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Multivariate analysis of MALDI imaging mass spectrometry data of mixtures of single pollen grains
(2018)
Here, we present an advanced approach to identify pollen grains in mixtures based on:
- a simplified sample preparation procedure
- MALDI imaging mass spectrometry
- chemometric tools
Our goals are to:
- explore the biomolecular variations in pollen
- determine species-specific peak patterns
- discriminate and identify single pollen grains in mixtures using MSI
The EC Recommendation on the definition of nanomaterial, based solely on size of the constituent particles, foresees development of harmonised measurement methods ensuring ‘consistent results across materials and over time’. The EU/FP7 research project NanoDefine has been exclusively dedicated to support the implementation of this EC Recommendation for the European Union’s legislation. For the first time, measurement techniques able to determine the size of nanoparticles have been evaluated systematically on a well-defined set of quality control materials (spherical, monodisperse) as well as industrial materials of complex shapes and considerable polydispersity.
Particularly based on the analytical performance of the measurement techniques as tested on the challenging real-world particulate materials, it was possible to formulate recommendations for use of a new tiered approach consisting of screening and confirmatory techniques. Thus, a consistent framework of guidance for nanomaterial identification according to the EC Definition has been issued in form of the NanoDefiner e-tool, with a transparent decision flow scheme and an extensive user manual. Selected examples of analysis and classification as nano-/non-nanomaterials will be given, highlighting the limits of applicability of the available measurement techniques in dependence on sample properties. On some recent relevant developments in sample preparation – as a crucial part for an accurate analysis - will be also reported. Further, ISO/TC 229 ‘Nanotechnologies’ activities aiming at establishing accurate TEM and SEM measurement of NP size and shape as robust, traceable, standard procedures are highlighted. With participation of BAM, study groups have been organizing inter-laboratory comparisons on well-selected NP systems according to the market needs, such as aggregated or shape-controlled titania nano-powder for which size and shape distribution of primary particles must be measured accurately.
Lasermaterialbearbeitung ist eine sich schnell entwickelnde Technologie, um eine Vielzahl von Oberflächenfunktionalitäten auf Basis optischer, mechanischer oder chemischer Eigenschaften zu realisieren. Die Verwendung ultrakurzer Laserimpulse mit Dauern im Femtosekundenbereich ermöglicht dabei neben einer herausragenden Bearbeitungs-präzision auch die selbstorganisierte Erzeugung verschiedener charakteristischer Ober-flächenstrukturen mit Größenskalen im Mikrometer- bis hinunter in den sub-100-nm-Bereich, z.B. sogenannte Ripples („Laser-Induced Periodic Surface Structures“, LIPSS), Grooves, oder Spikes.
In dem Vortrag wird ein Überblick über die in den vergangenen Jahren in Zusammenarbeit mit dem BAM Fachbereich 6.3 durchgeführten tribologischen Experimente gegeben. Besonderes Augenmerk liegt dabei auf den tribologischen Eigenschaften (Reibung und Verschleiß) der unterschiedlichen Femtosekunden-Laser-generierten Oberflächen-morphologien auf gängigen Metallen (z.B. Stahl, Titan). Einflüsse durch die Veränderungen der Härte des Werkstoffs infolge Laser-induzierter Oxidation, der Dicke und Struktur der Oxidschicht, und die Wirksamkeit unterschiedlicher Schmiermittel (z.B. additiviertes Motoröl) werden diskutiert.
The talk addresses the STANDARDIZATION OF ELLIPSOMETRY and the following points are discussed in more detail: historical background of ellipsometry, history of International Conferences on Ellipsometry, Workshops Ellipsometry in Germany and Europe, information on German/European Working Group Ellipsometry, technical/industrial importance of ellipsometry, applications on non-ideal material systems and standardization activities on ellipsometry.
Reliable standards are required to support research and development as well as end-user in application. Appropriate standards have to fulfill three requirements: small uncertainty, easy to use and low overall costs of application. For calibration of microscopes at nanoscale and/or element analysis special requirements for standards are given, which are challenging in manufacture.
UCST-type thermoresponsive polymers (i.e. that phase separate from solution upon cooling) present a tremendous potential not only in aqueous media where they can be used in drug delivery, diagnostic and microfluidic applications,but also in water/alcohol mixtures, where they can be used for instance in sensing systems for alcohol-soluble drugs. However, only a few thermoresponsive polymers have been reported that present an UCST in a relevant temperature range and “green” solvents such as water or Ethanol.
In this context, acrylamide-based monomers can be very useful building blocks for designing novel non-ionic UCST-type polymers because of their hydrophilic nature (with the appropriate side chain) and propensity to form hydrogen bonds. We will present our latest results on the UCST-type thermoresponsive behaviour of acrylamide- and/or 2,6-diaminopyridine-based homopolymers and copolymers in water or water/alcohol mixtures, and give some insights about the rational design of UCST polymers relying on H-bonding.
The interphase between the inorganic filler and the polymer matrix is considered as one of the most important characteristics of inorganic/polymer nanocomposites. The segmental dynamics of this interphase is expected to be altered as compared to the pure matrix, which might percolate into the entire system. For instance, it was found that a so-called Rigid Amorphous Phase (RAF) is formed by adsorption of segments onto the nanoparticles yielding to its immobilization. The RAF is available from the decrease of the specific heat capacity Δcp in the glass transition region of the nanocomposites. Here, precise Temperature Modulated DSC (TMDSC) was employed to study Δcp of epoxy/Boehmite nanocomposites with different nanofiller concentrations. Surprisingly, the investigated system showed an increase of Δcp with increasing filler concentration up to 10 wt%. This implies an increased fraction of mobile segments, and is in accordance with the found decreased value of the glass transition temperature Tg. Although for higher filler contents Tg further slightly decreases, Δcp decreases in contrary, indicating a formation of RAF. This behavior was discussed as a competition of mobilization effects, due to an incomplete crosslinking reaction, and the formation of RAF.
Thin mesoporous metal oxide films are versatile and attractive candidates for several energy applications like photovoltaics, electrolysis or batteries. Due to their high surface area and ordered pore structure, mesoporous metal oxides demonstrate higher activities. The performance of the porous films is affected by properties like size and shape of the mesopores as well as the crystallinity of the framework. The exact determination and metrological evaluation of the complex morphology of thin mesoporous films requires a new analytical approach employing to combined data of different analytical methods. In this contribution we present a novel evaluation procedure for spectroscopic ellipsometry (SE) to analyse thin mesoporous iridium oxide films. Mesoporous iridium oxide films were prepared via dip-coating of a solution containing a triblock-copolymer as structure directing agent and an Iridium precursor in ethanol. Deposited films were calcined in air at temperatures between 300 and 600 °C. Their morphology was studied with SEM and an electron probe microanalysis (EPMA) and correlated via SE with a Bruggeman effective medium approximation (BEMA). The developed SE model described the film thickness as well as the porosity.
... The contribution will assess in detail the novel approach to analyse the morphology and porosity of thin metal oxide films with spectroscopic ellipsometry. Moreover, the advantages of the new developed approach will be discussed as well as combination of datasets from multiple measurements to development new methods for innovative energy technologies.
In this contribution the mechanisms of formation and current applications of LIPSS are reviewed, including the colorization of technical surfaces, the control of surface wetting properties, the mimicry of the natural texture of animal integuments, the tailoring of surface colonization by bacterial biofilms, and the improvement of the tribological performance of nanostructured metal surfaces.
Thin mesoporous metal oxide films are versatile and attractive candidates for several energy applications like photovoltaics, electrolysis or batteries. Due to their high surface area and ordered pore structure, mesoporous metal oxides demonstrate higher activities. The performance of the porous films is affected by properties like size and shape of the mesopores as well as the crystallinity of the framework. The exact determination and metrological evaluation of the complex morphology of thin mesoporous films requires a new analytical approach employing to combined data of different analytical methods. In this contribution we present a novel evaluation procedure for spectroscopic ellipsometry (SE) to analyse thin mesoporous iridium oxide films.
Mesoporous iridium oxide films were prepared via dip-coating of a solution containing a triblock-copolymer as structure directing agent and an iridium precursor in ethanol. Deposited films were calcined in air at temperatures between 300 and 600 °C. Their morphology was studied with SEM and an electron probe microanalysis (EPMA) and correlated via SE with a Bruggeman effective medium approximation (BEMA). The developed SE model described the film thickness as well as the porosity.
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The contribution will assess in detail the novel approach to analyse the morphology and porosity of thin metal oxide films with spectroscopic ellipsometry. Moreover, the advantages of the new developed approach will be discussed as well as combination of datasets from multiple measurements to development new methods for innovative energy technologies.
Laser-induced periodic surface structures (LIPSS, ripples) are a universal phenomenon that can be observed on almost any material after the irradiation by linearly polarized laser beams, particularly when using ultrashort laser pulses with durations in the femtosecond to picosecond range.
During the past few years significantly increasing research activities have been reported in the field of LIPSS, since their generation in a single-step process provides a simple way of nanostructuring and surface functionalization towards the control of optical, mechanical, biological, or chemical surface properties. In this contribution the mechanisms of formation and current applications of LIPSS are reviewed, including the colorization of technical surfaces, the control of surface wetting properties, the mimicry of the natural texture of animal integuments, the tailoring of surface colonization by bacterial biofilms, the advancement of medical pacemakers, and the improvement of the tribological performance of nanostructured metal surfaces.
The damage caused by ionizing radiation to DNA and proteins is the reason to treat cancer by radiation therapy. A better understanding of the molecular processes and quantification of the different damaging mechanisms is the prerequisite to develop more efficient therapies. Hereby the understanding of the processes involved in the damage to DNA are of key interest due to its central role in reproduction and mutation.
For radiation with low linear energy transfer (LET), most of the damage is caused by the secondary particles produced by scattering of the ionizing radiation with water. Thereby a multitude of species are produced, whereby especially kinetic low energy electrons, prehydrated electrons, OH-radicals and ions are of importance.
With higher LET the relative amount of the direct damaging effects increases. This is especially important considering the increased usage of high LET particles in radiation therapy. Therefore, the quantification of the contribution to DNA damage of direct and indirect effects and the different secondary species is of high interest due to the increase of radio biological efficiency when applying high LET radiation.
Here we present an approach to investigate the relative contributions to DNA strand break yield for radiation of different LET within a single electron microscope in combination with electron scattering simulations.
Thin mesoporous metal oxide films are versatile and attractive candidates for several energy applications like photovoltaics, electrolysis or batteries. Due to their high surface area and ordered pore structure, mesoporous metal oxides demonstrate higher activities. The performance of the porous films is affected by properties like size and shape of the mesopores as well as the crystallinity of the framework. The exact determination and metrological evaluation of the complex morphology of thin mesoporous films requires a new analytical approach employing to combined data of different analytical methods. In this contribution we present a novel evaluation procedure for spectroscopic ellipsometry (SE) to analyse thin mesoporous iridium oxide films.
Mesoporous iridium oxide films were prepared via dip-coating of a solution containing a triblock-copolymer as structure directing agent and an iridium precursor in ethanol. Deposited films were calcined in air at temperatures between 300 and 600 °C. Their morphology was studied with SEM and an electron probe microanalysis (EPMA)and correlated via SE with a Bruggeman effective medium approximation (BEMA). The developed SE model described the film thickness as well as the porosity.
Figure 1a shows a top-view SEM image of mesoporous IrO2 film calcined at 375 °C. The image reveals that the films exhibit a well-ordered mesopore structure with an average pore diameter of 16 nm and a periodic distance between pore centres of 24 nm (FFT inset). Figure 1b is a parity plot of film thicknesses determined by cross-section SEM versus SE of IrO2 film samples prepared at different calcination temperatures. The porosity from the SE model is in good agreement to the porosity values obtained by EPMA.
The contribution will assess in detail the novel approach to analyse the morphology and porosity of thin metal oxide films with spectroscopic ellipsometry. Moreover, the advantages of the new developed approach will be discussed as well as combination of datasets from multiple measurements to development new methods for innovative energy technologies.
The EC’s recommendation for a definition of nanomaterial (2011/696/EU) should allow the identification of a particulate nanomaterial based on the number-based metric criterion according to which at least 50% of the constituent particles have the smallest dimension between 1 and 100 nm. However, it has been recently demonstrated that the implementation of this definition for regulatory purposes is conditioned by the large deviations between the results obtained by different sizing methods or due to practical reasons such as high costs and time-consuming (SEM, TEM).
Within the European project NanoDefine (www.nanodefine.eu) a two-tier approach has been developed, whereby firstly a screening method is applied for the rough classification as a nano-/non-nanomaterial, and for borderline cases a confirmatory method (imaging methods or field flow fractionation) must be considered.
One of the measurement methods well suited to particulate powder is the determination of volume-specific surface area (VSSA) by means of gas adsorption as well as skeletal density. The value of 60 m2/cm3 corresponding to spherical, monodisperse particles with a diameter of 100 nm constitutes the threshold for decisioning if the material is a nano- or non-nanomaterial. The correct identification of a nanomaterial by VSSA method is accepted by the EU recommendation.
However, the application of the VSSA method is associated also by some limitations. The threshold of 60 m2/cm3 is dependent on the particle shape, so that it changes considerably with the number of nano-dimensions of the particles. For particles containing micro-pores or having a microporous coating false positive results will be produced. Furthermore, broad particle size distributions make necessary to adjust the threshold. Based on examples of commercially available ceramic powders, the applicability of the VSSA approach will be tested (in relation with SEM and TEM measurements) in order to expand the actual knowledge and to improve this good available and agglomeration tolerant method.
The EU recommendation for a definition of nanomaterial (2011/696/EU) should allow the identification of a particulate nanomaterial based on the number-based metric criterion according to which at least 50% of the constituent particles have the smallest dimension between 1 and 100 nm. Within the European Project NanoDefine (www.nanodefine.eu) a two-tier approach has been developed, whereby firstly a screening method is applied for the rough classification as a nanomaterial or non-nanomaterial, and for borderline cases a confirmatory method (imaging methods or field flow fractionation) must be considered.
One of the measurement methods well suited to particulate powder is the determination of volume-specific surface area (VSSA) by means of gas adsorption as well as skeletal density. The value of 60 m2/cm3 corresponding to spherical, monodisperse particles with a diameter of 100 nm constitutes the threshold for decisioning if the material is a nanomaterial or non-nanomaterial. The correct identification of a nanomaterial by VSSA method (positive test) is accepted by the EU recommendation.
However, the application of the VSSA method is associated also by some limitations. The threshold of 60 m2/cm3 is dependent on the particle shape. For particles containing micro-pores or having a microporous coating, false positive results will be produced.
Furthermore, broad particle size distributions – as typically for ceramic materials – as well as multi-modal size distributions make necessary to adjust the threshold.
Based on examples of commercially available ceramic powders, the applicability of the VSSA approach will be tested (in relation with SEM and TEM measurements) in order to expand the actual knowledge and
improve the method.
Duplex (DSS) and austenitic stainless steels (ASS) are frequently used in many energy related applications. The duplex grade is considered to have outstanding mechanical properties as well as good corrosion resistance. The austenitic phase combines high ductility, even at low temperatures, with sufficient strength, and therefore such materials are applied in storage and transport of high-pressure hydrogen. During service in acidic environments large amounts of hydrogen can ingress into the microstructure and induce many changes in the mechanical properties of the steel. Embrittlement of steels by hydrogen remains unclear even though this topic has been intensively studied for several decades. The reason for that lies in the inability to validate the proposed theoretical models in the sub-micron scale. Among the very few available methods nowadays, Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) enables a highly accurate mapping of hydrogen in the microstructure in a spatial resolution below 100 nm. In the present work ToF-SIMS was used as a main tool in order to investigate the effect of deuterium on a duplex microstructure of lean and standard DSSs during and after the electrochemical charging process. Electrochemical charging simulates the service of a component in acidic environments under conditions of cathodic protection that are commonly applied to prevent corrosion reactions. ToF-SIMS after multivariate data analysis (MVA) was combined with high resolution topographic images and electron back-scattered diffraction (EBSD) data to characterize the structural changes. It was observed that the ferritic phase was affected almost identical in all steels whereas in the austenitic phase significant differences were obtained in the lean duplex in comparison to the standard DSS. The obtained results have been compared to similar investigations on a AISI 304L austenitic stainless steel. The advantage of the combined techniques is reflected by the ability to correlate the hydrogen distribution in the microstructure and the resulted phase transformation.
One-part geopolymers (OPGs) are a sort of alkali-activated materials (AAMs) which production avoids the use of highly-alkaline activator-solutions and contributes to a better acceptance of alternative mineral binders in terms of safety-related and economic aspects. In the present contribution OPGs were synthesized by blending silica sources (two industrial silicas and two biogenic silicas) with sodium aluminate and only water must be added to initiate the hardening, i.e. mixing is performed in the same way as for conventional Portland cements. The OPGs were characterized by XRD, and SEM and the degrees of reaction of the silicas were determined by a chemical dissolution method.
The industrial silicas led to the formation of geopolymer-zeolite composites, that contained, besides geopolymeric gel, crystalline tectosilicates (e.g. zeolite A and hydrosodalite) and depending on the starting composition also unreacted silica. The biogenic silicas provided a higher reactivity and avoided the formation of crystallite by-products. The differences in the microstructures caused differences in the mechanical strength of the specimens.
The treatment of the OPG composites at moderate elevated temperatures revealed promising behavior on thermal dehydration in terms of shrinkage and residual strength up to 700 °C. Above 700 °C sintering and partial melting occurred, and new phase formation commenced. After exposure to 1000 °C the specimens appeared virtually amorphous or formed stuffed silica structures of nepheline- or carnegieite-type type.
The investigations of the OPG based mortars on their resistance against sulfuric acid in accordance with DIN 19573 (Appendix A) revealed very high residual strengths up to 78 % after treatment with H2SO4 (pH 1) for 70d. A mechanism of dissolution of the primary aluminosilicate reaction products of the pastes and the precipitation of a silica gel that protects the remaining aluminosilicates and decelerates further corrosion was found to be the main reason for the good performance under acidic conditions. The addition of CaO-containing feedstocks enhanced hardening, but at a certain content the resistance against sulfuric acid decreased, due to the formation of gypsum on exposure to sulfate.
In addition, the mortars exhibited excellent shrinkage behavior as well as good bond to concrete substrates with pull-off strength up to > 3 MPa. The workability of the fresh mortars provided very good manual applicability; automatic applications such as sprayed and spun mortars will require further optimization regarding rheological properties. In summary, the studied OPG are promising materials for the construction and the repair of concrete structures, such as sewers, that are affected by biogenic sulfuric acid corrosion.
Graphene and its derivatives have recently attracted much attention for sensing and deactivating pathogens. However, the mechanism of multivalent interactions at the graphene–pathogen interface is not fully understood. Since different physicochemical parameters of graphene play a role at this interface, control over graphene’s structure is necessary to study the mechanism of these interactions. In this work, different graphene derivatives and also zwitterionic graphene nanomaterials (ZGNMs) were synthesized with defined exposure, in terms of polymer coverage and functionality, and isoelectric points. Then, the switchable interactions of these nanomaterials with E. coli and Bacillus cereus were investigated to study the validity of the generally proposed “trapping” and “nano-knives” mechanisms for inactivating bacteria by graphene derivatives. It was found that the antibacterial activity of graphene derivatives strongly depends on the accessible area, i.e. edges and basal plane of sheets and tightness of their agglomerations. Our data clearly confirm the authenticity of “trapping” and “nano-knives” mechanisms for the antibacterial activity of graphene sheets.