Shape-dependent plasmon resonances of gold nanoparticles

Localized surface plasmon resonances in noble metal nanoparticles cause enhanced optical absorption and scattering that is tunable through the visible and near-infrared. Furthermore, these resonances create large local electric field enhancements at the nanoparticle surfaces, essentially focussing light at the nanometer scale. These properties suggest a range of applications, including biomedical imaging, therapeutics, and molecular sensing. Here we review some recent advances regarding shape-dependent optical properties of two specific nanoparticle geometries: gold nanorods and branched gold nanoparticles

Anisotropic nanomaterials: structure, growth, assembly, and functions

Comprehensive knowledge over the shape of nanomaterials is a critical factor in designing devices with desired functions. Due to this reason, systematic efforts have been made to synthesize materials of diverse shape in the nanoscale regime. Anisotropic nanomaterials are a class of materials in which their properties are direction-dependent and more than one structural parameter is needed to describe them. Their unique and fine-tuned physical and chemical properties make them ideal candidates for devising new applications. In addition, the assembly of ordered one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) arrays of anisotropic nanoparticles brings novel properties into the resulting system, which would be entirely different from the properties of individual nanoparticles. This review presents an overview of current research in the area of anisotropic nanomaterials in general and noble metal nanoparticles in particular. We begin with an introduction to the advancements in this area followed by general aspects of the growth of anisotropic nanoparticles. Then we describe several important synthetic protocols for making anisotropic nanomaterials, followed by a summary of their assemblies, and conclude with major applications

Ruthenium Phosphide Synthesis and Electroactivity toward Oxygen Reduction in Acid Solutions

Ruthenium phosphides are known to be highly stable and conductive materials. A new process was developed to prepare ruthenium phosphide catalysts for oxygen reduction in acid solutions. Several synthesis methods have been applied to form pure RuP and Ru₂P as well as mixed phases of Ru and Ru_<i>x</i>P (<i>x</i> ≥ 1). These methods utilize high-temperature solid-state synthesis and reaction under autogenic pressure at elevated temperature (RAPET). On the basis of rotating ring–disk electrode (RRDE) experiments, oxygen reduction activity was observed on all Ru_<i>x</i>P materials. Characteristic kinetic parameters show specific exchange current densities in the range of 0.4–1.4 mA mg^–1, Tafel slopes of 129–135 mV dec^–1, and %H₂O₂ of 3–11% of the total current. Complementary XPS and Raman spectral analysis reveals a highly oxidized surface with significant presence of PO₄^3– and RuO₂ species. To the best of our knowledge, this is the first report identifying oxygen reduction activity on Ru_<i>x</i>P