparamagnetic Fe3O4 nanoparticles (SPIONs) with mesoporous CaCO3 microbeads to a magneto-fluorescent bead platform that can be surface-functionalized with bioligands, such as antibodies. This inorganic bead platform enables immuno-magnetic separation, target enrichment, and target quantification with optical readout. The beads can be detected with steady-state and time-resolved fluorescence microscopy and flow cytometry (FCM). Moreover, they are suited for readout by time gated emission. In the following, the preparation of these magneto-fluorescent CaCO3 beads, their spectroscopic and analytic characterization, and their conjugation with bacteria-specific antibodies are presented as well as proof-of-concept measurements with Legionella pneumophila including cell cultivation and plating experiments for bacteria quantification. Additionally, the possibility to discriminate between the long-lived emission of the LT-encoded capture and carrier CaCO3 beads and the short-lived Emission of the dye-stained bacteria with time-resolved fluorescence techniques and single wavelength excitation is demonstrated.
In summary, we report a highly modular solid TTA-UC system comprising of a crystalline, thermally stable PCN222(Pd) MOF with CA-coated MOF channels and with a DPA annihilator embedded in a solution-like environment in the MOF channels. This solid material displays blue upconverted delayed emission with a luminescence lifetime of 373 us, a threshold value of 329 mW*cm-2 and a triplet–triplet energy transfer efficiency of 82%. This optical application adds another facet to the versatile chemistry of PCN-222 MOFs. The design concept is also applicable to other TTA-UC pairs and enables tuning of the UCL color, for example, by replacing DPA with other dyes as exemplarily shown for 2,5,8,11-tetra-tert-butyl-perylene, that yields UCL at 450 nm. Current work aims to reduce the oxygen sensitivity and to increase the retention of the trapped annihilators in organic environments, for example, by tuning the chain length of the carboxylic acid and by coating the MOF surface. In addition, the TTA-UC efficiency will be further enhanced by reducing the reabsorption of the UC emission caused by Pd(TCPP) and by optimizing the sensitizer/annihilator interface.
Singlet oxygen can severely damage biological tissue, which is exploited in photodynamic therapy (PDT). In PDT, the effective range is limited by the distribution of the photosensitizer (PS) and the illuminated area. However, no distinction is made between healthy and pathological tissue, which can cause undesired damage. This encouraged us to exploit the more acidic pH of cancerous tissue and design pH-controllable singlet oxygen-generating boron-dipyrromethene (BODIPY) dyes. A pH sensitivity of the dyes is achieved by the introduction of an electronically decoupled, photoinduced electron transfer (PET)-capable subunit in meso-position of the BODIPY core. To favor triplet-state formation as required for singlet Oxygen generation, iodine substituents were introduced at the chromophore core. The resulting pH-controlled singlet oxygen-generating dyes with pKa values in the physiological range were subsequently assessed regarding their potential as pH-controlled PS for PDT.
Using HeLa cells, we could successfully demonstrate markedly different pH-dependent cytotoxicities upon illumination.
Diaminodicyanoquinones: Fluorescent dyes with high dipole moments and electron-acceptor properties
(2019)
Fluorescent dyes are applied in various fields of research,includingsolarcellsandlight-emittingdevices,andas reporters for assays and bioimaging studies.Fluorescent dyes with an added high dipole moment pave the way to nonlinear optics and polarity sensitivity.Redox activity makes it possible to switch the moleculeQsphotophysical properties.Diaminodicyanoquinone derivatives possess high dipole moments,yet only lowfluorescence quantum yields,and have therefore been neglected as fluorescent dyes.Here we investigate the fluorescencepropertiesofdiaminodicyanoquinonesusingacombined theoretical and experimental approach and derive molecules with afluorescence quantum yield exceeding 90%. The diaminodicyanoquinone core moiety provides chemical versatility and can be integrated into novel molecular architectures with unique photophysical features.
Structural modularity of polymer frameworks is a key advantage of covalent organic polymers, however, only C, N, O, Si and S have found their way into their building blocks so far. Here, we expand the toolbox available to polymer and materials chemists by one additional nonmetal, phosphorus. Starting with a building block that contains a λ⁵‐phosphinine (C₅P) moiety, we evaluate a number of polymerisation protocols, finally obtaining a π‐conjugated, covalent phosphinine‐based framework (CPF‐1) via Suzuki‐Miyaura coupling. CPF‐1 is a weakly porous polymer glass (72.4 m2 g‐1 N2 BET at 77 K) with green fluorescence (λmax 546 nm) and extremely high thermal stability. The polymer catalyzes hydrogen evolution from water under UV and visible light irradiation without the need for additional co‐catalyst at a rate of 33.3 μmol h‐¹ g‐¹. Our results demonstrate for the first time the incorporation of the phosphinine motif into a complex polymer framework. Phosphinine‐based frameworks show promising electronic and optical properties that might spark future interest in their applications in light‐emitting devices and heterogeneous catalysis.
The rational synthesis and use of nanomaterials require the characterization of many different properties, ranging from particle size and size distribution over surface chemistry to more applicationrelevant features like optical, electrochemical, and magnetic properties. In the following, several methods for the characterization of functional groups on nanomaterials, like polymer and silica nanoparticles, semiconductor quantum dots, and lanthanide-based upconversion nanocrystals are presented. Additionally, procedures for the measurement of the key spectroscopic performance parameters of nanomaterials with linear and nonlinear photoluminescence, such as the photoluminescence quantum yield, are presented for the UV/vis/NIR/SWIR.
We present a comprehensive investigation of the magnetic and optical properties of an ytterbium complex, which combines two desirable and practical features into a single molecular system. Based upon YbIII Ions that promote near-infrared optical activity and a chemical backbone that is ideal for an in-depth understanding of the magnetic behaviour, we have designed a multifunctional opto-magnetic species that operates as a luminescent thermometer and as a single-molecule magnet (SMM). Our magnetic investigations, in conjunction with ab initio calculations, reveal one of the highest energy barriers reported for an YbIII-based complex. Moreover, we correlate this anisotropic barrier with the Emission spectrum of the compound, wherein we provide a complete assignment of the energetic profile of the complex. Such studies lay the foundation for the design of exciting multi-faceted materials that are able to retain information at the single-molecule level and possess built-in thermal self-monitoring capabilities.
The comparison of different emitter classes and the rational design of the next generation of molecular and nanoscale reporters require accurate and quantitative photo-luminescence measurements. This is of special importance for all photoluminescence applications in the life and material sciences and nanobiophotonics. In the following, procedures for the determination of the spectroscopic key parameter photoluminescence quantum yield, i.e., the number of emitted per absorbed photons, in the UV/vis/NIR/SWIR are presented including pitfalls and achievable uncertainties and material-specific effects related to certain emitter classes are addressed.
We report the synthesis and characterization of carbon nanodots (CDs) with high quantum yield (>50%) and tailored optical absorption as well as emission properties. A well-described protocol with polyethyleneimine (PEI) as amine precursor is used as a reference to a new CD system which is stabilized by aromatic 2,3-diaminopyridine (DAP) molecules instead. The DAP stabilizer is installed in order to red-shift the absorption peak of the n-π* electron transition allowing efficient radiative recombination and light emission. Size, shape, and chemical composition of the samples are determined by (HR)TEM, EDX and FTIR-spectroscopy. Optical parameters are investigated using UV-VIS, PL and QY measurements. Several parameters such as concentration, excitation wavelength and pH are studied. Zeta-potential analysis indicate that pH-induced (de-)protonation processes of functional moieties directly affect the n-π* energy bands. This results in unique pH-dependent absorption and emission characteristics which are discussed on the specific chemical composition of each CD system.