J Zhou

Decomposition of dimethyl methylphosphonate on TiO2(110): principal component analysis applied to X-ray photoelectron spectroscopy

The surface chemistry of dimethyl methylphosphonate (DMMP) has been studied on a TiO2(1 1 0) surface using X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). The application of principal component analysis (PCA) to the C(1s) and P(2p) XPS data showed that at least two linearly independent carbon-containing species and two linearly independent phosphorous-containing species are present on the surface between room temperature and 700 K. At room temperature, the main surface species contains intact P–OCH3 bonds and is most likely molecularly adsorbed DMMP. Between room temperature and 700 K, the adsorbed DMMP decomposes to produce methane and H 2 as the primary gaseous products. Molecular DMMP also desorbs from the surface below 550 K. After heating to 800 K, all of the carbon is removed from the surface, whereas a single phosphorous-containing species is detected even after heating to 1000 K.

Design of a heating-cooling stage for scanning tunneling microscopy and temperature programmed desorption experiments

A heating-cooling stage with detachable thermocouple contacts and an electron beam heater has been designed and tested for use in temperature programmed desorption and scanning tunneling microscopy (STM) experiments. This sample stage is compatible with the Omicron variable temperature STM, and the thermocouple contacts can be used with both the standard Ta plates and the variable temperature sample holder. The stage can also be retrofitted to the standard Omicron manipulation stage without requiring any additional electrical connections.

Copper-Coated Self-Assembled Monolayers: Alkanethiols and Prospective Molecular Wires

The study of the effects of metal overlayers on organic self-assembled monolayers (SAMs) is of interest in many scientific areas. The self-assembly process leads to a well-defined substrate whereas the numerous combinations of end-groups and metals allows for the fine-tuning of the chemistry at the monolayer/metal interface. These unique features make metal/SAM interfaces a valuable tool for probing fundamental processes. SAM/metal interfaces, have been proposed as templates to elucidate details on, for example, metal/“organic host” interactions which are known to occur in biologically active metallic reaction sites [1]; reaction mechanisms at organic/metal/gas interfaces, such as those involved in heterogeneous catalysis and environmental chemistry [2]; the solvation and electron-transfer reactions of metals in molecular solvents or within molecular clusters [3, 4]; and the insertion of zero-valent metals into chemical bonds frequently found in homogeneous catalysis reactions [3, 4, 5, 6].