Functionalized monolayers, structure

The surface potential as function of particle area (AV A isotherm) is another indicator of the quality of the monolayer structure. The surface potential at the air-water interface changes as the film-forming molecules reorient themselves during the compression process. For a closely packed monolayer, the surface potential is directly proportional to the surface dipole moment (/r ) by [13] ... 

Figure 9.6 Activity for CO oxidation at room temperature as a function of gold coverage on an Mo(l 12)—(8 x 2)-TiOx surface. The CO 02 ratio was 2 1 and the total pressure 5 Torr. Two discrete gold structures were investigated, (lxl) and (1 x 3). The initial turn over frequencies (TOF) over the (1 x 1) gold monolayer structure were significantly lower than that for the (1 x 3) bilayer structure. (Reproduced from Ref. 20).

An example of this is the structural modification of a self-assembled monolayer of LA on gold polycrystalline gold wire electrode with l,8-diamino-3,6-dioxaoctane as a spacer and thiocholine which resulted in the formation of the functionalized monolayer 389 <1997JA1043>. 

The tilt angle derived from a detailed analysis of the peaks as a function of pressure is given in Fig. 11. In the absence of polymer one observes the reduction of t to zero whereas for PDADMAC t>25° even at the highest pressure. For comparison we also include the tilt angle measured for PAH in the subphase. The binding of this cationic polyelectrolyte apparently has only a minor influence on monolayer structure. The polyelectrolyte coupling may be best understood looking at the model of Fig. 12 which should hold specif-... 

Higashi N, Shimoguchi M, Niwa M. Stabilization and facilitated formation of a -structure polypeptide by a poly(L-glutamic acid)-functionalized monolayer on water. Langmuir 1992 8 1509-1510. 

P.L. Allara, Nanoscale Structures Engineered by Molecular Self-Assembly of Functionalized Monolayers, in Nanofabr. Biosyst., H.C. Hoch, L.W. Jelinski and H.G. Craighead (ed.), Cambridge University Press Cambridge, UK, (1996) 180. 

Fig. 11.17. Optimized monolayer structure for the water molecules adsorbed on a (110) Sn02 surface obtained using the B3LYP functional, [816] a) stable structure for molecular adsorption b) stable structure for dissociative adsorption. Large dark gray balls are O atoms light gray balls are Sn atoms small white balls are H atoms.

We have demonstrated for the first time that average macroscopic kinetics of reactions in SAMs can be correlated and explained by nanometer level force (adhesion) measurements in the confined environment of the monolayer studied. Using a modified CFM approach, which we termed inverted chemical force microscopy , reactions of as few as 10 to 100 molecules could be followed in situ. Structure-reactivity differences, arising from differences in monolayer structure, as observed on the nanometer scale, on average agree well with macroscopic behavior observed by FT-IR. The studies show that reagents penetrate functionalized monolayers at specific defect sites or at domain boundaries. 

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