Nanoparticles preparation

Rao, J. P. Geckeler, K. E. (2011). Polymer nanoparticles Preparation techniques and size-control parameters. Fh ogress in Polymer Science, Vol. 36, 7, (July 2011), pp. (887-913), ISSN 0079-6700... 

Similarly to Iridium and rhodium nanoparticle studies, Dupont describes benzene hydrogenation in various media by platinum(O) nanoparticles prepared by simple decomposition of Pt2(dba)3 in BMI PFe at 75 °C and under 4 bar H2 [68]. The Pt nanoparticles were isolated by centrifugation and char-... 

The bottom up methods of wet chemical nanoparticle preparation rely basically on the following methods ... 

Bimetallic Ag-core/Au-shell nanoparticles, prepared by a NaBH4 reduction method, were directly confirmed by HRTEM [124],... 

Figure 6. TEM images obtained at an accelerating voltage of 200 kV of Pt-core/Ru-shell nanoparticles prepared by sequential soni-cation of 1 mM Pt(ll) and 1 mM Ru(lll) ions at 213 kHz. Two representative particles are shown at different magnification. (Reprinted from Ref [141], 2006, with permission from American Chemical Society.)...

AuPt bimetallic nanoparticles, prepared by polyol method and stabilized with PVP, were studied by UV-Vis spectra [122]. In this preparation the reaction temperature... 

The XRD and TEM showed that the bimetallic nanoparticles with Ag-core/Rh-shell structure spontaneously form by the physical mixture of Ag and Rh nanoparticles. Luo et al. [168] carried out structure characterization of carbon-supported Au/Pt catalysts with different bimetallic compositions by XRD and direct current plasma-atomic emission spectroscopy. The bimetallic nanoparticles were alloy. Au-core/Pd-shell structure of bimetallic nanoparticles, prepared by co-reduction of Au(III) and Pd(II) precursors in toluene, were well supported by XRD data [119]. Pt/Cu bimetallic nanoparticles can be prepared by the co-reduction of H2PtClg and CuCl2 with hydrazine in w/o microemulsions of water/CTAB/ isooctane/n-butanol [112]. XRD results showed that there is only one peak in the pattern of bimetallic nanoparticles, corresponding to the (111) plane of the PtCu3 bulk alloy. 

Solla-Gullon et al. [Ill] carried out FT-IRs experiments of adsorbed CO for PdPt nanoparticles prepared by reduction of H2PtCl6 and K2PdCl4 with hydrazine in a w/o microemulsion of water/poly(ethyleneglycol) dodecyl ether (BRIJ(R)30)/ -heptane. The experiments gave information on the relative amount of linear- and bridge-bonded CO, which is known to depend on the surface distribution of the two elements. 

Figure 17. The magnetization hysteresis curve at 300 K of SmCos nanoparticles prepared from SnCF and Cofacacfs in the presence of PVP at 573 K. (Reprinted from Ref [235], 2006, with permission from Wiley-VCH.)...

Another thin film technology based nanoparticle preparation route is gas condensation, in which metal vapor is cooled to high levels of supersaturation in an inert gas ambient [126-128]. In these experiments particles necessarily nucleate in the gas phase. In a promising extension of this technique a pulsed laser beam replaces the conventionally used thermal metal vapor source [120,121,129-134]. 

Figure 9. TEM micrographs of nanocrystal superlattices of Au nanoparticles prepared by the inverse micelle method and digestive ripening, (a) and (b) low-magnification images (c (f) regularly-shaped nanocrystal superlattices (g) magnified image of a superlattice edge. Note the perfect arrangement of the Au nanoparticles. (Reprinted with permission from Ref. [30], 2003, American Chemical Society.)...

There are different ways in which the nanoparticles prepared by ME-technique can be used in catalysis. The use of ME per se [16,17] implies the addition of extra components to the catalytic reaction mixture (hydrocarbon, water, surfactant, excess of a metal reducing agent). This leads to a considerable increase of the reaction volume, and a catal5fiic reaction may be affected by the presence of ME via the medium and solubilization effects. The complex composition of ME does not allow performing solvent-free reactions. 

Figure 5. TEM image of the carbon-supported Pd nanoparticles prepared via a typical synthetic procedure.

Figure 4. TEM photograph of silver nanoparticles prepared by the thermolysis of Ci3H27C02Ag (reprinted from Ref. [18], 2006, with permission from Elsevier).

For transition and precious metals, thiols have been successfully employed as the stabilizing reagent (capping reagent) of metal nanoparticles [6]. In such cases, various functionalities can be added to the particles and the obtained nanoparticles may be very unique. It is well known that thiols provide good self-assembled monolayers (SAM) on various metal surfaces. When this SAM technique is applied to the nanoparticle preparation, nanoparticles can be covered constantly by functionalized moieties, which are connected to the terminal of thiol compounds. 

Thomas and his colleagues in Cambridge have pioneered the development of nanoparticles prepared from cluster compounds and supported in meso-porous silica.31 Highly active and effective catalysts have been developed for a number of hydrogenation reactions. The significant factors controlling... 

The drawbacks of the W/O emulsification method include the use of large amounts of oils as the external phase, which must be removed by washing with organic solvents, heat stability problems of drugs, possible interactions of the cross-linking agent with the drug, and, as with all nanoparticles prepared by emulsification techniques, a fairly broad particle size distribution. 

Finally, we can also find in the literature arrangements where the working electrode is also the emitter part of the transducer, normally named as sonotrode [22] or sonoelectrode [41]. Some authors have used only the main emitter surface as electrode [42], see Fig. 4.2b, and other authors have used the fully surface tip as working electrode [43], see Fig. 4.2c. In theory, this arrangement assures that all the specific effects derived from the ultrasound field propagation are directly focused on the surface electrode. Not only the shorted-lived bubbles non-uniformly collapse on the electrode surface but also the electrode surface itself oscillates. This provides additional effects which have been specifically used in the nanoparticles preparation. 

Fig. 6.2 Absorption spectrum of silver nanoparticles prepared from an aqueous solution (70 ml) of AgN03 (0.2 mM) containing polyethylene glycol (0.1 wt%) and ethylene glycol (0.1 M)...

Fig. 6.10 UV-vis absorption spectra of gold - ruthenium bimetallic nanoparticles prepared by the sonochemical co-reduction method using (a) 1 1 and (b) 1 5 gold - ruthenium compositions, respectively [45]...

Fig. 8.4 SEM image of the ZnO nanoparticles prepared by ultrasound in the presence of an ionic liquid [16]...

Stengl V, Bakardjieva S, Marikova M, Bezdicka P, Subrt J (2003) Magnesium oxide nanoparticles prepared by ultrasound enhanced hydrolysis of Mg-alkoxides. Mater Lett 57 3998 1003... 

Wan, J., Cai, W., Meng, X. and Liu, E. (2007) Monodisperse water-soluble magnetite nanoparticles prepared by polyol process for high-performance magnetic resonance imaging. Chemical Communications, (47), 5004—5006. 

The formation of ethylcellulose nanoemulsions by a low-energy method for nanoparticle preparation was reported recently. The nanoemulsions were obtained in a water-polyoxyethylene 4 sorbitan monolaurate-ethylcellulose solution system by the PIC method at 25 °C [54]. The solvent chosen for the preparation of the ethylcellulose solution was ethyl acetate, which is classed as a solvent with low toxic potential (Class 3) by ICH Guidelines [78]. Oil/water (O/W) nanoemulsions were formed at oil/ surfactant (O/S) ratios between 30 70 and 70 30 and water contents above 40 wt% (Figure 6.1). Compared with other nanoemulsions prepared by the same method, the O/S ratios at which they are formed are high, that is, the amount of surfactant needed for nanoemulsion preparation is rather low [14]. For further studies, compositions with volatile organic compound (VOC) contents below 7 wt% and surfactant concentrations between 3 and 5 wt% were chosen, that is, nanoemulsions with a constant water content of 90% and O/S ratios from 50 50 to 70 30. 

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