Room-temperature Polymerisation Of Ethylene On A Tio2 (anatase) Surface; Infrared Spectroscopic Evidence For An Alkylidene-ti4+ Polymer End-group And For A 'hydrogen-bonding' Type Of Interaction Of Ch Bonds Of The Polymer Chain With The Oxide Surface

An infrared spectroscopic study of the spontaneous polymerisation of ethylene on a sulphate-containing TiO2 (anatase) sample shows evidence for an alkylidene surface end-group of the polymer and for substantial perturbation of CH2 groups of the polymer chain by interaction with the oxide surface.2112581259DARPA; Defense Advanced Research Projects Agency; NSF; Defense Advanced Research Projects Agenc

Infrared studies of the diatomic molecules O2, N2, NO and H2 adsorbed on Fe2O3

An infrared spectroscopic study of the diatomic molecules O2, N2, NO and H2 adsorbed under different conditions on Fe2O3 has been performed. Complex patterns of absorption on both \u3b1-Fe2O3 and \u3b3-Fe2O3 activated in O2 at high temperature are assigned to vibrations of two different chemisorbed O2 species. N2 molecules do not interact with "oxygen rich" \u3b1-Fe2O3 surfaces, but give N2O- and N2O22- species when chemisorbed on evacuated surfaces. NO molecules give complex patterns of absorption, depending on the gas pressure. Three different types of nitrate structures can be identified, as well as NO, NO- and cis-N2O2 chemisorbed species. Chemisorbed water molecules are formed by contact of H2 with Fe2O3 surfaces even at room temperature. \ua9 1982

Infrared study of adsorption on oxygen-covered \u3b1-Fe2O3: Bands due to adsorbed oxygen and their modification by co-adsorbed hydrogen or water

\u3b1-Fe2O3 heated in oxygen for one hour at 400\ub0C exhibits two complex regions of infrared absorption between 1350 and 1250 cm-1 (the type A bands at 1350, 1325, 1300 and 1270 cm-1) and between 1100 and 900 cm-1 (the type B bands at 1090, 1060, 1035, 1010, 990 and 930 cm-1). Each group of absorptions is thought to characterise a particular type of species adsorbed on different cationic sites. The observed band wavenumbers lead to the tentative assignment of the type A bands to O2- species perturbed in the direction of O2, and the type B bands to O22- species perturbed in the direction of O2-. Evacuation at temperatures in excess of 150\ub0C led first to the type A and then to the type B bands becoming much reduced in intensity. These changes are correlated with previously obtained thermal desorption peaks from oxygen adsorbed on Fe2O3. The detailed appearance of the band patterns in the type A and type B regions depends on the temperature of the initial interaction of gas-phase O2 with the oxide. They are considered to reflect a frozen-in high-temperature distribution of the species over various surface sites. Redistributions of intensities within the two regions, as a result of prolonged room-temperature evacuation, are thought to reflect a relaxation to a room-temperature distribution of surface sites brought about through induced surface mobility. Similar changes are caused by the adsorption of water at room temperature or by heating in hydrogen. The type A band at 1270 cm-1 and the type B band at 990 cm-1 seem to be particularly affected by co-adsorption of water. The former band is shifted to ca. 1200 cm-1 and the latter is greatly decreased in intensity