Monodispersed nanoparticle

The synthesis of nanoparticles has been intensively pursued not only for their fundamental scientific interest, but also for many technological applications [1]. For many of these applications, the synthesis of monodisperse nanoparticles (standard deviations a < 5%) with controlled particle sizes is of key importance, because the electrical, optical, and... 

This approach of using 2D and 3D monodisperse nanoparticles in catalytic reaction studies ushers in a new era that will permit the identification of the molecular and structural features of selectivity [4,9]. Metal particle size, nanoparticle surface-structure, oxide-metal interface sites, selective site blocking, and hydrogen pressure have been implicated as important factors influencing reaction selectivity. We believe additional molecular ingredients of selectivity will be uncovered by coupling the synthesis of monodisperse nanoparticles with simultaneous studies of catalytic reaction selectivity as a function of the structural properties of these model nanoparticle catalyst systems. 

Thus, we see that the digestive ripening process leads to highly monodispersed nanoparticles that can come together to form ordered superstructures similar to atoms or molecules that form crystals from a supersaturated solution. Then if the superstructure formation can indeed be related to atomic/molecular crystallization, it should also be possible to make these supercrystals more soluble in the solvent with a change of temperature. Indeed, the optical spectra of the three colloids prepared by the different thiols discussed above exhibit only the gold plasmon band at 80 °C suggesting the solubilization of these superlattices at the elevated temperatures [49]. 

Figure 2 schematically presents a synthetic strategy for the preparation of the structured catalyst with ME-derived palladium nanoparticles. After the particles formation in a reverse ME [23], the hydrocarbon is evaporated and methanol is added to dissolve a surfactant and flocculate nanoparticles, which are subsequently isolated by centrifugation. Flocculated nanoparticles are redispersed in water by ultrasound giving macroscopically homogeneous solution. This can be used for the incipient wetness impregnation of the support. By varying a water-to-surfactant ratio in the initial ME, catalysts with size-controlled monodispersed nanoparticles may be obtained. 

The synthesis of Pd/ACF (0.42wt.% Pd) catalyst with monodispersed nanoparticles carried out at cuo = 3 is illustrated, as well as its catalytic performance in a liquid-phase hydrogenation of 1-hexyne in comparison with a traditional powdered Lindlar catalyst. 

The use of silica particles in bioapplications began with the publication by Stober et al. in 1968 on the preparation of monodisperse nanoparticles and microparticles from a silica alkoxide monomer (e.g., tetraethyl orthosilicate or TEOS). Subsequently, in the 1970s, silane modification techniques provided silica surface treatments that eliminated the nonspecific binding potential of raw silica for biomolecules (Regnier and Noel, 1976). Derivatization of silica with hydrophilic, hydroxylic silane compounds thoroughly passivated the surface and made possible the use of both porous and nonporous silica particles in all areas of bioapplications (Schiel et al., 2006). 

This method involves the thermolysis of organometallic or metal organic precursors in a high-boiling solvent. Mostly this solvent is also a capping agent for the nanoparticles. A typical synthetic route for monodisperse nanoparticles is shown in Fig. 1. 

Growth of Nuclei to Metal Nanoparticles. If the elemental cluster of 13 atoms is the nucleus, the growth of nuclei to metal nanoparticles could proceed by deposition of atoms or microclusters on the surface of nuclei. This process is understandable based on the consideration of the formation of monodispersed nanoparticles. However, structural analysis has often proposed the aggregation of elemental clusters to form fundamental clusters (64). A similar idea is discussed for the structural analysis of bimetallic nanoparticles with cluster-in-cluster structure (40,61). 

Figure 1 Cartoon illustration of nudeation and growth during the preparation of monodisperse nanoparticles.

Guo, Q. Teng, X. Rahman, S. Yang, H. Patterned Langmuir-Blodgett Rims of Monodisperse Nanoparticles of Iron Oxide Using Soft Lithography. J. Am. Chem. 

Peng [4] prepared monodispersed nanoparticles between 1 and 20 nm consisting of gold, silver, copper, and platinum, which were used as high efficiency industrial catalysts. 

The synthesis of novel materials (particularly multicomponent materials) with unusual properties for uses as catalytic converters is gaining interest [72]. Thus, nanoporous structures of materials obtained by high-US agglomeration of monodispersed nanoparticles exhibit excellent properties and do not require the thermal post-treatment usually needed for the crystallization of amorphous materials or removal of surfactants [73]. 

Recent developments in the preparation and use of nanoparticulate oxide materials, more specifically isolated nanoparticles of simple and compound oxides, are reviewed. While oxide nanoparticles have been known and studied for many decades, it is only in recent years that methods for their preparation have achieved the level of sophistication which permits monodisperse nanoparticles to be produced in quantity. In addition, it is only in recent years that the notion of capping of oxide nanoparticle surfaces by long-chain surfactants, with the corollary that they become soluble, has taken firm hold. The emphasis is on new routes for the preparation of oxide nanoparticles, and how these could be distinct from those used for metals or chalcogenides. Properties of oxide nanopartides are discussed with special reference to how they are distinct from the bulk material. Present and possible applications are discussed in context. 

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