The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

Chemistry and properties of nanocrystals of different shapes.

Reduced transition metal colloids: a novel family of reusable catalysts

Capping agents are frequently used in colloidal synthesis to inhibit nanoparticle overgrowth and aggregation as well as to control the structural characteristics of the resulted nanoparticles in a precise manner. Study of the effect of the residual capping agents on particle surface has unveiled various adverse and favorable behaviors in catalytic applications. In essence, while the capping agents usually act as a physical barrier to restrict the free access of reactants to catalytic nanoparticles, they can also be utilized to promote catalytic performance of nanocrystals. Due to the complexity of these effects, a general survey of capping agents in nanocatalysis is therefore necessary. This short review starts from a brief introduction of common capping agents in nanoparticle synthesis and their adverse impact on heterogeneous catalysis. Next, representative progresses in capping agent removal and surfactant-free synthesis for obtaining surface-clean nanocatalysts are summarized. Lastly, we discuss the r...

Removal and Utilization of Capping Agents in Nanocatalysis

Resolving heterogeneity problems and impurity artifacts in operationally homogeneous transition metal catalysts.

In the absence of any usual protective agent, stable platinum, rhodium, and ruthenium metal nanoclusters with small particle size in organic media are effectively prepared by heating corresponding ...

Preparation of Tractable Platinum, Rhodium, and Ruthenium Nanoclusters with Small Particle Size in Organic Media

Living colloidal palladium in nonaqueous solvents. Formation, stability, and film-forming properties. Clustering of metal atoms in organic media. 14

Colloidal metal particles dispersed in monomeric and polymeric styrene and methyl methacrylate

Palladium particles of nanometric dimensions were synthesized by the chemical liquid deposition method in which the Pd atoms were co-deposited at 77 K with 2-propanol, acetone, and tetrahydrofurane vapor to obtain colloidal dispersions. The colloidal dispersions were characterized by UV–visible spectrophotometry, transmission electron microscopy (TEM) and high-resolution TEM (HRTEM). The palladium colloids synthesized by use of these solvents are very stable. A strong absorption band in the UV region suggests that quantum confinement occurs in the nanoparticles obtained by this procedure. Studies of TEM micrographs reveal average size distributions between 1 and 5 nm for all Pd colloids. Whereas particle sizes in Pd–2-propanol colloids are not very sensitive to concentration change, the particle-size average in Pd–acetone and Pd–THF increases by 0.5 nm when the concentration increases from 10−3 to 10−2 mol l−1. The HRTEM results show the high crystallinity of Pd nanoparticles and three low-energy structure shapes were found: cuboctahedron, tetrakaidecahedron, and icosahedron.

Palladium nanoparticles from solvated atoms—stability and HRTEM characterization

Methyl methacrylate colloids were obtained by codeposition at 77K of the monomer with several metals such as: Au, Pd, Cu, Ge, Ga, In, Sn, Sb and Bi. The colloids were polymerized with different amounts of initiator (AIBN) at 60°C and a wide range of viscosity average molecular weights (Mv; 104–105) were obtained depending upon the metal used. The metal colloid concentrations are reported. The thermal stability and metal composition are also described. The polymers are stable even at 350°C and the metal content is 0.7 to 3.1%.

Galo Cárdenas-Triviño

Papers

Living colloidal palladium in nonaqueous solvents. Formation, stability, and film-forming properties. Clustering of metal atoms in organic media. 14

Colloidal metal particles dispersed in monomeric and polymeric styrene and methyl methacrylate

Palladium nanoparticles from solvated atoms—stability and HRTEM characterization

Synthesis and molecular weights of metal poly(methyl methacrylates)

Polystyrene metal polymers