An Au/SiO2 system with most of the metal particles less than 2.0 nm in size were prepared by deposition on
silica of preformed gold sols derived from Au(PPh3)3Cl. In this form, it was inactive in the CO + O2 reaction
at ca. 333 K, because of the presence of phosphine ligands on the surface of metal particles. The system
became catalytically active in this reaction after treatment in O2 at 673 K, which also resulted in a slight
sintering of the metal phase (mean size = 2.9 nm). By subsequent heating in H2 at 673 K, the mean size of
gold particles increased up to 3.4 nm. Such particles exhibited a lower amount of step surface sites able to
adsorb CO, but became more active in the CO + O2 reaction. This suggested that the reaction steps involving
oxygen can occur more effectively on Au sites present on larger and smoother gold particles.
We present an accurate ab initio study of the structure and surface energy of the low-index (100), ( 111) and (110) diamond faces, by using the hybrid Hartree-Fock/Density Functional B3LYP Hamiltonian and a localized all-electron Gaussian-type basis set. A 2D periodic slab model has been adopted, for which convergence on both structural and energetic parameters has been thoroughly investigated. For all the three surfaces possible relaxations and reconstructions have been considered. A detailed geometrical characterization is provided for the most stable structure of each orientation; surface energy is discussed for all the investigated faces. All data show a very good agreement with previous pure Density Functional calculations.
h i g h l i g h t s < A silver nanocluster silica composite coating was deposited on a polymeric film. < A co-sputtering technique was used for the coating deposition. < The coating induced an antibacterial effect on the polymer film. < The coating improved the nano-hardness and the resistance to tensile and perforation.
a b s t r a c tThe microbiological contamination on board of spacecraft and orbital stations is a relevant problem in prolonged space exploration. For this purpose, an antibacterial silver nanocluster silica composite coating was deposited on a commercial polymer Combitherm Ò , suitable for aerospace application, using the radio frequency (RF) co-sputtering technique. The presence of metallic silver nanoclusters and silica was confirmed by energy dispersion spectrometry (EDS), x-ray photoelectron spectroscopy (XPS) and localized surface plasmon resonance (LSPR) detected through UVevisible absorption spectrophotometry (UVeVis). The atomic force microscope (AFM) evidenced the coating morphology. The slight hydrophobicity of both coated and uncoated samples was revealed through the contact angle measurement. The antimicrobial behavior was verified through evaluation of the inhibition halo against several bacterial and fungal species. The coating enhanced the Combitherm Ò nano-hardness and its resistance to tensile and perforation tests; the coating wear resistance was measured by abrasion test against Kevlar. A folding procedure on the coated Combitherm Ò and storage in air for three months was also carried out without deterioration of the measured properties. The coating deposition did not influence the air permeability of Combitherm Ò .
In this paper we report about the role the diamond surface morphology and atomic termination plays in the survival and viability of neuronal cells, which represent an appropriate experimental model for the development of cell-based biosensors. The samples we have investigated were both CVD homoepitaxial diamond films and nanocrystalline diamond layers deposited on quartz substrates. Different surface terminations were induced through exposure to atomic hydrogen and to intense UV irradiation. GT1-7 cells, a neuronal line of hypothalamic origin, were plated directly onto the diamond surfaces without exogenous adhesion molecules, in order to correlate the surface topography and chemistry to cell growth and viability. The cell density on nanocrystalline diamonds after 48 h from plating was approximately 55% of the control on plastic dishes, whatever is the atomic termination of the surface, whereas the performances of homoepitaxial samples in terms of cell growth depend on surface termination and were significantly lower, 30%.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.