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Preparation of graphene oxide by cyanuric chloride as an effective and non-corrosive oxidizing agent
(2016)
In this work, we report a new method for the synthesis of graphene oxide (GO) using cyanuric chloride as a non-corrosive oxidizing agent.
The mild conditions, simple purification, and scalability of this method are significant advantages over common approaches in which harsh oxidizing agents are used. Moreover, a major drawback with the Hummers' method, the production of toxic gases, is not an issue with this process. This method is a safe and large-scale alternative for the production of GO under mild conditions.
IND15 JRP SurfChem: Traceable quantitative surface chemical analysis for industrial applications
(2016)
The SurfChem project has made a significant contribution to traceable quantitative surface chemical analysis for industrial applications by delivering new certified reference materials and test samples for specific technical applications. Regular performance tests of instruments, metrological methodology for the detection of (bio)organic surface species, ambient and non-destructive surface chemical analysis for in-line process control and new in situ characterisation techniques of catalytically active surfaces have been achieved.
Modifying or controlling surface chemistry is important in new product development, quality control and research. This is particularly true where functionality of surfaces, thin films and interfaces are key to the application, such as organic solar cells and devices for medical diagnostics. Surface chemical analysis aims to provide quantitative elemental, chemical state and functional group information from the surface of materials, but requires comparable test data and improved measurement traceability.
Measuring organic layers
(2016)
Many innovative products - from touchscreens to solar panels to pharmaceuticals – utilise multiple organic layers to create complex functionality. New techniques have been developed to remove and measure layers individually enabling improved product development and assisting with quality assurance. However, manufacturers cannot be certain of the depth of layer being removed and new reference materials for these techniques are needed to increase uptake, and remove a major barrier to innovation.
Materials and chemical producers require detailed knowledge of surface chemistry for research into new products. One way to understand a surface without damaging it is to bombard it with an electron beam, causing its atoms to emit characteristic X-rays enabling identification. The measurement of these must be precise as many elements emissions are close in energy – traceable reference materials will ensure instruments using this technique are stable and accurate.
In this work, fullerene has been functionalized with cyanuric Chloride at room temperature by a nitrene mediated [2 + 1] cycloaddition reaction. The adduct after functionalization is inherently in the form of azafulleroid and shows broad UV absorption in the wavelength range of 200–800 nm, as well as photothermal conversion and fluorescence with a high quantum yield.
Graphene prepared from Graphene oxide (GO) is used as a platform for functional 2D nanomaterials with diverse applications ranging from bios ensors to antimicrobial surfaces. C and N K-edge NEXAFS and XPS spectroscopies at BESSY’s HE-SGM beamline have been used to prove and control covalent functionalization of graphenic materials at ambient conditions for the synthesis of functional 2D-surfaces.
A novel photoswitchable rotaxane was synthesised and its switching behaviour in solution was analysed with NMR and UV-Vis. A monolayer of rotaxanes was deposited on glass surfaces and the on-surface photoswitching was investigated. Angle-resolved NEXAFS spectra revealed a preferential orientation that reversibly changes upon switching.
The project addresses chemical and topographical metrology at surfaces. The new methodologies of measurements at surfaces will be developed as good practice guides and new work item proposals for industrial ISO standards. The objectives of the Joint research project (JRP) are to provide measurement standards and methods with traceability wherever it is practicable to do so for quantitative surface chemical analysis for industrial applications.
The CCQM-K136 key comparison for determination of the porosity properties of aluminum oxide has been organized jointly by the surface and micro/nano analysis working groups of CCQM to test the abilities of the metrology institutes to measure the porosity properties (specific adsorption, BET specific surface area, specific pore volume and pore diameter) of nanoporous Al2O3.
Ural Scientific Research Institute for Metrology (UNIIM) acted as the coordinating laboratory for this comparison with BAM Federal Institute for Materials Research and Testing (BAM) as co-coordinating laboratory. Five NMIs and one DI participated in this key comparison. All participants used a gas adsorption method, here nitrogen adsorption at 77.3 K, for analysis according to the international standards ISO 15901-2 and 9277.
Soft x-ray spectromicroscopy techniques have seen great amount of development in the recent years, and with the development of new diffraction limited synchrotron source, many new nanoscale and mesoscale characterization opportunities of applied materials are foreseen. In this perspective, the authors present some examples that illustrate the capabilities of spectromicroscopy techniques, namely, 2D and 3D spatially resolved chemical quantification, surface and bulk sensitive measurements, and polarization dependent measurements as applied to iron oxide nanoparticulate materials of biological, geological, and other origins.
A novel Infinitesimal Columns (IC) simulation model is introduced in this study for the quantitativeanalysis of core-shell nanoparticles (CSNP) by means of XPS, which combines the advantages of exist-ing approaches. The IC model is applied to stabilised Lumidot™CdSe/ZnS 610 CSNP for an extensiveinvestigation of their internal structure, i.e. calculation of the two shell thicknesses (ZnS and stabiliser)and exploration of deviations from the idealised CSNP composition. The observed discrepancies betweendifferent model calculations can be attributed to the presence of excess stabiliser as well as synthesisresidues, demonstrating the necessity of sophisticated purification methods. An excellent agreement isfound in the comparison of the IC model with established models from the existing literature, the Shardmodel and the software SESSA.
Implantable drug delivery systems that provide controlled and sustained release of a therapeutic agent are used in a wide variety of applications. Drug eluting stents, which are used to treat coronary artery disease, are among the most widespread of these devices, with an estimated 3x10⁶ implants annually worldwide. Controlling the rate of drug release from these devices relies on precise control of the three dimensional (3D)-distribution of the drug, so methods for measuring this distribution are of great importance. The aims of this work were to determine how 3D-imaging of polymer-free sirolimus/probucol drug eluting stent coatings could be improved through the use of laser postionization secondary neutral mass spectrometry (Laser-
SNMS) and Ar cluster sputtering with time-of-flight secondary ion mass spectrometry (ToF-SIMS) and to optimize conditions for this analysis. In this study, 3D-imaging of a sirolimus/probucol dual drug eluting stent has been investigated using Laser-SNMS and ToF-SIMS. Laser-SNMS studies of pure sirolimus and probucol were undertaken using 30 keV Bi₃⁺ primary Ions and a 157 nm excimer postionization laser. Under optimal conditions, a greater than 100-fold increase in detected ion yield was observed for Laser-SNMS when compared to ToF-SIMS, although ToF-SIMS provided equal or greater yields for higher mass characteristic ions. Although the optimal laser power density for detecting probucol (5x10⁶W/cm²) was significantly lower than the optimum for sirolimus(7x10⁷W/cm²), an intermediate laser power density of 1x10⁷W/cm² was sufficient to allow imaging of both drugs. Using individual selected ion signals, ToF-SIMS and Laser-SNMS produced similar images of the two drug species. When using, however, a multivariate approach (Maximum autocorrelation factors), Laser-SNMS provided significant improvements in image contrast and small area detection when compared to ToF-SIMS.
Following optimization of the technique, 3D-images of the dual drug eluting stent coating were obtained using 10 keV Ar₂₀₀₀⁺ cluster ions for sputtering and 30 keV Bi₃⁺ cluster ions for Analysis for both ToF-SIMS and Laser-SNMS. This work demonstrates the advantages of Laser-SNMS for 3D-imaging of pharmaceutical devices, which has not been previously published. Both ToF-SIMS and Laser-SNMS revealed that the outermost surface of the drug eluting coating contained pure sirolimus to a depth of a few tens of nanometers, with a few channels of sirolimus extending to a depth of around 1 lm. Below about 1 lm, the two drugs were uniformly mixed. Using the 10 keV Ar₂₀₀₀⁺ sputter beam, the authors were able to sputter through the complete drug coating (~6 μm) without observing any accumulated damage in the organic layer. The two techniques showed complementary strengths: ToF-SIMS offers faster data collection and better detected ion yield for larger characteristic ions than Laser-SNMS, and Laser-SNMS offers significantly enhanced detected ion yield for smaller fragment ions, allowing for improved Image contrast and Resolution of smaller features.
The photoinduced pseudorotaxane formation between a photoresponsive axle and a tetralactam macrocycle was investigated in solution and on glass surfaces with immobilized multilayers of macrocycles. In the course of this reaction, a novel photoswitchable binding station with azobenzene as the photoswitchable unit and diketopiperazine as the binding station was synthesized and studied by NMR and UV/Vis spectroscopy. Glass surfaces have been functionalized with pyridine-terminated SAMs and subsequently withmultilayers of macrocycles through layer-by-layer self assembly.
A preferred orientation of the macrocycles could be confirmed by NEXAFS spectroscopy. The photocontrolled Deposition of the axle into the surface-bound macrocycle-multilayers was monitored by UV/Vis spectroscopy and led to an increase of the molecular order, as indicated by more substantial linear dichroism effects in angle-resolved NEXAFS spectra.
The certified reference material BAM-L200, a nanoscale stripe pattern for length calibration and specification of lateral resolution, is described. BAM-L200 is prepared from a cross-sectioned epitaxially grown layer stack of AlxGa1-xAs and InxGa1 xAs on a GaAs substrate. The surface of BAM-L200 provides a flat pattern with stripe widths ranging down to 1 nm. Calibration distances, grating periods and stripe widths have been certified by TEM with traceability to the length unit. The combination of gratings, isolated narrow stripes and sharp edges of wide stripes offers a plenty of options for the determination of lateral resolution, sharpness and calibration of length scale at selected settings of imaging surface analytical instruments. The feasibility of the reference material for an analysis of the lateral resolution is demonstrated in detail by evaluation of ToF-SIMS, AES and EDX images. Other applications developed in the community are summarized, too.
BAM-L200 fully supports the implementation of the revised International Standard ISO 18516 (in preparation) which is based on knowledge outlined in the Technical Report ISO/TR 19319:2013.
Reference-free XRF is a SI traceable technique for the
determination of the mass deposition (mass per unit area) of elements in films on the nano- and micro scale. The method is radiometrically calibrated instrumentation (PTB@BESSY II, Germany) and based on reliable knowledge of all relevant atomic fundamental, experimental and instrumental parameters. No calibration sample or reference materials are necessary. The approach had been validated in the CCQM-P140 pilot study and the K129 key comparison by determination of mole fractions in Cu(In,Ga)Se2 thin films.
CCQM key comparison K-129 for the quantitative analysis of Cu(In,Ga)Se2 (CIGS) films has been performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The objective of this key comparison is to compare the equivalency of the National Metrology Institutes (NMIs) and Designated Institutes (DIs) for the measurement of mole fractions of Cu, In, Ga and Se in a thin CIGS film. The measurand of this key comparison is the average mole fractions of Cu, In, Ga and Se of a test CIGS alloy film in the unit of mole fraction (mol/mol). Mole fraction with the metrological unit of mol/mol can be practically converted to atomic fraction with the unit of at%.
In this key comparison, a CIGS film with certified mole fractions was supplied as a reference specimen to determine the relative sensitivity factors (RSFs) of Cu, In, Ga and Se. The mole fractions of the reference specimen were certified by isotope dilution - inductively coupled plasma/mass spectrometry (ID-ICP/MS) and are traceable to the SI. A total number counting (TNC) method was recommended as a method to determine the signal intensities of the constituent elements acquired in the depth profiles by Secondary Ion Mass Spectrometry (SIMS), X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). Seven NMIs and one DI participated in this key comparison. The mole fractions of the CIGS films were measured by depth profiling based-SIMS, AES and XPS. The mole fractions were also measured by non-destructive X-Ray Fluorescence (XRF) Analysis and Electron Probe Micro Analysis (EPMA) with Energy Dispersive X-ray Spectrometry (EDX).
In this key comparison, the average degrees of equivalence uncertainties for Cu, In, Ga and Se are 0.0093 mol/mol, 0.0123 mol/mol, 0.0047 mol/mol and 0.0228 mol/mol, respectively. These values are much smaller than that of Fe in a Fe-Ni alloy film in CCQM K-67 (0.0330 mol/mol). This means that the quantification of multi-element alloy films is possible by depth profiling analysis using the TNC method.
The certified reference material BAM-L200, a nanoscale stripe pattern for length calibration and specification of lateral resolution, is described. BAM-L200 is prepared from a cross-sectioned epitaxially grown layer stack of AlxGa1-xAs and InxGa1-xAs on a GaAs substrate. The surface of BAM-L200 provides a flat pattern with stripe widths ranging down to 1 nm. Calibration distances, grating periods and stripe widths have been certified by TEM with traceability to the length unit. The combination of gratings, isolated narrow stripes and sharp edges of wide stripes offers a plenty of options for the determination of lateral resolution, sharpness and calibration of length scale at selected settings of imaging surface analytical instruments. The feasibility of the reference material for an analysis of the lateral resolution is demonstrated in detail by evaluation of ToF-SIMS, AES and EDX images. Other applications developed in the community are summarized, too.
BAM-L200 fully supports the implementation of the revised International Standard ISO 18516 (in preparation) which is based on knowledge outlined in the Technical Report ISO/TR 19319:2013. Fundamental approaches to determination of lateral resolution and sharpness in beam-based methods
Deuterium permeation and cracking in duplex steels as viewed by ToF-SIMS and HR-SEM with data fusion
(2016)
Better understanding of hydrogen assisted degradation and trapping mecha-nisms requires sufficient imaging techniques for respective hydrogen-microstructure interaction studies, in particular with multi-phase metallic micro-structures [1]. The present work is focusing on the elucidation of deuterium be-havior in two austenitic-ferritic duplex stainless steels (DSS) under the assumption that deuterium behaves in many ways similarly to hydrogen [2]. For case studies standard 2205 and lean 2101 DSSs were chosen due to the extensive use of these steels in industry [3]. The analyses were conducted by using a novel in-situ permeation and Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) imaging technique or by ex-situ ToF-SIMS imaging following electrochemical charging experiments. Another pioneering procedure was data fusion (including chemometry) of results of powerful laterally resolved chemical analysis and high resolution structural characterization techniques .
Results for the ex-situ observations showed a different influence of deuterium loading on the two steel grades as well as different damage mechanisms in each phase. Formation of sub-surface blisters between the ferrite and austenite were obtained in both the standard and the lean DSS. In both steels, an increased deuterium concentration was observed around deformed regions such as cracks, confirming that they originate from the presence of deuterium [4]. The formation of parallel cracks was obtained only in the austenite within the standard duplex whereas in the lean duplex the highest intensity of deuterium was obtained in the austenite along the ferrite-austenite interphase.
In comparison, application of the novel in-situ permeation technique enabled to register and record the deuterium permeation through the material and the respective saturation sequence of the two phases as well as the interfaces. Faster diffusion of the deuterium was observed in the ferrite and a direct proof for deuterium enrichment at the austenite-ferrite interface has been given [1]. The integration of the specified techniques gives a better insight into the processes leading to hydrogen induced failure. These two experimental techniques provide very valuable tools for elucidation of respective metallurgical failure mechanisms that can be used for the validation of respective numerical models for hydrogen assisted cracking (HAC).
In the present work, the influence of deuterium on the microstructure of a duplex stainless steel type EN 1.4462 has been characterized by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) supported by scanning electron microscopy (SEM), focused ion beam (FIB), electron back scattered diffraction(EBSD) and energy dispersive x-ray (EDX) investigations. Characterization has been carried out before and after electrochemical charging with deuterium which has been used as a tracer, due to its similar behavior to hydrogen in the steel microstructure. In a first approach, the distribution of the deuterium occurring at temperatures above 58 °C has been visualized. Further it turned out that sub-surface micro blisters are formed in the ferrite-austenite interface, followed by the formation of needle shaped plates and subsequent cracking at the ferrite surface. In the austenite phase, parallel cracking alongside twins and hexagonal close packed (martensitic) regions has been observed. In both phases and even in the apparent interface, cracking has been associated with high deuterium concentrations, as compared to the surrounding undamaged microstructure. Sub-surface blistering in the ferrite has to be attributed to the accumulation and recombination of deuterium at the ferrite-austenite interface underneath the respective ferrite grains and after fast diffusing through this phase. Generally, the present application of chemometric imaging and structural analyses allows characterization of hydrogen assisted degradation at a sub-micron lateral resolution.
Safe innovation & sustainable production with MNMs need that we:
Understand risks and benefits (diagnostic, assessment)
Identify and implement risk reduction strategies (manage)
Communicate on residual risks (acceptance)
Huge knowledge on characterization, hazards, diagnostic (science)
Little effective use of it for operational risk management (expertise)
Objectives of the centre:
Bridge the gap between research and application (public, private),
Bridge the gap between knowledge on risks and risk management,
Balance between Science and Appliance,
in a sustainable way:
Efficient & Sustainable structure
Collective, harmonized, shared expertise
EU scale, internationally connected.
Ionic liquids (ILs) are proposed as simple and efficient test materials to evaluate the performance of energy dispersive X-ray spectrometers (EDS) in the low energy range below 1 keV. By only one measurement, C Kα, N Kα, O Kα, and F Kα X-ray lines can be excited. Additionally, the S Kα line at 2.3 keV and, particularly, the S L series at 149 eV complete the picture with X-ray lines offered by the selected ILs. The well-known (certifiable) elemental composition of the ILs selected in the present study can be used to check the accuracy of results produced with the available EDS quantification routines in the low energy range, simultaneously, for several low atomic number elements. A comparison with other reference materials in use for testing the performance of EDS in the low energy range is included.
Research on carbohydrate based interactions with proteins, nucleic acids or antibodies has gained increased interest in the last years especially in clinical diagnosis or drug development. The efficiency of diagnostic interfaces depends upon the number of probe molecules, e.g. carbohydrates. The control of surface parameters as density and distribution of immobilized carbohydrates is essential for a reliable interaction with protein analytes. A controlled production of biomolecular interfaces can be reached by a stepwise quality control during buildup of these biointerfaces.
Here, ß-amino-cyclodextrin molecules were attached to amine-reactive silicon oxide surfaces via click chemistry to construct a model biosensor surface. The amount of surface bound carbohydrates was determined indirectly after chemical derivatization with 4-(trifluoromethyl)-benzylamine (TFMBA). Moreover, these surfaces were used to form host-guest complexes of ferrocene (guest) and β-cyclodextrin (host) moieties to mimic the target binding (sensing) of the model biosensor. Surface chemical analysis of all steps during biosensor construction was performed using X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). Our approach widens the possibilities to generate switchable surfaces based on ß-Cyclodextrin surfaces for biosensor applications.
In this study, a new direct functionalization method of silicon nitride (Si3N4) using azidation and click chemistry is presented. First, amino groups (NHx) were created on a Si3N4 substrate by fluoride etching. These NHx-terminated Si3N4 surfaces were analyzed by chemical derivatization X-ray photoelectron spectroscopy (CD-XPS) with 4-trifluoromethylbenzaldehyde (TFBA) and a derivatization yield of 20% was concluded. In the second step freshly prepared NHx surfaces were transformed into azides which were used immediately in a click reaction with halogenated alkynes. The presented combination of amination, azidation and click reaction is a promising alternative for common silane-based Si3N4 functionalization methods.
Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and high-resolution scanning electron microscopy are well-acknowledged tools in materials characterization. The ability to map chemical species on the surface of an investigated sample with often low mass detection limits makes ToF-SIMS an essential tool in fields where many question marks concerning Degradation processes and damage mechanisms exist. The aim of this paper is to describe the power of data fusion of ToF-SIMS and high-resolution scanning electron microscopy results employing computational methods for multivariate data Analysis such as principal component analysis. As a case study the investigation of hydrogen distribution in an artificially charged Duplex stainless steel microstructure is presented aiming on a better understanding of hydrogen embrittlement.
Analytical routines for a comprehensive in-depth morphological, structural, and chemical characterization of functionalized TiO2 films by using different state-of-the-art analytical techniques are presented and discussed with the main objective to identify potential reference TiO2 coating parameters able to be certified at a later stage. TiO2 films fabricated by two different synthetic procedures as representative for two main large-scale applications were selected: (i) pulsed d.c. magnetron sputtering for photocatalytic applications and (ii) screen printing from preformed anatase nanoparticles. The screen-printed films were further loaded with a sensitizing dye for application as a dye-sensitized solar cell. Film properties such as microstructure and crystallographic texture of pulsed d.c. magnetron sputtering synthesized films were systematically studied by means of scanning nanobeam electron diffraction in a transmission electron microscope and the surface and inner morphology by scanning electron microscopy. The dye distribution over the depth of screen-printed TiO2 layers was analyzed before and after dye-loading by means of energy dispersive X-ray spectroscopy at scanning electronmicroscope, Auger electron spectroscopy and time-of-flight secondary ion mass spectrometry. The long-term goal of the present study is the improvement of quality of the TiO2 film parameters as measured by using different types of reference TiO2 coatings having specific parameters certified.
A comprehensive characterization of plasma modified polymer surfaces or plasma-polymerized thin films needs access to parameters as
- concentration of saturated/unsaturated carbon species (e.g. aromaticity) or other double bonds as C=N or C=O,
- branching, and
- losses of crystallinty or other degrees of structural order.
Furthermore the complex ageing phenomena of plasma modified polymers/plasma-polymers and the measurement of an in-depth distribution of chemical species are challenges for the analyst. The talk will display selected examples where such challenges have been met by using advanced methods of surface chemical analyses as Photoelectron Spectroscopy with variable excitation energy (“SyncXPS”), X-ray Absorption Spectroscopy (NEXAFS) at C, N and O K-edges and Time-of-Flight Secondary Mass Spectroscopy (ToF-SIMS) combined with Principal Component analysis (PCA).
In Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy X-Ray photons are used to excite tightly bound core electrons to low-lying unoccupied orbitals of the system. This technique offers insight into the electronic structure of the system as well as useful structural information. In this work, we apply NEXAFS to two kinds of imidazolium based ionic liquids ([CnC₁im]⁺[NTf₂]⁻ and [C₄C₁im]⁺[I]⁻). A combination of measurements and quantum chemical calculations of C K and N K NEXAFS resonances is presented. The simulations, based on the transition potential density functional theory method (TP-DFT), reproduce all characteristic features observed by the experiment. Furthermore, a detailed assignment of resonance features to excitation centers (carbon or nitrogen atoms) leads to a consistent interpretation of the spectra.
The growing interest in artificial bioorganic Interfaces as a platform for applications in emerging Areas as personalized medicine, clinical diagnostics, biosensing, biofilms, prevention of biofouling, and other fields of bioengineering is the origin of a need for in Detail multitechnique characterizations of such layers and interfaces. The in-depth analysis of biointerfaces is of special interest as the properties of functional bioorganic coatings can be dramatically affected by in-depth variations of composition.
In worst cases, the functionality of a device produced using such coatings can be substantially reduced or even fully lost.
CCQM has established a framework of comparisons to demonstrate the international comparability of chemical measurements. The key point is the establishment of comparable measurements, with traceability to internationally or nationally stated references. The Surface Analysis Working Group (SAWG) has been formally founded in 2003. CCQM ratified the group as a full working group of CCQM in April 2003 with these terms of reference:
- to develop pilot studies and carry out key comparisons of national measurement standards for surface and micro/nano-analysis;
- to assist in identifying and establishing inter-laboratory work to improve the traceability of surface and micro/nano-analysis;
- to establish and update a work plan to be adopted by CCQM;
- to discuss and review the scope of the working group and to liase with other working groups related to nanotechnology.
Following the 2015 meeting of the CCQM, the pilot study CCQM-P130 “WD and ED Electron Probe Micro Analysis on Au-Cu alloys” lead by BAM&NIST has been finalized. The Key Comparison K-129 “Measurement of atomic fractions in Cu(In,Ga)Se2 Films” lead by KRISS has made substantial progress and is about to be finalized. The new Key Comparison K-136 on “BET specific surface of ” lead by UNIIM&BAM has made strong progress in 2015 and will be finished in 2016.
The implementation of new 2-D materials based technologies in production processes requires the development of quality management tools. These have to be underpinned by appropriate measurements. Consequently there is a need for the development of the metrology for measurement methods, the development of certified reference materials (CRM) and finally standardization. This chain represents the ideal way to practically useful standards. The presentation will give an overview on the main players in the field and summarize the recent status of activities. At the highest level the metrology of chemical characterization of 2D materials is in the scope of the International Meter Convention, specifically the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM). Pre-standardization is an activity field of the Versailles Project on Advanced Materials and Standards (VAMAS). Standardization is mainly addressed by addressed ISO Technical Committees. A summary on available CRMs relevant to the characterization of nano materials has been prepared by BAM. Examples from the work of BAM’s Division 6.1 “Surface Analysis and Interfacial Chemistry” showcasing the characterization of chemically modified graphene surfaces are given and specific needs for the development of metrology are addressed.
In the discussion the audience is invited to define specific needs which will be streamlined to the respective bodies!
The quantitative determination of surface functional groups is approached in a straightforward laboratory-based method with high reliability. The application of a multimode BODIPY-type fluorescence, photometry, and X-ray photoelectron spectroscopy (XPS) label allows estimation of the labeling ratio, i.e., the ratio of functional groups carrying a label after reaction, from the elemental ratios of nitrogen and fluorine. The amount of label on the surface is quantified with UV/vis spectrophotometry based on the molar absorption coefficient as molecular property. The investigated surfaces with varying density are prepared by codeposition of 3-(aminopropyl) triethoxysilane (APTES) and cyanoethyltriethoxysilane
(CETES) from vapor. These surfaces show high functional group densities that result in significant fluorescence quenching of surface-bound labels. Since alternative quantification of the label on the surface is available through XPS and photometry, a novel method to quantitatively account for fluorescence quenching based on fluorescence lifetime (τ) measurements is shown. Due to the complex distribution of τ on high-density surfaces, the stretched exponential (or Kohlrausch) function is required to determine representative mean lifetimes. The approach is extended to a commercial Rhodamine B isothiocyanate (RITC) label, clearly revealing the problems that arise from such charged labels used in conjunction with silane surfaces.
Real Time Imaging of Deuterium in a Duplex Stainless Steel Microstructure by Time-of-Flight SIMS
(2016)
For more than one century, hydrogen assisted degradation of metallic microstructures has been identified as origin for severe technical component failures but the mechanisms behind have not yet been completely understood so far. Any in-situ observation of hydrogen transport phenomena in microstructures will provide more details for further elucidation of these degradation mechanisms. A novel experiment is presented which is designed to elucidate the permeation behaviour of deuterium in a microstructure of duplex stainless steel (DSS). A hydrogen permeation cell within a TOF-SIMS instrument enables electrochemical charging with deuterium through the inner surface of the cell made from DSS. The outer surface of the DSS permeation cell exposed to the vacuum has been imaged by TOF-SIMS vs. increasing time of charging with subsequent chemometric treatment of image data. This in-situ experiment showed evidently that deuterium is permeating much faster through the ferrite phase than through the austenite phase. Moreover, a direct proof for deuterium enrichment at the austenite-ferrite interface has been found.
Synchrotron-radiation XPS analysis of ultra-thin silane films: Specifying the organic silicon
(2016)
The analysis of chemical and elemental in-depth variations in ultra-thin organic layers with thicknesses below 5 nm is very challenging. Energy- and angle-resolved XPS (ER/AR-XPS) opens up the possibility for non-destructive chemical ultra-shallow depth profiling of the outermost surface layer of ultra-thin organic films due to its exceptional surface sensitivity. For common organic materials a reliable chemical in-depth analysis with a lower limit of the XPS information depth z95 of about 1 nm can be performed. As a proof-of-principle example with relevance for industrial applications the ER/AR-XPS analysis of different organic monolayers made of amino- or benzamidosilane molecules on silicon oxide surfaces is presented. It is demonstrated how to use the Si 2p core-level region to non-destructively depth-profile the organic (silane monolayer) inorganic (SiO2/Si) interface and how to quantify Si species, ranging from elemental silicon over native silicon oxide to the silane itself. The main advantage of the applied ER/AR-XPS method is the improved specification of organic from inorganic silicon components in Si 2p core-level spectra with exceptional low uncertainties compared to conventional laboratory XPS.
A model system was used to simulate the properties of tribofilms which form during automotive braking. The model system was prepared by ball milling of a blend of 70 vol.% iron oxides, 15 vol.% molybdenum disulfide and 15 vol.% graphite. The resulting mixture was characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and various transmission electron microscopic (TEM) methods, including energy dispersive X-ray spectroscopy (EDXS), high resolution investigations (HRTEM) with corresponding simulation of the HRTEM images, diffraction methods such as scanning nano-beam electron diffraction (SNBED) and selected area electron diffraction (SAED). It could be shown that the ball milling caused a reduction of the grain size of the initial components to the nanometer range. Sometimes even amorphization or partial break-down of the crystal structure was observed for MoS2 and graphite. Moreover, chemical reactions lead to a formation of surface coverings of the nanoparticles by amorphous material, molybdenum oxides, and iron sulfates as derived from XPS.
As a chemical metrology tool time-of-flight secondary ion mass spectrometry (ToF-SIMS) has become a very popular technique to monitor the elemental, isotopic and molecular distribution in two or three dimensions. Its reduced sampling depth, high sensitivity, great structural specificity and the direct detection of hydrogen thereby increase the emergence of ToF-SIMS for material and analytical surface science, particularly due to recent instrumental developments improving mass, depth and lateral resolution. For basic surface science, adsorption processes and surface reactivity thus can be investigated in high detail on organic as well as inorganic samples. The use of multivariate data analysis in addition can effectively assist to identify trends in the complex SIMS raw data set and define key co-variances between certain samples or mass spectra. In this contribution the essence of ToF-SIMS is illustrated by discussing two highly relevant energy applications. First, for piezoelectric electroceramics oxygen exchange active zones have been visualized to determine the impact of external field-load to the oxygen vacancy distribution between anode and cathode. As a second case study the interaction of hydrogen species with the microstructure of a duplex stainless steel was investigated. It was concluded that ToF-SIMS has a valuable essence for detailing hydrogen related degradation mechanisms.