Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (15)
- Vortrag (9)
- Posterpräsentation (5)
- Beitrag zu einem Sammelband (3)
- Beitrag zu einem Tagungsband (2)
- Dissertation (1)
- Sonstiges (1)
Sprache
- Englisch (36)
Schlagworte
- Characterization (36) (entfernen)
Organisationseinheit der BAM
- 1 Analytische Chemie; Referenzmaterialien (4)
- 5 Werkstofftechnik (4)
- 6 Materialchemie (3)
- 8 Zerstörungsfreie Prüfung (3)
- 1.2 Biophotonik (2)
- 5.1 Mikrostruktur Design und Degradation (2)
- 5.5 Materialmodellierung (2)
- 6.1 Oberflächen- und Dünnschichtanalyse (2)
- 7 Bauwerkssicherheit (2)
- 7.4 Baustofftechnologie (2)
Eingeladener Vortrag
- nein (9)
The scope of our study was to prepare Fe-based highly active catalysts for water treatment processes. The reactive nanomaterials were
synthesized by chemical precipitation; the post-synthesis coating of the as obtained nanostructures was achieved by capping the magnetic cores with a
polymeric surfactant, polyethylene glycol (PEG). The resulted Fe3O4/PEG nanoparticles were further used to immobilize two types of reactive materials on
their surface, either ferrous oxalate (FO) or ferric citrate (FC), yielding the final products – two green Fenton-like heterogeneous nanocatalysts. The
sensitized catalysts were characterized by several microstructure characterization techniques such as X-ray diffraction (XRD), vibrating sample
magnetometry, BET, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). All experiments were performed on a
laboratory scale set-up. Important variables such as effect of hydrogen peroxide concentration, UV light, the amount of catalyst and contact time for the
catalytic wet peroxide oxidation (CWHPO) of BPA were examined. The results indicate that the oxidation rate increased under UV light in the presence of
low-concentration H2O2.
Two types of surface modified magnetite (Fe3O4) nanoparticles, coated with either tannic acid (TA) or dissolved natural organic matter (NOM), were evaluated as magnetic heterogeneous catalysts. Simple and efficient procedures for the synthesis of the magnetic catalysts were employed, their properties being fully assessed by various characterization techniques. The catalytic activity in heterogeneous oxidation of aqueous solutions containing Bisphenol A (BPA) over the catalysts was comparatively studied. The optimum experimental parameters were: 1g/L of catalysts, 10 mM H2O2, under UV irradiation. The highest mineralization rates were observed for Fe3O4-TA catalyst. More than 80% of BPA were removed after 30 minutes of reaction time under the specified experimental conditions. The results showed that the obtained catalysts are suitable candidates for the removal of pollutants in wastewaters by means of heterogeneous reaction
Green Fenton-like magnetic nanocatalysts: Synthesis, characterization and catalytic application
(2015)
Five iron oxalate core–shell magnetite nanoparticles catalysts are evaluated as magnetic heterogeneous materials. Simple and efficient procedures for the preparation of magnetic iron oxalate coated nanoparticles are presented. The catalysts are fully characterized using various investigation techniques. Additionally, the formation of photo-sensitized oxygen by spin-trapping using electron spin resonance is investigated. The catalytic activity of two model substrates (carbamazepine and bisphenol A) is also evaluated. The effect of operational parameters (catalyst and H2O2 concentration, UVA light) on the degradation performance of the oxidation process is investigated. The obtained reaction rates depend on the nature of the compound and increase with iron oxide shell thickness of the catalyst. Moreover, these materials show a significant activity during two consecutive tests. The optimum experimental parameters are found to be 1.0 g L−1 of catalysts, 10 mM H2O2, under UVA irradiation. More than 99% of both substrates are removed after 30 min of reaction time under the experimental conditions given above. The results obtained show that the catalysts are suitable candidates for the removal of pollutants in wastewaters by means of the Fenton heterogeneous reaction.
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.
We aim at preparing, characterising, and applying SURMOFs incorporating electro-active and -switchable mechanically interlocked molecules such as rotaxanes as the basis of functional devices.
Preparation and Positioning
Synthesis, purification and analytical characterization of electro-switchable rotaxanes suitable for SURMOF-formation as well as Layer-by-Layer assembly on surfaces.
Controlled deposition of electro-active SURMOFs and Layer-by-Layer self-assembled multilayers based on these switchable rotaxanes.
Construction of SURMOFs on micro-patterned surfaces.
Structural Characterisation and Physico-Chemical Properties
Electrochemical characterization of these rotaxanes in solution with cyclic voltammetry, chronoamperometry and impedance spectroscopy.
Surface characterization of SURMOFs and multilayers with XPS, NEXAFS, AFM, contact-angle measurements, transmission UV/Vis, ToF-SIMS and – in cooperation with partners from SPP – XRD.
Development of ToF-SIMS (also assisted by Principle Component Analysis of the fragment-ion data) as a method for imaging and depth-profiling.
Development of an appropriate electrochemical cell to perform cyclic voltammetry, chronoamperometry and impedance spectroscopy with SURMOFS and multilayers as working electrodes in a three-electrode cell.
Comparison of the structural and electrochemical properties of the redox-active unit in solution, multilayers and SURMOF focusing on the advantages of SURMOFs.
System Integration and Function Demonstration
Examination of the usability of the electroactive SURMOFS as optoelectronic switch or data storage device with a focus on the robustness of the system.
Usage of the SURMOFs as functional electrodes for electrochemical application.
Selective switching of ordered nanostructures to translate molecular motion to macroscopic property changes.
We aim at preparing, characterising, and applying SURMOFs incorporating electro-active and -switchable mechanically interlocked molecules such as rotaxanes as the basis of functional devices.
Preparation and Positioning
Synthesis, purification and analytical characterization of electro-switchable rotaxanes suitable for SURMOF-formation as well as Layer-by-Layer assembly on surfaces.
Controlled deposition of electro-active SURMOFs and Layer-by-Layer self-assembled multilayers based on these switchable rotaxanes.
Construction of SURMOFs on micro-patterned surfaces.
Structural Characterisation and Physico-Chemical Properties
Electrochemical characterization of these rotaxanes in solution with cyclic voltammetry, chronoamperometry and impedance spectroscopy.
Surface characterization of SURMOFs and multilayers with XPS, NEXAFS, AFM, contact-angle measurements, transmission UV/Vis, ToF-SIMS and – in cooperation with partners from SPP – XRD.
Development of ToF-SIMS (also assisted by Principle Component Analysis of the fragment-ion data) as a method for imaging and depth-profiling.
Development of an appropriate electrochemical cell to perform cyclic voltammetry, chronoamperometry and impedance spectroscopy with SURMOFS and multilayers as working electrodes in a three-electrode cell.
Comparison of the structural and electrochemical properties of the redox-active unit in solution, multilayers and SURMOF focusing on the advantages of SURMOFs.
System Integration and Function Demonstration
Examination of the usability of the electroactive SURMOFS as optoelectronic switch or data storage device with a focus on the robustness of the system.
Usage of the SURMOFs as functional electrodes for electrochemical application.
Selective switching of ordered nanostructures to translate molecular motion to macroscopic property changes.
The combination of tomographic, microstructural data with other experimental techniques and with modeling is paramount, if we want to extract the maximum amount of information on material and component properties. In particular, quantitative image analysis, statistical approaches, direct discretization of tomographic reconstructions represent concrete possibilities to extend the power of the tomographic 3D representation to insights into the material and component performance. This logic thread holds equally for industrial and academic research, and valorizes expensive experiments such as those carried out at synchrotron sources, which cannot be daily repeated.
Green Fenton-like magnetic nanocatalysts: Synthesis, characterization and catalytic application
(2015)
Five iron oxalate core–shell magnetite nanoparticles catalysts are evaluated as magnetic heterogeneous materials. Simple and efficient procedures for the preparation of magnetic iron oxalate coated nanoparticles are presented. The catalysts are fully characterized using various investigation techniques. Additionally, the formation of photo-sensitized oxygen by spin-trapping using electron spin resonance is investigated. The catalytic activity of two model substrates (carbamazepine and bisphenol A) is also evaluated. The effect of operational parameters (catalyst and H2O2 concentration, UVA light) on the degradation performance of the oxidation process is investigated. The obtained reaction rates depend on the nature of the compound and increase with iron oxide shell thickness of the catalyst. Moreover, these materials show a significant activity during two consecutive tests. The optimum experimental parameters are found to be 1.0 g L-1 of catalysts, 10 mM H2O2, under UVA irradiation. More than 99% of both substrates are removed after 30 min of reaction time under the experimental conditions given above. The results obtained show that the catalysts are suitable candidates for the removal of pollutants in wastewaters by means of the Fenton heterogeneous reaction.
Due to the recent widespread application of nanomaterials to biological systems, a careful consideration of their physiological impact is required. This demands an understanding of the complex processes at the bio–nano interface. Therefore, a comprehensive and accurate characterization of the material under physiological conditions is crucial to correlate the observed biological impact with defined colloidal properties. As promising candidates for biomedical applications, two SiO2-based nanomaterial systems were chosen for extensive size characterization to investigate the agglomeration behavior under physiological conditions. To combine the benefits of different characterization techniques and to compensate for their respective drawbacks, transmission electron microscopy, dynamic light scattering and asymmetric flow field-flow fractionation were applied. The investigated particle systems were (i) negatively charged silica particles and (ii) poly(organosiloxane) particles offering variable surface modification opportunities (positively charged, polymer coated). It is shown that the surface properties primarily determine the agglomeration state of the particles and therefore their effective size, especially under physiological conditions. Thus, the biological identity of a nanomaterial is clearly influenced by differentiating surface properties.
In the frame of the European project NanoValid, potential candidates of reference nanomaterials are manufactured and systematically characterized in particular with respect to their morphology (shape, size and size distribution). In this study, by exploiting the transmission operation mode in a high-resolution SEM, known as transmission SEM, the potential of this methodical approach is demonstrated by means of representative examples of nanoparticles. The method enables quick and accurate morphological inspection and systematic characterization. Energy dispersive X-ray spectroscopy imaging of single nanoparticles by using the transmission mode is demonstrated as feasible, too.