Spontaneous Nanotube Formation in Aqueous Mixture of Cationic Surfactant and Anionic Flat Compound

Abstract

In this article, we report a spontaneous nanotube formation through mixing two simple, achiral chemicals, dodecyltrimethylammonium bromide (DTAB), and 1-phenylazo-2-naphthol-6,8-disulfonic acid disodium salt (Orange G) in aqueous solution. Nanotubes with outer diameter of about 50 to 100 nm and length of several microns were formed after mixing, which was demonstrated by TEM, turbidity, and viscosity methods. The formation is attributed to the different configurations of of Orange G since its structure is flat, which has both narrow and broad sides. The molecule pairs of Orange G/cone-like DTAB will have two different configurations in the meantime, cup like at the front and cylinder-like at the profile. The cuplike molecule pairs constitute a vesicular curvature which form the transverse section of nanotube, whereas the cylinder-like molecule pairs constitute the planar curvature which form the nanotube's profile section. Nanotube with different curvature at lengthwise and crosswise are thus formed.

Keywords:

• Different configuration
• DTAB
• flat molecule
• nanotube
• Orange G

Acknowledgments

The authors thank the financial support from the Plan for Science & Technology Development of Shandong Province, P. R. China (No. 2005GG4203011) and from Key Lab for Colloid and Interface Chemistry of State Education Ministry, Shandong University, P. R. China (No. 200508).

Notes

^a DTAB/OG (molar ratio); b, temperature. I: initial state, F: final state, (▪) turbid, (•) viscous, (○) Newton fluid, (▴) flow birefringence, (▵) no flow birefringence.