Micelle-to-vesicle aggregate transition is investigated in this work through the addition of β-cyclodextrin 1 (β-CD) in mixed catanionic surfactant aqueous solutions. The catanionic system is composed of 1-hexadecyl-3-methylimidazolium chloride (C 16 mimCl) and sodium oleate (NaOle) which are cationic surfactant and anionic surfactant, respectively. The mixed surfactant solutions can self −assemble into micelles, which are studied by dynamic light scattering measurements and the calculation of molecular interaction parameter. The inclusion complexation of β-CD to C 16 mimCl-NaOle surfactants is studied by surface tension measurements and the calculation of association constants. The dynamic light scattering (DLS), rheological measurements, freeze-fracture transmission electron microscopy(FF-TEM)were conducted to indicate that micelles can transform into vesicles with the addition of β-CD. Finally, the transformation mechanism is proposed. The main reason for micelle-to-vesicle aggregate transition is the inclusion complexation of β-CD to surfactants and it will alter the composition of mixed C 16 mimCl-NaOle surfactant systems which should be responsible for the phase behavior.
Shanshan Yao,Jiang Cui,Ziheng Lu,Zheng-Long Xu,Lei Qin,Jiaqiang Huang,Zoya Sadighi,Francesco Ciucci,Jang-Kyo Kim
Carbon-coated van der Waals stacked Sb 2 S 3 nanorods (SSNR/C) are synthesized by facile hydrothermal growth as anodes for sodium ion batteries (SIBs). The sodiation kinetics and phase evolution behavior of the SSNR/C anode during the first and subsequent cycles are unraveled by coupling in situ transmission electron microscopy analysis with first-principles calculations. During the first sodiation process, Na + ions intercalate into the Sb 2 S 3 crystals with an ultrafast speed of 146 nm s −1 . The resulting amorphous Na x Sb 2 S 3 intermediate phases undergo sequential conversion and alloying reactions to form crystalline Na 2 S, Na 3 Sb, and minor metallic Sb. Upon desodiation, Na + ions extract from the nanocrystalline phases to leave behind the fully desodiated Sb 2 S 3 in an amorphous state. Such unique phase evolution behavior gives rise to superb electrochemical performance and leads to an unexpectedly small volume expansion of ≈54%. The first-principles calculations reveal distinctive phase evolution arising from the synergy between the extremely low Na + ion diffusion barrier of 190 meV and the sharply increased electronic conductivity upon the formation of amorphous Na x Sb 2 S 3 intermediate phases. These findings highlight an anomalous Na + ion storage mechanism and shed new light on the development of high performance SIB anodes based on van der Waals crystals.
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