Nanoscale particle

Exercise 3.15. Using metal cluster ideas, try various electron counts on [AI77R20]2 with an Al Ali2 Al44 (AlR)2o shell structure (consult Chapter 2). 

Answer. The eve count for [Al77R2o]2 is 253 so it is an odd electron cluster. Considering the inner two clusters with full radial and tangential bonding (the smaller one with an interstitial A1 atom) yields a count of 50 + 178 = 228. If the outer AIR fragments are attached by radial bonding alone the total count is 228 + 20 x 2 = 268 which is 15 more than observed and perhaps 14 more than a probable even electron species. Hence, one would have to assume seven tangential orbitals empty. 

Exercise 3.16. Calculate the total number of atoms and the % surface atoms in full-shell clusters of the type represented by two-shell Au55(PR3)i2Cl6 for 3,4 and 5 shells. 

Justify the observed compositions and shapes for the clusters shown in the following figure. Discuss the problem presented by any that do not obey the counting rules. 

How many different cluster structures can you devise for the molecular formula Os6(CO)2i You should be able generate more than a single shape. Four shapes are known for six-atom metal clusters with the same electron count as this cluster. 

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Attention has been particularly devoted to the application of nanoscale particles of zero-valent iron, and a range of halogenated aliphatic compounds has been examined. 

Liu Y, SA Majetich, RD Tilton, DS Sholl, GV Lowry (2005) TCE dechlorination rates, pathways, and eficiency of nanoscale particles with different properties. Environ Sci Technol 39 1338-1345. 

Klabunde, K. J., Ed. Free Atoms, Clusters, and Nanoscale Particles Academic San Diego, 1994. 

There is great interest in the electrical and optical properties of materials confined within small particles known as nanoparticles. These are materials made up of clusters (of atoms or molecules) that are small enough to have material properties very different from the bulk. Most of the atoms or molecules are near the surface and have different environments from those in the interior—indeed, the properties vary with the nanoparticle s actual size. These are key players in what is hoped to be the nanoscience revolution. There is still very active work to learn how to make nanoscale particles of defined size and composition, to measure their properties, and to understand how their special properties depend on particle size. One vision of this revolution includes the possibility of making tiny machines that can imitate many of the processes we see in single-cell organisms, that possess much of the information content of biological systems, and that have the ability to form tiny computer components and enable the design of much faster computers. However, like truisms of the past, nanoparticles are such an unknown area of chemical materials that predictions of their possible uses will evolve and expand rapidly in the future. 

Antimony telluride films have been grown from antimony(III) and tellurium(IV) oxides.167 Antimony telluride films were stoichimetric and consisted of nanoscale particles of the size 100 nm. The films had a good crystallinity.167 Indium selenide films were grown from indium sulphate and selenium oxide precursors.168 The films consisted of large particles, 70 to 200 nm in diameter. The band gap was 1.73 eV.168... 

The advent of a new class of materials systems based on nanoscale particles dispersed or suspended in carrier and/or binders has captured the attention of the microelectronics technical community. These materials provide the opportunity to use inexpensive solution processing equipment versus expensive vacuum deposition equipment commonly used in the microelectronics manufacturing industry. Experts in the microelectronics industry have suggested that over the course of the next live years, the industry will experience a paradigm shift in manufacturing and, more importantly, will enjoy revenue streams created from never-before-seen products based on printed electronics. 

Koper, O. Li, Y.-X. Klabunde, K.J. Destructive adsorption of chlorinated hydrocarbons on ultrafme (nanoscale) particles of calcium oxide. Chem. Mater. 1993,5, 500-505. 

Klabimde KJ (1994) Free atoms, clusters, and nanoscale particles. Academic Press, San Diego... 

Powers, K.W., Brown, S.C., Krishna, V.B., Wasdo, S.C., Moudgil, B.M., Roberts, S.M. (2006). Research strategies for safety evaluation of nanomaterials. Part VI. Characterization of nanoscale particles for toxicological evaluation. Toxicological Sciences, 90, 296-303. 

X-ray diffraction allows the identification of the crystalline phase of nanoparticles and, combined with HRTEM, permits the extraction of particular lattice plane spacings, estimate the lattice parameters, the crystallite size and the apparent diameter of the nanoscale particles. 

Bottom The broad color spectrum of quantum dots that is now available. These nanoscale particles can be functionalized and attached to a variety of different chemical species for tagging purposes. The great advantages of quantum dots are that they can all be excited at the same wavelength and are very resistant to photobleaching. 

The authors thank the US Air Force European Office of Aerospace Research and Development, the Marie Curie Training Site for the Controlled Fabrication of Nanoscale Materials, and the Minerva Center for Microscale and Nanoscale Particles and Films as Tailored Biomaterial Interfaces for support of this work. 

Nanoparticles maybe defined by size, which is common for toxicologists, who usually define them as particles with a mean diameter > 100 nm. However some scientists, particularly after the outburst of interest in the field, claim that any particle under study less than one micron should fall in the nanoscale particle group. 

Several pulmonary toxicology studies in rats have demonstrated that sometimes nanoscale particles, when administered to the lung of experimental animals, cause a greater inflammatory response when compared to micron-scale particles of identical composition, at equivalent mass concentrations. 

Nanopharmaceuticals Nanoscale particles that modulate drug transport in drug uptake and delivery applications. 

Advantages of nanostructure-mediated drug delivery include the ability to deliver drug molecules directly into cells and the capacity to target tumors within healthy tissue [50]. The mechanisms of cellular uptake of external particulates include calthrin- and caveoli-mediated endocytosis, pinocytosis, and phagocytosis. However, phagocytosis may not play a role in the uptake of nanoscale particles because of the small size of such particles. 

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