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21.
Meng Tao Janadass Shanmugam Michael Coviello Wiley P. Kirk 《Solid State Communications》2004,132(2):89-92
It is experimentally shown that, by terminating dangling bonds on Si(001) with a monatomic layer of selenium, the chemical reactivity of the surface is suppressed. In the case of nickel silicidation, transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy reveal that Se passivation suppresses Ni silicidation by over 100 °C as compared to the bare Si(001) surface. The formation of Ni subsilicide (Ni2Si) is not observed on Se-passivated Si(001). This interfacial silicidation appears to be linked with changes in electrical behavior of the interface between titanium and Se-passivated Si(001), which we reported previously. 相似文献
22.
Tommasina Coviello Laura Bertolo Pietro Matricardi Antonio Palleschi Gianfranco Bocchinfuso Adriana Maras Franco Alhaique 《Colloid and polymer science》2009,287(4):413-423
The peculiar unidirectional elongation observed during swelling of tablets prepared with scleroglucan (Sclg) and borax was
compared with that of other synthetic and natural polymers capable of physical/chemical interactions with borate ions. A dynamomechanical
characterization of “squared” Sclg/borax tablets was carried out to study the differences detectable on the two sides of the
matrix corresponding to the two directions, respectively, the parallel and perpendicular one with respect to the applied compression
force. Different compression forces were used and, in some cases, a second compression was applied on the tablets along a
direction perpendicular to the first one. Birefringence experiments were carried out on the swelled tablets along the two
directions. Obtained results allow correlating the anisotropic swelling behavior with the detected dynamomechanical and optical
properties of the Sclg/borax system. Among the various tested polymers, only guar gum and, to a lesser extent, locust bean
gum, showed an anisotropic elongation during swelling. 相似文献
23.
Bocchinfuso G Palleschi A Mazzuca C Coviello T Alhaique F Marletta G 《The journal of physical chemistry. B》2008,112(20):6473-6483
It is well-known that the polysaccharide scleroglucan (Sclg) exhibits a triple-helix conformation (triplex) and it is able to form hydrogels in water solution. Furthermore, these hydrogels are influenced by the presence of borax, in terms of rheological and drug release properties. In previous works, we showed that the presence of borax stabilizes the intertriplex interactions and that the property variations, induced by borax, can be fully explained, considering that the Sclg triplexes can form nanochannel-like structures. In this paper, the stability of these aggregates has been experimentally studied by means of atomic force microscopy (AFM) and theoretically investigated by means of molecular dynamics (MD) simulations. The simulations indicate that the borax stabilizes nanochannel-like structures when seven triplexes are considered. The simultaneous presence of different Sclg triplexes in a narrow space strongly influences the properties of confined water molecules in a way similar, in many aspects, to that of water molecules located in the inner part of well-defined nanochannels (e.g., diffusion inside carbon nanotubes). As a consequence, also the conformational properties of flanking regions of Sclg triplexes are influenced. Furthermore, differential scanning calorimetry (DSC) data show that the well-known conformational transition occurring at 280 K for Sclg does not take place in the presence of borax. The MD simulations suggest that such lack of transition is a direct consequence of the presence of borax. The role of Na+ counterions in the hydrogel structure is also investigated. 相似文献
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