Force imaging spectroscopy

These include contact force imaging (CFI) mode, in which the tip is scanned across the sample surface at constant force, tapping mode in which the tip oscillates close to the surface enabling either the forces or phase relationships between load and displacement to be used to form the image, and local force spectroscopy or force/volume imaging in which the variation of force with tip/sample separation at a point can be used to study local interachons. 

The third chapter, by Wasan and Nikolov, discusses fundamental processes in emulsions, i.e., ereaming/sed-imentation, flocculation, coalescence, and final phase separation. A number of novel experimental facilities for characterization of emulsions and the above-mentioned processes are presented. This chapter highlights recent techniques such as film rheometry for dynamic film properties, capillary force balance in eonjunetion with differential microinterferometry for drainage of curved emulsion films, Kossel diffraction, imaging of interdroplet interactions, and piezo imaging spectroscopy for drop-homophase coalescence rate processes. 

Moreover AFM-derived methods, namely force spectroscopy and phase and lateral force imaging, allow investigating nanobubble mechanical properties. 

Whitman, L.J. and Colton, R.J., Design and calibration of a scanning force microscope for friction, adhesion, and contact potential studies. Rev. Sci. Instrum., 66, I (1995). Ba.selt, D.R. and Baldeschwieler, J.D., Imaging spectroscopy with the atomic-force microscope. J. Appl. Pltys., 76(1), 33-38 (1994). 

If infrared absorption or Raman scattering is used as the contrast mechanism, vibrational spectra of samples can be obtained. The combination of the nanoscale spatial resolution of a scanned probe with the chemical specificity of vibrational spectroscopy allows in situ mapping of chemical functional groups with subwavelength spatial resolution. Figure 12 is a shear force image of a thin polystyrene film along with a representative near-field spectrum of the... 

FIGURE 6.2 Diagrams of different AFM operating modes. (A) Contact mode and (B) dynamic mode for topographic imaging. (C) Force spectroscopy mode for interaction probing. Reprinted with permission from Liu and Wang (2010). 

A number of methods are available for the characterization and examination of SAMs as well as for the observation of the reactions with the immobilized biomolecules. Only some of these methods are mentioned briefly here. These include surface plasmon resonance (SPR) [46], quartz crystal microbalance (QCM) [47,48], ellipsometry [12,49], contact angle measurement [50], infrared spectroscopy (FT-IR) [51,52], Raman spectroscopy [53], scanning tunneling microscopy (STM) [54], atomic force microscopy (AFM) [55,56], sum frequency spectroscopy. X-ray photoelectron spectroscopy (XPS) [57, 58], surface acoustic wave and acoustic plate mode devices, confocal imaging and optical microscopy, low-angle X-ray reflectometry, electrochemical methods [59] and Raster electron microscopy [60]. 

This paper contributes to the literature by quantifying anionic polymer adsorption onto the clay minerals kaolinite, feldspar, mica and quartz by X-ray photoelectron spectroscopy (XPS). XPS measures the sorbed amount directly rather than by a subtraction technique. This enables an insight into how effective selective flocculation is for obtaining kaolinite from a mineral mixture. Atomic force microscopy (AFM) is also used to image polymer adsorption onto mineral surfaces and the effectiveness of this technique applied to mineral surfaces is discussed here. 

The dynamical behaviour of the atoms in a crystal is described by the phonon (sound) spectrum which can be measured by inelastic neutron spectroscopy, though in practice this is only possible for relatively simple materials. Infrared and Raman spectra provide images of the phonon spectrum in the long wavelength limit but, because they contain relatively few lines, these spectra can only be used to fit a force model that is too simple to reproduce the full phonon spectrum of the crystal. Nevertheless a useful description of the bond dynamics can be obtained from such force constants using the methods described by Turrell (1972). 

Image forces, 819, 924, 921, 946, 964 and metal-water interactions, 896 Imaginary impedance, 1128, 1135, 1160 Imaginary number, 1129 Impedance spectroscopy, 1127, 1160 acanddc, 1134... 

Fig. 10 (a) Molecular imprinting of cytochrome c immobilized on mica, and AFM images of the surfaces, (b) Molecular force spectroscopy with a cytochrome c-derivatized AFM cantilever of the cytochrome c-imprinted polymer (MIP) and the non-imprinted control polymer (NIP). Adapted from [104] with permission from Elsevier... 

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