Core-shell synthesis

Liz-Marzan L M, Giersig M and Mulvaney P 1996 Synthesis of nanosized gold-silica core-shell particles Langmuir 12 4329-35... 

Synthesis of Ni/Pd bimetallic core/shell nanoparticles and their applications to Sonogashira coupling reactions... 

Nanoparticles of Mn and Pr-doped ZnS and CdS-ZnS were synthesized by wrt chemical method and inverse micelle method. Physical and fluorescent properties wra cbaractmzed by X-ray diffraction (XRD) and photoluminescence (PL). ZnS nanopatlicles aniKaled optically in air shows higher PL intensity than in vacuum. PL intensity of Mn and Pr-doped ZnS nanoparticles was enhanced by the photo-oxidation and the diffusion of luminescent ion. The prepared CdS nanoparticles show cubic or hexagonal phase, depending on synthesis conditions. Core-shell nanoparticles rahanced PL intensity by passivation. The interfacial state between CdS core and shell material was unchan d by different surface treatment. 

Kim S, Fisher B, Eisler HJ, Bawendi M (2003) Type-11 Quantum Dots CdTe/CdSe (core/sheU) and CdSe/ZnTe(core/shell) heterostructures. J Am Chem Soc 125 11466-11467 Aharoni A, Mokaii T, Popov 1, Banin U (2006) Synthesis of InAs/CdSe/ZnSe core/ shelll/shell2 structures with bright and stable near-infrared fluorescence. J Am Chem Soc 128 257-264... 

Dabbousi, B. O., Rodriguez-Viejo, J., Mikulec, F. V, Heine, J. R., Mattoussi, H., Ober, R., Jensen, K. F. and Bawendi, M. G. (1997) (CdSe)ZnS core-shell quantum dots synthesis and characterization of a size series of highly luminescent nanocrystallites. J. Phys. Chem. B, 101, 9463-9475. 

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. 

We have extended the seed-mediated technique for the synthesis of bimetallic nanoparticles, having core-shell type structure appending photoreduction of metal ions. It has been proved that the deposition of a less noble metal (M) as shell on a preformed nobler nanoparticle core (M ) seems to be very effective by UV activation. Using this seed-mediated method we were able to synthesize Aucore Agsheii particles. First for the preparation of gold seeds (S), TX-lOO (10 M) and HAuC (5.0 x 10 %) were taken in a quartz cuvette so that the final concentration of Au(III) ion remained 5.0 x 10 M. Then the... 

Abstract A convenient method to synthesize metal nanoparticles with unique properties is highly desirable for many applications. The sonochemical reduction of metal ions has been found to be useful for synthesizing nanoparticles of desired size range. In addition, bimetallic alloys or particles with core-shell morphology can also be synthesized depending upon the experimental conditions used during the sonochemical preparation process. The photocatalytic efficiency of semiconductor particles can be improved by simultaneous reduction and loading of metal nanoparticles on the surface of semiconductor particles. The current review focuses on the recent developments in the sonochemical synthesis of monometallic and bimetallic metal nanoparticles and metal-loaded semiconductor nanoparticles. 

Anandan et al. [37] reported the sonochemical synthesis of gold-silver bimetallic nanoparticles with core-shell geometry by the sonochemical co-reduction of Au and... 

Anandan S, Ashokkumar M, Grieser F (2008) Sonochemical synthesis of Au-Ag core-shell bimetallic nanoparticles. J Phys Chem C 112 15102-15105... 

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. 

Each step in dendrimer synthesis occurs independent of the other steps therefore, a dendrimer can take on the characteristics defined by the chemical properties of the monomers used to construct it. Dendrimers thus can have almost limitless properties depending on the methods and materials used for their synthesis. Characteristics can include hydrophilic or hydrophobic regions, the presence of functional groups or reactive groups, metal chelating properties, core/shell dissimilarity, electrical conductivity, hemispherical divergence, biospecific affinity, photoactivity, or the dendrimers can be selectively cleavable at particular points within their structure. 

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. 

Efforts at synthesis and studies of temperature-dependent solution behaviour of these chemically hydrophobized polyacrylamides are now in progress. However, it is reasonable to point out that in this case, contrary to the hydrophilization of the hydrophobic precursor, the problems associated with additional swelling of the globular core (as the modification proceeds) are absent however, the problem of the choice of working concentration for the precursor is still present since above the coil overlapping concentration the intermolecular aggregation processes at elevated temperatures can compete with the intramolecular formation of core-shell structures. 

Li, J. J. Wang, Y. A. Guo, W. Keay, J. C. Mishima, T. D. Johnson, M. B. Peng, X. 2003. Large-scale synthesis of nearly monodisperse CdSe/CdS core/shell nanocrystals using air-stable reagents via successive ion layer adsorption and reaction. J.Am. Chem. Soc. 125 12567-12575. 

Fig. 6. a PDMS device for sol-gel synthesis of core shell Si02-Ti02 colloids, b SEM image of synthesized colloids, c TEM image of colloids TiC>2 is shell-visible (Khan 2006)... 

Figure 1.6 Solvent accessibility and photobleaching behaviour of nanoparticle synthesis intermediates. (A-C) Excitation and emission spectra of nanoparticle intermediates ((A) TRITC (B) core (C) core-shell) in ethanol (blue) and water (red). (D) Photobleaching behaviour of nanoparticle intermediates (blue, TRITC green, core red, core-shell) and fluorescein (black). All curves in (A)-(D) are normalized by the peak values. (Reproduced from ref. 13, with permission.)...

Further elaboration of these dendrigraft principles allowed the synthesis of a variety of core-shell type dendrigrafts, wherein elemental composition as well as the hydrophobic/hydrophilic character in the core can be controlled independently. 

Tomalia et al. reported that the surface amines of PAM AM dendrimer can successfully react with methyl esters of other PAMAM dendrimers to afford core-shell tecto-(dendrimer) molecules [65]. Furthermore, they also reported the synthesis of rod-shaped cylindrical dendronized polymers from poly(ethyleneimine) cores without any crosslinking, albeit with the use of excess reagents [58]. These reports lead us to propose a new approach toward hybridized dendrimers and polymers (path C, Figure 15.3). As shown in Scheme 12,... 

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