Präsentation
Filtern
Dokumenttyp
- Vortrag (3)
- Posterpräsentation (2)
Sprache
- Englisch (5)
Referierte Publikation
- nein (5)
Schlagworte
- Fluorescence spectroscopy (5) (entfernen)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (3)
Substitution of lead oxide in low-melting glasses, e.g., for application in silver metallization pastes, is a current research goal. This work is focused on the investigation of silver diffusion in alkali zinc borate glasses (X2O-ZnO-B2O3, X = Li, Na, K, Rb). In addition, the redox state of silver (Ag) and thus the type of diffusing silver species were studied. For this purpose, a metallic silver coating was applied on glass cubes by means of sputtering. Heat treatment of the samples was performed close to the glass transition temperatures at 470 °C for 2 h under air and nitrogen atmosphere. Coating thickness was 1.8 µm after heat treatment, measured by a white light interferometer.
Silver diffusion profiles were measured by means of secondary neutral mass spectrometry. The silver diffusion coefficients are in the range of ~10-14 cm2/s and indicate no significant differences depending on the type of alkali ions in the glass. Dissolved Ag+-ions and [Agm]n+-clusters in the glasses were differentiated using fluorescence spectroscopy.
Precipitated metallic silver particles in the sodium containing glass were observed by means of transmission electron microcopy. Their mean particle diameter was ~6 nm.
Aiming at the development of a non-destructive optical measurement methods for the characterization of nano-sized airborne particulate pollutants we performed fluorescence spectroscopic investigations of their relevant emission properties. Here, we present first results from studies of soot particles from synthetic aerosols deposited on PTFE membranes.
Fluorescence microscopic and spectroscopic monitoring of degradation processes upon polymer ageing
(2017)
The majority of all routinely used methods to assess polymer aging are based on destructive tests and methods. Early indicators for the deterioration of polymer materials are e.g., physical or mechanical properties like tensile strength, adhesion, brittleness, and color. It is well-known, however, that predominantly chemical changes are the underlying process of the physical changes that occur in organic materials upon aging over time. Typical initial steps during polymer degradation are crosslinking or chain breaking, alteration of autofluorescence, “yellowing” or bleaching caused by the formation of new functional groups. A straightforward strategy towards the sensitive detection and monitoring of chemical changes in the course of polymer aging is based on non-destructive optical measurements. Luminescence techniques, one of the most sensitive spectroscopic methods are the method of choice. Here, we present first results of luminescence-based monitoring of polymer degradation induced by different environmentally relevant weathering factors (e.g. humidity and UV exposure). Our studies include fluorescence spectroscopy as well as spectral scanning confocal fluorescence microscopy and clearly demonstrate the possibility to follow accelerate-aging processes by luminescence detection.
BODIPY fluorophores are popular functional dyes in a multitude of fields in chemistry, physics, and materials sciences due to their excellent properties such as a good photostability, high fluorescence quantum yields, and almost unlimited possibilities for tailoring their properties by chemical functionalization. In sensing applications, BODIPY dyes are widely employed.
In this work, we present an approach for creating a BODIPY-based pocket-like structure for the recognition of volatile organic compounds (VOC) such as benzene and its derivatives. This may lead to the development of sensing devices for this class of compounds, which receive special attention by environmental chemists and regulatory authorities due to severe adverse effects on humans in particular and the environment in general. The low reactivity of benzene-derived hazardous compounds is thereby a major fact that has to be taken into consideration. While for other reactive gaseous compounds, fluorophore-based detection performance is achieved by the chemical modification of the fluorophore itself, e.g. by bond cleavage, addition, oxidation or reduction reactions; this is not possible for many VOCs. Several metal complexes were described for the sensing of benzene and its derivatives, but no organic dyes such as BODIPYs are known with these capabilities. Our unique concept towards BODIPY-based molecules acting as scavengers for VOCs is supposed to overcome the problem of benzene’s low reactivity by enforcing π-π-interactions between the fluorophore and the volatile aromatic analyte in pocket-like molecular structures.
Covalent modification of surfaces with carbohydrates (glycans) is a prerequisite for a variety of glycomics-based biomedical applications, including functional biomaterials, glycan-arrays, and glycan-based biosensors. The chemistry of glycan immobilization plays an essential role in the bioavailability and function of surface bound carbohydrate moieties. For biomedical applications the stability over time (shelf life) of a glycan-array is a crucial factor. Basic requirements for the production of microarrays are first of all stable signals without any loss of quality. Therefore, the investigation of the shelf life for carbohydrate microarrays is an important part in the development of glycan-arrays.
Motivated by the need of reliable quality control for glycan microarrays, we developed reference arrays using fluorescent model glycans. Since the long term stability of glycan microarrays is a crucial factor for their clinical application the shelf life at different storage conditions of glycan microarrays was studied in detail using the two model glycan compounds.
Herein, we present a shelf life study of model glycan microarrays on epoxy modified glass surfaces over a period of 320 days. This was carried out using different analyzing techniques such as Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), X-ray Photoelectron Spectroscopy (XPS) and Fluorescence Spectroscopy. To analyze and interpret the ToF-SIMS dataset the multivariate technique principal component analysis (PCA) was used. The dependence of the array´s shelf life upon storage conditions was specifically studied.