Characterization techniques chemical force microscopy

This chapter describes the results of an ongoing study we are conducting into the nanoscale mechanical properties, chemical composition and structure of healthy enamel, carious lesions and the acquired salivary pellicle layer. A variety of material characterization techniques are being used, including nanoindentation, scanning electron microscopy (SEM), electron microprobe analysis (EMPA), scanning acoustic microscopy, atomic force microscopy (AFM) and time-of-flight secondary ion mass spectroscopy (TOF SIMS). 

Characterizing these many aspects of microstructure is necessary to establish relationships between primary chemical structure, processing, and performance. Currently, the most commonly used methods are scanning probe microscopy techniques such as atomic force microscopy (AFM) or kelvin probe force microscopy... 

Although the tubular geometry is normally preferred in the chemical industry, both tubular and fiat plate geometries have been used for making composite Pd and Pd/alloy membranes. Methods used for the membrane characterization include, among others, macroscopic permeation flux measurements and microscopic surface and microstructure analysis by various techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM). 

Therefore, selected spectroscopic and microscopic techniques are applied to the characterization of chemical structure formation and morphology in thin polyurethane (PU) layers on Au, Al, and Cu Infrared spectroscopy offers convenient access to the integral chemical properties of thin-fihn and bulk-like polymer samples, while optical (OM) and scanning force microscopy (SFM) allow detailed insights into homogeneity and topology. 

Upon introduction in vivo, the interface between the delivery system and the biological tissue and/or fluid is critically important to the in vivo performance [5]. Accordingly, surface properties including surface chemical composition and surface area must be well characterized. X-ray photoelectron spectroscopy (XPS) is a widely used technique to obtain surface elemental composition, and Branauer, Emmett, and Teller (BET) measurement is used to provide information on surface area. Surface morphology is typically assessed via light, electron, and atomic force microscopy (AFM). The amorphous and crystalline nature of materials can be determined from X-ray diffraction (XRD) and density measurements. 

Spectroscopy (IR), Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS) or Electron Spectroscopy for Chemical Analysis (ESCA), and Secondary Ion Mass Spectrometry (SIMS). More recently. Atomic Force Microscopy (AFM) has also found important use in the characterization of the local surface distribution of paper. Below, we will briefly discuss the use of some different surface-sensitive techniques in paper applications and relate the results obtained to paper characteristics and end-use properties. For a more detailed description of these and other available techniques for characterizing the chemistry of paper surfaces, readers are referred to ref. (60). 

The chemical changes caused by pre-treatments may be studied by the use of contact angle measurements (see Surface characterization by contact angles polymers) or preferably with surface techniques such as X-ray photoelectron spectroscopy (XPS). The topographical changes are best studied by means of Scanning electron microscopy (SEM) or Atomic force microscopy (AFM). 

SECM (Scanning electrochemical microscopy) is a technique to characterize the local electrochemical nature of various materials by scanning a probe microelectrode [1,2]. The spatial resolution of SECM is inferior to the conventional scanning probe microscopes such as scanning tunneling microscopy (STM) and atomic force microscopy (AFM) as the fabrication of the probe, microelectrode, with nanometer sizes is quite difficult and the faradaic current of the microprobe is very small (often picoamps or less). However, SECM has unique characteristics that cannot be expected for STM and AFM SECM can image localized chemical reactions and it also can induce localized chemical reactions in a controlled manner. 

From a methodological point of view, of particularly interest have been improvements in the chemical sensitivity of STM and AFM characterization. This is especially desirable for electrochemists, as electrochemical environments prevent the combined characterization by other surface techniques, as are frequently used for composition determinations in vacuum. Tunneling spectroscopy measurements to obtain 7 y and d//dV y relationships may provide a certain degree of information regarding the electronic structure of the substrate surface and adsorbed molecules [77], and the use of ionic liquids of large electrochemical windows is favorable in this respect. One major enhancement would be to complement SPM with other spatial, time- and energy-resolved surface in-situ techniques. For example, a combination of scanning electrochemical microscopy and atomic force microscopy... 

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