Scanning probe techniques applications

When the first edition was published in 1992, the resolution of the acoustic microscope techniques used at the time was controlled by the wavelength. In practice the frequency-dependent attenuation of the acoustic wave in the coupling fluid sets a lower limit to the wavelength, and therefore to the resolution, of about 1 pm for routine applications. Since then scanning probe techniques with nanometre scale resolution have been developed along the lines of the atomic force microscope. This has resulted in the development of the ultrasonic force microscopy techniques, in which the sample is excited by... 

Agreement of a spatially averaged quantity, such as a reaction rate and a temperature-programmed desorption spectrum, is often insufficient to test whether the underlying mechanisms and input in a molecular model are correct. Ideally, validation of molecular simulation predictions demands spatiotemporal data over a multitude of length and time scales. Unfortunately, such data are rarely available (see the membrane application example earlier). However, advances in scanning probe techniques start rendering such comparisons feasible. 

These examples have been chosen to illustrate just how manifold the applications of scanning probe techniques are to the field of supramolecular chemistry. The increasing number of publications each year leads to the conclusion that we are probably only at the beginning of many more interesting investigations. 

Recently, STS and STM have been applied to study the onset of the catalytic activity of Au particles grown on titania [238], which appeared to be correlated with the layer thickness of the particles on the surface and, as shown above, the bonding of CO with small gold clusters could be characterized in STM/STS experiments (Fig. 1.39 see Morphological Properties of Supported Clusters ) [190]. The above presentation of the spectroscopic results on deposited, size-selected clusters clearly shows that valuable information on these nanosystems can only be obtained by the application of an arsenal of local and nonlocal surface science analysis methods. Therefore, in the near future a much more intense employment of scanning probe techniques such as STM, STS, AFM, and others will beyond any doubt improve considerably assembly, characterization, and functionalization of size-selected clusters on solid surfaces. 

If speed is an obstacle to the wide application of scanning probe techniques as surface modification tools, their resolution keeps them in the running. The resolution of the patterns formed by the SECM depends on the size and geometry of the UME, as well as the distance it is held above the surface. At the same time, the resolution of the patterns can easily be controlled (as compared to other SPM techniques) by approaches such as the chemical lens. Pattern width can be controlled merely by varying the electrolyte and the surface-UME distance. The UME need not be altered. 

All emerging scanning probe techniques, which appear superior to previous electron microscopy techniques in many respects, have been collected, insofar as they are related to photochemistry and spectroscopy. All of these recent techniques will certainly find application. 

The atomic surface order is described in terms of a simple unit cell and techniques for the preparation of surfaces with defined atomic order are well established. The description of mesoscopic structures is not as straightforward for a single-crystal surface mesoscopic properties can be, e. g., terrace widths and step densities, for dispersed electrodes the size and distribution of particles. Real-space information under in-situ electrochemical conditions is required for the characterization of such mesoscopic properties. This information can only be derived from the application of scanning probe techniques, which were introduced to electrochemistry in the mid-1980s and give high-resolution real-space images of electrode siufaces under in-situ electrochemical conditions. 

Nanoscale sciences are strongly driven by scanned probe techniques, which allow us to investigate and manipulate surfaces down to the atomic scale. While the imaging capabilities of techniques such as STM, SFM, SNOM etc. dominated the application of these methods at their early development stages, the physics of probe-sample interactions, and the quantitative analysis of elastic, electronic and magnetic surface and transport properties are becoming now of increasing interest. 

The contributions in this volume are representative of the richness of research topics in colloid and polymer science. They cover a broad field including the application of scanning probe techniques to colloid and interface science, surface induced ordering, novel developments in amphiphilic systans as well as the synthesis and applications of nano-colloids. 

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