Using a surface forces apparatus (SFA) we have investigated the effects of normal load (compressi... more Using a surface forces apparatus (SFA) we have investigated the effects of normal load (compression) and shear on the tribological properties of mica surfaces bearing Porphyridium sp. (a common naturally-occurring polysaccharide of the red microalgae, which molecular weight has been estimated to be 2-7 x 106 daltons) adsorbed from aqueous solution. The friction forces were monitored as a function of
ABSTRACT Si and Ge nanocrystals were formed in alumina matrix by ion implantation and subsequent ... more ABSTRACT Si and Ge nanocrystals were formed in alumina matrix by ion implantation and subsequent annealing. The phase separation of the Si nanocrystals was observed using X-ray photoelectron spectroscopy by monitoring Si 2p electrons. During nanocrystal formation with a high temperature annealing Si 0 signals corresponding to Si nanoclusters increases while Si 4+ signals related to a-SiO 2 disappears from the spectrum. The transition from amorphous to nanocrystalline phase for both Si and Ge nanoclusters and the compressive ...
We report a new phase in the binary SnS system, obtained as highly symmetric nanotetrahedra. Due ... more We report a new phase in the binary SnS system, obtained as highly symmetric nanotetrahedra. Due to the nanoscale size and minute amounts of these particles in the synthesis yield, the structure was exclusively solved using electron diffraction methods. The atomic model of the new phase (a = 11.7 Å, P213) was deduced and found to be associated with the rocksalt-type structure. Kramers-Kronig analysis predicted different optical and electronic properties for the new phase, as compared to α-SnS.
We studied the effect of light availability on the skeletal aragonite microstructure of the reef-... more We studied the effect of light availability on the skeletal aragonite microstructure of the reef-building coral Fungia simplex. Scanning electron microscopy (SEM) of samples transplanted from light to shade conditions showed that the latter promoted a well-defined crystal alignment and dense packing. An X-ray diffraction (XRD) study of newly formed coral skeleton tissue showed a twofold increase in coherence length
ABSTRACT CdS semiconductor nanoparticles, with dimensions above and below the Bohr radius (2.5 nm... more ABSTRACT CdS semiconductor nanoparticles, with dimensions above and below the Bohr radius (2.5 nm) of bulk material, were prepared in a single-step benchtop procedure. The degree of quantum confinement in these nanoparticles was determined from their optical absorption and photoluminescence spectra. The size-dependent properties of the nanocrystals were studied by resonance Raman spectroscopy as a function of excitation wavelength and temperature. The spectra were composed of the fundamental longitudinal optical (LO) mode around 300 cm-1, along with the first and second overtones. The shapes and positions of the Raman peaks exhibited only a weak dependence on particle size even for the two extreme cases of bulk and nanostructures. We show that the ratio of the overtone to the fundamental LO frequency was sensitive to the particle diameter and decreased upon reduction of the particle diameter to values below the Bohr radius. Temperature-dependent Raman measurements of ultranarrow nanorods showed a small red shift with decreasing temperature. Very high anti-Stokes intensities were observed for the CdS nanoparticles.
Protection of Metals and Physical Chemistry of Surfaces, 2010
... Deposition conditions of PbS nanocrystals in chemical bath from XPb(NO3)2 + 0.205 CS(NH2)2 ..... more ... Deposition conditions of PbS nanocrystals in chemical bath from XPb(NO3)2 + 0.205 CS(NH2)2 ... gap becomes smoother together with increasing of its effective width in nanocrystallinePbS (Fig. ... in opposite directions from the Fermi level with a decrease in the nanoparticle size. ...
ABSTRACT Photoelectron spectroscopic measurements have been performed, with synchrotron radiation... more ABSTRACT Photoelectron spectroscopic measurements have been performed, with synchrotron radiation on PbSe/CdSe heteronanocrystals that initially consist of core-shell structures. The study of the chemical states of the main elements in the nanocrystals shows a reproducible and progressive change in the valence-band and core-level spectra under photon irradiation, whatever the core and shell sizes are. Such chemical modifications are explained in light of transmission electron microscopy observations and reveal a phase transformation of the nanocrystals: The core-shell nanocrystals undergo a morphological change toward a Janus structure with the formation of semidetached PbSe and CdSe clusters. Photoelectron spectroscopy gives new insight into the reorganization of the ligands anchored at the surface of the nanocrystals and the modification of the electronic structure of these heteronanocrystals.
Using a surface forces apparatus (SFA) we have investigated the effects of normal load (compressi... more Using a surface forces apparatus (SFA) we have investigated the effects of normal load (compression) and shear on the tribological properties of mica surfaces bearing Porphyridium sp. (a common naturally-occurring polysaccharide of the red microalgae, which molecular weight has been estimated to be 2-7 x 106 daltons) adsorbed from aqueous solution. The friction forces were monitored as a function of
ABSTRACT Si and Ge nanocrystals were formed in alumina matrix by ion implantation and subsequent ... more ABSTRACT Si and Ge nanocrystals were formed in alumina matrix by ion implantation and subsequent annealing. The phase separation of the Si nanocrystals was observed using X-ray photoelectron spectroscopy by monitoring Si 2p electrons. During nanocrystal formation with a high temperature annealing Si 0 signals corresponding to Si nanoclusters increases while Si 4+ signals related to a-SiO 2 disappears from the spectrum. The transition from amorphous to nanocrystalline phase for both Si and Ge nanoclusters and the compressive ...
We report a new phase in the binary SnS system, obtained as highly symmetric nanotetrahedra. Due ... more We report a new phase in the binary SnS system, obtained as highly symmetric nanotetrahedra. Due to the nanoscale size and minute amounts of these particles in the synthesis yield, the structure was exclusively solved using electron diffraction methods. The atomic model of the new phase (a = 11.7 Å, P213) was deduced and found to be associated with the rocksalt-type structure. Kramers-Kronig analysis predicted different optical and electronic properties for the new phase, as compared to α-SnS.
We studied the effect of light availability on the skeletal aragonite microstructure of the reef-... more We studied the effect of light availability on the skeletal aragonite microstructure of the reef-building coral Fungia simplex. Scanning electron microscopy (SEM) of samples transplanted from light to shade conditions showed that the latter promoted a well-defined crystal alignment and dense packing. An X-ray diffraction (XRD) study of newly formed coral skeleton tissue showed a twofold increase in coherence length
ABSTRACT CdS semiconductor nanoparticles, with dimensions above and below the Bohr radius (2.5 nm... more ABSTRACT CdS semiconductor nanoparticles, with dimensions above and below the Bohr radius (2.5 nm) of bulk material, were prepared in a single-step benchtop procedure. The degree of quantum confinement in these nanoparticles was determined from their optical absorption and photoluminescence spectra. The size-dependent properties of the nanocrystals were studied by resonance Raman spectroscopy as a function of excitation wavelength and temperature. The spectra were composed of the fundamental longitudinal optical (LO) mode around 300 cm-1, along with the first and second overtones. The shapes and positions of the Raman peaks exhibited only a weak dependence on particle size even for the two extreme cases of bulk and nanostructures. We show that the ratio of the overtone to the fundamental LO frequency was sensitive to the particle diameter and decreased upon reduction of the particle diameter to values below the Bohr radius. Temperature-dependent Raman measurements of ultranarrow nanorods showed a small red shift with decreasing temperature. Very high anti-Stokes intensities were observed for the CdS nanoparticles.
Protection of Metals and Physical Chemistry of Surfaces, 2010
... Deposition conditions of PbS nanocrystals in chemical bath from XPb(NO3)2 + 0.205 CS(NH2)2 ..... more ... Deposition conditions of PbS nanocrystals in chemical bath from XPb(NO3)2 + 0.205 CS(NH2)2 ... gap becomes smoother together with increasing of its effective width in nanocrystallinePbS (Fig. ... in opposite directions from the Fermi level with a decrease in the nanoparticle size. ...
ABSTRACT Photoelectron spectroscopic measurements have been performed, with synchrotron radiation... more ABSTRACT Photoelectron spectroscopic measurements have been performed, with synchrotron radiation on PbSe/CdSe heteronanocrystals that initially consist of core-shell structures. The study of the chemical states of the main elements in the nanocrystals shows a reproducible and progressive change in the valence-band and core-level spectra under photon irradiation, whatever the core and shell sizes are. Such chemical modifications are explained in light of transmission electron microscopy observations and reveal a phase transformation of the nanocrystals: The core-shell nanocrystals undergo a morphological change toward a Janus structure with the formation of semidetached PbSe and CdSe clusters. Photoelectron spectroscopy gives new insight into the reorganization of the ligands anchored at the surface of the nanocrystals and the modification of the electronic structure of these heteronanocrystals.
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