Simulation of Near Edge X-ray Absorption Fine Structure (NEXAFS) Measurements of CO on Supported Pd Nanoparticles

Near edge X-ray absorption fine structure (NEXAFS) measurements of CO on Pd nanoparticles have been simulated. This was achieved by calculating the CO π* resonance signal of CO on a nanoparticle both as a function of the angle of incidence (I vs θ) and the direction of the electric field vector E of the incident photon beam (I vs β), with the nanoparticle defined as a (111) top facet with {111} and {100} side facets. The dependence of the π* resonance intensity signal of CO covered nanoparticles on the particle geometry and orientation as well as the bond orientation of CO is examined. In addition, we compare our simulations to a set of C K-edge NEXAFS experimental data obtained from a single Pd nanoparticle decorated with CO. Our simulation predicts that the nanoparticle has a high lateral aspect ratio of 37.7 ± 4.1

Probing the local electronic structure of the cross-linked (1×2) reconstruction of rutile TiO2(110)

The electronic structure of cross-linked TiO2(110)-(1×2) has been investigated using scanning tunneling spectroscopy (STS) and by monitoring changes in ultraviolet photoelectron spectroscopy (UPS) following exposure of the surface to O2. STS reveals two states located in the bandgap, at 0.7 and 1.5 eV below the Fermi level. The population of these two states varies over different parts of the (1×2)- reconstructed surface. An addition state at 1.1 eV above the Fermi level is observed at the double link part of the structure. All of the bandgap states are attenuated following exposure to O2, while the workfunction is increased. We attribute this to an electron transfer from the surface to the adsorbed oxygen

Direct Visualization of Soliton CO Overlayers on Supported Pd Nanoparticles

The interaction of carbon monoxide (CO) molecules with the facets of noble metal nanoparticles forms the basis of many important catalytic reactions. Using scanning tunneling microscopy (STM), we have studied the adsorption of CO molecules on the (111) facets of Pd nanocrystals supported on a rutile TiO2(110) substrate. We observed four compact CO overlayers with coverages ranging between 0.5 and 0.6 monolayers. Examination of the positions of the CO molecules in each of the unit cells reveals that one of the overlayers has a rhombic (√7 × √7) R19.1°-4CO structure. The other three form rectangular structures, namely, (7 × √3) rect-8CO, c(5 × √3) rect-3CO, and c(9 × √3) rect-5CO. These are closely related via a soliton model previously proposed on the basis of infrared absorption spectroscopy and low-energy electron diffraction. By imaging the CO molecules, we provide direct evidence for the soliton model

A qualitative exploration of perspectives of physical activity and sedentary behaviour among Indian migrants in Melbourne, Australia: how are they defined and what can we learn?

BackgroundAlthough perceptions of what constitutes physical activity (PA) may vary between culturally diverse populations, very little research has explored the perceptions of PA among Indian migrants. This study aimed to identify how PA and sedentary behaviour (SB) are defined and describe how these definitions are shaped by cultural background and migration among a sample of Indian migrants living in Australia.MethodsUsing an exploratory qualitative approach, semi-structured interviews were conducted with twenty-one Indian migrants living in Melbourne (10 men and 11 women; age range: 18 to 65 years). Interviews were audio-recorded and transcribed verbatim. Data were coded and analysed inductively using thematic analyses.ResultsData revealed two emerging themes: 1) Holistic perspectives related to PA, where although the majority of participants described PA as "any sort of movement", or "physical exercise", several of these descriptions had interwoven ideas related to the mind (mind-body connect), social, cultural, and to the outdoor environment; 2) Broader perspectives for SB, where descriptions of SB as "not having movement", "doing nothing" or "being lazy", were shaped with ideas of purpose and duration. Women spoke about how their perspectives of PA and SB may be shaped by native Indian experiences, particularly the gender roles, social caste, and regional subcultural norms which they perceived were important to consider among women who migrate to western settings.ConclusionsCultural background is important in shaping the perspectives of PA and SB among Indian migrants in Australia. Practitioners and researchers should consider the varying perspectives of PA to communicate and promote PA among migrant populations more effectively

Variation of SMSI with the Au:Pd Ratio of Bimetallic Nanoparticles on TiO2(110)

Au/Pd nanoparticles are important in a number of catalytic processes. Here we investigate the formation of Au–Pd bimetallic nanoparticles on TiO 2 (110) and their susceptibility to encapsulation using scanning tunneling microscopy, as well as Auger spectroscopy and low energy electron diffraction. Sequentially depositing 5 MLE Pd and 1 MLE Au at 298 K followed by annealing to 573 K results in a bimetallic core and Pd shell, with TiO x encapsulation on annealing to ~ 800 K. Further deposition of Au on the pinwheel type TiO x layer results in a template-assisted nucleation of Au nanoclusters, while on the zigzag type TiO x layer no preferential adsorption site of Au was observed. Increasing the Au:Pd ratio to 3 MLE Pd and 2 MLE Au results in nanoparticles that are enriched in Au at their surface, which exhibit a strong resistance towards encapsulation. Hence the degree of encapsulation of the nanoparticles during sintering can be controlled by tuning the Au:Pd ratio

Oxygen Vacancy Origin of the Surface Band-Gap State of TiO2(110)

Scanning tunneling microscopy and photoemission spectroscopy have been used to determine the origin of the band-gap state in rutile TiO2(110). This state has long been attributed to oxygen vacancies (O-b vac). However, recently an alternative origin has been suggested, namely, subsurface interstitial Ti species. Here, we use electron bombardment to vary the O-b vac density while monitoring the band-gap state with photoemission spectroscopy. Our results show that O-b vac make the dominant contribution to the photoemission peak and that its magnitude is directly proportional to the O-b vac density