1.2 Biophotonik
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We designed and synthesized triphenylamine based and coumarin fused rhodamine hybrid dyes and characterized using 1H, 13C NMR and HR-LCMS analysis. Both the newly synthesized hybrid dyes were found to show red shifted absorption as well as emissions and large Stokes shift (40e68 nm) as compared to the small Stokes shift (25e30 nm) of reported dyes Rhodamine B and 101. Photophysical properties of these dyes were studied in different solvents and according to the solvents acidity or basicity they preferred to remain in their spirocyclic or open form in different ratio. We studied the spirocyclic as well as open form derivatives of these dyes for their viscosity sensitivity in three different mixture of solvents i.e. polar-protic [EtOH-PEG 400], polar-aprotic [toluene-PEG 400] and non-polaraprotic [toluene-paraffin]. They are found to show very high viscosity sensitivity in polar-protic mixture of solvents [EtOH-PEG 400] and hence concluded that both polarity as well as viscosity factor worked together for the higher emission enhancement rather than only viscosity factor. As these dyes showed very high viscosity sensitivity in their spirocyclic as well as open form, they can be utilized as viscosity sensors in visible as well as deep red region. We also correlated our experimental finding theoretically by using Density Functional theory computations.
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.
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.
Der kürzlich publizierte Chrom(III)-Komplex 13+([Cr(ddpd)2]3+) zeigt in wässriger Lösung unter Umgebungsbedingungen eine bemerkenswert starke Emission im nahen Infrarot-Bereich mit einer Emissionswellenlänge von 775 nm.
Geschicktes Ligandendesign verhindert strahlungslose Desaktivierungsprozesse wie Photosubstitution, Rück-Intersystem-Crossing und trigonale Verzerrungen und führt damit zu einer Phosphoreszenzlebensdauer im Bereich von Mikrosekunden.
In Abwesenheit von Energieakzeptoren wie molekularem Sauerstoff verbleibt nur Energietransfer zu hochenergetischen Oszillatoren der Liganden und Lösungsmittelmoleküle wie beispielsweise OH- und CH-Streckschwingungen als Desaktivierungspfad. Selektive Deuterierung der ddpd-Liganden und der Lösungsmittel l-sst die Effizienz dieser Oszillatoren bei der Desaktivierung angeregter Zustände erkennbar werden. Gezieltes Ausschalten dieser Relaxationspfade führt zu einer Quantenausbeute von 30% und einer Lebensdauer von 2.3 Millisekunden bei Raumtemperatur in Lösung – Rekordwerte für einen Komplex, der auf dem Element Chrom basiert. Diese fundamentalen Erkenntnisse ebnen den Weg für gezieltes Ligandendesign zur Synthese lumineszierender Komplexe mit gut verfügbaren Übergangsmetallen.
The recently reported luminescent chromium(III) complex 13+ ([Cr(ddpd)2]3+; ddpd=N,N’-dimethyl-N,N’-dipyridine-2-yl-pyridine-2,6-diamine) shows exceptionally strong near-IR emission at 775 nm in water under ambient conditions (F=11%) with a microsecond lifetime as the ligand design in 13+ effectively eliminates non-radiative decay pathways, such as photosubstitution, back-intersystem crossing, and trigonal twists. In the absence of energy acceptors, such as dioxygen, the remaining decay pathways are energy transfer to high energy solvent and ligand oscillators, namely OH and CH stretching vibrations. Selective deuteration of the solvents and the ddpd ligands probes the efficiency of these oscillators in the excited state deactivation. Addressing these energytransfer pathways in the first and second coordination sphere furnishes a record 30% quantum yield and a 2.3 millisecond lifetime for a metal complex with an earth-abundant metal ion in solution at room temperature.
Multifunctional efficiency: Extending the concept of atom economy to functional nanomaterials
(2018)
Green chemistry, in particular, the principle of atom economy, has defined new criteria for the efficient and sustainable production of synthetic compounds. In complex nanomaterials, the number of embedded functional entities and the energy expenditure of the assembly process represent additional compound-associated parameters that can be evaluated from an economic viewpoint. In this Perspective, we extend the principle of atom economy to the study and characterization of multifunctionality in nanocarriers, which we define as “multifunctional efficiency”. This concept focuses on the design of highly active nanomaterials by maximizing integrated functional building units while minimizing inactive components. Furthermore, synthetic strategies aim to minimize the number of steps and unique reagents required to make multifunctional nanocarriers. The ultimate goal is to synthesize a nanocarrier that is highly specialized but practical and simple to make. Owing to straightforward crystal engineering, metal−organic framework (MOF) nanoparticles are an excellent example to illustrate the idea behind this concept and have the potential to emerge as next-generation drug delivery systems. Here, we highlight examples showing how the combination of the properties of MOFs (e.g., their organic−inorganic hybrid nature, high surface area, and biodegradability) and induced systematic modifications and functionalizations of the MOF’s scaffold itself lead to a nanocarrier with high multifunctional efficiency.
Nano- and microparticles are of increasing importance for a wide range of applications in the material and life sciences. Examples are their use as carriers for dye molecules and drugs, multichromophoric reporters for signal enhancement strategies in optical assays, targeted probes for bioimaging, and biosensors. All these applications require surface functionalization of the particles with e.g., ligands (to tune the dispersibility and prevent unspecific interactions), crosslinkers, sensor dyes, or analyte recognition moieties like biomolecules, and subsequently, the knowledge of the chemical nature and total number of surface groups as well as the number of groups accessible for coupling reactions. Particularly attractive for the latter are sensitive and fast photometric or fluorometric assays, which can be read out with simple, inexpensive instrumentation. Here, we present a novel family of cleavable photometric and multimodal reporters for the quantification of conjugatable amino and carboxyl surface groups on nano- and microparticles. These probes allow for the determination of particle-bound labels, unbound reporters in the supernatant, and reporters cleaved off from the particle surface as well as the remaining thiol groups on the particles by photometry and inductively coupled optical emission spectrometry (32S ICP-OES).3 Comparison of the performance of these cleavable reporters with conventional labels, utilizing changes in intensity and/or colour of absorption and/or emission, underlines the analytical potential of this versatile concept which elegantly circumvents signal distortions by light scattering and encoding dyes, and enables straightforward validation by method comparison.
Many applications of nanometer- and micrometer-sized particles include their surface functionalization with linkers, sensor molecules, and analyte recognition moieties like (bio)ligands. This requires knowledge of the chemical nature and number of surface groups accessible for subsequent coupling reactions. Particularly attractive for the quantification of these groups are spectrophotometric and fluorometric assays, which can be read out with simple instrumentation. In this respect, we present here a novel Family of cleavable spectrophotometric and multimodal reporters for conjugatable amino and carboxyl surface groups on nano- and microparticles. This allows determination of particle-bound labels, unbound reporters in the supernatant, and reporters cleaved off from the particle surface, as well as the remaining thiol groups on particle, by spectrophotometry and inductively coupled optical emission spectrometry (32S ICP-OES). Comparison of the performance of these cleavable reporters with conductometry and conventional labels, utilizing changes in intensity or Color of absorption or emission, underlines the analytical potential of this versatile concept which elegantly circumvents Signal distortions by scattering and Encoding dyes and enables straightforward validation by method comparison.
Polymeric nanoparticles (NP) are of increasing importance for a wide range of applications in the material and life sciences, including their use as drug carriers, fluorescent sensors and multimodal reporters in a large variety of bioassays and bioimaging studies. Application-relevant properties of NP include their size (and size distribution), shape, optical properties, and ease of subsequent functionalization, e.g. with linkers, sensor molecules, and bioligands. In this respect, knowledge of the chemical nature, the total number of surface groups and the number of groups accessible for subsequent coupling reactions is mandatory.1 Commercially available polystyrene NP often contain different additives like stabilizers, radical starters and crosslinkers, which can influence the quantification of surface functionalities. Moreover, they often have unknown surface group densities that may vary from batch to batch, which complicates or even hampers their reliable use in many (bio)applications. To circumvent these issues, we synthesized amino- and carboxy-functionalized, monodisperse 100 nm polystyrene NP with three different, well-defined surface group densities. Using a recently developed approach for the quantification of functional groups on nano- and microparticles with cleavable reporters,2 we quantified the assessible functional groups on the self-synthesised PS particles via optical spectroscopy (photometry) and inductively coupled optical emission spectrometry (32S ICP-OES). In addition, we developed a fluorimetric approach for the quantification of surface functional groups on nanoparticles based on the labelling with luminescent lanthanide complexes (LLC). In contrast to common organic dyes, LLC are not prone to photo¬luminescence quenching arising from reabsorption or dye aggregation, and thus, enable a reliable fluorometric quantification of the assessible functional groups on NP surfaces. Moreover, lanthanide tags can be detected with high specificity and sensitivity with analytical techniques such as XPS and ICP-MS, which allow for the multimodal validation of the fluorometric quantification approach.
Colloidal semiconductor nanoparticles with a spherical core and an elongated shell form bright emitters with a high absorption cross section. They show great potential for a multitude of optoelectronic applications such as LEDs or photovoltaic cells and can be used as gain material or as markers for bio imaging. For most of these applications high fluorescence quantum yields are a figure of merit for the emitter quality. In this work we investigate how the ensemble quantum yield is affected by the properties of the individual particles. In particular, we prove the role of non-emitting particles as well as the role of blinking. Using a combination of AFM and spatially resolved photoluminescence spectroscopy we measured hundreds of individual CdSe/CdS dot/rod particles of different shell lengths exciting with two different excitation wavelengths for shell or core excitation, respectively.