Analytische Chemie
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Mechanochemistry is a fast and efficient method applicable for the synthesis of new organic, metal-organic, and inorganic compounds. The direct monitoring of milling reactions is still challenging. The underlying reaction mechanisms often remain unclear. In the last years, we have established a tandem in situ approach for investigating mechanochemical reactions using time-resolved in situ XRD coupled with Raman spectroscopy. A further development is the in situ coupling of synchrotron XRD, Raman spectroscopy, and thermography allowing the observation of mechanochemical reactions in real time. [5] Information on the crystalline, molecular, and temperature state of the materials during grinding could be collected. The chemical composition of the reaction mixture was found to be directly correlated with changes in the temperature profile of the reaction. Furthermore, the presented setup allows the detection of crystalline, amorphous, eutectic as well as liquid intermediates. Based on these data, metastable polymorphs of cocrystals and coordination polymorphs could be isolated and struc-turally characterized. A multi-step diffusion mechanism was identified for most systems. Crystalline phases were obtained intermediately, suggesting that the synthesis is following Ostwald’s rules of stages. The resulting deeper kinetic and thermodynamic understanding of milling processes is the key for future optimization of mechanochemical syntheses.
BAM and Division 6.1
(2018)
Polymers at interfaces play a major role in a broad variety of applications ranging from engineering purposes (for instance polymer based nanocomposites) to high tech implications (for instance light emitting diodes).
Here, thin films with thicknesses down to few nanometers are prepared on different substrates as model systems for polymer composites. The thin films are investigated by a combination of surface analytical and volume sensitive methods. As surface analytical methods atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements (CAM) are employed. As volume sensitive broadband dielectric spectroscopy (BDS), specific heat spectroscopy (SHS), and ellipsometry are used. Especially attention is paid to understand the glass transition behavior of thin films because the glass transition is the key phenomenon determines the application of polymers also in thin films.
To understand the glass transition behavior of thin films, which is controversially discussed in literature, a three layer model is discussed. Firstly, a mobile surface layer is assumed at polymer air interface of the film due to missing of segment/segment interactions. Secondly, in the middle of the film a bulk-like layer should be expected. Thirdly, for polymers having non-repulsive interactions with the substrate an irreversibly adsorbed layer is expected to be formed. Due the adsorption the molecular mobility of the segments in this layer is slowed down. What is measured for the glass transition of thin films is a complicated average of all of these effects. The different layers are hardly to address separately. Therefore, in the presentation especially model systems are selected and investigated to verify the layer model.
In dieser Präsentation werden Aktivitäten im Bereich der 'nano'-Charakterisierung bei der BAM vorgestellt. Beispiele von F&E-Projekten und -Kooperationen im nano-Analytik-Bereich bei der BAM werden genannt. Thematische Kooperations-Möglichkeiten zwischen BAM und dem Netzwerk NanoAnalytik und -Messtechnik in der Produktion werden diskutiert.
This presentation explains the outline and scientific content of the ISO technical report 23173 "Measurement of the thickness and nature of nanoparticle coatings using electron spectroscopies". This technical report deals with those electron spectroscopy methods that are able to determine the coating thickness of nanoparticles. This specifically includes X-ray photoelectron spectroscopy (XPS), energy-resolved X-Ray photoelectron spectroscopy (ERXPS) using synchrotron radiation, near abient pressure photoelectron spectroscopy (NAPXPS) and Auger electron spectroscopy (AES).
The proposed ISO Technical Report provides a description of a variety of physical methods of analytical chemistry by which bacteria and biofilms can be analysed. The state of the art, sample requirements and strengths associated with each method are identified. Presented at the DIN-meeting for NA 062-08-16 AA „Chemische Oberflächenanalyse und Rastersondenmikroskopie“
Graphene is a two-dimensional carbon network with unique properties. However, its low solubility, poor reactivity and the limited accessibility of a well-defined basal plane are major challenges for applications. An ideal method to overcome these problems is the covalent attachment of functional molecules to its surface which enable further reactive modifications for specific applications. There are several technologies for surface functionalization of graphene and related CNT materials. To get control on the functionalization process and to optimize the performance of the modified surfaces analytical tools for surface chemical characterization are required. X-ray absorption (NEXAFS) and photoelectron spectroscopy (XPS) have been identified to be rather powerful here [1-3]. Specifically, NEXAFS spectroscopy underpinned by quantum chemical spectrum simulations [4] is unique in a way to address changes of aromaticity and defect formation at the graphene surface during functionalization.
For relevant surface modification technologies, we present examples on how NEXAFS and XPS can do a good job. All presented modifications aim on the production of platforms for defined functional 2D nanomaterials, as for example multifunctional hybrid architectures. In detail, we investigated:
• A wet chemical method for covalent functionalization of graphene sheets by a one-pot nitrene [2+1] cycloaddition reaction under mild conditions. Here a reaction between 2,4,6-trichloro-1,3,5-triazine and sodium azide with thermally reduced graphene oxide (TRGO) results in defined dichlorotriazine-functionalized graphene sheets.
• Graphene and carbon nanotube functionalized by Vacuum-Ultraviolet (VUV) induced photochemical or r.f. cw low pressure plasma processes to introduce amino, hydroxy or brominated functionalities.
To underpin finger-print information delivered by C K-edge NEXAFS we studied the effects of selected point and line defects as well as chemical modifications for a single graphene layer model by density functional theory based spectrum simulations.
References
[1] P.-L. Girard-Lauriault et al., Appl. Surf. Sci., 258 2012 8448-8454, DOI: 10.1016/j.apsusc.2012.03.012
[2] A. Lippitz et al., Surf. Sci., 611 2013 L1-L7, DOI: 10.1016/j.susc.2013.01.020
[3] A. Faghani et al., Angew. Chemie (International ed.), 56 2017 2675-2679, DOI:10.1002/anie.201612422
[4] C. Ehlert, et al., Phys.Chem.Chem.Phys., 16 2014 14083-14095, DOI: 10.1039/c4cp01106f
In this talk sample prep/handling, instrument calibration and data acquisition methods with examples from XPS, Auger and SIMS will be addressed in terms of their contributions to the reproducibility of data delivered by the methods.
Active parties in the field are VAMAS TWA 2 “Surface chemical analysis” (http://www.vamas.org/twa2/index.html), ISO/TC 201 “Surface chemical analysis” (https://www.iso.org/committee/54618.html) and the Surface Analysis Working Group (SAWG) at the International Meter Convention (https://www.bipm.org/en/ committees/cc/wg/sawg.html). The tools to improve the reproducibility of spectra, depth profiles and images at these international platforms are inter-laboratory comparisons, validated SOPs, standards and certified reference materials (CRM) as well as uncertainty budgets and establishment of traceability chains. The last point is of specific importance because all the methods, XPS, Auger and SIMS, are not primary methods.
To address quantitative XPS, AES and SIMS results of relevant inter-laboratory comparisons organized by SAWG considering measurands as alloy surface composition and thickness of thin films will be introduced. These comparisons delivered results which are viewed to be benchmarking, some of them resulted in ISO/TC 201 standards. For quantitative XPS and AES the principal outline of an uncertainty budget will be discussed together with the audience. Another issue of quantitative XPS which definitely needs consideration are valid methods for a determination of the transmission function of the instruments and even for the emission angle in the respective experiments.
Concerning the field of depth profiling it has to be investigated together with the audience whether the ISO (or ASTM) standards we have are sufficient to guarantee comparable results. Having in mind the number of different sputter ion species available today and range of samples of interest (metals, semiconductors, organic films) this might be questionable. And, how do depth profiling by AR-XPS and variable excitation energy XPS compete here?
For imaging surface chemical analysis, the characterization of the imaging system is an issue to be investigated. Here the determination of lateral resolution is a relevant topic.
Finally, the future needs to develop metrology for new applications e.g., ambient-pressure XPS, bio samples, and core-shell nanoparticles, will be issues raised for a discussion with the audience.
Gold ist eines der sieben schon im Altertum bekannten Metalle und wurde wg. seines Glanzes und seiner Seltenheit von alters her als Tauschmittel und zur Herstellung von Schmuck benutzt. Außerdem ist es einfach bearbeitbar und weitestgehend gegen chemische Einflüsse resistent. Die Untersuchungen von Gold mit synchrotronstrahlungsangeregter Röntgenfluoreszenzanalyse sind zerstörungsfrei und geben Auskunft über die in der untersuchten Probe vorhandenen chemischen Elemente. Bei den hier vorgestellten Untersuchungen an der BAMline stehen Fragestellungen wie Herkunft, Herstellungsverfahren und Zusammengehörigkeit von Goldfunden im Vordergrund. Die verschiedenen Fragestellungen werden an einer Reihe von Beispielen erläutert die vom Wikingerschatz aus Hiddensee über die Himmelsscheibe von Nebra bis hin zu Funden aus Ägypten langen. Zusätzlich werden die modernen Messmethoden vorgestellt, die am Synchrotron heutzutage zur Verfügung stehen.
In-Situ SAXS Techniques
(2018)
Our project's aim is to enhance the capabilities of additive manufacturing techniques, where enabling a Two-Photon-Polymerization (TPP) 3D printer of producing arrays of precisely aligned nanoparticles is of an enormous value. As heterogeneous functional nanostructures with arrays of oriented nanoparticles are very promising in many fields; electrochemistry, energy storage, nanoelectronics among other vital fields.
The feasibility and the convenience of orienting nanoparticles using magnetic, electric fields and ultrasonic vibrations will be systematically investigated, using Small Angle X-ray Scattering (SAXS), since SAXS can provide detailed information about the orientation characteristics of nano-Ensembles. Corresponding to our prerequisites, a set ad hoc functional sample holders, sample stages and other In-Situ SAXS solutions were developed, and incorporated to be compatible with a state-of-the-arts SAXS machine, called Multi-scale Analyzer for Ultrafine Structures (MAUS).
The MAUS has been customized and engineered to serve as a miniaturized synchrotron, and that is exactly what we need.
Experiments attempting to orient superparamagnetic nanoparticles will be discussed, where the outcomes will not only help in understanding the mechanics of field-particle interactions, it will also help in further developing the adequate needed set of corrections to the SAXS data, that is especially regards oriented samples.
Absorption edge tomography, also known as differential tomography at absorption edges, is a method which exploits the sudden change of the attenuation coefficient, when the photon energy crosses the absorption edge of an element. Synchrotron radiation is the best source for absorption edge tomography, because of its small bandwidth, high intensity and easily adjustable photon energy. The synchrotron beamline BAMline at the synchrotron radiation facility BESSY II in Berlin, which is operated by the Bundesanstalt für Materialforschung und -prüfung (BAM), provides a monochromatized beam in a photon energy range from 5 keV up to 80 keV with a bandwidth of 2%, when the double multilayer monochromator is used. Together with the microtomography setup, this enables differential tomography with submicron resolution at the K edge of the elements from chromium up to the lanthanides, and up to uranium, when the L edges are used as well.
In this work, metal organic frameworks (MOFs) embedded in polymer are characterized using differential tomography. MOFs are microporous structures of metal ions, coordinated by organic linker molecules, that can be used in a broad field of applications, especially in gas storage and catalysis. In this work, polymer embedded MOFs were extruded into filaments, which could be used for 3d-printing to profit from the specific properties of the MOFs in polymeric materials combined with the arbitrary shapes provided by 3d-printing. For the extrusion, different polymer classes like ABS, polyester- and polyetherurethanes, as well as different MOFs (ZIF-8, ZIF-67, HKUST-1) were used to create MOF containing filaments with a nominal diameter of 3.0 mm. Differential tomography at the edges of the Zn, Co, and Cu was then used to find the distribution of the corresponding MOF in the filament and to analyze the shape of the inclusions.
Transparent conductive oxide (TCO) films are a vital part of a large part of modern technology. The production of TCO materials has sparked much development in plasma coating technology. Quality control measurements of these layers are therefore important in many fields of optics and electronics such as high efficiency thin film photovoltaics. In this presentation, we report on optical measurements of ZnSnOx layers generated by DC/RF magnetron plasma co-sputtering. By changing the respective power on two different targets, the overall power, the gas composition and post-treatment, the properties of this type of layers can be varied in a number of parameters. The optical, electrical, and chemical properties of TCO layers are the technically most important properties together with the layer thickness. The dielectric function of layers is accessible by means of spectroscopic ellipsometry, which also yields the very important value for the layer thickness at the same time. It would be a significant step forward in quality control to use this non-destructive method also as a fast test for electrical properties. Therefore, we report on the optical properties connected to the production parameters, and also on our preliminary results connecting the optical dielectric function (in the visible and near infrared) to the electrical conductivity of the layers. We discuss the effect of deposition parameters on the optical properties of the layers and present an approach for correlating optical and electrical properties. Further, we discuss the question of accuracy of optical properties gained from model-fit-based optical methods and the use of different parameterised models for the dielectric function to achieve this.
Mechanochemistry is a suitable method for synthesizing a variety of metal phosphonates. By varying the ratio of the reactants, it is possible to control the reaction pathway. With this approach targeted synthesis of a certain composition is possible. Several new metal phosphonate structures were solved from the powder X-ray diffraction data including molecular metal phosphonates. The results demonstrate a new fast, facile, and environmental friendly alternative for the preparation of metal phosphonates. In situ investigations of the milling processes provided insights into the formation process of metal phosphonates. A multi-step diffusion mechanism was identified for most systems. Crystalline phases were obtained intermediately, suggesting that the synthesis is following Ostwald’s rules of stages.
The Color X-ray Camera CXC or SLcam® is an energy-resolving X-ray camera capable of energy- and space-resolved measurements. It consists of a high-speed CCD detector coupled to a polycapil-lary optic that conducts the X-ray photons from the probe to distinct pixels onto the detector. The camera is capable of fast acquisition of spatially and energy resolved fluorescence images. A dedicated software enables the acquisition and the online processing of the spectral data for all 69696 pixels, leading to a real-time visualization of the elements distribution in a sample. It was developed in a joint project with BAM, IFG Berlin and PN Sensors. In this contribution we will mainly discuss the use of the CXC at our beamline, the BAMline at BESSY II and imaging applications of the CXC from different areas, like biology and archaeometry. Additionally new developments for the use of the detector without optics, like wavelength dispersive detection or 1shot-XANES, will be presented.
X-ray absorption fine structure spectroscopy (XAFS) is a frequently employed technique in order to investigate structural composition and change of chemical compounds such as catalytic species. These structural properties are essential (i) to understand underlying reaction mechanism and (ii) to further improve the design of efficient catalysts.
This investigation is based on a newly developed XAFS setup comprising both time- and lateral-resolved XAFS information simultaneously in a single-shot (S2XAFS). The primary broadband beam is generated by a filter/X-ray-mirror combination (bandpass). The transmitted beam through the sample is diffracted by a convexly bent Si (111) crystal, producing a divergent beam. This, in turn, is collected by an area sensitive detector with a theta to 2 theta geometry. This facile, stable and scanningless setup was tested at the BAMline @ BESSY-II (Berlin, Germany).
This contribution focuses on further experimental optimizations allowing the characterization of supported vanadium oxide (VOx) based catalysts at the lower hard X-ray regime (5 to 6 keV). First S2XAFS measurements of these catalysts are presented herein. Supported VOx catalysts show promising results in the oxidation of methane to formaldehyde.
S2XAFS allows determining the structural composition of the metal (i.e. vanadium) based on a fast and smart setup. It is therefore an ideal tool to identify crucial roles of chemical compounds in catalytic reactions.
XAFS@BAMline
(2018)
X-ray Absorption fine structure spectroscopy (XAFS) is a frequently employed technique in order to investigate structural composition and Change of chemical compounds such as catalytic species or corrosion processes. These structural properties are essential (i) to understand underlying reaction mechanism and (ii) to further improve the design of materials.
While XAFS measurements are usually performed with ionization Chambers or simple fluorescence detectors, we at BAMline specialize in measurements with innovative set-ups that meet Specialrequirements such as time resolution, (3D-) spatial Resolution or demanding sample environments.
This contribution presents various available XAFS configurations with their corresponding applications. In particular, these comprise single -shot XAFS for time- resolved measurements, grazing-exit XAFS with energy and a spatially resolved detector for the characterization of thin films and an in situ grazing incidence Setup for the characterization of corrosion layers.
Additionally,the possibility of analyzing Minute samples in total-reflection geometry is demonstrated.
Zinc oxide (ZnO) as a wide-bandgap II-VI semiconductor finds application in areas like optoelectronics, photocatalysis as well as in detection systems. While band-gap engineering in macroscopic ZnO can be performed by alloying, the band-gap of ZnO nanoparticles is also dependent on their size. Since small-angle X-ray scattering (SAXS) provides a much higher resolution in terms of ultra-small nanoparticle size analysis compared to other techniques, it allows for a careful examination of the correlation between particle size and band-gap.
We report on the microwave-assisted synthesis of oleate-capped, photoluminescent zinc oxide nanoparticles with adjustable size as dispersions in organic solvents. The spherical particles were obtained by hydrolysis of the metal precursor in presence of a strong base at temperatures above the solvent’s boiling point. Hence, the reaction is dramatically accelerated and within seconds – instead of hours at lower temperatures –, narrowly dispersed particle systems are yielded. The particles’ sizes as derived from SAXS strongly depend on the reaction temperature and time. Choosing the right reaction conditions, the particle size and thus their band gap can be finely tuned. A size increase can be achieved both by increasing the reaction temperature and the reaction time.
See Figure 1 for an exemplary comparison of five-minute syntheses at different temperatures. Here, the yielded particles display diameters between 5.0 and 7.6 nm and corresponding band-gaps of 3.32 up to 3.41 eV. The size increase is accompanied by a red-shift of the UV/Vis absorption edges and fluorescence emission.
Furthermore, these particles can be transferred into water by coating with polysorbates.
ZnSnOx coatings were deposited from two 2in magnetron targets made of
ZnO and SnO2 connected to DC pulsed and RF power supplies, respectively.
The pure Ar and reactive gas mixture Ar/O2 were used. DC pulsed power applied on ZnO target was kept constant 50W 50kHz, 20% d.c. and the RF power applied on SnO2 target was set to values from 0W (pure ZnO deposited) up to 150W (up to 8 at.% of Sn in films). The deposited films were investigated by multiple techniques as deposited at RT as well as after annealing at temperatures 200o C and 450o C. The lower annealing temperature is still compatible with many of common polymeric substrates.
The amount of Sn in the films is proportional to applied RF power on SnO2 target. But there is also significant influence of the post Deposition annealing on the film compositions. The ratio Zn/Sn is reduced by the annealing process. Therefore the annealing is promoting the migration of Sn toward the surface and Zn to inside. Moreover the films deposited in oxygen rich reactive gas mixture does not reduces the resistivity with added Sn in contrary to films deposited in Ar where the resistivity was reduced by 5 orders of magnitudes. The plasma parameters were investigated and mean energies of dominant species were in DC pulsed only about 3eV and DC + RF powered plasma up to 15eV. The expected higher energetic particles in the RF influenced plasma deliver an additional energy to the growing film. Therefore, we observed systematic differences between refractive indexes in the films deposited with low RF powered SnO2 magnetron at RT and post-annealed at 200 ° and practically no difference between RT and post-annealed film at higher RF power above 50 W. The XRD results proved the transitions from an amorphous to more crystalline structure by post-annealing of the films.
The paper addresses the “State-of-the-Art in Multiple-Sample Evaluation of Adhesive and Bonding Strength” and the following points are discussed in more detail:
1. Motivation (coatings, varnishes, tapes, laminates, CFRP, adhesive-bonded joints)
2. Conventional single-sample testing (evaluation of adhesive and bonding strength; failure pattern)
3. Multiple-sample handling (MSH), bonding (MSB), and testing: centrifugal adhesion testing (CAT) (multiple-sample approach, tensile test within a centrifuge)
4. Application examples of CAT-Technology™ (laminates, optical coatings, CFRP joints)
Finally, a summary is given regarding status quo and benefits of CAT-technology under tensile stress conditions whereas examples of testing in a centrifuge under compressive stress conditions are mentioned in the outlook.
Mechanochemie
(2018)
Products containing engineered nanoparticles already encounter us in most areas of our daily life including cosmetics, clothing, detergents, paints, batteries and displays. In most cases the particles exhibit a core-shell morphology either voluntarily or involuntarily. The properties of the nanoparticle shell determine the interaction with their environment and, thus, reliable control over these properties means reliable control over the particles performance and their toxicity. Therefore, sophisticated techniques to measure thickness and elemental composition of the nanoparticle shell are urgently required.
Scanning Auger microscopy (SAM) is a powerful technique with a lateral resolution below 10 nm and a chemical contrast based on the characteristic kinetic energy of Auger electrons related to specific atomic levels and, thus, to a specific element. This work explores the potential of SAM for characterizing the core-shell structure of nanoparticles. A sample system of upconversion NaYF4:Yb,Er cores coated with SiO2 is investigated. Auger spectra, line scans and elemental maps of single nanoparticles will be presented. Challenges encountered will be highlighted, such as damage to the sample by electron beam irradiation. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) are performed on the same samples, in order to verify the SAM results.
Recent years have seen increasing development of nanoparticles for applications in a wide range of fields, including but not limited to areas of great impact such as catalysis, medicine, energy, optoelectronics, cosmetics, and many others. In particular, nanoparticles bearing some form of coating layer, whether by design or due to incidental processes such as contamination or oxidation, are among the most commonly studied and utilised. In the characterisation of nanoparticles, the surface properties are of great importance, because a large proportion of the particle forms a part of the surface or interface. In the case of coated nanoparticles, the thickness of the coating is significant in determining the properties of the nanoparticle, and defines its interactions with its environment. Measurement of surface chemistry and coating thickness of nanoparticles is a challenge to which electron spectroscopies are well suited, due to high surface sensitivity, well-understood physical principles and accessibility.
The main objectives of the new EMPIR project nPSize are to establish EU capability of traceable measurement of NP size and shape, lower uncertainties of NP size measurement by developement of new nano-CRMs, new models (physical and machine learning), 3D method combination, and also by new ISO and CEN standards on accurate NP size measurement and guidance and knowledge transfer. The envisaged outcomes of the project will be presented and their suitability will be discussed to be taken over as pertinent contributions to normative projects within CEN/TC 352 Nanotechnologies.
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.
The analysis of nanomaterials is currently an important task - especially in case of risk assessment – as the properties of these material class are not well understood and their growing use in everyday life. The rather high surface area of these objects renders their interactions significantly different to their corresponding bulk. Thus, the surface’s chemical composition must be investigated to get a better understanding and prediction of the nanomaterials’ behaviour. ToF-SIMS and XPS have proven to be powerful tools to determine the general chemical composition. The superior surface sensitivity of ToF-SIMS furthermore allows us to study mainly the utmost atomic layers and thus gives us an idea of possible interactions involved. Supported by multivariate data analysis such as principal component analysis (PCA), the method can also be used for sub-classification of different materials using slight differences in surface chemistry.
Here, we present data of the analysis of Hyflon®-polystyrene core-shell nanoparticles which can be used as a model system due to the known preparation and a rather good chemical as well as physical separation of core and shell. Principle component analysis (PCA) will be used to detect the influence of sample preparation and for a better separation of different samples. This is achieved by measurement of a statistically relevant set of samples for every particle sample. We acquired surface spectra under static SIMS conditions with Bi32+ and analysed the resulting spectra by PCA. The carefully selected and refined peaks allow a reasonable categorization and further a reliable allocation of blank feeds. In detail, the fluorine containing, organic fragments are an indication for a heterogeneous shell that has errors. Furthermore, results on Au nanoparticles with and without an antibody shell are presented. ToF-SIMS imaging is desired to be implemented for single particle detection as well.
The analysis of nanomaterials is currently an important task - especially in case of risk assessment – as the properties of these material class are not well understood. The rather high surface area of these objects renders their interactions significantly different to their corresponding bulk. Thus, the surface’s chemical composition must be investigated to get a better understanding and prediction of the nanomaterials’ behavior. ToF-SIMS and XPS have proven to be powerful tools to determine the general chemical composition. The superior surface sensitivity of ToF-SIMS furthermore allows us to study mainly the utmost atomic layers and thus gives us an idea of the interactions involved.
Here, we present initial data on the analysis of Hyflon®-polystyrene core-shell nanoparticles which can be used as a model system due to the known preparation and a rather good chemical as well as physical separation of core and shell. Furthermore, results on Au nanoparticles with and without an antibody shell are presented. Principle component analysis (PCA) will be used to detect the influence of sample preparation and for a better separation of different samples. ToF-SIMS imaging is desired to be implemented for single particle detection as well.
X-ray photoelectron spectroscopy (XPS) provides elemental and chemical information from the outermost ~10 nm of the sample surface. This is in the same order of magnitude as the thickness of the outer bacterial membrane of gram-negative bacteria, as well as outer membrane molecules as exopolysaccharides and lipopolysaccharides, commonly attached to the cell surface. With the development of near-ambient pressure (NAP)-XPS, bacteria can be analysed with minimal sample preparation.
EnviroESCA is a laboratory based NAP-XPS instrument, equipped with a monochromated Al Kα radiation source and a differentially pumped energy analyser connected to an exchangeable sample environment. It allows for measurements in various gas-atmospheres, including water vapor, which makes it possible to characterise bacteria and other biological samples close to their natural, hydrated state. Artificial model-biofilms of exopolysaccharides, planktonic Pseudomonas Fluorescens and biofilms of Escherichia Coli have been characterised in hydrated and dried state.
High-resolution XPS-spectra from carbon, oxygen, nitrogen and phosphorous can be assigned to carbohydrates, lipids and proteins in general agreement with literature. Especially the carbon 1s peak is of interest. A series of measurements of an E. coli biofilm from 11 mbar in humid environment to 1 mbar air reveal changes in the C1s peak, which suggests that the bacterial surface undergo substantial Change.
The CLEAN ENERGY Flagship is an initiative designed to utilize recent game changing developments in digital, materials and manufacturing technologies to catalyze a radical paradigm shift towards clean, reliable, efficient and cost-optimal energy.
Unifying and drastically accelerating radically new energy material design, processing and integration across the entire value chain addressing energy production, conversion, storage and systems.
CLEAN ENERGY participants are all distinguished research organisations that each benefit from their own industry networks and contacts with regions and state-level activities and have a long history of collaborating with each other (for 10 years now under the umbrella of EERA) within a European collaborative framework.
Through EERA, CLEAN ENERGY aims to become a crucial partner in the SET-Plan, supporting long-lasting approaches through its established networks and internal collaborations.
Bonding strength is crucial on polymers of low surface energy, for clean surfaces limited to 0.5, 1, and 2 MPa for PTFE, PP, and PE. Plasma treatment may improve bonding strength by a factor of 2 (PTFE) or 5 (PP and PE). The efficiency of treatment is usually 10% as both low pressure and atmospheric pressure processes show low topographic conformity.
Besides, lifetime of activation/modification is rather short. Hence, bonding has to be carried out immediately after plasma treatment.
The concept of plasma-assisted ALD (atomic layer deposition) interlayers was introduced in the project HARFE of SENTECH (modification/deposition/in-situ monitoring) and BAM (bonding, characterization, testing). ALD deposition has a high surface conformity and for dielectric films of Al2O3 also a good long-term stability given that the films are dense enough.
Based on TMA and O2/O3 precursors, ALD layer stacks from 60 to 375 monolayers were prepared under different conditions. For a transfer time of 24 hours from deposition to measurement, bonding strength could be increased up to 5 MPa (PTFE) respectively 10 MPa (PP, PE). The huge potential of ALD layers as adhesive interlayers was demonstrated for Al2O3 on stainless steel with bonding strength beyond 15 MPa, i.e. interface
strength within the ALD stack is also in this range.
This is a prerequisite for subsequent PVD/CVD-deposition in hybrid systems. By means of the SI ALD LL system of SENTECH thermal and plasma-supported ALD processes can be alternatively realized.
Ellipsometric in-situ monitoring provides monolayer sensitivity and reveals that the efficient bonding of the lower ALD layers on the polymer has to be further improved. Testing of bonding strength was realized by CAT (centrifugal adhesion testing) technology. It was shown that ALD modification correlates with the increase of surface energy and bonding strength.
The majority of all products have coated surfaces designed to fulfil different requirements. Building constructions are exposed to external influences like a wide temperature and humidity range, rain and UV radiation to name a few. The extension of machine life for metal cutting tools, like drills or milling cutters is another field of application for coated surfaces. The surfaces have to be modified in a way to maintain their specific functionality. Although adhesion testing of coatings is of great interest, it is still a challenge to obtain reliable quantitative results and to meet economic requirements.
In this talk we deal with the curing behaviour of different 2-component epoxy paint systems for corrosion protection of metal constructions. After preparation of specimens the strength was determined in specified time intervals during curing. It could be shown that epoxy paints differ significantly on curing time as well as final strength. The second experimental study deals with coating systems on glass fibre reinforced plastics which are used for wind power turbines to reduce abrasive wear and ice adhesion for aerodynamic and safety reasons.
All measurements have been carried out by CAT-TechnologyTM (Centrifugal Adhesion Testing), which uses the radially directed centrifugal force as test-load. The multi-sample test instrument analyses up to eight test specimen under identical testing conditions. By varying the rotational speed (100 rpm up to 13,000 rpm), forces from 0.1 N to 6.5 kN are applied. Upon reaching the critical rupture force, the stamp separates from the substrate and a sample related IR-signal is sent from the spinning rotor. For each test specimen breaking force is calculated and displayed in real-time. The innovative measurement principle meets the requirements of DIN EN 15870 and ISO 4624.
In der klinischen Diagnostik werden für zytometrische Messverfahren bereits eine Reihe von Reagenzien eingesetzt zur Markierung von Antikörper eingesetzt, um die Detektion von Biomarkern mittels Fluoreszenz- oder Flugzeitmassenspektrometrie zu ermöglichen.
Seit kurzem ist auch eine Imaging Mass Cytometry Kombination direkt erhältlich, wodurch der Nachweis von Biomarkern in Gewebeschnitten erreicht werden kann. Dazu wird eine Kopplung von Laser Ablation und induktiv gekoppeltem Plasma Massenspektrometrie eingesetzt, wobei ähnlich der Massenzytometrie, zuvor Antikörper mit Metallen markiert, und im Anschluss mit dem Gewebeschnitt inkubiert werden. Durch die hohe Ortsauflösung können die Biomarker lokalisiert, und zukünftig vielleicht auch quantifiziert werden.
Insbesondere Lanthanide eignen sich als Markierungsmetalle, da sie einen niedrigen Untergrund und chemisch ähnliches Verhalten zueinander aufweisen. Allein durch diese Elemente können bereits etwa 15 Parameter unterschieden werden, was durch isotopenreine Standards weiter gesteigert werden kann.
Vom Markierungsgrad abhängig werden unterschiedlich viele Metalle am Antikörper gebunden, und beeinflussen so die Sichtbarkeit im ICP-MS. Nanopartikel könnten daher eine deutliche Steigerung der Sensitivität bewirken. GdVO4 Nanokristalle scheinen bisher sehr vielversprechend und bieten neben multiparametrischen Anwendungen auch Multimodalität.
Die Synthese der Nanokristalle zeigte hohe Homogenität und Reproduzierbarkeit in Partikelgröße in der Zusammensetzung. Ein erstes Experiment mit einer Zellkultur konnte bereits die effiziente Markierung der Zellen unter Beweis stellen, wobei durch hohe Signalstärke auch subzelluläre Auflösung in der LA-ICP-MS erreicht werden konnte.
Nowadays the Instrumented Indentation Testing (IIT) is one of the most commonly used methods to determine the mechanical properties of materials in the nano range. This method is already extensive standardized in EN ISO 14577 part 1-4. Because of the great interest of researchers and industries in investigations of time depending material behavior mostly all suppliers of IIT equipment are offering the possibility of dynamic testing. Realizing this development ISO/TC 164/SC3 Hardness Testing has proposed to start the new standardization project “Linear elastic dynamic instrumented indentation testing DIIT”. The development of this standard is accompanied by the first international intercomparing exercise comparing results of dynamic instrumented indentation testing from testing machines using different hardware solutions and different models for data evaluation.
The draft of part 5 of ISO 14577 “Linear elastic dynamic instrumented indentation testing DIIT” specifies verification and calibration of testing machines for carrying out the measurement of the dynamic material response when an oscillatory force or displacement, with amplitudes small in comparison to the prescribed target values, is imparted to the indenter while the indenter is continuously loaded to a prescribed target load or target depth or while the load or displacement is held constant at a prescribed target value. In case of a material showing plastic-elastic behavior, the measured dynamic response is used for continuous evaluation of the dynamic stiffness of the contact as a function of depth and frequency. Using the dynamic stiffness of the contact a reduced dynamic modulus will be calculated. In case of a material showing visco-elastic behavior from the measured dynamic response also the dynamic contact damping coefficient as function of depth and frequency is evaluated continuously. Using dynamic contact stiffness and dynamic contact damping coefficient reduced lost and storage modulus for visco-elastic materials will be calculated.
The main normative requirements of the draft will be presented and discussed in the light of the first results of the intercomparing excise.
In well-annealed thin polymer films, with non-repulsive polymer/substrate interactions, an irreversibly adsorbed layer is expected to from. These adsorbed layers have shown greate potential for technological applications. However, their growth kinetics and molecular dynamics are still not fully understood. This is partly due to the hard accessibility of these layers in thin films. Here, the irreversibly adsorbed layers of homopolymer thin films are revealed by solvent-leaching experiments. First, the growth kinetics of these layers is investigated as a function of annealing time, annealing temperature, leaching time and the original filme thickness. The film thickness, topography and the quality of the adsorbed layer is controlled by Atomic Force Microscopy (AFM). Secondly, the molecular mobility of the adsorbed layer is investigated by Broadband Dielectric Spectroscopy (BDS). A recently developed nanostructured capacitor arrangement is employed to measure the layer with a free surface. The results are quantitatively compared and discussed with respect to recently published work.
The test material EDS-TM001 together with an accompanying software package, “EDX spectrometer check”, have been made available in 2009 by BAM to be employed by EDS (energy dispersive spectrometer) users to check the performance of an EDS attached to the SEM. Particularly for test laboratories operating under accreditation schemes like ISO/IEC 17025, a periodical control of the critical instrumental parameters in end-user laboratories is required. With EDS-TM001 or EDS-TM002 (second generation) test material, this periodical check is simplified to the acquisition of only one 10 kV spectrum. The software “EDX spectrometer check” is destined to evaluate automatically this spectrum and determine the performance of the EDS in terms of energy resolution and calibration as well as possible alteration of low-energy efficiency due to detector contamination. Energy resolution can be compared with the specified values according to the international ISO standard ISO 15632:2012. EDS-TM is a synthetic material consisting of a thick layer of C, Al, Mn, Cu and Zr in a well-defined composition, deposited on a steel (in case of EDS-TM001) or silicon (in case of EDS-TM002) substrate. Meanwhile, more than one hundred laboratories use the EDS-TM001 or EDS-TM002 test material for the periodical check of their EDS. A detailed description of the test material and software together with examples of application was published recently. New results and gained experiences will be presented as well.
When the FWHM of lines appearing in the EDS-TM spectrum are determined, the spectrum background must be subtracted accurately. The applied physical background subtraction procedure is robust and takes into account the transmission of the detector window. While the previous version considers only Moxtek AP windows, the new version includes selection of silicon nitride window and the case of windowless detector. Moreover, the new version allows importing of spectra in Bruker spx format and EMSA/MSA files from EDAX TEAM software.
Extraction of true, 3D shape (and size) of non-spherical nanoparticles (NPs) is associated with errors by conventional 2D electron microscopy using projection images. Significant efforts within the ISO technical committee TC 229 ‘Nanotechnologies’ are aimed at establishing accurate TEM and SEM measurement of NP size and shape as robust, standard procedures. Study groups have been organizing inter-laboratory comparisons on well-selected NP systems according to the market needs, such as aggregated titania nano-powder for which size and shape distribution of primary crystallites of irregular shape must be measured accurately. To be noticed is e. g. the fact that the measurement procedure allows only manual selection of the particles clearly distinguishable for analysis as well as manual definition of the contour of the imaged NPs.
An inter-laboratory exercise on titania NPs (pure anatase, grown by hydrothermal synthesis) of well-defined non-spherical shape, i.e. bipyramidal has been recently started within ISO/TC 229 under similar conditions as for the irregular shaped titania. Overlapped particles were allowed to be considered, as long as they are clearly distinguishable. One decisive NP selection criterion was to analyze only those NPs with a roundness value below 0.7, i.e. the NPs laying on the support foil and, hence, with projection areas clearly deviating from perfect circles (R=1). The overall evaluation (for 15 labs) of the size descriptors (area, Feret, minFeret, perimeter) and shape descriptors (aspect ratio, roundness, compactness, extent) by analysis of variance is just to be finished and included in ISO/WD 21363 Nanotechnologies -- Protocol for particle size distribution by transmission electron microscopy.
Fluorometric sensing is a versatile approach for trace analysis outside of the laboratory, requiring suitable sensor materials and their integration into sensing devices. The versatility of fluorophores as probes, especially in terms of the possibility to tailor their optical as well as their recognition properties by synthetic modifications in a wide range, renders them as superior active component for the preparation of optical sensing devices. Recent works at BAM in this field include, for example, the detection of nerve gas agents, illustrating impressively the aforementioned benefits of fluorophores in optical sensing applications.
In the interdisciplinary project presented here, we target hazardous gases such as ammonia, benzene, and hydrogen sulfide, next to others, which pose a major threat to human health and environmental safety and for which the availability of a sensitive and reliable detection method is highly desirable. The dyes presented follow a “turn-on” fluorescence schematic, which allows for the selective and sensitive detection of the respective gaseous analyte. The immobilization of the probe in polymeric matrices is then the next step toward the fabrication of a prototype device for molecular sensing. Further steps in the project include the assembly of instruments for test-atmosphere generation, the referencing of the sensor system, development and implementation of an optical setup, and the testing of the prototype device under laboratory conditions and in the field.
In this presentation, we give an overview over the recent developments on this topic in our groups. Highlights are hydrogen sulfide sensitive, BODIPY based transition metal complexes, which allow for a sensitive as well as selective detection of the toxic gas. In addition, we present a novel class of highly substituted BODIPY derivatives – pocket-BODIPYs – which are of a synthetically high versatility and can readily be modified to create pockets in the periphery of the molecule of defined geometries. This is illustrated on the successful encapsulation of benzene by a pocket-BODIPY derivative, confirmed by X-ray crystallographic analysis as well as by further spectroscopic and analytical methods.
Titanium dioxide is one of the most studied metal oxides due to its chemical, surface, electronic and (photo)catalytic properties, providing this material of multisectorial applications ranging from healthcare, photocatalysis, smart materials with self cleaning and self sterilizing properties and solar energy harvesting. However it is difficult to correlate the functional properties of TiO2 nanomaterials to the properties at single nanoparticle level due to the high polydispersity in shape, size and surface features of the currently available TiO2 nanoparticles (NPs). Although intensive experimental and theoretical studies have been conducted on the reactivity of different surfaces of metal oxides such as TiO2 much less attention is paid on the dependence of functional properties, like photocatalytic activity, dye adsorption, open circuit potential and fill factor in dye sensitized solar cells, on crystal facets in different orientations. One of the goal of SETNanoMetro project was the development of design rules to tune crystal facets of TiO2 NPs in order to optimize and control functional properties. In the present work we have developed a series of design rules in order to obtain sets of anatase TiO2 NPs with low polydispersity and to tune their shape and size by hydrothermal processing of Ti(IV)-Triethanolamine complex in presence of different shape controllers. Through a careful experimental design, a predictive soft model was developed. The model is able to predict the synthesis outcome allowing to tune the shape factor from 5 (prisms) to 1.5 (bipyramids) to 0.2 (platelets). This allows to control the main crystal facets exposed ranging from (100) to (001). Due to the dependence of functional properties of nanomaterials on shape distribution and not only size, the availability of NPs sets with uniform and well defined and tunable shapes can be of paramount relevance in order to produce reference nanomaterials for shape measurement.
The European Commission's recommendation on the definition of nanomaterial [2011/696/EU] is broadly applicable across different regulatory sectors and requires the quantitative size determination of constituent particles in samples down to 1 nm. A material is a nanomaterial if 50 % or more of the particles are in the size range 1-100 nm. The implementation of the definition in a regulatory context challenges measurement methods to reliably identify nanomaterials and ideally also non-nanomaterials as substance or product ingredient as well as in various matrices.
The EU FP7 NanoDefine project [www.nanodefine.eu] addressed these challenges by developing a robust, readily implementable and cost-effective measurement strategy to decide for the widest possible range of materials whether it is a nanomaterial or not. It is based on existing and emerging particle measurement techniques evaluated against harmonized, material-dependent performance criteria and by intra- and inter-lab comparisons. Procedures were established to reliably measure the size of particles within 1-100 nm, and beyond, taking into account different shapes, coatings and chemical compositions in industrial materials and consumer products. Case studies prove their applicability for various sectors, including food, pigments and cosmetics.
A main outcome is the establishment of an integrated tiered approach including rapid screening (tier 1) and confirmatory methods (tier 2), a decision support flow scheme and a user manual to guide end-users, such as manufacturers, in selecting appropriate methods. Another main product is the “NanoDefiner” e-Tool which implements the flow scheme in a user-friendly software and guides the user in a semi-automated way through the entire decision procedure. It allows a cost-effective selection of appropriate methods for material classification according to the EC's nanomaterial definition and provides a comprehensive report with extensive explanation of all decision steps to arrive at a transparent identification of nanomaterials as well as non-nanomaterials for regulatory purposes.
The project has received funding from the European Union’s Seventh Programme for research, technological development and demonstration under grant agreement No 604347.
A presentation held for the seminar "Ausgewählte analytische Methoden der Physik" hosted by Prof. Birgit Kanngießer at TU Berlin. The first part focus on depth-dependent XPS-measurements (XPS, synchrotron HAXPES) to obtain a concentration profile of iodine in an artificial biofilm. In the second part, NAP-XPS measurements of various bacterial samples are presented.
The molecular dynamics and ionic conductivity of ionic liquid crystals (ILCs) forming a columnar mesophase, two linear-shaped tetramethylated guanidinium triflates ILCs having different lengths of alkyl chains, were investigated by a combination of Broadband Dielectric Spectroscopy (BDS) and Specific Heat Spectroscopy (SHS). Three processes were detected by BDS; at low temperature γ-process, at higher temperatures α-process and at even higher temperatures conductivity. The γ-process indicates localized fluctuations, and the α-process designates cooperative fluctuations. Slightly different restrictions were found for conductivity processes of LC536 and LC537 due to the slightly different lengths of alky chains. The conductivity mechanisms in the plastic crystalline and the columnar mesophase have been revealed by BDS and different charge carriers were assigned for the different phases. Furthermore, the cooperative dynamics were also probed by SHS. The cooperative dynamics probed by the different techniques (BDS and SHS) compared, and assigned to the different restrictions on the cooperativity due to the difference in the sensitivity of the techniques.