Nanopartides core-shell

Cortie, M.B., Dowd, A., Harris, N. and Ford, M.J. (2007) Core-shell nanopartides with self-regulating plasmonic functionality. Physical Review B -Condensed Matter, 75, 113405. 

Ag Ti02 core—shell nanopartides. Journal of Colloid and Interface Science, 323 (1), 182-186. 

Y. Wang, X. Teng, J.-S. Wang, H. Yang, Solvent-free atom transfer radical polymerization in the synthesis of FcjOj polystyrene core-shell nanopartides, NanoLetters 2003, 3, 789 793. 

Core-shell nanopartides (CSNs) can be produced by miniemulsion polymerization [62, 63]. So far the research on the preparation of core-shell nanopartides via miniemulsion polymerization in laboratory scale has made immense progress in the last years. There are several different applications for polymer-coated particles, for example, for medical products, paints, and catalysts. The polymer coating prevents the partides from agglomerating that results in a better color intensity or in an improvement of catalytic performance [64]. In medical applications, organic coating is required to depress toxic reactions [65]. 

Hun, X. and Zhang, Z. 2007) Functionalized fluorescent core-shell nanopartides used as a fluorescent labels... 

Pastoriza-Santos, L, Koktysh, D.S., Mamedov, A.A., Giersig, M., Kotov, N.A. and Liz-Marzan, LM. (2000) One-pot synthesis of Ag Ti02 core-shell nanopartides and their layer-by-layer assembly. Langmuir, 16, 2731-5. 

Bimetallic nanoparticles, either as alloys or as core-shell structures, exhibit unique electronic, optical and catalytic properties compared to pure metallic nanopartides [24]. Cu-Ag alloy nanoparticles were obtained through the simultaneous reduction of copper and silver ions again in aqueous starch matrix. The optical properties of these alloy nanopartides vary with their composition, which is seen from the digital photographs in Fig. 8. The formation of alloy was confirmed by single SP maxima which varied depending on the composition of the alloy. 

Gomes, J.D., Sousa, M.H., Tourinho, F.A. and Aquino, R. da Silva, G.J., Depeyrot, J., Dubois, E., Perzynski, R. (2008) Synthesis of core-shell ferrite nanopartides for ferrofluids chemical and magnetic analysis. Journal of Physical Chemistry C, 112 (16), 6220-6227. 

With these considerations in mind, synthetic chemists have begun to address the needs of metal particle research by developing the synthetic chemistry of nanosized metals, with a view to using the strategies of molecular chemistry to prepare well-defined metal nanopartides. The goal may be stated as ... the search for synthetic methods for metal nanopartides of narrow size distribution and, if possible, with shape-control. Furthermore, bimetallic spedes will be considered, either with core-shell architecture or in alloyed form. 

The preparation of core-shell -type magnetic nanopartides was reported [92,93] as a two-step synthesis in which nanopartides of one metal served as the seeds for growth of the shell from another metal. Thus, the reduction of platinum salts in the presence of Co nanopartides would allow the preparation of air-stable CocorePtsheii nanopartides [92]. The thermal decomposition of cobalt carbonyl in the presence of silver salt led to the formation of AgcoreCOgheii nanopartides [93]. The syntheses of these multicomponent magnetic nanostructures are discussed in Section 3.3.2.4. 

Composite Nanopartides, Fig. 1 Schematic representation for the basic structures of composite nanoparticles (a) simple hybrid (10-100 nm) (b) core/shell structured (10-100 nm) (c) multifimctional quantum dots (1-20 nm)... 

Figure 49 General synthetic scheme of magnetic and semiconducting hybrid nanowires templated from core-shell molecular bmshes (a) a molecular brush with a PAA core and a PriBA shell (b) the PAA core neutralized into poly(sodium acrylate) (c) a polychelate consisting of a polymer brush and Fe, Fe, or Cd ions and (d) a hybrid nanowire of a polymer bmsh with a wire-like assembly of magnetic/semiconducting nanopartides in its core. Reprinted from Zhang, M. Muller, A. H. E. J. Pofym. Sci. Part A Polym. Chem. 2005, 43 (16), 3461-3481, with permission from Wiley-VCH. ...

Moreover, it is interesting to note that for both Ag and Pd composite particles the catalytic activities of metal nanoparti-cles immobilized in SPEB are higher than that of a core-shell miaogel system. This can be explained by the diffusion speed of reactant molecules to metal nanopartides encapsulated in both carrier systems. For the microgels, the cross-linked PNIPAM shdl restricts diffusion and the reactant molecules need a longer time to reach the catalytic active center. The SPEBs have an open structure, and reactant molecules can diffuse through to reach the metal nanopartides more quickly. This demonstrates that SPB can work as stable carrier systems for metal nanopartides used in catalysis. 

PMMA)-coated PPy nanopartides were prepared by microemulsion polymerization, and the composite particles were incorporated into a PMMA matrix to obtain transparent conductive coatings. The prepared particle showed core-shell morphology (Fig. 6.15). 

In this chapter we focused on the characterization of core-shell magnetic nanopartides as determined by X-ray photoelectron spectroscopy (XPS). XPS, also known as Eledron Spectroscopy for Chemical Analysis (ESCA), is an elemental analysis technique and used to determine quantitatively the atomic composition and surface chemistry. XPS spedra are obtained by irradiating a material with a beam of X-rays while simultaneously measuring the kinetic energy and number of electrons that escape from the top 1 to 10 nm of the material being analysed (Watts et al., 2003 http //en. Wikipedia org/wiki/X-ray photoelectron spectroscopy). 

The phase separation might lead to either the formation of a core-sheU stmcture (as studied here) or to the disintegration into two new nanopartides. The condition to obtain the core-shell structure is that the two phases wet each other. Let us look at the evolution of the surface energy when the core-shell structure appears. The initial surface energy of the particle is equal to ... 

FIGURE 4.6 Synthesis steps for Pt monolayer catalysts on nonnoble metal core-noble metal shell nanopartides. Reprinted with permission from Ref. [21]. Copyright 2005 American Chemical Society. 

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