Index of content:
Volume 23, Issue 1, June 2016
23(2016); http://dx.doi.org/10.1116/1.4943099View Description Hide Description
Cellulose and lignin reference samples have been investigated to enable the easier identification of the composition of pine wood strands in XPS. Presented here are the survey and high resolution x-ray photoelectron spectra of cellulose and lignin. Cellulose is characterised by a lack of intensity of the aliphatic carbon peak in addition to an intense carbon-oxygen peak corresponding to alcohols groups. Lignin is characterised by the presence of an intense aliphatic peak and a π-π* shake-up.
23(2016); http://dx.doi.org/10.1116/1.4948526View Description Hide Description
Switchable ionic liquids (SWIL) play an important role in green chemistry. Due to the nature of SWIL chemistry, such as air sensitivity, pressure, and temperature dependence, it is difficult to characterize SWIL using vacuum-based surface techniques. The fully CO2 loaded 1:1 mixtures of 1,8-diazabicycloundec-7-ene (DBU) and 1-hexanol (a SWIL system) and non-CO2 loaded DBU and 1-hexanol mixture were analyzed by in situ time-of-flight secondary ion mass spectrometry (ToF-SIMS) coupled with the system for analysis at the liquid vacuum interface (SALVI), respectively. The DBU/1-hexanol/CO2 SWIL was injected into the microchannel before liquidsecondary ion mass spectrometryanalysis. Bi3+ primary ion beam was used. The positive and negative spectra of the SWIL chemical components are presented. The characteristic peaks m/z 153 (protonated DBU) in the positive mode and m/z 101 (deprotonated 1-hexanol) in the negative mode were observed. In addition, ion pair peaks including m/z 253, 319, 305, and 451 in the positive mode and m/z 145, 223, and 257 in the negative mode are first observed using this approach. These results demonstrate that the SALVI microfluidic reactor enables the vacuum-based surface technique (i.e., ToF-SIMS) for in situ characterization of challenging liquid samples such as ionic liquids.
23(2016); http://dx.doi.org/10.1116/1.4953792View Description Hide Description
Silver nanoparticles of many types are widely used in consumer and medical products. The surface chemistry of particles and the coatings that form during synthesis or use in many types of media can significantly impact the behaviors of particles including dissolution, transformation and biological or environmental impact. Consequently it is useful to be able to extract information about the thickness of surface coatings and other attributes of nanoparticles produced in a variety of ways. It has been demonstrated that X-ray Photoelectron Spectroscopy (XPS) can be reliably used to determine the thickness of coatings and shells. However, care is required to produce reliable and consistent information. Here we report XPS spectra from gold/silver core-shell nanoparticles of nominal size 20 nm removed from a citrate saturated solution after one washing cycle. The Simulation of Electron Spectra for Surface Analysis (SESSA) program has been used to model peak amplitudes to obtain information on citrate coatings that remain after washing and demonstrate the presence of the gold core. This data is provided in digital form so that others can compare use of SESSA or other modeling approaches to quantify the nature of coatings to those already published and to explore the impacts particle non-uniformities on XPS signals from core-shell nanoparticles.
XPS examination of the native oxide layer on Kovar using aluminium, magnesium and silver x-ray sources23(2016); http://dx.doi.org/10.1116/1.4954179View Description Hide Description
Kovar, a common glass-to-metal sealing alloy, has been analysed by XPS. Monochromatic aluminium and silver sources as well as an achromatic magnesium x-ray source have been utilised to demonstrate the increased clarity of spectra that can be obtained through the use of each x-ray source in the analysis of a transition metal rich alloy.