Si-OH surface groups

Paraschiv et al. demonstrated a functionalized surface with locally isolated functional groups (Fig. 13.1).9 Au nanoparticles d 3 nm) stabilized with propanethiol and monofunctionalized with (mercaptopropyl)methyldimethoxysilane (MPMD) were first prepared by a place-exchange reaction. The Au nanoparticles were covalently assembled onto the surface via a single methyldimethoxysilane unit by reaction with Si-OH surface groups. AFM images revealed the attachment of Au nanoparticles... 

The silanol (Si-OH) surface groups are replaced by chemical groups Si—OR which exhibit a hydrophobic effect. A silica aerogel obtained by alcohol SCO floats when placed onto water. With time, air moisture will react again with j-Si—OR. Consequently the aerogel becomes hydrophilic according to the reverse reaction... 

For anodic oxidation of a silicon electrode in fluoride-free electrolytes, the reaction of step 2 is only expected during the first seconds of anodization, until all Si-H surface groups are replaced by Si-OH. 

The activity and selectivity of catalyst HZSM5-1 was constant over 1 hour on stream although the formation of a linear hydrocarbon species at the catalyst was noticed. The IR spectra suggest that this species is a linear aliphatic hydrocarbon (coke precursor) increasing in concentration with time on stream [13], It is concluded that this species is adsorbed at the (catalytically inactive) Si-OH groups of the catalyst. During our measurements, the catalytically active Si-OH-AI groups were not blocked by this surface species and the product selectivity was not altered... 

All these H-altered H- Si CP-MAS experiments, together with a spin-exchange experiment in which H- Si cross-polarization follows a sequence analogous to the predetection portion of the H CRAMPS spin-exchange experiment described in Fig. 18 [60], lead to a model of the silica surface that corresponds to the 100 face of p-cristobalite for Si(OH)2 silanols and to the 111 face of p-cristobalite for SiOH silanols. These faces are depicted in Fig. 29, in which one can see that the distance between OH groups on adjacent Si(OH)2 groups is much smaller than between adjacent SiOH groups, or even between the... 

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