Functionalization of self-assembled monolayer (SAM) of alkanethiolate with metal containing unit is one of the versatile methods to obtain functional surfaces such as heterogeneous catalysts. However, organic molecules that strongly bind to transition metals at SAM terminal are limited. Recently N-heterocyclic carbenes (NHCs) such as cyclic diaminocarbenes have emerged as strongly σ-donating ligands forming a robust bond with broad spectrum of transition metals. In the present study, for the purpose of establishment of a new robust basement for heterogeneous metal catalysts, a SAM of the alkanethiolate terminated with NHC-rhodium(I) complex moiety was prepared by utilizing a newly designed disulfide molecule bearing NHC-metal complex terminals. X-ray photoelectron spectroscopy (XPS) analysis and angle resolved XPS measurement revealed successful formation of the Rh-complex-terminated SAM on a gold substrate. Infrared reflection absorption spectroscopy (IRRAS) analysis suggested that the linker methylene chains connecting the rhodium complex moiety and the gold surface are in a loosely packed structure. This unique chemical species, NHC, would be a promising candidate as a basement for the construction of functional surface. 相似文献
Iron alloys and aluminum were nitrogen implanted in a controlled oxygen atmosphere and the role of hydrogen on the surface etching mechanisms studied. The surface composition was analyzed by in situ photoemission electron spectroscopy (XPS). In iron alloys, hydrogen strongly etches oxygen, improving nitrogen retention on the surface. On the other hand, hydrogen removes nitrogen from aluminum surfaces, with a deleterious effect on the nitriding effectiveness. The oxygen removal in iron alloys is associated with the catalytic effect of electrons in d-orbitals and the nitrogen removal in aluminum is associated with a steric effect. 相似文献
Thin films of a-SiOx (0 < x < 2) were prepared by reactive r.f. magnetron sputtering from a polycrystalline-silicon target in an Ar/O2 gas mixture. The oxygen partial pressure in the deposition chamber was varied so as to obtain films with different values of x. The plasma was monitored, during depositions, by optical emission spectroscopy (OES) system. Energy dispersive X-ray (EDX) measurements and infra-red (IR) spectroscopy were used to study the compositional and structural properties of the deposited layers.Structural modifications of SiOx thin films have been induced by UV photons’ bombardment (wavelength of 248 nm) using a pulsed laser. IR spectroscopy and X-ray photoemission spectroscopy (XPS) were used to investigate the structural changes as a function of x value and incident energy. SiOx phase separation by spinodal decomposition was revealed. The IR peak position shifted towards high wavenumber values when the laser energy is increased. Values corresponding to the SiO2 material (only Si4+) have been found for laser irradiated samples, independently on the original x value. The phase separation process has a threshold energy that is in agreement with theoretical values calculated for the dissociation energy of the investigated material.For high values of the laser energy, crystalline silicon embedded in oxygen-rich silicon oxide was revealed by Raman spectroscopy. 相似文献
X-ray photoelectron spectroscopy (XPS) was adopted for the analytical characterization of composite titanium dioxide–poly(vinylidenefluoride) (TiO2–PVDF) films developed for applications in the photocatalytic degradation of pollutants.
The composites were deposited on glass substrates by casting or spin coating from TiO2–PVDF suspensions in dimethylformamide (DMF). XPS data on the TiO2–PVDF surface composition were used to optimize preparation conditions (composition of the TiO2/PVDF suspension, deposition technique) in terms of titanium dioxide surface amount and film stability.
The use of spin-coating deposition and the increase of TiO2 amount in the DMF suspensions were found to improve the titanium surface content, although high TiO2/PVDF ratios led to film instability. PVDF–TiO2 films were also used in preliminary photocatalytic degradation tests on isoproturon, a phenylurea herbicide, under solar UV irradiation; the results were compared to direct photolysis to evaluate the catalytic efficiency of immobilized TiO2 and the role played by the PVDF film during the degradation process. 相似文献
Nanoporous alumina membrane prepared by anodic oxidation using sulfuric acid electrolyte was subjected to TG-DTA and X-ray
Photoelectron Spectroscopy (XPS or ESCA) to further study the distribution of sulfur. In XPS study, Ar+ ion bombardment was performed on the sample to etch the surface at a rate of 3 nm min-1. As a result, sulfur was found to be concentrated within a depth of 3nm from the surface. The S content of the surface was
found to be 2.7±0.5 wt%, and that at a depth of ca. 3 nm and ca. 10 nm was found to be as low as about 0.6±0.11 wt% (5.37±1.0
wt%→ 1.26±0.2wt% SO2). In TG-DTA, the mass loss of 7.3% was in fair agreement with that calculated on XPS results (7.1±1.2%).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
In this paper, nitridation process of GaAs (1 0 0) substrates was studied in-situ using X-ray photoelectron spectroscopy (XPS) and ex-situ by means of electrical method I-V and photoluminescence surface state spectroscopy (PLS3) in order to determine chemical, electrical and electronic properties of the elaborated GaN/GaAs interfaces.The elaborated structures were characterised by I-V analysis. The saturation current IS, the ideality factor n, the barrier height ΦBn and the serial resistance RS are determined.The elaborated GaN/GaAs structures are also exhibited a high PL intensity at room temperature. From the computer-aided analysis of the power-dependent PL efficiency measurements (PLS3 technique), the value of the interface state density NSS(E) close to the mid-gap was estimated to be in the range of 2-4 × 1011 eV−1 cm−2, indicating a good electronic quality of the obtained interfaces.Correlation among chemical, electronic and electrical properties of the GaN/GaAs interface was discussed. 相似文献