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- 2011 (4) (entfernen)
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- Englisch (4)
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- ToF-SIMS (3)
- Carbohydrates (2)
- NEXAFS (2)
- XPS (2)
- Amine-functionalized polymer (1)
- Ammonia plasma (1)
- Ammonia plasma treatment (1)
- Deuterated ammonia (1)
- Deuterated polyolefins (1)
- H-D exchange (1)
A combined XPS, NEXAFS, and ToF-SIMS chemical surface characterization of carbohydrate-functionalized gold and glass surfaces is presented. Spot shape and chemical composition across a spot surface are provided by surface-sensitive methods as ToF-SIMS and XPS, used in their imaging modes. Moreover, the feasibility of this multimethod approach to control relevant production steps of a carbohydrate microarray prototype is demonstrated.
Carbohydrate films on gold based on dimannoside thiols (DMT) were prepared, and a complementary surface chemical analysis was performed in detail by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), near-edge X-ray absorption fine structure (NEXAFS), FT-IR, and contact angle measurements in order to verify formation of ω-carbohydrate-functionalized alkylthiol films. XPS (C 1s, O 1s, and S 2p) reveals information on carbohydrate specific alkoxy (C–O) and acetal moieties (O–C–O) as well as thiolate species attached to gold. Angle-resolved synchrotron XPS was used for chemical speciation at ultimate surface sensitivity. Angle-resolved XPS analysis suggests the presence of an excess top layer composed of unbound sulfur components combined with alkyl moieties. Further support for DMT attachment on Au is given by ToF-SIMS and FT-IR analysis. Carbon and oxygen K-edge NEXAFS spectra were interpreted by applying the building block model supported by comparison to data of 1-undecanethiol, poly(vinyl alcohol), and polyoxymethylene. No linear dichroism effect was observed in the angle-resolved C K-edge NEXAFS.
Since more than 40 years ammonia plasma exposure of polyolefins is used for introduction of primary amino groups. The selectivity of this reaction and the yield in primary amino groups was found to be low. Here, a prominent side-reactions of this process was investigated, the hydrogenation by NH3 plasma. For identification of hydrogenation ammonia (NH3) and deuterated ammonia (ND3) were exposed to Polyethylene (h-PE) and fully deuterated polyethylene (d-PE) as well as hexatriacontane (h-HTC) and fully deuterated hexatriacontane (d-HTC) as low-molecular weight model for PE. HD exchange was assumed and detected by Time-of-Flight Secondary Ion Mass Spectrometry (ToFSIMS), X-ray Photoelectron Spectroscopy (XPS), Attenuated Total Reflectance (ATR-FTIR) and 1H and 2H Nuclear magnetic Resonance. Results show a significant HD exchange within the sampling depth of ATR (2.5 µm). However, N- and NH2 introduction was limited to the topmost surface as shown by SIMS and XPS (a few nanometers).
ToF-SIMS has been used to study the surface functionalization of polypropylene and polyethylene samples by exposure to low-pressure ammonia plasma. Static secondary ion mass spectrometry is an appropriate tool to determine hydrogen isotopes as elements and in fragment ions with high sensitivity and selectivity. Specifically the exchange of hydrogen isotopes and the incorporation of N-containing moieties in the near-surface layer of the polyolefins have been studied in ND3 plasma experiments with conventional polypropylene (h-PP) and polyethylene (h-PE) and NH3 plasma experiments with deuterated polyethylene (d-PE). Considering the exchange of hydrogen between the plasma and the polymer surface studied by using deuterated ammonia and polyolefin samples the conclusion has been derived that polypropylene with its side chain methyl groups is more susceptible to hydrogen exchange reactions. For ND3 plasma treatment of polyethylene and polypropylene similar N-containing fragments were obtained and the measured semi-quantitative ToF-SIMS N-uptake data are rather similar. The observation of a wide range of characteristic mixed CkNlHmDn+ secondary fragment ions suggests complex and manifold reaction pathways at the polymer–plasma interface besides simple grafting of –ND2 or –NH2 moieties formed by ammonia fragmentation in the plasma. Finally, indications of an isotopic effect for hydrogen isotopes in the plasma process have been observed by comparison of ND3/h-PE results with those of NH3/d-PE.