Core-shell strategies

To build a nanoparticle in a core-shell strategy. The cores are synthesized first and then the functional molecules are added as a shell by simple adhesion (physical adsorption in an insolubilization strategy). Examples are given in the literature [71, 72]. Organic molecules forming the core of an ONP usually include functional groups to which other molecules are added, such as peptides/ proteins and nucleic acids. 

It was thus found that the core/shell strategy is promising for noble-metal/ photocatalyst systems to allow for H2 and O2 evolution from water, because H2-O2 recombination is effectively suppressed by Cr203 shell surrounding noble... 

Zhang N, Xu Y-J (2013) Aggregation- and leaching-resistant, reusable, and multifunctional Pd Ce02 as a robust nanocatalyst achieved by a hollow core-shell strategy. Chem MatCT 25(9) 1979-1988... 

In order to realize the precise control of core/shell structures of small bimetallic nanoparticles, some problems have to be overcome. For example, one problem is that the oxidation of the preformed metal core often takes place by the metal ions for making the shell when the metal ions have a high-redox potential, and large islands of shell metal are produced on the preformed metal core. Therefore, we previously developed a so-called hydrogen-sacrificial protective strategy to prepare the bimetallic nanoparticles in the size range 1.5-5.5nm with controllable core/shell structures [132]. The strategy can be extended to other systems of bi- or multimetallic nanoparticles. 

Reduction of two different precious metal ions by refluxing in ethanol/water in the presence of PVP gave a colloidal dispersion of core/shell structured bimetallic nanoparticles. In the case of Pd and Au ions, e.g., the colloidal dispersions of bimetallic nanoparticles with a Au core/Pd shell structure are produced. In contrast, it is difficult to prepare bimetallic nanoparticles with the inverted core/shell (in this case, Pd-core/Au-shell) structure. The sacrificial hydrogen strategy was used to construct the inverted core/shell structure, where the colloidal dispersions of Pd-cores are treated with hydrogen and then the solution of the second element, Au ions, is slowly added to the dispersions. This novel method, developed by us, gave the inverted core/shell structured bimetallic nanoparticles. The Pd-core/Au-shell structure was confirmed by FT-IR spectra of adsorbed CO [144]. 

A similar strategy was used to prepare BaFe12019-Ti02 core-shell materials, with the core of BaFei20i9 used to magnetically recover the catalyst and the shell ofTi02 that promoted degradation of dyes. The activity was dependent on the shell thick-... 

This strategy was first realized by Lozinsky et al., who studied the redox-initiated free-radical copolymerization of thermosensitive N-vinylcaprolactam with hydrophilic N-vinylimidazole at different temperatures, as well as by Chi Wu and coworkers. Lozinsky presents an extensive review of the experimental approaches, both already described in the literature and potential new ones, to chemical synthesis of protein-like copolymers capable of forming core-shell nanostructures in a solution. 

Zhou, W., et al., A general strategy toward graphene metal oxide core-shell nanostructures for high-performance lithium storage. Energy Environmental Science, 2011. 4(12) p. 4954-4961. 

The thickness of the imprinted polymer shell can be also tuned in the range 10—40 nm by changing the relative amounts of functionalised silica nanoparticles and polymer shell precursors. The resulting core-shell particles exhibit enhanced capacity of rebinding the TNT template over 2,4-dinitrotoluene in comparison to particles prepared by precipitation polymerisation. Nevertheless, this strategy, although leading to impressive results, cannot be easily applied to other templates and monomers. 

Fig. 10 Schematic description of the strategy followed by Whitcombe et al. for the preparation of core-shell MIP nanoparticles with imprinted sites located on the particle surface. Reproduced with permission from [124]...

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