Analytische Chemie
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Chemical and electrochemical interaction mechanisms of metal-reducing bacteria with gold surfaces
(2016)
Bacterial biofilms are considered one of the salient contributing factors to the deterioration of metals and their alloys, occurring in virtually all environments and across various industrial systems. Considering the sheer magnitude of detrimental effects, it is of pertinent interest to elucidate the interaction mechanisms of sessile bacteria with metal and metal oxide surfaces to facilitate the development of efficient antifouling strategies. A common constituent of microbial communities within aquatic and sedimentary settings, the Shewanella genus consists of facultatively aerobic, Gram-negative bacterium which exhibit exceptional plasticity in respiratory capacities. During aerobic conditions, Shewanella utilizes oxygen as a terminal electron acceptor; conversely, under anaerobic conditions, it is able to undertake respiration by reducing alternative terminal electron acceptors such as oxidized metals via extracellular electron transfer mechanisms not yet thoroughly discerned.
The aim of this work is to explicate the mechanisms governing the initial bacterial adhesion and subsequent biofilm formation on metallic surfaces. To investigate this dynamic interplay, a combined approach has been followed which couples surface enhanced Raman spectroscopy (SERS) with electrochemical techniques using Shewanella sp. model biofilms. Gold nano-islands deposited on thin glass slides have been chosen as inert model substrates with good uniformity and high surface enhancement factor. Furthermore, the utilization of gold as substrate material not only allowed the differentiation of the sole effect of substrate polarization on bacterial attachment but also enabled a precise adjustment of the surface chemistry and surface energy by means of surface functionalization with organothiol self-assembled monolayers.
The results present the correlation of the primary settlement rate of bacteria on metallic substrates with the environmental parameters such as electrolyte composition and pH as well as surface-related properties like hydrophobicity/hydrophilicity and polarization. With the overall strategic goal of transferring this methodology to technical systems the results provide the fundamental basis for the bottom-up design of anti-fouling surfaces.
Chemical and electrochemical interaction mechanisms of metal-reducing bacteria with gold surfaces
(2016)
Bacterial biofilms are considered one of the salient contributing factors to the deterioration of metals and their alloys, occurring in virtually all environments and across various industrial systems. Considering the sheer magnitude of detrimental effects, it is of pertinent interest to elucidate the interaction mechanisms of sessile bacteria with metal and metal oxide surfaces to facilitate the development of efficient antifouling strategies. A common constituent of microbial communities within aquatic and sedimentary settings, the Shewanella genus consists of facultatively aerobic, Gram-negative bacterium which exhibit exceptional plasticity in respiratory capacities. During aerobic conditions, Shewanella utilizes oxygen as a terminal electron acceptor; conversely, under anaerobic conditions, it is able to undertake respiration by reducing alternative terminal electron acceptors such as oxidized metals via extracellular electron transfer mechanisms not yet thoroughly discerned.
The aim of this work is to explicate the mechanisms governing the initial bacterial adhesion and subsequent biofilm formation on metallic surfaces. To investigate this dynamic interplay, a combined approach has been followed which couples surface enhanced Raman spectroscopy (SERS) with electrochemical techniques using Shewanella sp. model biofilms. Gold nano-islands deposited on thin glass slides have been chosen as inert model substrates with good uniformity and high surface enhancement factor. Furthermore, the utilization of gold as substrate material not only allowed the differentiation of the sole effect of substrate polarization on bacterial attachment but also enabled a precise adjustment of the surface chemistry and surface energy by means of surface functionalization with organothiol self-assembled monolayers.
The results present the correlation of the primary settlement rate of bacteria on metallic substrates with the environmental parameters such as electrolyte composition and pH as well as surface-related properties like hydrophobicity/hydrophilicity and polarization. With the overall strategic goal of transferring this methodology to technical systems the results provide the fundamental basis for the bottom-up design of anti-fouling surfaces.
Chemical and electrochemical interaction mechanisms of metal-reducing bacteria with gold surfaces
(2016)
Bacterial biofilms are considered one of the salient contributing factors to the deterioration of metals and their alloys, occurring in virtually all environments and across various industrial systems. Considering the sheer magnitude of detrimental effects, it is of pertinent interest to elucidate the interaction mechanisms of sessile bacteria with metal and metal oxide surfaces to facilitate the development of efficient antifouling strategies. A common constituent of microbial communities within aquatic and sedimentary settings, the Shewanella genus consists of facultatively aerobic, Gram-negative bacterium which exhibit exceptional plasticity in respiratory capacities. During aerobic conditions, Shewanella utilizes oxygen as a terminal electron acceptor; conversely, under anaerobic conditions, it is able to undertake respiration by reducing alternative terminal electron acceptors such as oxidized metals via extracellular electron transfer mechanisms not yet thoroughly discerned.
The aim of this work is to explicate the mechanisms governing the initial bacterial adhesion and subsequent biofilm formation on metallic surfaces. To investigate this dynamic interplay, a combined approach has been followed which couples surface enhanced Raman spectroscopy (SERS) with electrochemical techniques using Shewanella sp. model biofilms. Gold nano-islands deposited on thin glass slides have been chosen as inert model substrates with good uniformity and high surface enhancement factor. Furthermore, the utilization of gold as substrate material not only allowed the differentiation of the sole effect of substrate polarization on bacterial attachment but also enabled a precise adjustment of the surface chemistry and surface energy by means of surface functionalization with organothiol self-assembled monolayers.
The results present the correlation of the primary settlement rate of bacteria on metallic substrates with the environmental parameters such as electrolyte composition and pH as well as surface-related properties like hydrophobicity/hydrophilicity and polarization. With the overall strategic goal of transferring this methodology to technical systems the results provide the fundamental basis for the bottom-up design of anti-fouling surfaces.
Currently available separation channels for asymmetric flow
field-flow fractionation (AF4), which results in long analysis
time and solvent consumption, limits the application of AF4 in
[1} the field of nanoparticle analysis .
A miniaturized AF4 channel was introduced for the rapid
analysis of different nanoparticle samples. UV-Vis-MALS
provides the possibility to measure the particle size and molar
mass and offers a powerful tool for the investigation of
[2] separation performances of different AF4 channels .
Our objective was to develop fast and reliable separation
methods for both channels and enable a direct comparison by
the corresponding chromatographic parameters.
Reliable analysis of chemical indicators in water, sediment and soil samples for the purpose of environmental pollution assessment poses one of the greatest analytical challenges, having in mind the complexity of sample matrix and low concentrations of pollutants. Organics (pesticides, PAHs, PFOS, etc.) and heavy metals (Hg, Cd, Ni, Pb and As) represent target parameters. Laboratories performing sampling and tests in this field regulated by respective EU directives, need strong support in order to establish a quality system. It is necessary to provide appropriate calibrators i.e. matrix CRMs relates to the unique sample matrices representing typical samples in the geomorphological and anthropological sense. In addition to that, bearing in mind the complexity and instability of environmental samples, it is very difficult to obtain appropriate referents materials with no local providers.
Our project is aiming to develop capacity to produce CRMs for environmental analysis by transferring the theoretical and practical know-how between the partners and combining their skills to focus on environmental CRM production in accordance with ISO Guide 34. Our project will have an impact on environmental monitoring in the partnering countries and on the scientific community, who will use the newly developed reference materials. Furthermore, partners will develop strategies for producing new CRMs either on their own or in cooperation. This will lead to regional CRM producers serving scientific and official laboratories.
This project aims to develop capacity to produce certified reference materials (CRMs) for environmental analysis by transferring know-how between the partners and combining their skills to focus on environmental CRM production. The production process includes good manufacturing practices for processing materials, method development, the validation and application of homogeneity, stability and characterisation tests, the calculation of individual uncertainties (between-unit inhomogeneity, long term stability, characterisation) and combination of uncertainties to determine overall uncertainty of the matrix reference materials. An inter laboratory comparison registered as a EURAMET project is set as the ultimate project outcome, confirming the partners’ capabilities in applying newly acquired skills.
The objective of this study is to find out how far geochemical characteristics of the blue mineral pigment can be confirmed in respect to its provenance. In dependence of the quantity of samples analysed from a special geological region and the methods applied, a range of variation is taken into consideration. To provide clues, a multi-technique analytical approach with µXRF and ESEM is applied to samples from the most famous deposits.
Special elements determined as fingerprint are related to the textural features corresponding directly to the geological conditions of forming. The results and the statistical output allow a differentiation that enables an optimized local classification of the blue stone. To be aware of the limits of analysis is an absolute requirement for each geo-tracing implemented on blue coloured cultural objects of unknown provenance. For testing the possible sources of lapis lazuli, the blue pigment used as paint on murals and as ink on manuscripts from the Silk Road is analysed in an exemplary way.
Multiply negatively charged DNA oligonucleotides of small sizes (n=15-40 bases) have been subjected to a comprehensive tandem mass spectrometric study (MS/MS). Collision induced dissociation (CID) mass spectrometry (MS) was applied as a tool to break down isolated DNA oligonucleotides with a defined number of charges. Various lenghts and sequences were analyzed unravelling a comparable direct correlation between the threshold collision energy for fragmentation and the charge-per-base density in the precusor ion. It was also revealed that the increase in charges and thus Coulomb repulsion results in the transition from a folded, compact form to an elongated structure of the precusor ions.
Multiply negatively charged DNA oligonucleotides of small sizes (n=15-40) have been subjected to a comprehensive tandem mass spectrometric study (MS/MS). Collision induced dissociation (CID) mass spectrometry (MS) was applied as a tool to break down isolated DNA oligonucleotides with a defined number of charges. Various lenghts and sequences were analyzed and all of them showed a comparable direct correlation regarding the threshold collision energy for fragmentation and dependence on number of charges on the precursor ions. It was also revealed that the increase in charges and thus Coulomb repulsion results in the transition from a folded, compact form to an elongated structure of the precursor ions.
Dislocations, as carriers of plastic deformation, affect important properties in technical materials, e. g., plasticity. The realistic description of plastic deformation caused by dislocations demands the representative measurement of their features, e.g., line direction, slip plane, Burgers vector and density. Bulk deformation of structural and functional alloys requires reliable data from large regions. The filiform nature of dislocations interacting with complex microstructures additionally demands observation and analysis techniques that allow resolving the details of their interactions in space. The use of electron tomography for this purpose is bound to difficult and time consuming experimental setups, which are not always applicable to any material. In this contribution a new tool is presented, which enables the three-dimensional reconstruction, visualization and quantification of dislocation densities and directions from manual tracing of scanning transmission electron microscopy (STEM) stereo-pairs. Examples are shown from samples of a creep-deformed monocrystalline Ni-base superalloy.