TY - JOUR A1 - Unger, Wolfgang A1 - Swaraj, S. A1 - Dietrich, Paul M. T1 - X-ray spectromicroscopy of nanoparticulate iron oxide phases JF - Biointerphases N2 - 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. KW - X-ray spectromicroscopy KW - STXM KW - Iron oxide PY - 2016 DO - https://doi.org/10.1116/1.4966654 SN - 1934-8630 SN - 1559-4106 VL - 11 IS - 4 SP - 04B402-1 EP - 04B402-6 PB - AVS: Science & Technology of Materials, Interfaces, and Processing AN - OPUS4-38274 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Unger, Wolfgang A1 - Schwarz, F. A1 - Heinrich, Thomas A1 - Kaufmann, J. O. A1 - Lippitz, Andreas A1 - Puttreddy, R. A1 - Rissanen, K. A1 - Schalley, C. A. T1 - Photocontrolled on-surface pseudorotaxane formation with well-ordered macrocycle multilayers JF - Chemistry A European Journal N2 - 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. KW - Well-ordered macrocycle multilayers KW - XPS KW - NEXAFS PY - 2016 DO - https://doi.org/10.1002/chem.201603156 SN - 0947-6539 SN - 1521-3765 VL - 22 IS - 40 SP - 14383 EP - 14389 PB - Wiley-VCH Verlag GmbH & Co. KGaA CY - Weinheim AN - OPUS4-38270 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Unger, Wolfgang A1 - Pelster, A. A1 - Tyler, B.J. A1 - Kösgen, M. A1 - Kassenböhmer, R. A1 - Peterson, R.E. A1 - Stöver, M. A1 - Arlinghaus, H. F. T1 - Improved 3D-imaging of a sirolimus/probucol eluting stent coating using laser postionization secondary neutral mass spectrometry and time-of-flight secondary ion mass spectrometry JF - Biointerphases N2 - 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. KW - Imaging ToF SIMS KW - Eluting stent PY - 2016 DO - https://doi.org/10.1116/1.4964687 SN - 1934-8630 SN - 1559-4106 VL - 11 IS - 4 SP - 041001-1 EP - 041001-10 PB - AVS: Science & Technology of Materials, Interfaces, and Processing AN - OPUS4-38272 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Unger, Wolfgang A1 - Khani, M. A1 - Mehdipour, E. A1 - Faghani, A. A1 - Guday, G. A1 - Donskyi, Ievgen A1 - Haag, R. A1 - Adeli, M. T1 - Preparation of graphene oxide by cyanuric chloride as an effective and non-corrosive oxidizing agent JF - RSC ADVANCES N2 - 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. KW - Graphene oxide KW - Synthesis KW - XPS KW - AFM KW - IR KW - TGA PY - 2016 DO - https://doi.org/10.1039/c6ra23702a SN - 2046-2069 VL - 6 IS - 116 SP - 115055 EP - 115057 PB - The Royal Society of Chemistry AN - OPUS4-39111 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Unger, Wolfgang A1 - Kalbe, Henryk A1 - Rades, Steffi T1 - Determining shell thicknesses in stabilised CdSe@ZnS core-shell nanoparticles by quantitative XPS analysis using an infinitesimal columns model JF - Journal of Electron Spectroscopy and Related Phenomena N2 - 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. KW - XPS KW - Quantum dot KW - Core shell nano particle PY - 2016 DO - https://doi.org/10.1016/j.elspec.2016.08.002 SN - 0368-2048 VL - 212 SP - 34 EP - 43 PB - Elsevier B.V. AN - OPUS4-38273 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Unger, Wolfgang A1 - Beiranvand, Z. A1 - Kakanejadifard, A. A1 - Donskyi, Ievgen A1 - Faghani, A. A1 - Tu, Z. A1 - Lippitz, Andreas A1 - Sasanpour, P. A1 - Maschietto, F. A1 - Paulus, B. A1 - Haag, R. A1 - Adeli, M. T1 - Functionalization of fullerene at room temperature: toward new carbon vectors with improved physicochemical properties JF - RSC Advances N2 - 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. KW - Functionalization of fullerenes KW - XPS KW - NEXAFS PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-387076 DO - https://doi.org/10.1039/c6ra23419d SN - 2046-2069 VL - 6 IS - 114 SP - 112771 EP - 112775 PB - Royal Society of Chemistry (RSC) AN - OPUS4-38707 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang T1 - Advanced surface chemical analysis of plasma modified polymers and plasma-polymers N2 - 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). T2 - IAP workshop – IAP 2016 "Organic surface modifications by plasmas and plasma-polymers" CY - Nancy, France DA - 08.06.2016 KW - XPS KW - NEXAFS KW - SIMS KW - Plasmapolymer PY - 2016 AN - OPUS4-36725 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang A1 - Streeck, Cornelia A1 - Beckhoff, Burkhard T1 - Improved quantitative XRF analysis of industrial thin film samples by calibration using thin film RMs certified by reference-free XRF enabling traceability to the SI N2 - 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. T2 - Annual Meeting of ISO TC 201 SC 10 XRR/XRF CY - Seoul, Korea DA - 12.10.2016 KW - Reference-free XRF KW - CIGS thin films PY - 2016 AN - OPUS4-38265 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang A1 - Senoner, Mathias A1 - Wirth, Thomas A1 - Bütefisch, S. A1 - Busch, I. A1 - Rossi, A. A1 - Passiu, C. A1 - Spencer, N.D. T1 - Testing lateral resolution and field of view in imaging and small area analysis: reference materials and standardization N2 - 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. T2 - 7th International Symposium on Practical Surface Analysis(PSA-16) CY - Daejeon, Korea DA - 17.10.2016 KW - BAM L200 KW - SIMS KW - AES KW - XPS PY - 2016 AN - OPUS4-38266 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang A1 - Donskyi, Ievgen A1 - Lippitz, Andreas A1 - Haag, Rainer T1 - NEXAFS and XPS analysis of functionalized graphene surfaces for bio applications N2 - 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. T2 - 8th Jouint BER II and BESSY II User Meeting CY - Berlin, Germany DA - 7.12.2016 KW - XPS KW - NEXAFS KW - Graphene PY - 2016 AN - OPUS4-38683 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -