An electrochemical cell for 2-dimensional surface optical reflectance during anodization and cyclic voltammetry.

We have developed an electrochemical cell for in situ 2-Dimensional Surface Optical Reflectance (2D-SOR) studies during anodization and cyclic voltammetry. The 2D-SOR signal was recorded from electrodes made of polycrystalline Al, Au(111), and Pt(100) single crystals. The changes can be followed at a video rate acquisition frequency of 200 Hz and demonstrate a strong contrast between oxidizing and reducing conditions. Good correlation between the 2D-SOR signal and the anodization conditions or the cyclic voltammetry current is also observed. The power of this approach is discussed, with a focus on applications in various fields of electrochemistry. The combination of 2D-SOR with other techniques, as well as its spatial resolution and sensitivity, has also been discussed.

Combining high-energy X-ray diffraction with Surface Optical Reflectance and Planar Laser Induced Fluorescence for operando catalyst surface characterization.

We have combined three techniques, High Energy Surface X-Ray Diffraction (HESXRD), Surface Optical Reflectance, and Planar Laser Induced Fluorescence in an operando study of CO oxidation over a Pd(100) catalyst. We show that these techniques provide useful new insights such as the ability to verify that the finite region being probed by techniques such as HESXRD is representative of the sample surface as a whole. The combination is also suitable to determine when changes in gas composition or surface structure and/or morphology occur and to subsequently correlate them with high temporal resolution. In the study, we confirm previous results which show that the Pd(100) surface reaches high activity before an oxide can be detected. Furthermore, we show that the single crystal catalyst surface does not behave homogeneously, which we attribute to the surface being exposed to inhomogeneous gas conditions in mass transfer limited scenarios.

An in situ set up for the detection of CO2 from catalytic CO oxidation by using planar laser-induced fluorescence.

We report the first experiment carried out on an in situ setup, which allows for detection of CO(2) from catalytic CO oxidation close to a model catalyst under realistic reaction conditions by the means of planar laser-induced fluorescence (PLIF) in the mid-infrared spectral range. The onset of the catalytic reaction as a function of temperature was followed by PLIF in a steady state flow reactor. After taking into account the self-absorption of CO(2), a good agreement between the detected CO(2) fluorescence signal and the CO(2) mass spectrometry signal was shown. The observed difference to previously measured onset temperatures for the catalytic ignition is discussed and the potential impact of IR-PLIF as a detection technique in catalysis is outlined.

Midinfrared polarization spectroscopy of OH and hot water in low pressure lean premixed flames.

The application of midinfrared polarization spectroscopy (mid-IRPS) is demonstrated for sensitive detection of minor molecular species in combustion environments by probing rovibrational transitions. High resolution mid-IRPS spectra of low pressure flames were obtained in the spectral range around 3 microm. Rotational lines of the fundamental vibrational band of the hydroxyl radical (OH) were fully resolved and properly assigned among the abundant hot water lines in the flame mid-IRPS spectra. The high signal-to-noise ratio of the recorded OH lines indicates the feasibility of sensitive mid-IRPS OH detection. This constitutes, to the best of our knowledge, the first reported OH flame detection in the midinfrared spectral range. A simulation of hot water mid-IRPS lines with molecular parameters extracted from the HITRAN/HITEMP database was performed and compared with the observed flame spectra. The proper prediction of the hot water lines may help to clarify the potential spectral interferences associated with minor species measurements.

Single-shot imaging of ground-state hydrogen atoms with a nonlinear laser spectroscopic technique.

We report on a novel nonlinear laser spectroscopic technique for single-shot imaging of ground-state hydrogen atoms in harsh environments. H atoms from the ground state were first pumped to the 2s state via a two-photon excitation with a 243 nm laser beam, and the population of the 2s state was further probed through the 2s-4p transition with conventional polarization spectroscopy at 486 nm. A single Nd:YAG-pumped optical parametric oscillator laser system was enough to provide both laser beams. Single-shot visualization of native H atoms in an atmospheric pressure premixed H(2)/O(2) flame is demonstrated.

Measurements of collisional broadening coefficients by infrared polarization spectroscopy.

We present measurements of collisional broadening coefficients, obtained at atmospheric pressure, by polarization spectroscopy. Using tunable single mode laser radiation at approximately 2 microm, high-resolution infrared polarization spectra were recorded for CO2-Ar and CO2-He binary mixtures. The recorded polarization spectra were fitted with a Lorentzian cubed function form to obtain the broadening coefficients. The full-width at half-maxima (FWHM) collisional broadening rates of CO2 by Ar and He, for the R14 (12 degrees1<--00 degrees0) line, have been determined to be 0.161+/-0.018 cm-1 atm-1 and 0.1823+/-0.0032 cm-1 atm-1, respectively.

The presence of IgE on the surface of lymphocytes in nasal polyps.

The presence of IgE-bearing lymphocytes in nasal polyps was correlated with the patients' atopic status. Following surgical removal, the polyp tissue was treated with hyaluronidase and a single-cell suspension was obtained. Lymphocytes were isolated by gradient centrifugation, and the fluorescent antibody technique was used to study the presence of various immunoglobulin markers on the surface of lymphocytes. The presence of IgE-bearing cells was correlated with serum IgE levels, history of allergy, and skin test reactions. Patients with a positive atopic history had intermediate to high serum IgE levels. There was no correlation between IgE level and skin reactivity in these patients. Good correlation was obtained between the number of IgE-bearing cells in nasal polyps and serum IgE levels in atopic patients. The IgE-bearing cells represented 10 to 40 per cent of total immunoglobulin-bearing lymphocytes. No IgE-bearing cells were detected in five of six patients with a negative atopic history and negative skin tests. Thus IgE may be synthesized within nasal polyps of atopic patients, and the polyps in atopic patients may have a different etiology from those in nonatopic patients.