Surfactant-assisted

Surfactants are probably the materials which most affect the performance of alkali cleaners. Surfactants are complex chemicals which modify the solubility of various materials in, and their surface affinity for, oil and water. The diverse composite which makes up the surface of a metal object must be fully wetted out if the cleaner is to perform properly. Surfactants lower the surface tension to allow wetting out to occur. Oils and greases must either be dissolved off the surface or lifted from it surfactants assist in both areas. 

K. Shen, S. Curran, H. Xu, S. Rogelj, Y. Jiang, J. Dewald, and T. Pietrass, Single-walled carbon nanotube purification, pelletization, and surfactant-assisted dispersion a combined term and resonant micro-Raman spectroscopy study. J. Phys. Chem. B 109, 4455 1463 (2005). 

Ngamsinlapasathian, S. Pavasupree, S. Suzuki, Y. Yoshikawa, S. 2006. Dye-sensitized solar cell made of mesoporous titania by surfactant-assisted templating method. Solar Energy Mater. Solar Cells 90 3187-3192. 

Gong XY, Liu J, Baskaran S, Voise RD, Young JS (2000). Surfactant-assisted processing of carbon nanotube/polymer composites. Chem. Mater. 12 1049-1052. 

Yurekli K, Mitchell CA, Krishnamoorti R (2004) Small-angle neutron scattering from surfactant-assisted aqueous dispersions of carbon nanotubes. J Am Chem Soc 126 9902-9903. 

It is worth reviewing how kinetic and thermodynamic factors generally affect the growth of nanostructures under the influence of surfactants. Though they used CdSe and PbS respectively to study the surfactant-assisted synthesis of nanorods, Peng et al. and Lee et al. have produced a pair of quite complimentary studies. Peng etal. observed that kinetic control via monomer concentration was the principle factor in their growth... 

Liu L, Kou HZ, Mo W, Liu H, Wang Y (2006) Surfactant assisted synthesis of a-Fe203 nanotubes and nanorods with shape dependent magnetic properties. J Phys Chem B 110 15218-15223... 

Sreethawong T, Ngamsinlapasathian S, Suzuki Y, Yoshikawa S (2005) Nanociystalline mesoporus Taz-based photocatalysts prepapred by surfactant-assisted templating sol-gel process photocatalytic H2 evolution. J Mol Catal A Chem 235 1-11... 

A new family of hexagonal mesoporous all-germanium semiconductors was prepared by the surfactant-assisted cross-linking polymerization reaction of Zintl [Geg]" anions (Scheme 1) with Ge(lV) bridges in formamide/ethylenediamine solution (1) [43]. 

Haskouri JE, Cabrera S, Caldes M, Guillem C, Latorre J, Beltran A, Beltran D, Marcos MD, Amoros P (2002) Surfactant-assisted synthesis of the SBA-8 mesoporous silica by using nonrigid commercial alkyltrimethyl ammonium surfactants. Chem Mater 14 2637-2643... 

Fan HY, Leve HY, Scullin C, Gabaldon J, TallantD, Bimge S, Boyle T, Wilson MC, Brinker CJ (2005) Surfactant-assisted synthesis of water-soluble and biocompatible semiconductor quantum dot micelles. Nano Lett 5 645-648... 

Other groups [99, 100] investigated the possibility of carrying out a surfactant-assisted polymerization of VDF in scC02, using diethyl peroxydicarbonate (DEPDC) as a free radical initiator, with the aim of testing several perfluoropolyether compounds synthesized by Solvay Solexis as stabilizers. When ammonium carboxylate derivatives were used, an effective stabilization of the polymer particles was obtained, and the polymer was collected from the reactor with yields of up to 63%. This corresponded to a solid content in the reactor of 220 g I in the form... 

Scheme 2 Schematic of a seed-mediated, surfactant-assisted gold nanorod synthesis. The small black dots represent Ag+ ions, the orange stars are CTAB molecules forming micelles, the yellow circles and green squares are AuCLf and AuC12 , respectively, forming complexes with the CTAB micelles. Freshly-prepared gold nanoparticle seeds are injected into the growth solution in the final step of the nanorod synthesis [166]. (Copyright 2008, American Chemical Society)...

Ning, J., Zhang, J., Pan, Y. and Guo, J., Surfactants assisted processing of carbon nanotube-reinforced Si02 matrix composites , Ceramics International, 2004, 30, 63-67. 

Surfactants assist wetting because they lower surface and interfacial tension. The energy balance that determines spreading is expressed by the spreading coefficient, S, and is illustrated in Figure 6.21. 

Nanotubes and nanowires of II—VI semiconductor compounds such as CdS and CdSe have been obtained by a soft chemical route involving surfactant-assisted synthesis.28,75 For CdSe nanotubes, the metal oxide was reacted with the selenidizing reagent in the presence of a surfactant such as Triton 1G0X. Substantial amounts of nanotubes were obtained by this method (Fig. 25a and b). Annealing of the as-prepared nano-... 

Different approaches have been used to optimize the dispersion of CNTs in the polymeric medium. Composites can be prepared by different techniques including in-situ polymerization, solution mixing, surfactant-assisted processing and melt compounding. 

Ciesla U., Schacht S., Stucky G. D., Unger K. K., and Schiith F., Formation of a porous zirconium oxo phosphate with a high surface area by a surfactant-assisted synthesis,/Ingew. Chem. Int. Ed. Engl. 35 (1996) 541-543. 

Ceria-zirconia nanophases were synthesied by a surfactant-assisted method. The refined structural data concerning the crystallite size, lattice parameters, structural microstrain, cationic occupy number and cationic defect concentration are reported. Zirconium addition into the cubic structure of ceria inhibits crystal sintering but leads to structure distortion. Different CO-metal bonds are formed when CO chemisorbs on Pd-loaded CesZr. x02 catalysts. Catalytic tests reveal that the lower zirconium content benefits the CO oxidation. 

Nanosized ceria-zirconia materials with improved thermal stability can be prepared by using the surfactant-assisted method. Structural refinements confirm that the nanocrystals contain structural microstrain and cationic lattice defects. Zirconium addition to ceria supresses the crystal sintering and imporves the thermal stability but leads to structure distortion. Both catalytic tests and CO-chemisorption show that Pd supported ceria-zirconia nanoparticles are active for CO oxidation. 

Sol-gel processes are also suitable for lanthanide oxide formation, as could be shown by the use of Tb(acac)3 and Dy(OBu- )3 in acetylacetone" . Tb203 crack- and pine-hole-free, dense and smooth microstructured buffer layers were produced on nickel tapes by a reel-to-reel continuous sol-gel process. The authors report that the film properties can be strongly influenced by solution components, temperature, time and atmosphere. Nanocrystalline mesoporous dysprosium oxide Dy203 with narrow monomodal pore size distribution can be approached by a combined sol-gel process with a surfactant-assisted templating technique . The spherical Dy203 nanoparticles were formed with aggregations. 

Mesoporous ceria and ceria-zirconia powders with high surface area have also been prepared using a surfactant-assisted method to prepare catalysts containing Ce02... 

Huang C-C, Hwu JR, Su W-C, Shieh D-B, Tzeng Y, Yeh C-S (2006) Surfactant-assisted hollowing of Cu nanoparticles involving halide-induced corrosion-oxidation processes. Chemistry 12(14) 3805-3810... 

There exist a variety of methods to synthesize quasi-one-dimensional nanostructured materials, which include but not limited to vapor phase growth, template-assisted synthesis, sol-gel deposition, surfactant-assisted growth, sonochemical method, hydrothermal method, and electrochemical deposition [21], Among the various methods, the electrochemical anodization method is one of the simplest and cheapest methods to synthesize ordered quasi-one-dimensional nanostructure. 

J. El Haskouri, S. Cabrera, M. Caldes, C. Guillem, J. Latorre, A. Beltran, D. Beltran, M.D. Marcos, and P. Amoros, Surfactant-assisted Synthesis of the SBA-8 Mesoporous Silica by Using Nonrigid Commercial Alkyltrimethyl Ammonium Surfactants. Chem. Mater., 2002, 14, 2637-2643. 

In a conventional fabric softener formulation the level of the quaternary surfactants is about 5%. Low concentrations of leveling agents can also be present. These materials, often nonionic surfactants, assist in the uniform deposition of the softening quats. In addition, a buffering system is used to ensure an acidic pH. Finally, a solvent, such as isopropanol, present at a level of about 10 to 15%, ensures a viscosity range suitable for easy dispensing from the bottle. 

Jana, N.R. (2003) Nanorod shape separation using surfactant assisted self-assembly. Chem. Commun., 15, 1950-1951. 

Many of the non-silica compositions showed problems with the stability and quality of the structure. Efforts to address these issues have been on going and quite successful in some cases such as all-alumina compositions (see below). Silica-based materials remain dominant as the most versatile and best quality molecular sieves (structure and stability) available by a facile synthesis. These attributes, especially the convenient synthesis made mesoporous silicate attractive for post-synthesis functionalization with other elements as well as organic moieties with active groups/ccnters. Recently the compositional diversity has been extended further to include both silica and organic moieties within the framework. The new class is referred to as periodic mesoporous organosilicas (PMOs). The synthesis involves surfactant-assisted assembly by hydrolysis of organo-silicon compounds. Additional discussion of the PMOs is presented below. 

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