In this work we investigated phase diagrams of CTAB and different polar solvents such as water, formamide, and glycerol in order to compare the effects of a nonaqueous solvent on the existence of intermediate phases. A small-angle X-ray scattering setup was used to observe the diffraction peak corresponding to the high values of the phase parameters and their transformations. We developed a method for rapid and continuous observation of the surfactant-solvent system over their transitions from the micellar to the lamellar phase. The following sequence of intermediate phases was identified in the CTAB/water system: hexagonal-monoclinic (close to a centered rectangular phase)-cubic-lamellar. Comparison with the results from CTAB/formamide and CTAB/glycerol systems showed the same sequence (except that the monoclinic phase existence was only found with water), but the existence regions of these phases are different and the parameters are smaller.
eV for an indirect transition, and 1.24 eV for a direct transition are close to the reported single value of 1.21 eV (again, the mode was not assigned).The occurrence of both an indirect and direct transition is common for the CdIn2VI4 family of materials, and the difference between £ind and £d has been reported to be 0.1 eV for CdIn2Te4.12 Our value of 0.08 eV is close to the 0.1 eV value. We also obtained a value of 0.16 eV for the difference between £ind and £d for p-Hg!n2Te4. It seems that the difference between £ind and £d decreases from 0.22 eV for CdIn2Se4 to 0.08 eV for CdIn2Te412 and increases from 0.08 eV for CdIn2Te4 to 0.16 eV for HgIn2Te4.The Mott-Schottky plot intercept value of -0.48 V was close to that of the onset of photocurrent (-0.53 V, see Table I); therefore, the open circuit photovoltage is expected to be ~0.6 V (£redox = -1.09 V). Considering a band gap value of 1.20 eV (0.9 eV for HgIn2Te4) and an analysis parallel to that given for p-HgIn2Te4 above, the valence band would be located at -0.4 V (-0.6 V for HgIn2Te4) and the conduction band near -1.6 V (-1.5 V for HgIn2Te4).The photocurrent onset and the maximum power efficiency in[Cr(III)EDTA]' with monochromatic light irradiation were close to that in Fe(III)TEA complex solution, but the maximum power efficiency in [Cr(III)EDTA]' with polychromatic light irradiation was less than that in Fe(III)TEA complex solution (the reason for this is given above). Therefore, the Fe(III)TEA complex solution is a preferred one for both p-HgIn2Te4 and p-CdIn2Te4 electrodes.
A fast method for the analysis of the phase diagrams of lyotropic compounds was employed to study the formation of liquid crystals from two surfactants, cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPBr) in water. Studies were also carried out in the protic solvents, glycerol (G), formamide (FA), ethylene glycol (EG), and N-methylformamide (NMF), and the aprotic solvents, dimethylformamide (DMF) and N-methylsydnone (NMS). While the normal succession of ordered phases appeared to be governed by geometric constraints of interface curvature, the differences in behavior were accounted for by the differences in cohesion energy of the solvents and the different natures of the polar heads of the two surfactants. In DMF, a solvent with low cohesion energy, both surfactants showed only lamellar phases, whereas CPBr with a highly delocalized charge on the polar head displayed a succession of conventional phases in all the other solvents. CTAB with a localized charge formed only lamellar phases in NMF and NMS. This behavior was interpreted as resulting from headgroup solvation due to dipoledipole interactions or hydrogen bonding. The particular case of NMS was accounted for by better stacking between the planar molecules of this solvent and the pyridinium rings of CPBr.
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