Water-soluble metallic nanoparticles

Reduction of Double Complexes. Except for Ag/Au bimetallic nanoparticles, bimetallic nanoparticle dispersions containing Ag have not been studied extensively. One of the possible reasons is that an Ag1 ion readily reacts with a halide ion to produce water-insoluble silver halide. Also, many other water-soluble metal salts other than halides are not as suitable as precursors for the production of metallic particles by mild reduction. 

Effect of the metallic precursor. An important factor controlling the final particle size of the catalysts is the metallic precursor. Most papers on the subject report the use of water-soluble metallic salts as precursors. However, this is not always a straightforward option in order to obtain better catalysts. For instance, it was stated for Pt catalysts that a better control of both particle size and particle size distribution could be achieved by the preparation of Pt complexes, nanoparticles, formed in water in oil microemulsions . ... 

Extraction by an organic solvent or water can be used to separate metal nanoparticles soluble in an organic solvent or water. This technique can be used only for the nanoparticles protected by organic ligands or pol5mers. The solubility of protecting reagents with the solvent is crucially important in this technique. 

Kaifer and coworkers showed interest in the modification of metal nanoparticles with organic monolayers prepared with suitable molecular hosts. They reported the preparation of water-soluble platinum and palladium nanoparticles modified with thiolated /1-cyclodexlrin (/ -CD) [69]. Nanoparticle synthesis was... 

The immobilization of metal nanoparticles with a water-soluble polymeric material such as PVP has also been described. The groups of Choukroun and Chaudret have described the hydrogenation of benzene in a biphasic mixture with PVP-protected native Rh nanoparticles synthesized from the organometal-... 

Dendrimer synthesis, 26 787-788 breakthrough approaches in, 26 788 Dendritic box, 26 790 Dendritic metallic silver, 19 367—368 Dendritic nanoparticles, water-soluble, 26 796... 

Abstract Quantum clusters of gold are materials with a core dimension in the subnanometer regime. They exhibit a totally different chemistry when compared with the metallic nanoparticles. In this chapter, we present this new family of materials. Various approaches used for the synthesis of both water and organic soluble clusters are described. After reviewing the various properties of these clusters with special reference to their luminescent properties, we look at their bio-labeling applications. We hope that this chapter initiates the reader into a new family of materials in the context of luminescence imaging and other purposes. 

The catalysts can be obtained by a coprecipitation method consisting of two steps (Figure 6.2). In the first step, a stable suspension of protected metal nanoparticles is obtained according to the method reported by Schulz and co-workers [75-77]. The metal particles are prepared in the presence of a highly water-soluble ionic surfactant which is able, due to its nature, to modulate the particle size and to prevent their aggregation. Modifying parameters such as pH, temperature and surfactant concentration, it is possible to tune the metal particle size [71]. Moreover, the role of the... 

PEBBLEs are water-soluble nanoparticles based on biologically inert matrices of cross-linked polymers, typically poly(acrylamide), poly(decylmethacrylate), silica, or organically modified silicates (ORMOSILs), which encapsulate a fluorescent chemo-sensor and, often, a reference dye. These matrices have been used to make sensors for pH, metal ions, as well as for some nonionic species. The small size of the PEBBLE sensors (from 20 to 600 nm) enables their noninvasive insertion into a living cell, minimizing physical interference. The semipermeable and transparent nature of the matrix allows the analyte to interact with the indicator dye that reports the interaction via a change in the emitted fluorescence. Moreover, when compared to naked chemosensors, nanoparticles can protect the indicator from chemical interferences and minimize its toxicity. Another important feature of PEBBLEs, particularly valuable in intracellular sensing applications, is that the polymer matrix creates a separate... 

Kramer and coworkers recently reported on water-soluble dendritic coreshell architectures and studied the influence of the attached carbohydrate shell on the formation and stabilization of metal nanoparticles in water. For this purpose, they used hyperbranched poly(ethylenimine) (PEI) as core molecules and covalently attached different carbohydrates as shells, i.e., glycidol, gluconolactone and lactobionic acid, to obtain the corresponding PEI-glycol, PEI-gluconamide and PEI-lactobionamide. Different molecular weights of PEIX (x = 0.8, 5, 21 or 25 with different Mw = xlO3) were employed [81]. 

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