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

Diffusion Limited Photoluminescence Quantum Yields in 1-D Semiconductors: Single-Wall Carbon Nanotubes

Photoluminescence quantum yields and nonradiative decay of the excitonic S-1, state in length fractionated (6,5) single-wall carbon nanotubes (SWNTs) are studied by continuous wave and time-resolved fluorescence spectroscopy. The experimental data are modeled by diffusion limited contact quenching of excitons at stationary quenching sites including tube ends. A combined analysis of the time-resolved photoluminescence decay and the length dependence of photoluminescence quantum yields (PL QYs) from SWNTs in sodium cholate suspensions allows to determine the exciton diffusion coefficient D = 10.7 +/- 0.4 cm(2)s(-1) and lifetime T-pL for long tubes of 20 +/- 1 ps. PL quantum yields Phi(pL) are found to scale with the inverse diffusion coefficient and the square of the mean quenching site distance, here I-d = 120 +/- 25 nm. The results suggest that low PL QYs of SWNTs are due to the combination of high-diffusive exciton mobility with the presence of only a few quenching sites

Synergistic effect of Ag and Pd ions on shape-selective growth of polyhedral Au nanocrystals with high-index facets

10.1021/jp111997sJournal of Physical Chemistry C11593638-364