Bad Münster am Stein-Ebernburg, Germany
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PubMed | ION TOF GmbH, University of Manchester, University of Washington, Tascon GmbH and 16 more.
Type: Journal Article | Journal: The journal of physical chemistry. C, Nanomaterials and interfaces | Year: 2016

We report the results of a VAMAS (Versailles Project on Advanced Materials and Standards) inter-laboratory study on the measurement of the shell thickness and chemistry of nanoparticle coatings. Peptide-coated gold particles were supplied to laboratories in two forms: a colloidal suspension in pure water and; particles dried onto a silicon wafer. Participants prepared and analyzed these samples using either X-ray photoelectron spectroscopy (XPS) or low energy ion scattering (LEIS). Careful data analysis revealed some significant sources of discrepancy, particularly for XPS. Degradation during transportation, storage or sample preparation resulted in a variability in thickness of 53 %. The calculation method chosen by XPS participants contributed a variability of 67 %. However, variability of 12 % was achieved for the samples deposited using a single method and by choosing photoelectron peaks that were not adversely affected by instrumental transmission effects. The study identified a need for more consistency in instrumental transmission functions and relative sensitivity factors, since this contributed a variability of 33 %. The results from the LEIS participants were more consistent, with variability of less than 10 % in thickness and this is mostly due to a common method of data analysis. The calculation was performed using a model developed for uniform, flat films and some participants employed a correction factor to account for the sample geometry, which appears warranted based upon a simulation of LEIS data from one of the participants and comparison to the XPS results.


Liu J.,Imperial College London | Chater R.J.,Imperial College London | Hagenhoff B.,TASCON GmbH | Morris R.J.H.,University of Warwick | Skinner S.J.,Imperial College London
Solid State Ionics | Year: 2010

Isotopic surface oxygen exchange and its subsequent diffusion have been measured using secondary ion mass spectrometry in the fast ionic conductor La2Mo2O9. A silver coating was applied to the sample surface to enhance the surface exchange process for dry oxygen. Contrary to previous studies performed using a wet atmosphere, no grain boundary diffusion tail was observed under these optimized dry exchange conditions. The activation energy for oxygen diffusion was found to be 0.66(± 0.09) eV at high temperature (> 570 °C), and 1.25(± 0.01) eV at low temperature (< 570 °C). Time-of-Flight secondary ion mass spectrometry was employed to investigate the correlation between the silver coating and the 18O concentration on the sample surface. A close correlation between the presence of silver and oxygen incorporation on the surface was observed. © 2010 Elsevier B.V. All rights reserved.


Clark P.A.,Tascon United States | Hagenhoff B.,Tascon GmbH | Kersting R.,Tascon GmbH | Tallarek E.,Tascon GmbH
Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics | Year: 2016

The development of cluster primary ion sources such as Aun +, Bin +, SF5 +, C60 +, and Arn + has been an exciting advancement in SIMS analysis. Relative to atomic primary ion sources, cluster ion sources provide higher secondary ion yields. Furthermore, C60 + and Arn + impart significantly less chemical damage to the sample thus enabling molecular depth profiling. Molecular depth profiling using cluster primary ion sources is routinely used to characterize a wide range of commercially important materials, including organic light emitting diode, biomaterials and pharmaceuticals, adhesives, and architectural paints and coatings. This paper highlights the application of time of flight secondary ion mass spectrometry (ToF-SIMS) to study contact lenses and acrylic-based paints. In the first application, ToF-SIMS was used to investigate the surface composition of two commercial contact lenses. Lens material I is composed of 2-hydroxy-ethyl methacrylate (HEMA) and glycerol methacrylate while lens material II is composed of HEMA and 2-methacryloxyethyl phosphorylcholine cross-linked with ethyleneglycol dimethacrylate. The ToF-SIMS data confirm the presence of the 2-methacryloxyethyl phosphorylcholine on the surface of lens material II. ToF-SIMS was also used to characterize a HEMA-based contact lens which had been worn for about 4 weeks. The analysis reveals the presence of N-containing species, fatty acids, phosphorylcholine, and dioctyldecyl dimethyl ammonium. Arn + gas cluster ion beams (GCIB) depth profiling indicates the N-containing species, the fatty acids, and the dioctyldecyl dimethyl ammonium are concentrated at the surface. In the second application, a combination of O2 + and Arn + GCIB depth profiling was used to study the pigment levels in acrylic-based paints. The O2 + beam was used to profile into the bulk of the dried paint film and Arn + gas cluster beam was then used to remove the damaged material. ToF-SIMS analysis of the crater bottom reveals differences in pigment levels. The combined O2 + and Arn + GCIB depth profiling is an effective way of characterizing materials composed of both organic and inorganic components. © 2016 American Vacuum Society.


Gruner M.,University of Munster | Siozios V.,University of Munster | Hagenhoff B.,Tascon GmbH | Breitenstein D.,Tascon GmbH | Strassert C.A.,University of Munster
Photochemistry and Photobiology | Year: 2013

In this work, we have quantified for the first time the fluorescence and singlet oxygen quantum yields of a silicon(IV) phthalocyanine bound to the surface of zeolite L nanocrystals. The photophysical properties were correlated with the absorption spectra and the morphology of the nanoparticles, and most importantly, with the fraction of photoactive chromophores. By comparison with the fluorescence and singlet oxygen quantum yields of the free phthalocyaninate in dilute solution (ΦF = 0.50 and ΦΔ = 0.50, respectively), we conclude that for the most efficient nanoparticles nearly 80% of chromophores are active as monomeric units on the surface, as indicated by the corresponding quantum yields (ΦF = 0.40 and ΦΔ = 0.40). We further functionalized and raised the ζ-potential of the best performing nanomaterial to improve its water dispersibility. The functionalization was monitored by thermogravimetric analysis and time-of-flight secondary-ion mass spectrometry, and its influence on the photophysical properties was assessed. The resulting nanomaterials are capable of establishing stable suspensions in water while retaining the ability to form reactive oxygen species upon irradiation with red light. This provides a basis for the rational design of photoactive nanomaterials for photodynamic therapy or water decontamination. © 2013 The American Society of Photobiology.


Niehuis E.,ION TOF GmbH | Mollers R.,ION TOF GmbH | Rading D.,ION TOF GmbH | Cramer H.-G.,ION TOF GmbH | Kersting R.,TASCON GmbH
Surface and Interface Analysis | Year: 2013

Ar cluster sputtering of organic multilayers such as organic light-emitting diode model structures and Irganox delta layers is studied with time-of-flight secondary ion mass spectroscopy in the dual beam mode. Results for sputtering yield volumes and depth resolution are presented for Ar clusters with sizes from 500 to 5000 atoms in the energy range from 2.5 to 20 keV. The sputtering yield volume shows a linear dependence on the energy per atom for all materials in this study with a material-dependent threshold below 1 eV/atom. The sputtering yield volume at a given energy per atom increases with the cluster size. At constant beam energies, the sputtering yield volume decreases slightly with increasing cluster size. The depth resolution is investigated for the two model systems as a function of energy and cluster size, and it will be shown that the depth resolution depends mainly on the sample roughening. The depth resolution is approximately proportional to the depth of the impact crater at a given cluster size and energy. The optimum depth resolution achieved is in the range of 4-5 nm and is fairly constant with depth. At very low energies per atom close to the threshold energy, ripple formation is observed that leads to a fast degradation of the depth resolution with depth. This can be completely eliminated by fast sample rotation. Finally, the perspective of 3D analysis of organic devices with high depth resolution in the dual beam mode will be discussed. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd.


Hagenhoff B.,Tascon GmbH | Breitenstein D.,Tascon GmbH | Tallarek E.,Tascon GmbH | Mollers R.,ION TOF GmbH | And 4 more authors.
Surface and Interface Analysis | Year: 2013

The present study describes the detection and localization of silica particles with diameters between 2 μm and 150 nm within the cytoplasm of mammalian cells by means of ToF-SIMS 3D analysis. The particles were selected as model objects for non-luminescent, unlabeled particles that are hard to localize by other experimental approaches. ToF-SIMS analysis proved the uptake of the particles into the cell body, provided images of their distribution around the cell nucleus and indications that the cell membranes are undulated by the μm-sized particles beneath the membrane. Two ion sources (Cs+ and O2+) were applied for sputtering the organic material and expose deeper sections of the cells. The resulting images are presented and compared. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd.


Kersting R.,Tascon GmbH | Breitenstein D.,Tascon GmbH | Hagenhoff B.,Tascon GmbH | Fartmann M.,Tascon GmbH | And 4 more authors.
Surface and Interface Analysis | Year: 2013

The rapidly growing interest in nanoparticles (NPs) as part of technical products conflicts with the limited knowledge about potential health risks. This dilemma is the initial point of the project NanoPaCT where, based on the chemical composition of NPs and toxicological tests, a forecast on their biological activity should be made. For the chemical characterization of the outer surface of core-shell NPs, an excellent surface sensitivity of the applied analytical techniques is required. In this article, we will present data on an approach to optimise time-of-flight secondary ion mass spectrometry (ToF-SIMS) to this need. The effect of primary ion parameters (species, energy) was studied on a model system (HfO2 on Si) as well as on Lumidot core-shell NPs. The full layer closure of both films was proofed by means of low energy ion scattering. On the flat high-K sample, a clear variation of surface sensitivity could be observed as function of primary ion (PI) parameters. In contrast to this, almost no effect was found on core-shell NPs which behave in the experiment like homogeneous particles. These results indicate that NPs probably melt-up or evaporate after direct or grazing impact of PI at typical energies used in ToF-SIMS. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd.


Rafati A.,University of Washington | Ter Veen R.,Tascon GmbH | Castner D.G.,University of Washington
Surface and Interface Analysis | Year: 2013

With the widespread use of engineered nanoparticles for biomedical applications, detailed surface characterization is essential for ensuring reproducibility and the quality/suitability of the surface chemistry to the task at hand. One important surface property to be quantified is the overlayer thickness of self-assembled monolayer (SAM) functionalized nanoparticles, as this information provides insight into SAM ordering and assembly. We demonstrate the application of high sensitivity low-energy ion scattering (HS-LEIS) as a new analytical method for the fast thickness characterization of SAM functionalized gold nanoparticles (AuNPs). HS-LEIS demonstrates that a complete SAM is formed on 16-mercaptohexadecanoic acid (C16COOH) functionalized 14 nm AuNPs. HS-LEIS also experimentally provides SAM thickness values that are in good agreement with previously reported results from simulated electron spectra for surface analysis of X-ray photoelectron spectroscopy data. These results indicate HS-LEIS is a valuable surface analytical method for the characterization of SAM functionalized nanomaterials. © 2013 John Wiley & Sons, Ltd.


Heller D.,Tascon GmbH | Hagenhoff B.,Tascon GmbH | Engelhard C.,University of Siegen
Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics | Year: 2016

This paper presents a case study for the application of multivariate data analysis (MVA) to time-of-flight secondary ion mass spectrometry (ToF-SIMS) data from sample sets of mainly unknown surface composition. Aged lithium-ion battery (LIB) anodes were used as the test sample set due to their relatively complex composition. For example, LIB samples typically contain a large variety of different and often unidentified degradation products that complicate manual data processing. In this work, principal component analysis (PCA) was applied as a first step to find and classify relevant but unknown peaks in the ToF-SIMS mass spectra. As a result, peak identification was simplified in such a way that the chemical nature of 76% of the characteristic but previously unknown peaks was successfully identified. In a second step, multivariate curve resolution (MCR) was applied to depth profiles of the battery anodes for the first time, and a layered structure of the model samples was successfully determined. This approach also provided an efficient way to compare the layers' structure and the thickness across different samples. In addition to MCR, PCA was used on ToF-SIMS data to investigate all of the layer compositions of the complete sample set simultaneously. It is demonstrated that ToF-SIMS data from rarely characterized data sets can be processed successfully using MVA methods even if a priori knowledge of the sample sets is very limited. With respect to the test samples, the combination ToF-SIMS and MVA proved to be an attractive method to study the influence of different additives (vinylene carbonate, fluoroethylene carbonate, and ethylene sulfite) that appeared in the mass spectra, and was therefore helpful in understanding the formation of different degradation products in LiPF6-containing battery anodes. © 2016 American Vacuum Society.


Pietrowski M.J.,RWTH Aachen | De Souza R.A.,RWTH Aachen | Fartmann M.,Tascon GmbH | Ter Veen R.,Tascon GmbH | Martin M.,RWTH Aachen
Fuel Cells | Year: 2013

Oxygen isotope exchange experiments, H2 18O/H 2 16O ("wet" anneals) and 18O 2/16O2 ("dry" anneals), were performed on single crystal samples of yttria-stabilized zirconia (YSZ) at a temperature of T = 1073 K with subsequent determination of the oxygen isotope profiles in the solid by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Such experiments yielded oxygen tracer diffusion coefficients (D*) and oxygen tracer surface exchange coefficients (k*), from both the polished (smooth) and unpolished (rough) sides of single crystal samples, as a function of water partial pressure pH2O and oxygen partial pressure pO2. Isothermal values of D* were found to depend on neither pO2 nor pH2O (nor surface roughness). Isothermal values of k*, in contrast, displayed a strong dependence on pO2 or pH2O; k*wet was, in addition, 2-3 orders of magnitude higher than k*dry. Surprisingly, surface roughness had little effect on k*wet, whereas rough surfaces exhibited much higher k*dry values than smooth surfaces. Data for k*wet obtained as a function of temperature at pH2O = 18 mbar show a change in activation enthalpy at T ≈ 973 K. The behavior of k* is discussed in terms of surface composition, surface area and surface reaction mechanisms. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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