An electroacoustic chemical sensor based on thin-film bulk acoustic wave resonators (TFBAR) is presented. It operates on the same principle of the well-known quartz crystal micro-balance, at an operation frequency extended up to several GHz. The larger output signal, associated to the higher operation frequency, is a condition to improve the device sensitivity. TFBARs have been implemented on (001) Si wafers, using Si3N4∕AlN membranes, obtained by anisotropic etching of Si. Time response and calibration curves have been tested on TFBAR sensors exploiting two different chemically interactive membranes: Pd and Co-tetra-phenyl-porphyrin, both deposited in the form of thin-films by thermal evaporation. Measurements performed upon exposure to H2, CO, and ethanol have shown the ability of the device to detect low concentrations of the analyte with a fast and repeatable response.
Rhodium-catalyzed deuterioformylation of 1-hexene, at partial substrate conversion, has been investigated at different temperatures and pressures, and the incorporation of deuterium in the residual substrate has been detected by MS and 2H NMR analyses. At room temperature, 1-hexene does not isomerize to internal olefins nor is deuterium present in the residual 1-hexene. At high temperature, 1-hexene incorporates deuterium mainly at carbon atom Cz and isomerization to 2-hexene, nondeuterated or deuterated at carbon atom C1, occurs. These findings indicate that the formation of alkylrhodium intermediates is not reversible at room temperature. A t high temperature a &hydride elimination process occurs to an extent which is greater for the branched than for the linear alkyl accounting for the influence of the reaction parameters on the regio-and chemoselectivity of the reaction.
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