Nanoparticles structure identification

This approach of using 2D and 3D monodisperse nanoparticles in catalytic reaction studies ushers in a new era that will permit the identification of the molecular and structural features of selectivity [4,9]. Metal particle size, nanoparticle surface-structure, oxide-metal interface sites, selective site blocking, and hydrogen pressure have been implicated as important factors influencing reaction selectivity. We believe additional molecular ingredients of selectivity will be uncovered by coupling the synthesis of monodisperse nanoparticles with simultaneous studies of catalytic reaction selectivity as a function of the structural properties of these model nanoparticle catalyst systems. 

The identification of structure sensitivity would be both impossible and useless if there did not exist reproducible recipes able to generate metal nanoparticles on a small scale and under controlled conditions, that is, with narrow size and/or shape distribution onto supports. Metal nanoparticles of controlled size, shape, and structure are attractive not only for catalytic applications, but are important, for example in optics, data storage, or electronics (c.f. Chapter 5). In order not to anticipate other chapters of this book (esp. Chapter 2), remarks will therefore be confined to few examples. 

Yang J, Lee JY, Too PIP (2006) Phase-transfer identification of core-shell structures in bimetallic nanoparticles. Plasmonics 1 67-78... 

To determine the phase properties of the calcined bimetallic nanoparticles, a detailed x-ray diffraction (XRD) study was carried out. The XRD data of AuPt/C showed that the diffraction patterns for the carbon-supported nanoparticles show a series of broad Bragg peaks, a picture typical for materials of limited structural coherence. Nevertheless, the peaks are defined well enough to allow a definitive phase identification and structural characterization. The diffraction patterns of Au/C and Pt/C could be unambiguously indexed into an fcc-type cubic lattice occurring with bulk gold and platinum. We estimated the corresponding lattice parameters by carefully determining... 

The voltammograms are unique for each basal plane and are often used as a diagnostic tool for the identification of primary Pt-surface sites [2-6,54]. The structure-sensitivity of the voltammogram serves as a means to characterize the preferential orientation of a given sample [55]. The voltammogram for platinum nanoparticles obtained by different preparation procedures is shown in Figure 6.13. The difference in voltammetric behavior displays the influence of preparation procedures on the fraction of (100), (110) and (111) atomic sites on the surface of the nanoparticles. 

Up to now, a large part of the international scientific attention was devoted to the study of metallic nanoparticles (either single particles or in a colloid ensemble) (3, 14). Milling nanometric apertures in a metallic film is an intuitive way to manufacture new nanophotonics devices that are robust and highly reproducible. Although this concept appears very simple, such apertures exhibit attractive physical properties, such as localization of excitation light, strong isolation fi om emission produced by unbound species, and an increase in apparent absorption and emission yield. The simplicity of the structures and their ease of use should further expand their application towards the real-time detection and identification of a small number of molecules. 

XRD has been one of the most versatile techniques utilized for the structural characterization of nanocrystalline metal powders. The modem improvements in electronics, computers, and x-ray sources have allowed it to become a powerful indispensable tool for identilying nanocrystalline phases as well as crystal size and crystal strains. Comparison of the crystallite size obtained by the XRD dififractogram using the Scherrer formula with the grain size obtained from a TFM image allows identification of the mono- or polycrystalline nature of the nanoparticles. 

Density-based methods Wave function-based methods Some technical aspects Excitations in various systems Excitations in metal clusters Excitations in semiconductor nanoparticles Excitations in organic and biological systems Identification of structure Dynamics in excited states Conclusions... 

Nanoscience and technology is a field that focuses on 1) the development of synthetic methods and surface analytical tools for building structures and materials, typically on the sub-100 nanometer scale, 2) the identification of the chemical and physical consequences of miniaturization, and 3) the use of such properties in the development of novel and functional materials and devices. Thus, this field is of greatest interest to handle nanoparticles, nanostructured materials, nanoporous materials, nanopigments, nanotubes, nanoimprinting, quantum dots, and so on and has already led to many innovative applications, particularly in materials science [18, 19]. For basic investigations, an important role is played by manipulation or imaging nanoscale techniques (e.g., AFM and STM). 

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