Micelles system

In both cases, the Au nanoparticles behave as molecular crystals in respect that they can be dissolved, precipitated, and redispersed in solvents without change in properties. The first method is based on a reduction process carried out in an inverse micelle system. The second synthetic route involves vaporization of a metal under vacuum and co-deposition of the atoms with the vapors of a solvent on the walls of a reactor cooled to liquid nitrogen temperature (77 K). Nucleation and growth of the nanoparticles take place during the warm-up stage. This procedure is known as the solvated metal atom dispersion (SMAD) method. 

Figure 6. TEM micrographs representing the transformations of (a) polydispersed nanoparticles upon (b) alkanethiol addition at room temperature and (c) after digestive ripening (inverse micelle system). (Reprinted with permission from Ref [49], 2002 American Chemical Society.)...

Figure 20. A TEM snapshot of large polyhedral particles prepared by the inverse micelle system being broken by the ligand addition. The ligand featured here is decanethiol. (Reprinted with permission from Ref. [32], 2005, American Chemical Society.)...

Fig. 2.8.10 (a) Grey scale map of shear taken across gap of 7° cone-and-plate device, for the semi-dilute wormlike micelle system 60 mM cetylpyridinium chloride—100 mM sodium... 

Fig. 2.8.11 Schematic constitutive relationship (shear stress versus shear rate) for a wormlike micelle system exhibiting constitutive instability. When the average shear rate exceeds yc the fluid subdivides into two coexisting shear bands residing on stable branches of the constitutive relationship.

LJ Naylor, V Bakatselou, JB Dressman. Comparison of the mechanism of dissolution of hydrocortisone in simple and mixed micelle systems. Pharm Res 10 865-870, 1993. 

Kitchens, C.L., McLeod, M.C. and Roberts, C.B. (2003) Solvent effects on the growth and steric stabilization of copper metallic nanoparticles in AOT reverse micelle systems. Journal of Physical Chemistry B, 107 (41), 11331-11338. 

Sethuraman VA, Lee MC, Bae YH (2008) A biodegradable pH-sensitive micelle system for targeting acidic solid tumors. Pharm Res 25 657-666... 

Tab. 5.1 Summary of peptide structures determined in micelle systems...

M. R. Eftink and C. A. Ghiron, Fluorescence quenching of indole and model micelle systems, J. Phys. Chem. 80, 486 193 (1976). 

R. W. Redmond, Enhancement of the sensitivity of radiative and nonradiative detection techniques in the study of photosensitization by water soluble sensitizers using a reverse micelle system, Photochem. Photobiol. 54. 547-556(1991). 

The non-aqueous system of spherical micelles of poly(styrene)(PS)-poly-(isoprene)(PI) in decane has been investigated by Farago et al. and Kanaya et al. [298,299]. The data were interpreted in terms of corona brush fluctuations that are described by a differential equation formulated by de Gennes for the breathing mode of tethered polymer chains on a surface [300]. A fair description of S(Q,t) with a minimum number of parameters could be achieved. Kanaya et al. [299] extended the investigation to a concentrated (30%, PI volume fraction) PS-PI micelle system and found a significant slowing down of the relaxation. The latter is explained by a reduction of osmotic compressibihty in the corona due to chain overlap. 

In an early report to a process using three oxidoreductases, namely hydrogenase (ECl.12.2.1), lipoamide dehydrogenase (EC 1.6.4.3) and 20(3-hydroxysteroid dehydrogenase (ECl.1.1.53), a reverse micelle system was used to facilitate stereo- and site-specific reduction of apolar ketosteroids, assisted by the in situ NADH-regenerating enzyme system [61]. 

Size analyses of (using light scatter) some spherical micelles of SDS have indeed shown that the radius of the micelle is almost the same as the length of the SDS molecule. However, if the solute interferes with the outer polar part of the micelle, then the micelle system may change in such a way that the CMC and other properties change. This is observed in the case of the addition of dodecanol to SDS solutions. However, very small additions of solutes show very little effect on CMC. The data in Figure 3.18 show the change in the solubility of naphthalene in SDS aqueous solutions. 

Van der Waals forces There has been some success in relating these forces to micellar stability. However, the steric stabilization has been found to be also of some importance. Especially, the hairy layer interferes with the interparticle approach. There are several factors that will affect the stability of the casein micelle system ... 

Yang XH, Wu QS, Li L, Ding YP, Zhang GX (2005) Controlled synthesis of the semiconductor CdS quasi-nanospheres, nanoshuttles, nanowires and nanotubes by the reverse micelle systems with different surfactants. Colloids Surf A 264 172-178... 

Recently, Rubingh ll) and Scamehorn et al. (9) have shown that the activity coefficients obtained by fitting the mixture CMC data can be correlated by assuming the mixed micelle to be a regular solution. This model proposed by Rubingh for binary mixtures has been extended to include multicomponent surfactant mixtures by Holland and Rubingh (10). Based on this concept Kamrath and Frances (11) have made extensive calculations for mixed micelle systems. 

The need -for a simple. universal method o-f measuring individual monomer activities in mixed micelle systems is the most pressing problem in this -field o-f research and deserves substantial attention. 

Noipa T, Srijaranai S, Tuntulani T, Ngeontae W. New approach for evaluation of the antioxidant capacity based on scavenging DPPH free radical in micelle systems. Food Research International. 2011 44(3) 798-806. 

The synthesis of Si02 particles by ammonia-catalyzed hydrolysis of TEOS has been also carried out in Aerosol OT reversed micelle systems. The particles precipitated in this systems are spheres, but they have generally a broad size distribution comparing with that of nonionic reversed micelles compared to the normalized standard deviation of <10% in polyoxyethylene(5) nonylphenyl ether, that in Aero-... 

Unlike TEOS hydrolysis, Si02 particles have been also prepared by hydrolysis of Na2Si02 and Na4Si02 in nonionic reversed micelle systems. Spherical and poly-disperse particles of 31.8 nm mean diameter were produced in polyoxyethylene(9.5) octylphenyl ether-hexanol-cyclohexane systems (25), but more uniform and dense particles were precipitated by hydrochloric acid-catalyzed hydrolysis in a mixture of polyoxyethylene(5) nonylphenyl ether and polyoxyethylene(9) nonylphenyl ether in cyclohexane systems at pH 11 (26). The uniform particle formation at higher pH is attributed to the charge repulsion by OH- adsorbed on particle surface. The particles of specific surface area of 347 m2 g-1 can be obtained by calcination of particles produced at pH 2. 

Table 4.3.2 Size of Silver Halide Particles in Various Reversed Micelle Systems...

The ionic field of micells increases the efficiency of photoinduced charge separation. Laser flash photolysis showed a longer lifetime of the e formed by irradiation of a donor molecule (D pyrene, perylene etc.) solubilized in anionic micells such as sodium lauryl sulfate (SDS) than in a non-micell systems 19b). This is why the e is repulsed by the anionic field at the micellar surface into the bulk solution (Eq. (10)). 

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