Time-of-flight secondary ion mass spectrometry (ToF–SIMS) has recently been shown to be a valuable tool for cultural heritage studies, especially when used in conjunction with established analytical techniques in the field. The ability of ToF–SIMS to simultaneously image inorganic and organic species within a paint cross section at micrometer-level spatial resolution makes it a uniquely qualified analytical technique to aid in further understanding the processes of pigment and binder alteration, as well as pigment–binder interactions. In this study, ToF–SIMS was used to detect and image both molecular and elemental species related to CdS pigment and binding medium alteration on the painting Le Bonheur de vivre (1905–1906, The Barnes Foundation) by Henri Matisse. Three categories of inorganic and organic components were found throughout Le Bonheur de vivre and co-localized in cross-sectional samples using high spatial resolution ToF–SIMS analysis: (1) species relating to the preparation and photo-induced oxidation of CdS yellow pigments (2) varying amounts of long-chain fatty acids present in both the paint and primary ground layer and (3) specific amino acid fragments, possibly relating to the painting’s complex restoration history. ToF–SIMS’s ability to discern both organic and inorganic species via cross-sectional imaging was used to compare samples collected from Le Bonheur de vivre to artificially aged reference paints in an effort to gather mechanistic information relating to alteration processes that have been previously explored using μXANES, SR-μXRF, SEM–EDX, and SR-FTIR. The relatively high sensitivity offered by ToF–SIMS imaging coupled to the high spatial resolution allowed for the positive identification of degradation products (such as cadmium oxalate) in specific paint regions that have before been unobserved. The imaging of organic materials has provided an insight into the extent of destruction of the original binding medium, as well as identifying unexpected organic materials in specific paint layers.
Analysis of the surface of thin Irganox 1010 films before and after sputtering with an argon gas-cluster ion beam was performed with AFM and XPS to determine the effect that Zalar rotation has on the chemistry and morphology of the surface. The analysis is based on the change in roughness of the surface by comparing the same location on the surface before and after sputtering. The ion beam used was an of size= 1000 and energy 4 keV. The XPS analysis agreed with previous results in which the ion beam did not cause measurable accumulation of damaged material. Based on the AFM results, the Irganox 1010 surface became rougher as a result of ion sputtering, and the degree of roughening was quantified, as was the sputter rate. Furthermore, Zalar rotation during ion sputtering did not have a significant effect on surface roughening, surprisingly.
Herein is a study of the soft sputtering method, gas cluster ion sputtering (GCIS), and its effects on the atomic, morphologic, and band structure properties of polyaniline (PAni) as studied with X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry, atomic force microscopy, and scanning tunneling spectroscopy (STS). The GCIS source used was a 1000 argon atom cluster with 4 keV energy, which resulted in a sputter yield of 3.4 ± 0.2 × 10−3 nm3 per argon atom. Soft ion sputtering reduced the sample by explicitly removing the oxidized contaminants as determined by surface sensitive techniques: XPS and Time-of-flight secondary ion mass spectrometry (TOF-SIMS). By the use of STS we found that by removing the oxidized components, an overall shift of electronic states occurred, transitioning the states closer to the Fermi edge by 0.3 V.
A large body of work has been established in the field of pigment alteration covering several artistic eras [1][2][3]. While these studies are fundamental in understanding the physical and chemical properties pertaining to color as seen in paintings, they do not cover the important facet of molecular alteration due to degradation of the binding medium of these paintings. By using surface analytical techniques proven in the study of cultural heritage materials it is possible to elucidate the effects of degradation inherent to binding media and also add to the knowledge of pigment-binder interactions. For this study, chemical information gathered by both TOF-SIMS and XPS, a complete characterization of both short-range (XPS) and long-range (TOF-SIMS) molecular alteration related to egg tempera degradation is presented herein. By utilizing gas cluster ion beam (GCIB) technology with XPS it was possible to elucidate any changes in chemical oxidation and reduction as a function of depth for a given material and its exposure to its surroundings.Thin films were prepared by spin casting freshly made egg tempera (1:1 w/w egg yolk:water) onto clean 1 × 1 inch silicon wafers. Samples were then placed as a set inside of a weathering chamber to simulate environmental degradation effects. Detailed in Figure 1, the chamber consists of an N2 purge, heat source, UV light source, and a relative humidity (RH) source. The variables to start the degradation process were to be tested across two major sources: heat/humidity exposure and UV exposure. The three trials set forth in the experiment were to expose the egg tempera thin films to the following conditions: i) 60 °C, >80% RH, and a dark chamber; ii) 20 °C, 0% RH, and UV exposure; and iii) 60 °C, >80% RH, and UV exposure.XPS and GCIB depth profiling were conducted with a K-Alpha+ with MAGCIS (Thermo-Scientific, Inc.) located in the Surface Analysis Facility at the University of Delaware. Monochromated Al Kα x-rays (1486.6 eV) with a spot size of 100 µm and pass energy of 20 eV for all high resolution scans. GCIB profiling was done with a 4 kV Ar2000 cluster for 60 s each level of sputtering. All curve-fitting was done in CasaXPS using Shirley-type background correction. The sputter rate of the egg tempera was measured using atomic force microscopy and found to be 4.5×10 -3 nm/Ar atom. TOF-SIMS was conducted with a TOF-SIMS IV (ION-TOF GmbH), upgraded to TOF-SIMS V capabilities, located in the Surface Analysis Facility at the University of Delaware. 25-kV Bi 3 + primary ions were directed towards the sample surface in "high-current bunched mode" with secondary ion extraction with ±2 kV into the TOF mass analyzer and given a 10 kV post-acceleration. All spectra were collected over an area of 250 µm 2 with primary ion beam dosage taken to the static SIMS limit of 1×10 12 ion/cm 2 . All data processing was completed in Matlab, using the correlated optimized warping (COW) package and the PLSToolbox. After COW alignment of the TOF-SIMS data to remove sample variance due to miscalibrati...
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