Surface properties techniques description

Before studying the reactivity of the nanoparticles, it is necessary to evaluate whether the synthetic method employed would lead to particles of clean unoxidized surface, able to react with incoming molecules. For this purpose we used, besides physical techniques (which are sometimes difficult to handle due to the high oxidability of particles prepared in this way), molecular methods, namely IR and NMR spectroscopy, as well as magnetic measurements which can give a precise description of the surface properties of the particles. 

Since the thickness and properties of the interphase strongly influence the characteristics of composites and the strength of the interaction determines the dominating micromechanical deformation process, many attempts have been made to characterize them quantitatively. Many various techniques are used for this purpose, and it is impossible to give a detailed account here. As a consequence a general overview of the most often used techniques is given with a more detailed account of some specific methods which have increased importance. A more detailed description of the surface characterization techniques can be found in a recent monograph by Rothon [15],... 

With the ability to obtain information about the concentrations of various types of metal surface sites in complex metal nanocluster catalysts, HRTEM provides new opportunities to include nanoparticle structure and dynamics into fundamental descriptions of the catalyst properties. This chapter is a survey of recent HRTEM investigations that illustrate the possibilities for characterization of catalysts in the functioning state. This chapter is not intended to be a comprehensive review of the applications of TEM to characterize catalysts in reactive atmospheres such reviews are available elsewhere (e.g., 1,8,9 )). Rather, the aim here is to demonstrate the future potential of the technique used in combination with surface science techniques, density functional theory (DFT), other characterization techniques, and catalyst testing. 

Different experimental techniques have been used to describe various characteristics of the solids and liquids formed in the laboratory which simulate those present in the atmosphere. An important physical parameter of each liquid or solid substance, which determines whether that phase could be present in the atmosphere, constitutes its vapour pressure. Furthermore, knowledge of spectroscopic and surface properties has become a useful diagnostic tool to interpret the uptake measurements. A detailed survey of all techniques used to determine the above physical parameters is beyond the scope of this article. An excellent detailed description of all techniques has been prepared [42], Other short surveys on experimental techniques have been reported [44,45]. 

In all of these systems, certain aspects of the reactions can be uniquely related to the properties of a surface. Surface properties may include those representative of the bulk material, ones unique to the interface because of the abrupt change in density of the material, or properties arising from the two-dimensional nature of the surface. In this article, the structural, thermodynamic, electrical, optical, and dynamic properties of solid surfaces are discussed in instances where properties are different from those of the bulk material. Predominantly, this discussion focuses on metal surfaces and their interaction with gas-phase atoms and molecules. The majority of fundamental knowledge of molecular-level surface properties has been derived from such low surface area systems. The solid-gas interface of high surface area materials has received much attention in the context of separation science, however, will not be discussed in detail here. The solid-liquid interface has primarily been treated from an electrochemical perspective and is discussed elsewhere see Electrochemistry Applications in Inorganic Chemistry). The surface properties of liquids (liquid-gas interface) are largely unexplored on the molecular level experimental techniques for their study have begun only recently to be developed. The information presented here is a summary of concepts a more complete description can be found in one of several texts which discuss surface properties in more detail. ... 

I devoted a significant effort in the next chapter to nanomaterials, due to their increasing popularity and relevance for current/future applications. In addition to structure/property descriptions and applications, essential topics such as nomenclature, synthetic techniques, and mechanistic theories are described in detail. The last chapter is also of paramount importance for the materials community -characterization. From electron microscopy to surface analysis techniques, and everything in between, this chapter provides a thorough description of modern techniques used to characterize materials. A flowchart is provided at the end of the chapter that will assist the materials scientist in choosing the most suitable technique(s) to characterize a particular material. 

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). 

Each of the surface property evaluation tools is outlined below, including contact angle wettability profiles, XPS, ToF SIMS, and AFM. The outlines give some insight into the strengths and weaknesses of the techniques. Brief equipment descriptions are also included. 

Modified electrodes can be characterized by electrochemical methods, spectroscopic methods (such as X-ray photoelectron spectroscopy), and microscopy methods (such as atomic force microscopy and scanning electron microscopy). These techniques when combined give a good idea of the effectiveness of the modification, the properties of the layer and the integrity of the surface coverage. A description of a selection of characterization techniques follows. 

The available experimental techniques give very rough estimation of the liquid density profiles near the surfaces. Currently, quantitative description of the fluid density profiles by experimental methods is problematic, and computer simulation is the main experiment that provides such information. In simulations, the properties of a fluid near a surface can be studied in the pore geometry only because a semiinfinite system can not be simulated. Liquid-vapor coexistence of fluids confined in pores occurs at different chemical potential compared with the bulk coexistence, and the shift of the phase transition depends on the pore size, shape, and fluid-wall interaction. Confinement may strongly affect fluid density profiles in nanow pores (see Section 4.2), but insight into the surface transitions may be obtained by the increasing pore size, with some meaningful extrapolation on semiinfinite system. 

The full description of the gradient in surface-to-bulk properties would include a density profile, the macromolecular configurations (center of mass of the molecules), and the positions of chain ends—both parallel and perpendicular to the surface. These details of the state of the polymer at the surface can affect both the mechanical aspects of its performance, such as scratch and mar resistance, and the diffusion coefficient of coatings and of solvent into the surface. Additionally, chemical characteristics such as surface speciation (chain-end concentration) can affect specific interactions with a coating. Over the last 10 to 15 years new surface analytical techniques have been developed that significantly increase our understanding of these characteristics of polymer surfaces and interphases. Some of these analytical techniques are listed in Table 6. 

Particle shapes influence properties such as surface area, bulk density, flow, and so on. A number of methods are available for describing shape from simpler qualitative descriptions, through property ratios, to techniques that employ fast Fourier transformations to describe the projected perimeter of the particle. The measurement of the shape and the relevance of the data obtained are generally the two difficulties associated with particle shape. Fortunately, in the processing of materials physically unlike those in chemical processing, shape is perhaps is less significant and is more often than not inherently accounted for in the nominal diameter. 

---