The aim of this article is to provide a comprehensive review of current research activities that center on superparamagnetic colloids. We begin with an overview of synthetic strategies that have been developed for generating both nanoscale and mesoscale superparamagnetic colloids, with a focus on those systems that can be prepared as monodisperse samples and in relatively large quantities. We then discuss a variety of techniques that have been exploited for modifying surface properties, as well as for controlling the assembly and patterning of these magnetically active colloids. Towards the end, we highlight a range of innovative applications enabled by the unique combination of superparamagnetism and colloidal suspension. We conclude this review article with personal remarks and perspectives on the directions toward which future research in this area might be directed.

In this paper, we present a study of a series of carbon-supported Pd−Sn binary alloyed catalysts prepared through a modified Polyol method as anode electrocatalysts for direct ethanol fuel cell reactions in an alkaline medium. Transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and aberration-corrected scanning transmission electron microscopy equipped with electron energy loss spectroscopy were used to characterize the Pd−Sn/C catalysts, where homogeneous Pd−Sn alloys were determined to be present with the surface Sn being partially oxidized. Among various Pd−Sn catalysts, Pd 86 Sn 14 /C catalysts showed much enhanced current densities in cyclic voltammetric and chronoamperometric measurements, compared to commercial Pd/C (Johnson Matthey). The overall rate law of ethanol oxidation reaction for both Pd 86 Sn 14 /C and commercial Pd/C were also determined, which clearly showed that Pd 86 Sn 14 /C was more favorable in high ethanol concentration and/or high pH environment. Density functional theory calculations also confirmed Pd−Sn alloy structures would result in lower reaction energies for the dehydrogenation of ethanol, compared to the pure Pd crystal.

Pt@Fe 2 O 3 core−shell nanoparticles have been made using a sequential synthetic method. Platinum nanoparticles were synthesized via reduction of platinum acetylacetonate in octyl ether, and layers of iron oxide were subsequently deposited on the surface of Pt nanoparticles through thermal decomposition of iron pentacarbonyl. The core−shell nanoparticles were characterized by powder X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoemission spectroscopy. Thickness of the shell can be controlled by changing concentrations of the reactants and the reaction conditions. These Pt@Fe 2 O 3 core−shell nanoparticles could have potential applications in catalysis and as precursors for making property-tunable magnetic nanoparticles, thin films, and nanocomposites.