PM-RAIRS

The catalytic preformance of Co crystals with two surface conditions were compared annealed crystals with large atomically flat terraces and Ar+ ion sputtered surfaces which produced a high population of surface defects. A sequence of PM-RAIRS spectra are shown in Figure 3.2 during exposure of a sputtered Co (0001) surface to mixtures of H2 and CO, with the temperature and pressure for each spectrum indicated in the figure. 

Figure 3.2. Sequence of PM-RAIR spectra taken on a sputtered Co(0001) surface. The starting conditions were lOOmbar of CO at 298 K 200mbar of H2 was then added and the temperature increased stepwise to 490 K. It can be seen that the absorption signal due to CO attached to defect sites is removed in an irreversible process. The lowest curve was obtained at room temperature and under vacuum conditions and the hydrogen desorbs from the Co, while the CO and hydrocarbons remain. (After Beitel et al. 1997.)...

Beitel, G. A., de Groot, C. P. M., Oosterbeek, H., and Wilson, J. H. 1997. A combined in-situ PM-RAIRS and kinetic study of single-crystal cobalt catalysts under synthesis gas at pressures up to 300 mbar. J. Phys. Chem. B 101 4035-43. 

Polarization modulation reflection absorption infrared spectroscopy (PM-RAIRS) was employed to follow the reaction of CO, C2H4 and CO/C2H4 with microcrystalline ]Pd(Me)(OTf)(dppp)] deposited onto a gold coated wafer. Single insertion steps were observed by alternately exposing the catalyst precursor to low CO (500-333 mbar) and ethene (333 mbar) pressures (Figure 7.12). 

The PM-RAIRS study clearly showed that the p- and y-chelate complexes... 

Figure 7.12 In situ PM-RAIRS spectra of a microcrystalline sample of [Pd(Me)(OTf)(dppp)]. (a) At room temperature (b) under 500 mbar CO (c) under 2 mbar CO and 333 mbar of ethene (d) under subsequent exposure to 750 mbar CO (e) during subsequent polymerisation under 666 mbar of ethene/CO (evolution of the spectrum at 15 min intervals).

On the basis of the PM-RAIRS evidence, Drent has proposed a catalytic cycle (Scheme 7.8) where ethene insertion in the propagation step is CO-assisted and the substitution of the chelating ketone in c by ethene would proceed in two consecutive steps associative substitution of the chelating ketone by CO (c —> d —> e), followed by associative substitution of CO by ethene (e —> f —> i). The disruption of the chelate structure of c would be more facile for CO than for ethene for steric reasons (end-on vs. side-on approach). 

In the case of OP decontamination, parathion and paraoxon were spin-coated on glass or gold film surfaces from 0.023 ttiM solution in ethanol. The loadings of parathion and paraoxon were determined with a quartz crystal microbalance (QCM). The deposited amount of parathion and paraoxon film was 8.5 pg/cm and 5.0 pg/cm, respectively. These OP films were then treated with an 02/Ar plasma. The treated samples were analyzed with polarization-modulcation reflection absorption infrared spectroscopy (PM-RAIRS Thermo Nicholet Nexus 670 with a Hindz polarization modulation imit and a GWC demodulator) and tested for residual toxicity. 

For deposition of hydrophobic coatings, a mixture of CHVHe gases was used in the plasma. Superhydrophobic coatings were created with a Cp4/H2/He plasma. The deposited coatings were analyzed with PM-RAIRS, x-ray photoelectron spectroscopy, scanning electron microscopy (SEM, JEOL 6700 F - FESEM), atomicforce microscopy (AFM, Molecular Imaging SPM microscope with RHK controllers), ellipsometiy, and water contact angle measurements. 

Figure 3. PM-RAIRS spectra of parathion films after being treated with (a) 02/Ar plasma (rf power = 200 W), (b) UV, and (c) UV/ozone.(10)...

Figure 5. PM-RAIRS andXPS (inset) spectra of the hydrophobic coating deposted with scanning atmospheric CH/He plasma on a gold film. The number of plasma scanning is indicated in the figure. (17)...

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