Transmission electron microscopy surfactants

In 1997, a Chinese research group [78] used the colloidal solution of 70-nm-sized carboxylated latex particles as a subphase and spread mixtures of cationic and other surfactants at the air-solution interface. If the pH was sufficiently low (1.5-3.0), the electrostatic interaction between the polar headgroups of the monolayer and the surface groups of the latex particles was strong enough to attract the latex to the surface. A fairly densely packed array of particles could be obtained if a 2 1 mixture of octadecylamine and stearic acid was spread at the interface. The particle films could be transferred onto solid substrates using the LB technique. The structure was studied using transmission electron microscopy. 

Figure 1.22 This surfactant orientation is supported by the 4-spacing values that were obtained from transmission electron microscopy measurements. In (A) the first suggested orientation the surfactant length is 2.4 nm and in (B) another orientation the surfactant length is 1.85 nm. (Reproduced from ref. 49, with permission.)... 

Figure 15.2 Transmission electron microscopy image of iridium nanoparticles of 1.9 0.7nm in diameter (400 particles counted) prepared in the presence of the surfactant N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl)ammonium chloride. (Reproduced with permission from Ref [13] 2004 Wiley-VCH).

Transmission electron microscopy (TEM) has been an underutilized yet valuable too in particle size characterization of MC particles in LB films. Monolayer films of trioctylphosphine oxide-capped CdSe (18), spread as a monolayer on an aqueous subphase, were transferred to a TEM grid. A close-packed hexagonal arrangement of 5.3-nm (cr —4%) crystallites was found. TEM images were also obtained for HMP-stabilized CdS incorporated in BeH/octadecylamine films (79) and for CdS formed under an amine-based surfactant monolayer and transferred to a TEM grid (14). In one study, direct viewing of CdS and CdSe particles made from Cd2+-FA films on TEM grids was not possible due to poor phase contrast between the particles and the film (30). Diffraction patterns were observed, however, that were consistent with crystalline (3-CdS or CdSe. Approximately spherical particles of CdSe could... 

Powdered, particulate MCM-41 molecular sieves (Si/Al = 37) with varied pore diameters (1.80, 2.18, 2.54 and 3.04 nm) were synthesized following the conventional procedure using sodium silicate, sodium aluminate and C TMAB (n = 12, 14, 16 and 18) as the source materials for Si, A1 and quaternary ammonium surfactants, respectively [13]. Each sample was subjected to calcination in air at 560 °C for 6 h to remove the organic templates. The structure of the synthesized material was confirmed by powder X-ray diffraction (XRD) and by scanning/transmission electron microscopy. Their average pore sizes were deduced from the adsorption curve of the N2 adsorption-desorption isotherm obtained at 77 K by means of the BJH method (Table 1). 

Transmission Electron Microscopy The primary site of surfactant activity appears to be the cell membrane (25, 32). Other effects have been reported such as the denaturation of proteins, inactivation of enzymes and inhibition of mitosis. 

The dispersions were obtained by emulsification via ultrasonication of a toluene solution of the unsaturated homopolymer in an aqueous surfactant solution. This was followed by exhaustive hydrogenation with Wilkinson s catalyst at 60°C and 80 bar H2 to produce a dispersion with an average particle size of 35 nm (dynamic light scattering and transmission electron microscopy analyses). The same a,co-diene was used as comonomer in the ADMET polymerization of a phosphorus-based monomer, also containing two 10-undecenoic acid moieties... 

The main properties of these materials were characterized by means of x-ray diffraction (Siemens D-500 with A.Cu radiation of 1.54 A), Transmission Electron Microscopy (Phillips-CM200) and N2 adsorption (Micromeritics ASAP-2000), 29Si-NMR(MAS). As the textural properties of the catalytic materials, for example the inner pore structure, is a key parameter for their performance, in the present work the N2 adsorption isotherms of the calcined mesoporous Si02-based solids were determined. The solids were prepared using different CTAB surfactant and some co-surfactants based in the light alcohols, i.e. MeOH, EtOH and PrOH. Thus, Figure 15.5 shows the isotherms of the mesoporous solids prepared with MeOH (co-surfactant). In all... 

Egelhaaf, S.U., Schurtenberger, P., and Muller, M. (2000). New controlled environment vitrification system for cryo-transmission electron microscopy design and application to surfactant solutions. J. Microsc. 200, 128-139. 

The mesoporosity of these materials has been established by BET measurements and gas adsorption experiments. As the chain length of the surfactant was increased from Cs to G 5, the amount of adsorbed benzene was increased, indicating that there was a relationship between the size of the surfactant and the amount of gas adsorbent taken up by the MCM-41 material. In terms of a comparison to zeolite materials, experiments were done at 60 torr pressure and at 25< C. llie US-Y zeolite sample had an uptake that was about 4 times less than that of MCM-41. The above mentioned MCM-41 materials all show pore size distributions with broad bands centered around 40 A. The pore size distribution measurements are a true indication of the size of the pores and can be used to verify the existence of mesopores. Further evidence of mesoporosity comes from X-ray powder difraction experiments which were done to determine the crystallinity of these materials. The position of the (100) reflection was found to correlate with the amount of uptake by the different materials, or in therwords, with the mesoporosity of these systems. Pores of the MCM-41 materials were shown to form in a hexagonal shape by using high resolution transmission electron microscopy data. 10... 

Drugs. Farkas et al. " have used a combination of polarizing microscopy, SANS, and transmission electron microscopy to characterize the liquid crystalline phases produced by the non-ionic surfactants, Syn-peronic A7 (PEG7-C13.15), alone and in the presence of two chlorhexidine species, chlorhexidine base, and its diacetate salt. Polarizing microscopy and electron microscopy were used to examine the nature of the liquid crystals formed, while SANS was used to determine their interlayer spacing. For the SANS studies. 

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