Palladium Pd nanoparticles

A second metallic contaminant of interest is Cr. Remediation of Cr-contaminated soils is centered around the reduction of Cr(VI), a more toxic and soluble form, to Cr(III), which is considerably less soluble and which readily precipitates out of solution. A number of different nanoparticles have been shown to possess this capability, including ferritin protein cages containing fenihydrite (Fe(O)OH), palladium (Pd) nanoparticles, and carboxymethyl cellulose (CMC)-stabilized Fe ) (87, 89, 93). In both the ferritin cages and the CMC-Fe p), the active species was a form of Fe, either Fe(0) in the case of the CMC-Fe p), or Fe(II) in the case of the ferritin cages. The reaction known to reduce Cr(VI) utilizing Fe(II) is shown in Equation (20.2). 

Poly(alkyl metharylate)s belong to the group of weak reducing agents. Yin and Horiuchi have applied the reducing power of some block copolymers to produce and assemble palladium (Pd) nanoparticles in two-dimensional (2D) periodic arrays in... 

Ni/Pd nanoparticles and similar sized Pd nanoparticles for the following Sonogashira coupling reactions using equal amount of palladium in the reaction mixtures. As expected, the Ni/Pd... 

Several types of palladium-based hydrogen sensors have been reported in the literature. The most notable ones are based on Pd thin-film resistors, FETs, Pd nanowires, Pd nanoparticle networks, Pd nanoclusters, and Pd nanotubes as shown in Table 15.2. 

Addition of pvp significantly extends catalyst lifetime (Scheme 2). This is a well-known protocol whereby the Pd nanoparticles are wrapped up in the polymer chains, which prevents their aggregation into catalytically inactive palladium black. 

The same authors also reported the dispersion of palladium nanoparticles in a water/AOT/n-hexane microemulsion by hydrogen gas reduction of PdClJ and its efficiency for hydrogenation of alkenes in organic solvents [79]. UV-visible spectroscopy and TEM analysis revealed the formation of Pd nanoparticles with diameters in the range of 4 to 10 nm. Three olefins (1-phenyl-l-cyclohexene, methyl trans-cinnamate, and trans-stilbene) were used as substrates for the catalytic hydrogenation experiments under 1 atm of H2 (Table 9.12). All of the Start-... 

Reetz,M.T. and Westermann, E., Phosphane-free palladium-catalyzed coupling reactions thedecisive role of Pd nanoparticles, Angew. Chem. Int. Ed., 39, 165, 2000. 

Pt(S2CNMe(Hex))2] and [Pd(S2CNMe(Hex))2] have been synthesized and used as precursors to grow the first TOPO-capped PtS and PdS nanoparticles and thin films of PtS and PdS by the metallo-organic chemical vapor deposition (MOCVD) method [204]. Platinum and palladium chalcogenides find applications in catalysis [205-210] and materials science [211,212]. The synthesis of thiocarbamato complexes of platinum and palladium from reaction of an aqueous solution of ammonium dithiocarbamate with the platinum or palladium salt has been reported by Nakamoto et al. [213]. However... 

Catalytic isomerization of 3,4-dichlorobutene catalyzed by Pd nanoparticles of Pd-PPX film was studied at 100°C [91], The ratio of trans- to cis-1, 4-dichlorobutene for the reaction in this system with low concentration of Pd nanoparticles is 10, and coincides with the ratio obtained for the reaction with the usual palladium catalyst. But the selectivity of the reaction decreases with increasing of Pd concentration the yield of trans-l, 4-dichlorobutene decreases while the yield of cA-1,4-dichlorobutene remains constant. This result shows that the change in the catalytic properties of the composite is determined by interactions between nanoparticles rather than by the size effects. At catalytic reaction catalyzed by Pd-PPX films, where the volume content of Pd nanoparticles is close to percolation threshold, the trans-to-cis ratio for produced isomers of 1,4-dichlorobutene is 2.9 that is close to equilibrium value of this ratio. 

Using this approach, we have examined [64] the properties and concentration of electroactive (being able to take part in the electrode processes) Pd nanoparticles formed by the different methods (i) combined pyrolysis of palladium chloride and titanium resinate... 

Some other recent examples are the use of palladium nanoparticles entrapped in aluminum hydroxide [181], resin-dispersed Pd nanoparticles [182], and poly (ethylene glycol)-stabilized palladium nanoparticles in scC02 [183]. Although in some cases the activities for activated alcohols obtained with these Pd-nanoparti-cles are impressive, the conversion of aliphatic alcohols is still rather slow. 

C4)4N]Br Supported Pd nanoparticles Bu3N 130 °C. Phosphine-free arylation of styrene with arylchlorides palladium immobilised on layered double hydroxide microwave irradiation leads to significant rate acceleration product isolated by distillation. [81]... 

C imHPFe] Silica-supported Pd nanoparticles Et3N 80 °C. Phosphine-free arylation of acrylates with aryliodide PdCl2(NH3)2 as catalyst precursor palladium leaches from the support into the ionic liquid phase product extracted with tert-butyl methyl ether. [85]... 

Other examples include palladium species immobilised on other solid supports181,821 as well as isolated (naked) Pd-nanoparticles[31 831... 

In an ESI-MS monitoring study of the Suzuki-Miyaura reaction using a dichloro-bis(aminophosphine) palladium precatalyst, binuclear Pd complexes were detected after the reaction went to completion, indicating a catalyst sink or a resting state. Addition of starting reagents resumes the reaction, suggesting the active role of the binuclear complex as a reservoir of mononuclear active catalyst. Other interpretations propose the involvement of Pd nanoparticles in which binuclear Pd complexes act as a precursor or perhaps even the active catalyst, but the last possibility seems unlikely. A mechanism for this transformation was proposed based on the intercepted species (Scheme 10) [62]. 

Synthesis of alloyed silver-palladium bimetallic nanoparticles was achieved by /-irradiation of aqueous solutions containing a mixture of Ag and Pd metal ions using different Ag/Pd ratios. The synthesis of alloys implies the simultaneous radio-induced reduction of silver and palladium ions. The nanoparticles were characterized by UV-visible spectroscopy, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The Ag-Pd nanoparticles display a face-centered cubic (fee) crystalline structure. The lattice parameter was measured for several Ag/Pd ratios and was found to closely follow Vegard s law, which indicates the formation of homogeneous alloys. In order to avoid the simultaneous reduction of silver and palladium ions which leads to alloyed bimetallic nanoparticles. 

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