Colloidal Nanoparticles (colloidal + nanoparticle)

Distribution by Scientific Domains

Selected Abstracts

Oxygen-Generating Gel Systems Induced by Visible Light

Kosuke Okeyoshi
Abstract Toward complete artificial photosynthesis systems to generate hydrogen and oxygen using visible light and water, oxygen-generating gel systems are designed and fabricated using the electrostatic interactions of ionic functional groups and steric effects of a polymer network. By using a graft polymer chain with Ru(bpy)32+ units as sensitizers to closely arrange RuO2 nanoparticles as catalyst, the functional groups transmit multiple electrons cooperatively to generate oxygen. In this paper, a novel strategy is shown to design a hierarchical network structure using colloidal nanoparticles and macromonomers. Such a soft material to oxidize water inside a hydrogel is useful as a solar-energy converting system. [source]

Nondestructive characterization of ferrofluids by wide-angle synchrotron light diffraction: crystalline structure and size distribution of colloidal nanoparticles

Alexei Vorobiev
The combination of magnetic and nonmagnetic interactions between the colloidal particles in ferrofluids results in various local inter-particle correlations that, in turn, change the macroscopic properties of the whole system. Therefore, characterization of the particle ensemble is a crucial point, allowing optimization of a ferrofluid for a particular application. Here it is shown how the crystal structure of the particles can be easily obtained in a fast synchrotron light diffraction experiment without any special treatment of the ferrofluid sample. Moreover, from the same diffraction patterns, such important parameters as particle mean size and dispersion are retrieved; these are compared with the corresponding parameters obtained from electron microscopy data. A particular problem of magnetite,maghemite transformation in nanoparticles stabilized by the surfactant shell is pointed out. [source]

Conversion of silver nanoprisms into colloidal nanoparticles induced by femtosecond laser pulses

Qitao Zhao
Abstract Shape transformation of silver nanoprisms in aqueous solution was studied using femtosecond laser pulses. Irradiation of a pulsed Ti:Sapphire laser at 800 nm caused the shape change of the nanoprisms from triangle into sphere, forming a stable colloid of a narrow size distribution with the particle diameters having ,10 nm. The effects of laser fluence on fragmentation and conversion were investigated using UV-vis absorption spectroscopy and transmission electron microscopy. The mechanism of laser-induced colloid formation is discussed. ( 2004 by HMS Consultants. Inc. Published exclusively by WILEY-VCH Verlag GmbH & Co.KGaA) [source]

Study of Langmuir,Blodgett phospholipidic films deposited on surface enhanced Raman scattering active gold nanoparticle monolayers

BIOPOLYMERS, Issue 4-5 2002
S. Bernard
Abstract Surface enhanced Raman scattering (SERS) was used to study phospholipid monolayers transferred by the Langmuir,Blodgett (LB) technique to SERS active substrates. These substrates, which were constituted of gold colloidal nanoparticles bound to polysilane films grafted onto glass plates, showed a uniform and homogeneous layer with strong interacting particles as revealed from UV,visible extinction spectra and atomic force microscopy images. Laser excitation at 632.8 nm within the red part of the localized surface plasmon resonance leads to intense and reproducible SERS spectra of trans -1,2-bis(4-pyridyl)ethylene (BPE). From SERS measurements at different pHs it was possible to determine the apparent pKa of BPE adsorbed on gold-coated silanized substrates in the absence and presence of one LB monomolecular layer of phospholipids. These SERS titrations allowed the estimation of the pH at the metal,LB film interface. 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 67: 314,318, 2002 [source]

Ion and pH Sensing with Colloidal Nanoparticles: Influence of Surface Charge on Sensing and Colloidal Properties

CHEMPHYSCHEM, Issue 3 2010
Feng Zhang Dr.
Abstract Ion sensors based on colloidal nanoparticles (NPs), either as actively ion-sensing NPs or as nanoscale carrier systems for organic ion-sensing fluorescent chelators typically require a charged surface in order to be colloidally stable. We demonstrate that this surface charge significantly impacts the ion binding and affects the read-out. Sensor read-out should be thus not determined by the bulk ion concentration, but by the local ion concentration in the nano-environment of the NP surface. We present a conclusive model corroborated by experimental data that reproduces the strong distance-dependence of the effect. The experimental data are based on the capability of tuning the distance of a pH-sensitive fluorophore to the surface of NPs in the nanometer (nm) range. This in turn allows for modification of the effective acid dissociation constant value (its logarithmic form, pKa) of analyte-sensitive fluorophores by tuning their distance to the underlying colloidal NPs. [source]