Structure and phase behaviour of the ternary system water, n -heptane and the nonionic surfactant Igepal ® CA520

Abstract

The phase behavior of the system water, n-heptane and the nonionic surfactant Igepal CA520 has been studied by visual inspection, high-performance liquid chromatography, polarizing microscopy and freeze-fracture electron microscopy. The phase diagram at 25°C contains two large homogeneous microemulsion phases, an extended region of a lamellar liquid crystalline structure and some twoand three-phase regions. The oil-rich part of the phase diagram has been investigated by static and dynamic light scattering in order to examine the behavior of the collective diffusion coefficient and the scattering intensity in the presence of increasing concentrations of water, starting from the binary system of n-heptane and Igepal CA520. The results suggested that at a very low water content the aggregates of the microemulsion are small. With the exception of this region the structure is bicontinuous.

Dye-doped silica nanoparticle labels/protein microarray for detection of protein biomarkers

“…Aqueous ammonia acts as both a reactant (H 2 O) and a catalyst (NH 3 ) for the hydrolysis of TEOS. As discussed earlier, surfactant CA-520 was used because of the stable microemuslion region that does not require a co-solvent to stabilize the micellar droplets 37. The prepared silica nanoparticles were characterized with TEM and fluorescence spectrometer.…”

Rate constants of the thermal cis-trans isomerization of azobenzene dyes in solvents, acetone/water mixtures, and in microheterogeneous surfactant solutions

“…Different from micellar solutions, beside the extended water/surfactant interface layer a large volume of unpolar oil domains may dissolve the dye molecules and distributions between different solubilization sites must be considered. We prepared transparent bicontinuous microemulsions of different compositions within the one-phase region from igepal CA-520, heptane and water, based on a published phase diagram [45]. Igepal CA-520 structure is similar to that of triton X-100, but has an unbranched hydrocarbon tail.…”

Evaluation of proton activity in microemulsions by a kinetic probe

“…The ternary system with n-heptane at 25°C consists of two large homogeneous phases and an extended lamellar region [14]. Fig.…”

“…The parameters A = (2qpN A ) 1/2 Â (e 2 /4pe 0 k B T) 3/2 and B = e (2N A q/e 0 e r k B T) 1/2 were evaluated introducing the relative permittivities [3,18] and densities [14,19] reported for heptane and cyclohexane (Table 1S, Supporting material). According to Eq.…”