OTS on mica

Adsorbed monolayer, attenuation of optical signal, 241-243 Adsorption isotherm(s) experimental methods, 227 OTS on mica, 249/... 

Figure 15.3 AFM images of SWNTs on mica placed at the top ((a) and (b)), the middle (c), and the bottom (d) positions using magnet apparatus (vertical direction of magnetic field) and outside position (e) of the bore tube (OT).

Figure 6. Spectrum of an OTS monolayer on mica recorded in the presence of CCI4.

Figure 6.4 (Left] Electrostatic NC-AFM profiles of surfulric acid droplets on mica (reprinted with permission from Ref. 15, copyright 1998, American Chemical Society], (Right] NC-AFM profiles of dodecane droplets on OTS-coated silicon (reprinted with permission from Ref. 17, copyright 2006, American Chemical Society].

The transfer of alkylsilane monolayers onto mica was explored by Knobler and coworkers [331]. Monolayers of octadecyltrichlorosilane (OTS) were spread at the water-air interface. The trichlorosilane head groups rapidly undergo hydrolysis and cross-linking reactions to produce two-dimensional polysiloxanes on acidic subphases. On less acidic subphases, the polymerization rate is slower and the monolayer can be spread and transferred before the polymerization is significant. The II-A isotherm for OTS spread on... 

Figure 3. Spectra of OTS monolayer on two separate mica sheets. Both a) and b) were recorded separately and c) were a and b combined separated by 5 mm.

As Newton recognized, this short range of action of molecular forces has made the force measurement extremely difficult. Only in the past few years or so has it been possible to make the necessary measurements at the nanometer level to prove these ideas. Two problems have been overcome. The first one was the measurement technique. Optical methods, such as multiple beam interferometry and laser optical levers, have been developed to measure atomic distances. Piezoelectric actuators were invented to control nanomovements. The second issue was surface smoothness. Smooth surfaces of oxides such as mica, silica ot alumina have been found. Also tiny smooth probes have been made on a large scale by electronic wafer fabrication routes. Tbese new techniques have allowed a new and proper definition of molecular adhesion. 

In addition to NAA, neutrons are widely used in prompt radiation analysis for the determination of concentration and spatial distribution of elements in different matrices. For example, a track-etched detector (LR-115, Makrofol KG, CR 39, mica) placed on the polished surface of a sample is irradiated with fast or thermal neutrons then etched with a suitable chemical to deduce the concentration profiles from the track distributions. This method can also be used for the detection of suspended and dissolved U, Th, and Pu in water by (n,f) reactions N in polymers by the N(n,p) C reaction B and Li in semiconductors or glasses by the B(n,a) Li and Li(n,ot) H reactions, respectively. For the detection of fission fragments the use of mica is recommended. 

Previous NEXAFS studies on n-octadecyltrichlorosilane (OTS-C18) on silicon [29] and mica [30] indicate that monolayer films of OTS are highly oriented. The angular dependence of the resonances is indicative of a preferential molecular orientation of the polymeric C-C chains perpendicular to the surface (standing up), and the C-H bond plane is parallel to the surface. It should be noted that the orientation in the form of tilt angle or order calculated from NEXAFS are average values. 

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