Hydrogen-surface interactions adsorption

The model in Figure 3.20a applies to ACM-silica, while Figure 3.20b suits the ENR-silica system. Kraus constant, C, determined from the slope of the plots in Figure 3.19, quantifies the mbber-silica interaction in these systems. CACM/siUca is 1-85 and CENR/siika is 2.30 and these values are significantly higher than the reinforcing black-filled mbber composites [65]. Hydrogen-bonded interaction between the SiOH and the vicinal diols in ENR is responsible for this, whereas dipolar interaction between ester and SiOH in ACM-silica only results in weaker adsorption of the mbber over the filler surfaces. 

Sanyal A, Norsten TB, Uzun O, Rotello VM. Adsorption/desorption of mono- and diblock copol3Tners on surfaces using specific hydrogen bonding interactions. Langmuir 2004 20 5958-5964. 

The amine may enter into hydrogen bonding interaction with a surface hydroxyl (figure 9.23 a). The hydrogen bond formation is responsible for the fast adsorption of the silane molecules onto the silica surface, as discussed above. The basic amine function may abstract a proton from a silanol and form an ionic bond (figure 9.23 b). This type of interaction is much more stable than the first one. The hydrogen bonded molecules may self-catalyse the condensation of the silicon side of the silane molecule (figure 9.23 c). Thus, a covalent siloxane bond is formed. 

There are countless examples of the interactions of various atoms and molecules with the clean Si(100) surface. In addition these adsorbate-surface interactions can differ with deposition conditions, such as the rate of deposition or temperature of the sample. For example, even the simplest adsorbate, hydrogen, can etch the surface at room temperature and also form a variety of ordered structures at elevated sample temperatures [57]. A number of adsorbates can form ordered structures commensurate with the surface (e.g. Ag [58], Ga [59], Bi [60]), most transition metals react with the surface to form silicides (e.g. Ni [61], Co [62], Er [63]), halogens can etch the surface at room temperature (e.g. F2 [64], CI2 [65], Br2 [66]), some molecules dissociate on the surface (e.g. PH3 [67], B2H6 [68], NH3 [37]) and other molecules can bond to the silicon in different adsorption configurations but remain intact (e.g. Benzene [69], Cu-phthalocyanine [70], C60 [71]). A detailed review of a number of adsorbate-Si(lOO) interactions can be found in [23,72] and a more specific review relating to organic adsorbates can be found in [22]. As an example of an adsorbate-silicon system we shall here consider the adsorption of a molecule that our group has extensive experience with phosphine. 

A number of locations and orientations of Sarin on the regular nanosurface and on the small fragment of MgO were found. In this study it was revealed that Sarin is physisorbed (the nanosurface and hydroxylated small fragment this is undestructive adsorption) or chemisorbed (destructive adsorption) on MgO (see Figure 16-1). The physisorption of GB on the surface of MgO occurs due to the formation of hydrogen bonds and ion-dipole and dipole-dipole interactions between adsorbed GB and the surface. The chemisorption occurs due to the formation of covalent bonds between the molecule and the surface. The adsorption results in the polarization and the electron density redistribution of GB. The adsorption energy obtained at the MP2/6-31G(d) level of theory for the most stable chemisorbed system is... 

Carbon dioxide and hydrogen also interact with the formation of surface formate. This was documented for ZnO by the IR investigation of Ueno et al. (117) and, less directly, by coadsorption-thermal decomposition study (84). Surface complex was formed from C02 with H2 at temperatures above 180°C, which decomposed at 300°C with the evolution of carbon monoxide and hydrogen at the ratio CO Hs 1 1. When carbon dioxide and hydrogen were adsorbed separately, the C02 and H2 desorption temperatures were different, indicating conclusively that a surface complex was formed from C02 and H2. A complex with the same decomposition temperature was obtained upon adsorption of formaldehyde and methanol. Based upon the observed stoichiometry of decomposition products and upon earlier reported IR spectra of C02 + H2 coadsorbates, this complex was identified as surface formate. Table XVI compares the thermal decomposition peak temperatures and activation energies, product composition, and surface... 

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