Nanoparticles roles

Cumbal, L. and Sengupta, A.K. (2005) Arsenic removal using polymer-supported hydrated iron(III) oxide nanoparticles Role of Donnan membrane effect. Environmental Science and Technology, 39(17), 6508-15. 

Lucas, LT. et al., Surface charge density of maghemite nanoparticles Role of electrostatics in the proton exchange, J. Phys. Chem. C. Ill, 18568, 2007. 

S. Hussain, S. Boland, A. Baeza-Squiban, et al.. Oxidative stress and proinflammatory effects of carbon black and titanium dioxide nanoparticles role of particle surface area and internalized amount. Toxicology 260 (1-3) (2009) 142-149. 

Vandebril S, Vermant J, Moldenaers P. Efficiently suppressing coalescence in polymer blends using nanoparticles Role of interfacial rheology. Soft Matter 2010 6(14) 3353-3362. 

The carbon-arc plasma of extremely high temperatures and the presence of an electric field near the electrodes play important roles in the formation of nanotubes[ 1,2] and nanoparticles[3]. A nanoparticle is made up of concentric layers of closed graphitic sheets, leaving a nanoscale cavity in its center. Nanoparticles are also called nanopolyhedra because of their polyhedral shape, and are sometimes dubbed as nanoballs because of their hollow structure. 

However, the main research result from those years was the discovery of the room-temperature single-electron phenomenon. In the 1990s, STM experiments on liquid crystal had shown a very weak staircase (Nejoh 1991) only one year later, the clear observations of the coulomb blockade and the coulomb staircase were demonstrated on gold nanoparticles (Shonenberger et al. 1992a) and the role of system symmetry on the appearance of these two phenomena was outlined (Shonenberger et al. 1992b). 

Thus, previously described experiments had demonstrated the possibility of realization of single-electron junctions based on CdS nanoparticles. Nevertheless, because only one type of particle was tested, the question about the role of the material s properties for successful single-electron junction formation was still open. 

The aim of the next stage of the work was to study the possibility of the realization of structures that would exhibit single-electron phenomena by forming the nanoparticles with the same technique but from different materials. Comparison of the properties of such structures with those built up with CdS particles will make clearer the role of a material s characteristics on the final properties of the structure. 

Spherical vaterite crystals were obtained with 4-mercaptobenzoic acid protected gold nanoparticles as the nucleation template by the carbonate diffusion method [51]. The crystallization of calcium carbonate in the absence of the 4-MBA capped gold nanoparticles resulted in calcite crystals. This indicates that the polymorphs of CaCOj were controlled by the acid-terminated gold nanoparticles. This result indicates that the rigid carboxylic acid structures can play a role in initiating the nucleation of vaterite as in the case of the G4.5 PAMAM dendrimer described above. 

Ancillary Hgands, the role of which is to stabiHze complexes or nanoparticles and Hberate a vacant coordination site when necessary... 

Active Hgands, which may take an important role in the reactivity of the complexes/nanoparticles (e.g., hydrides, alkyl groups, carbenes, etc.)... 

In summary, control of the surface chemistry and the presence of clean surfaces allow the coalescence of initially isotropic nanoparticles into regular, often monodisperse, nano-objects of anisotropic shape (cubes, rods, wires). It is possible that the inclusion of the initially present nanoparticles into superlattices play an important role in these coalescence processes. 

The size of metal nanoparticles plays also a role in a quite different field of nanoscience the interaction with biosystems with nanoparticles in general, here especially with metal nanoparticles. Chapter 4 will deal with some very recent aspects considering the interaction of noble metal nanoparticles with biomolecules and living cells. 

The size of metal nanoparticles obviously plays also a significant role considering the interaction with biosystems. The 1.4 nm gold nanoclusters interact irreversibly with DNA due to an extremely stable fixation in the major groves. These findings may lead to the development of novel cancer drugs, as can be concluded from a series of cell experiments. 

The synthesis of bimetallic nanoparticles is mainly divided into two methods, i.e., chemical and physical method, or bottom-up and top-down method. The chemical method involves (1) simultaneous or co-reduction, (2) successive or two-stepped reduction of two kinds of metal ions, and (3) self-organization of bimetallic nanoparticle by physically mixing two kinds of already-prepared monometallic nanoparticles with or without after-treatments. Bimetallic nanoparticle alloys are prepared usually by the simultaneous reduction while bimetallic nanoparticles with core/shell structures are prepared usually by the successive reduction. In the preparation of bimetallic nanoparticles, one of the most interesting aspects is a core/shell structure. The surface element plays an important role in the functions of metal nanoparticles like catal5dic and optical properties, but these properties can be tuned by addition of the second element which may be located on the surface or in the center of the particles adjacent to the surface element. So, we would like to use following marks to inscribe the bimetallic nanoparticles composed of metal 1, Mi and metal 2, M2. 

In summary the simultaneous reduction method usually provides alloyed bimetallic nanoparticles or mixtures of two kinds of monometallic nanoparticles. The bimetallic nanoparticles with core/shell structure also form in the simultaneous reduction when the reduction is carried out under mild conditions. In these cases, however, there is difference in redox potentials between the two kinds of metals. Usually the metal with higher redox potential is first reduced to form core part of the bimetallic nanoparticles, and then the metal with lower redox potential is reduced to form shell part on the core, as shown in Figure 2. The coordination ability may play a role in some extent to form a core/shell structure. Therefore, the simultaneous reduction method cannot provide bimetallic nanoparticles with so-called inverted core/ shell structure in which the metal of the core has lower redox potential. 

Correlation has been suggested between the morphology, electronic structure and catalytic properties of supported gold nanoparticles with special attention to the role of the substrate/interface behaviour. 

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