We have performed an X-ray photoelectron spectroscopy (XPS) study in order to investigate thiolate monolayers on gold and indium phosphide. Evidence is presented that alkanethiols (chain length 10, 12, 16, and 18) also adsorb to form passivating monolayers on InP(110). An increasing degradation of the thiolate films has been observed on both types of substrates during extended exposure to X-rays. Several features in the spectral shapes of the core level spectra and their intensity evolution are discussed in terms of different types of layer damage. The chemical damage is indicated by the appearance of a new radiation-induced sulfur species. Spectroscopic evidence as obtained from both XPS and X-ray absorption near edge structure has been provided that indicates this species might be of disulfidic nature. Both sulfur and carbon disappear from the surface in about comparable amounts, clearly demonstrating significant structural damage of the thiolate films. The layer damage by the X-rays proceeds much faster and significantly stronger on gold films than on InP. This result is discussed in terms of structural defects and electron-induced effects. Evidence is provided for a significant contribution of backscattered and secondary electrons to the damage of the adsorbed organic layers. Patterning of alkanethiolate layers by an electron probe of a scanning Auger unit has been demonstrated.

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Superparamagnetic microbeads play an important role in a number of scientific and biotechnology applications including single-molecule force measurements, affinity separation, and in vivo and in vitro diagnostics. Magneto-optically active nanorods composed of single-crystalline Au and polycrystalline Fe segments were synthesized with diameters of 60 or 295 nm using templated electrodeposition. The Fe section was magnetically soft and had a saturation magnetization of approximately 200 emu/g, resulting in a 10-fold increase in magnetization relative to that iron oxide nanoparticles. The strong plasmonic response of the Au segment of the rod in both the longitudinal and transverse directions made it possible to detect the orientation of a single rod in a polarized light microscope with nanometer resolution. These nanorods provide significantly improved physical properties over iron oxide superparamagnetic beads, making it possible to simultaneously manipulate and monitor the orientation of biomolecules with well-defined forces at the nanometer scale.

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Rice, J.H. (2015) "Quantifying nanoscale biochemical heterogeneity in human epithelial cancer cells using combined AFM and PTIR absorption nanoimaging" Journal of Biophotonics, 8(1-2) : 133-141 which has been published in final form at http://dx