Frank J. M. Rutten

Infrared microscopy of epithelial cancer cells in whole tissues and in tissue culture, using synchrotron radiation

Oral epithelial tumour tissue, and cultured cervical epithelial carcinoma cells have been studied using synchrotron infrared microspectroscopy. Mid infrared absorption spectra collected at cellular spatial resolution from within oral tumours were found to be sufficiently distinct, when analysed by principal component analysis, to distinguish between three different cell types within the tumour. The resulting data were sufficiently robust to allow correct classification of spectra from cells within subsequent tissue samples. These results go some way to demonstrate the potential of infrared spectroscopy as a tool in the post-operative screening of oral cancer patients by the examination of exfoliated epithelial cells. To gain a better understanding of the inherent variability in the infrared spectra of such epithelial cells, we have studied A431 carcinoma cells under the stimulus of the growth-stimulating hormone EGF. We have detected key changes in the infrared spectrum that relate to the activation of the growth factor signalling mechanism.

Enhanced hole injection in organic light-emitting diodes using a SAM-derivatised ultra-thin gold anode supported on ITO glass

In order to increase the performance of organic light-emitting diodes (OLEDs) we report the modification of the indium-tin oxide (ITO) anode invariably used in OLEDs, with a dipolar self-assembled monolayer-derivatised (4-nitrophenylthiolate) ultra-thin gold overlayer. This composite approach allows the work function of the anode to be tuned to the hole-transporting band of the adjacent semiconductor, while facilitating good mechanical adhesion at this interface. When this modification is incorporated into the model OLED system ITO/TPD/Alq3/C6H5CO2Li/Al [where TPD is N,N′-bis(3-methylphenyl)-N,N-diphenyl-1,1-biphenyl-4,4′-diamine, Alq3 is tris(quinolin-8-olato)aluminium and C6H5CO2Li is lithium benzoate], the power efficiency is dramatically enhanced. Furthermore, these devices exhibit a maximum external quantum efficiency of more than 5 cd A−1 and a peak luminance of ∼36,000 cd m−2. In combination with the current–voltage–luminance (LIV) characterisation of these devices, scanning Kelvin probe, polarisation modulation reflection absorption infrared spectroscopy and time of flight secondary ion mass spectroscopic techniques have been employed to probe the ITO–Au–SAM interface. This research builds on our earlier work with dipolar organosilanes, phosphonic acids and charge-transfer films at the ITO–organic interface.

Osteoblast activity on carbonated hydroxyapatite

Hydroxyapatite (HA), has been used commonly as a bone substitute and as a scaffold in bone tissue engineering. However it has certain drawbacks such as limited biodegradability and osteointegration properties. Other forms of HA, for example, carbonated hydroxyapatite (CHA) could prove to have enhanced bioactivity as they more closely mimic the chemical composition of the apatite found in human bone. The aim of this study was to test the efficacy of CHA in comparison to HA used as a control. The CHA (4.9 wt %) and the HA discs were seeded with MC3T3-E1 osteoblastic cells. Results revealed a trend of increased cell attachment on the HA discs at day 0, however, the cell proliferation on the CHA discs at 7 and 28 days showed no significant difference in comparison to the HA control. SEM of the CHA discs showed surface irregularities at 7 days indicating dissolution. Also at 7 days, SEM demonstrated cell attachment and extracellular matrix production on both the CHA and HA samples. There was no significant difference in the total amount of collagen produced in the CHA samples relative to the HA control samples at 28 days as evaluated by the hydroxyproline assay. Real time PCR revealed mRNA increase by 2.08, 7.62, and 9.86 fold for collagen I a1, collagen III a1, and osteocalcin respectively on the CHA as compared to the HA discs. This study demonstrates the use of CHA as a biocompatible material that has potentially increased biodegradation properties and osteogenic capability in comparison to HA.

The chemistry of simple alkyl species on Pt(111) generated by hyperthermal collisions

The identification of the primary dissociation products of hyperthermal collisions of methane and ethane with a Pt(111) surface at ∼150 K and the study of their subsequent thermal evolution has been afforded by the use of reflection–absorption infrared spectroscopy, temperature programmed desorption, and Auger electron spectroscopy. In both cases, the primary dissociation products have been identified as an adsorbed alkyl moiety (methyl, CH3, and ethyl, C2H5, respectively) and an adsorbed hydrogen atom. The thermal treatment of both alkyl adlayers ultimately results in the formation of the ethylidyne (≡CCH3) moiety at temperatures between 300 and 400 K. At ∼500 K, this species itself thermally decomposes to yield adsorbed carbon atoms and gaseous hydrogen. While this behavior may not be unexpected for the C2 ethyl fragment, the formation of the C2 ethylidyne fragment from the C1 methyl fragment can only be explained through the occurrence of carbon–carbon coupling reactions. Such reactions have only recen...

Thermal desorption of C6H6 from surfaces of astrophysical relevance

The thermal desorption of C(6)H(6) from two astrophysically relevant surfaces has been studied using temperature programmed desorption. Desorption from an amorphous SiO(2) substrate was used as a mimic for bare interstellar grains, while multilayer films of amorphous solid water (ASW) were used to study the adsorption of C(6)H(6) on grains surrounded by H(2)O dominated icy mantles. Kinetic parameters were obtained through a combination of kinetic modeling, leading edge analysis, and by considering a distribution of binding sites on the substrate. The latter is shown to have a significant impact on the desorption of small exposures of C(6)H(6) from the amorphous SiO(2) substrate. In the case of adsorption on ASW, dewetting behavior and fractional order desorption at low coverage strongly suggest the formation of islands of C(6)H(6) on the H(2)O surface. The astrophysical implications of these observations are briefly outlined.

High-energy electron beam lithography of octadecylphosphonic acid monolayers on aluminum.

Monolayers of octadecylphosphonic acid were self-assembled on silicon substrates sputter coated with aluminum. Patterning of the self-assembled monolayer was achieved by high-energy electron (50 kV) illumination using an electron beam lithography tool. The change in chemical composition of the exposed monolayer was investigated by time-of-flight secondary ion mass spectrometry over an area of 100 x 100 microm2. The electron dose required to fully expose the SAM was found to be about 6 mC/cm2. Gratings were exposed with line widths from 10 microm to 100 nm. The resulting patterns were imaged using friction force microscopy. It was found that the minimum line width is limited to ca. 100 nm by the patterning resolution. The pattern resolution achieved, ca. 40 nm, is equal to the grain size of the sputter-coated aluminum layer, and the possibility that the grain size limits the pattern resolution is discussed.

The CONO and COO2 reactions studied over Pt-Rh single crystal surfaces under steady state conditions

Abstract The CONO reaction was studied in the 10 −7 mbar range as a function of temperature and CO/NO ratio on the (111), (100), (410) and (210) surfaces of a Pt 0.25 -Rh 0.75 single crystal. At low temperatures (T (100) > (410) > (210). The results are compared with those obtained for the COO 2 reaction over the same surfaces and the effects of the surface composition and structure on both reactions are discussed. This comparison shows that the dissociation of NO is not the rate determining step in NO reduction by CO at low temperature. However, at T > 500K desorption of NO from Pt-Rh(111) becomes competitive with the dissociation of NO. As a result, the CONO reaction rate decreases much more strongly with increasing temperature over Pt-Rh(111) at T > 500K than the rate of the COO 2 reaction.

The application of ToF-SIMS to the analysis of herbicide formulation penetration into and through leaf cuticles.

Understanding the movement of the active ingredient in relation to the other formulation components following application is crucial to an overall understanding of herbicide performance. We describe the novel use of time-of-flight secondary ion mass spectrometry (ToF-SIMS) as a tool for following the movement of herbicide formulation components into and across plant cuticles. This technique provides new insights since it provides both high (sub-micron) spatial resolution combined with the chemical specificity associated with organic mass spectrometry. The components studied include the oligomeric ethoxylate surfactants Synperonic A7 and A20 and active ingredient Sulfosate (trimesium glyphosate). The movement of these molecules, both separately and when combined in a simple formulation, into the surface of Prunus laurocerasus leaves and across the isolated plant cuticle was investigated and clear differences in penetration/diffusion behaviour were identified. ToF-SIMS was uniquely able to (simultaneously) spatially resolve all the species involved, including the anion and cation components of the active ingredient. Also, using spectral reconstructions from the imaging raw data streams, the behaviour of individual oligomers within the surfactant distributions, could be assessed. The observations are discussed with reference to the action of surfactants identified in parallel micro-structural studies and the current understanding of herbicide uptake.

Photon- and electron-stimulated desorption from laboratory models of interstellar ice grains

The nonthermal desorption of water from ice films induced by photon and low energy electron irradiation has been studied under conditions mimicking those found in dense interstellar clouds. Water desorption following photon irradiation at 250 nm relies on the presence of an absorbing species within the H2O ice, in this case benzene. Desorption cross sections are obtained and used to derive first order rate coefficients for the desorption processes. Kinetic modeling has been used to compare the efficiencies of these desorption mechanisms with others known to be in operation in dense clouds.

An experimental study of vibrational enhancement of the dissociative chemisorption of ethane on Pt(111)

Abstract Measurements have been made of the initial sticking coefficient, S 0 diss , of ethane on a Pt(111) substrate which provide clear evidence for the enhancement sticking of vibrationally excited molecules. An analysis of the results, based on an harmonic density-of-states calculation, suggests that combinations involving deformation vibrational modes of the molecule are responsible for this enhancement.