This Account reports the synthesis and characterization of dendrimer-encapsulated metal nanoparticles and their applications to catalysis. These materials are prepared by sequestering metal ions within dendrimers followed by chemical reduction to yield the corresponding zerovalent metal nanoparticle. The size of such particles depends on the number of metal ions initially loaded into the dendrimer. Intradendrimer hydrogenation and carbon-carbon coupling reactions in water, organic solvents, biphasic fluorous/ organic solvents, and supercritical CO 2 are also described.

Pulsed electron-electron double resonance techniques such as the four-pulse double electron-electron resonance experiment measure a dipolar evolution function of the sample. For a sample consisting of spin-carrying nanoobjects, this function is the product of a form factor, corresponding to the internal structure of the nanoobject, and a background factor, corresponding to the distribution of nanoobjects in space. The form factor contains information on the spin-to-spin distance distribution within the nanoobject and on the average number of spins per nanoobject, while the background factor depends on constraints, such as a confinement of the nanoobjects to a two-dimensional layer. Separation of the dipolar evolution function into these two contributions and extraction of the spinto-spin distance distribution require numerically stable mathematical algorithms that can handle data for different classes of samples, e.g., spin-labelled biomacromolecules and synthetic materials. Furthermore, experimental imperfections such as the limited excitation bandwidth of microwave pulses need to be considered. The software package DeerAnalysis2006 provides access to a comprehensive set of tools for such data analysis within a common user interface. This interface allows for several tests of the reliability and precision of the extracted information. User-supplied models for the spinto-spin distance distribution within a certain class of nanoobjects can be added to an existing library and be fitted with a universal algorithm.

Non‐thermal atmospheric pressure plasma has attracted considerable attention in recent years due to its potential for biomedical applications. Determining the mechanism of the formation of reactive species in liquid treated with plasma is thus of paramount importance for both fundamental and applied research. In this work, the origin of reactive species in plasma‐treated aqueous solutions was investigated by using spin‐trapping, hydrogen and oxygen isotopic labelling and electron paramagnetic resonance (EPR) spectroscopy. The species originating from molecules in the liquid phase and those introduced with the feed gas were differentiated by EPR and 1H NMR analysis of liquid samples. The effects of water vapour and oxygen admixtures in the feed gas were investigated. All the reactive species detected in the liquid samples were shown to be formed largely in the plasma gas phase. It is suggested that hydrogen peroxide (determined by UV/Vis analysis) is formed primarily in the plasma tube, whereas the radical species ⋅OOH, ⋅OH and ⋅H are proposed to originate from the region between the plasma nozzle and the liquid sample.

Self‐assembled monolayers (SAMs) are excellent models for studying interfacial reactions. Here monolayer chemistry is reviewed, focusing on the features that have no analogues in solution chemistry. The growth of surface‐attached polymers, intrafilm reactions, chemistry, photochemistry and reactivity issues are all discussed.

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Ligand exchange reaction is a very important and useful tool for preparing functionalised metal nanoparticles. Understanding the mechanism of this process is essential for rational design of nanoparticle-based devices. However the underlying chemistry was found to be very rich. In this article, we summarise the research efforts of several groups to unravel the mechanisms of ligand exchange reaction, and discuss implications for future developments.

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Electron paramagnetic resonance (EPR) spectroscopy and spin trapping were used to explore the mechanism of alcohol oxidation over gold catalysts. Reaction of secondary alcohols with supported and unsupported gold catalysts (e.g., Au/CeO(2), polymer-incarcerated Au nanoparticles, PPh(3)-protected Au nanoparticles) in the presence of spin traps led to the formation of a hydrogen spin adduct. Using isotope labeling, we confirmed that the hydrogen in the spin adduct originates from the cleavage of the C-H bond in the alcohol molecule. The formation of the hydrogen spin adduct most likely results from the abstraction of hydrogen from the Au surface by a spin trap. These results thus strongly suggest intermediate formation of Au-H species during alcohol oxidation. The role of oxygen in this mechanism is to restore the catalytic activity rather than oxidize alcohol. This was further confirmed by carrying out gold-catalyzed alcohol oxidation in the absence of oxygen, with nitroxides as hydrogen abstractors. The support (e.g., metal oxides) can activate oxygen and act as an H abstractor from the gold surface and hence lead to a faster recovery of the activity. Peroxyl radicals were also observed during alcohol oxidation, consistent with a free-radical autoxidation mechanism. However, this mechanism is likely to be a minor side reaction, which does not lead to the formation of an appreciable amount of oxidation products.