Atomic force microscopy section analysis

The thickness of the ordered crystalline regions, termed crystallite or lamellar thickness (Lc), is an important parameter for correlations with thermodynamic and physical properties. Lc and the distribution of lamellar thicknesses can be determined by different experimental methods, including thin-section TEM mentioned earlier, atomic force microscopy, small-angle X-ray scattering and analysis of the LAM in Raman spectroscopy. 

Theoretical models based on first principles, such as Langmuir s adsorption model, help us understand what is happening at the catalyst surface. However, there is (still) no substitute for empirical evidence, and most of the papers published on heterogeneous catalysis include a characterization of surfaces and surface-bound species. Chemists are faced with a plethora of characterization methods, from micrometer-scale particle size measurement, all the way to angstrom-scale atomic force microscopy [77]. Some methods require UHV conditions and room temperature, while others work at 200 bar and 750 °C. Some methods use real industrial catalysts, while others require very clean single-crystal model catalysts. In this book, I will focus on four main areas classic surface characterization methods, temperature-programmed techniques, spectroscopy and microscopy, and analysis of macroscopic properties. For more details on the specific methods see the references in each section, as well as the books by Niemantsverdriet [78] and Thomas [79]. 

The following section describes the use of the two-timing approximation for the analysis of QCM data. The same formalism is also used in the field of non-contact atomic force microscopy [28,29]. In the latter context, the tip-sample interaction perturbs the oscillation of the cantilever. As long as the tip-sample force is weak compared to the force needed to bend the cantilever, the interaction potential can be reconstructed from the frequency of the cantilever as a function of amplitude and mean vertical distance. 

In this section we will outline the basic methodology of the plasma treatment process. First, the theory behind plasma treatment will be presented. Following this, experimental protocol outlining the treatment process, pertinent parameters, and their relevance will be discussed. Finally, surface analysis methods for plasma-treated surfaces will be described, such as X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measuring tools. 

In this section experimental results are discussed, concerned with analyses of melting and crystallization kinetics, as well as reversibility of the phase transition. The frame of the discussion is set by Fig. 3.76, which will be supported by experimental data on poly(oxyethylene). The thermal analysis tools involved are TMDSC, optical and atomic-force microscopy, DSC, adiabatic calorimetry, and dilatometry. Most of these techniques are described in more detail in Chap. 4. Results from isothermal crystallization, and reorganization are attempted to be fitted to the Avrami equation. This is followed by a short remark on crystallization regimes and finally some data are presented on the polymerization and crystallization of trioxane crystals. 

Various techniques can be used for the characterization of surface-modified nanoparticles (Muller, 1991). In the case of PEG-covered nanospheres, atomic force microscopy and freeze-fracture have been used to determine their morphology, light scattering has been employed to measure their size, and surface analysis techniques have been applied to detect the presence of PEG on the surface and the stability of this coating, etc. Some of these techniques are presented in this section. 

Figure 21.15 AFM section analysis of isolated cyclic PS combs corresponding to samples (a), (b), (c), and (d), of Figure 21.14. (Reprinted with permission from M. Schappacher and A. Deffieux, Atomic force microscopy imaging and dilute solution properties of cyclic and linear polystyrene combs, Journal of the American Chemical Society, 130, 14684-14689, 2008. 2008 American Chemical Society.)...

Based on the method of analysis employed, one can distinguish between real or reciprocal-space techniques. The first class includes optical microscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Techniques such as light scattering and neutron and X-ray scattering are part of the latter category. All these experimental methods are discussed in the following sections. 

In the following section, some examples of separated polymeric nanoparticles are presented.Figure 35 shows the fractionation of aqueous bimodal pofyorganosiloxane nanospheres and analysis by UV detection. The size determination obtained by AF-FFF nicely corresponds to the data obtained by transmission electron microscopy (TEM) and atomic force miaoscopy (AFM). 

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