Nanoparticle monodisperse size distribution

Before investigating the effect of size, shape, and structure on catalytic behavior, that is, TOFs, a set of five requirements concerning the metal particles has to be met. Besides a monodisperse size distribution, the nanoparticles should be fully reduced, unpoisoned, unperturbed by... 

An interesting method to produce water-soluble iridium nanoparticles was proposed by Chaudret and coworkers [13]. Here, aqueous soluble iridium nanoparticles were synthesized by the chemical reduction of iridium trichloride with sodium borohydride in an aqueous solution of the surfactant N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl)ammonium chloride (Scheme 15.2). The precursor reduction was assisted by sonication, while the gradual conversion of Ir(lll) ions to lr(0) nanoparticles was followed using UV spectroscopy. The use of a molar surfactant Ir ratio of 10 proved sufficient to obtain stable aqueous soluble iridium nanoparticles however, if the molar surfactant Ir ratio used was <10 then agglomeration was observed in solution after several days. TEM analysis of the iridium nanoparticles revealed a monodispersed size distribution and a mean diameter of 1.9 0.7nm (Figure 15.2). 

Nanoparticles of PS (M =1.0xl0 -3.0xl0 mol ) microlatexes (10-30 nm) have also been successfully prepared from their respective commercial PS for the first time [75]. The dilute PS solutions (cyclohexane, toluene/methanol or cyclohexane/toluene) were induced to form polymer particles at their respective theta temperatures. The cationic CTAB was used to stabihze th microlatexes. The characteristics of these as-formed PS latex particles were quite similar to those obtained from the microemulsion polymerization of styrene as reported in literature. These microlatexes could also be grown to about 50 nm by seeding the polymerization of styrene with a monodisperse size distribution of D /Djj=1.08. This new physical method for preparing polymer nano-sized latexes from commercial polymers may have some potential applications, and therefore warrants further study. 

Gold nanoparticles have received significant attention in recent years because of their unique catalytic activity [37 3]. Supported gold nanoparticles in the range of 2-5 nm are effective as catalysts for a variety of reactions including selective oxidation of propane to propylene oxide [44] and low-temperature CO oxidation [45]. Numerous experimental studies have focused on understanding the effect of particle size in gold catalysts however, the picture is often complicated by the lack of a monodisperse size distribution. 

As early as 1997, Antonietti and coworkers [167] showed that palladium nanoparticles supported by polystyrene-polyvinylpyrrolidone block copolymer effect the Mizoroki-Heck reaction while retaining a monodisperse size distribution throughout. Very recently, a similar effect was demonstrated for A-vinylimidazole-A-vinylcaprolactam copolymer, in the presence of which a monodisperse palladium sol was generated directly in the reacting system [168]. 

The chemical reactions that take place in the liquid phase and the formation of high-quality nanoparticles (that is, those with a defined diameter, almost monodisperse size distribution and small degree of agglomeration) are in general limited by two major boundary conditions firstly, the precise and directed control of... 

The primary goal of the researchers has been to produce Q-dots possessing all of the attributes of the Q-dots prepared using liquid-phase synthetic methods (that is adjustability of the nanocrystal identity and diameter and size monodispersity) and also the technological utility of Q-dots prepared by MBE (specifically, the deposition of nanocrystals with a defined orientation and an electrical output contact). It was shown that the E/C-synthesized 5-CuI and CdS Q-dots were indeed epitaxial with narrow size distribution and strong photoluminescence tunable by the particle size. Qne of the advantages of the E/C method is that it can be made size selective. The key point is that the size as well as the size dispersion of product nanoparticles are directed actually by the corresponding properties of the metal nanoparticles therefore the first deposition step assumes special importance. 

All Pt nanoparticles were monodisperse and the size distribution was less than 10%. The average particle sizes... 

In 2000, Sun and co-workers succeeded in synthesis of monodispersed Fe/Pt nanoparticles by the reduction of platinum acetylacetonate and decomposition of Fe(CO)5 in the presence of oleic acid and oleylamine stabilizers [18]. The Fe/Pt nanoparticle composition is readily controlled, and the size is tunable from 3 to 10 nm in diameter with a standard deviation of less than 5%. For practical use, we developed the novel symthetic method of FePt nanoparticles by the polyol reduction of platinum acetylacetonate (Pt(acac)2) and iron acetylacetonate (Fe(acac)3) in the presence of oleic acid and oleylamine stabilizers in di- -octylether [19,20]. The Fe contents in FePt nanoparticles can be tuned from 23 to 67atomic%, and the particle sizes are not significantly affected by the compositions, retaining to be 3.1 nm with a very narrow size distribution, as shown in Figure 6. 

Figure 14.1 shows a representative TEM micrograph and size distribution for decanethiolate-capped Au72Pt2s nanoparticles. The nanoparticles display a relatively high monodispersity ( 0.4 nm), with an average size of 1.8 nm. As evidenced by... 

Fig. 14. HRTEM images of G4-OH(Pt4o), G4-OH(P1

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