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Surfactant Molecules (surfactant + molecule)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

NMR studies of surfactants

CONCEPTS IN MAGNETIC RESONANCE, Issue 2 2004
Olle Söderman
Abstract Surfactant molecules are amphipathic and posses complicated solution chemistry and self-assembly properties. In addition to being of enormous practical significance, the physical characterization of surfactant systems presents a rich area of condensed matter physics. This article focuses on the application and interpretation of the commonly used NMR approaches for probing these systems. In particular, the use of NMR relaxation, diffusometry and, more briefly, electrophoretic NMR to determine characteristics such as micellar size and structure, ion-binding and solubilization are considered. The application of these NMR techniques is illustrated by a number of pertinent examples. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson 23A:, 121,135, 2004. [source]

A new method for the aqueous functionalization of superparamagnetic Fe2O3 nanoparticles

CONTRAST MEDIA & MOLECULAR IMAGING, Issue 6 2008
Fernando Herranz
Abstract A new methodology for the synthesis of hydrophilic iron oxide nanoparticles has been developed. This new method is based on the direct chemical modification of the nanoparticles' surfactant molecules. Using this methodology both USPIO (ultrasmall super paramagnetic iron oxide) (hydrodynamic size smaller than 50,nm) and SPIO (super paramagnetic iron oxide) (hydrodynamic size bigger than 50,nm) were obtained. In addition, we also show that it is possible to further functionalize the hydrophilic nanoparticles via covalent chemistry in water. The magnetic properties of these nanoparticles were also studied, showing their potential as MRI contrast agents. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Ordered Mesoporous Silica Derived from Layered Silicates

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2009
Tatsuo Kimura
Abstract Here, the development of ordered mesoporous silica prepared by the reaction of layered silicates with organoammonium surfactants is reviewed. The specific features of mesoporous silica are discussed with relation to the probable formation mechanisms. The recent understanding of the unusual structural changes from the 2D structure to periodic 3D mesostructures is presented. The formation of mesophase silicates from layered silicates with single silicate sheets depends on combined factors including the reactivity of layered silicates, the presence of layered intermediates, the variation of the silicate sheets, and the assemblies of surfactant molecules in the interlayer spaces. FSM-16-type (p6mm) mesoporous silica is formed via layered intermediates composed of fragmented silicate sheets and alkyltrimethylammonium (CnTMA) cations. KSW-2-type (c2mm) mesoporous silica can be prepared through the bending of the individual silicate sheets with intralayer and interlayer condensation. Although the structure of the silicate sheets changes during the reactions with CnTMA cations in a complex manner, the structural units caused by kanemite in the frameworks are retained. Recent development of the structural design in the silicate framework is very important for obtaining KSW-2-based mesoporous silica with molecularly ordered frameworks. The structural units originating from layered silicates are chemically designed and structurally stabilized by direct silylation of as-synthesized KSW-2. Some proposed applications using these mesoporous silica are also summarized with some remarks on the uniqueness of the use of layered silicates by comparison with MCM-type mesoporous silica. [source]

Surfactant-Assisted Preparation of Novel Layered Silver Bromide-Based Inorganic/Organic Nanosheets by Pulsed Laser Ablation in Aqueous Media,

ADVANCED FUNCTIONAL MATERIALS, Issue 17 2007
C. He
Abstract A novel layered AgBr-based inorganic/organic nanocomposite was prepared by pulsed laser ablation (PLA) of Ag in aqueous media in the presence of cetyltrimethylammonium bromide (CTAB), and the formation mechanism of two-dimensional nanosheet was discussed. TEM observations indicate that the obtained AgBr-based inorganic/organic nanocomposite possesses a well-defined two-dimensional shape and that the size of the nanosheet can be changed with the surfactant concentration in the solution. X-ray diffraction (XRD) pattern was composed of a series of peaks that could be indexed to (00l) reflections of a layered structure, and the basal spacing of 20.0,Å indicated that the surfactant was included between the AgBr interlayers in an interdigitated bilayer arrangement. In contrast, a layered inorganic/organic nanocomposite cannot be formed at a CTAB concentration lower than the critical micelle concentration (CMC). Based on our detailed investigation, we proposed the nanocomposite formation process, that is, that negatively charged inorganic AgBr was produced by a strong reaction between the ablated Ag species and the bromide ions, which are concurrently assembling with cationic surfactant molecules controlled by the charge-matching mechanism. [source]