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Nanoparticle Shapes (nanoparticle + shape)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

The Effect of Nanoparticle Shape on the Photocarrier Dynamics and Photovoltaic Device Performance of Poly(3-hexylthiophene):CdSe Nanoparticle Bulk Heterojunction Solar Cells

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2010
Smita Dayal
Abstract The charge separation and transport dynamics in CdSe nanoparticle:poly(3-hexylthiophene) (P3HT) blends are reported as a function of the shape of the CdSe-nanoparticle electron acceptor (dot, rod, and tetrapod). For optimization of organic photovoltaic device performance it is crucial to understand the role of various nanostructures in the generation and transport of charge carriers. The sample processing conditions are carefully controlled to eliminate any processing-related effects on the carrier generation and on device performance with the aim of keeping the conjugated polymer phase constant and only varying the shape of the inorganic nanoparticle acceptor phase. The electrodeless, flash photolysis time-resolved microwave conductivity (FP-TRMC) technique is used and the results are compared to the efficiency of photovoltaic devices that incorporate the same active layer. It is observed that in nanorods and tetrapods blended with P3HT, the high aspect ratios provide a pathway for the electrons to move away from the dissociation site even in the absence of an applied electric field, resulting in enhanced carrier lifetimes that correlate to increased efficiencies in devices. The processing conditions that yield optimum performance in high aspect ratio CdSe nanoparticles blended with P3HT result in poorly performing quantum dot CdSe:P3HT devices, indicating that the latter devices are inherently limited by the absence of the dimensionality that allows for efficient, prolonged charge separation at the polymer:CdSe interface. [source]

Gold Nanorods: From Synthesis and Properties to Biological and Biomedical Applications

ADVANCED MATERIALS, Issue 48 2009
Xiaohua Huang
Abstract Noble metal nanoparticles are capable of confining resonant photons in such a manner as to induce coherent surface plasmon oscillation of their conduction band electrons, a phenomenon leading to two important properties. Firstly, the confinement of the photon to the nanoparticle's dimensions leads to a large increase in its electromagnetic field and consequently great enhancement of all the nanoparticle's radiative properties, such as absorption and scattering. Moreover, by confining the photon's wavelength to the nanoparticle's small dimensions, there exists enhanced imaging resolving powers, which extend well below the diffraction limit, a property of considerable importance in potential device applications. Secondly, the strongly absorbed light by the nanoparticles is followed by a rapid dephasing of the coherent electron motion in tandem with an equally rapid energy transfer to the lattice, a process integral to the technologically relevant photothermal properties of plasmonic nanoparticles. Of all the possible nanoparticle shapes, gold nanorods are especially intriguing as they offer strong plasmonic fields while exhibiting excellent tunability and biocompatibility. We begin this review of gold nanorods by summarizing their radiative and nonradiative properties. Their various synthetic methods are then outlined with an emphasis on the seed-mediated chemical growth. In particular, we describe nanorod spontaneous self-assembly, chemically driven assembly, and polymer-based alignment. The final section details current studies aimed at applications in the biological and biomedical fields. [source]

Optical properties of silver nanoparticles

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2007
A. L. González
Abstract The optical response of embedded silver nanoparticles in terms of their morphology and dielectric environment is studied. Employing a discrete dipole approximation, the extinction efficiencies are calculated for nanoparticles of different shapes and in diverse ambient conditions. A clear dependence of the number, width and position of the surface plasmon resonances (SPRs) is identified for various nanoparticle shapes. For faceted particles, it is found that as the truncation of sides increases, the main resonance is always blue shifted, the SPRs at smaller wavelength are closer to the dominant mode, so, they overlap, and the width of the main resonance increases. The SPRs vanish as the number of faces increases, or when the symmetry of the NP becomes larger. As the vertices become sharper, the number of resonances increases significantly. By changing the refraction index of the environment, the number of SPRs is not affected, although their width and position are modified, so that, for larger the refraction indeces the resonances are red shifted. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Self-Assembled Heavy Lanthanide Orthovanadate Architecture with Controlled Dimensionality and Morphology

CHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2009
Liwu Qian Dr.
Abstract Nearly monodisperse YVO4 architectures with persimmon-like, cube-like and nanoparticle shapes have been synthesised on a large scale by means of a complexing-agent-assisted solution route. The shape and size of these as-prepared architectures can be tuned effectively by controlling the reaction conditions, such as reaction time, the molar ratio of complexing agent/Y3+ and different complexing agents. As a typical morphology, the growth process of monodisperse nanopersimmons has been examined. To extend this method, other LnVO4 (Ln=Ce, Gd, Dy, Er) complexes with well-defined shape and dimensionality can also be achieved by adjusting different rare earth precursors. Further studies reveal that the morphology of the as-synthesised lanthanide orthovanadate is determined mainly by the interaction between rare earth ion and the complexing agent. Ultraviolet (UV) absorption and photoluminescence spectra show that the optical properties of YVO4 nanopersimmons are relevant to their size and shape. This work sheds some light on the design of well-defined complex nanostructures, and explores the potential applications of the as-synthesised architectures. [source]