Two-Dimensional Alignment of Self-Assembled Organic Nanotubes through Langmuir−Blodgett Technique Xiaoqin Zhou, †,‡,∥ Hai Cao, †,∥ Dong Yang, † Li Zhang,* ,† Long Jiang, † and Minghua Liu* ,†,‡,§ † Beijing National Laboratory for Molecular Science, CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China ‡ University of Chinese Academy of Sciences, Beijing 100049, P. R. China § Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, P. R. China * S Supporting Information ABSTRACT: A C 3 -symmetric molecule was found to form organic nanotubes through supramolecular gel formation in organic solvents. These nanotubes can be dispersed in toluene without destroying the tubular nanostructures. Using the dispersions of these organic nanotubes as “spreading solutions”, Langmuir-spreading films of these nanotubes were formed. Through repeated compression and expansion cycles, the nanotubes can be aligned to a certain extent. The formed Langmuir films could be subsequently transferred to a solid substrate, and the well-aligned nanotube films were constructed by Langmuir−Blodgett film deposition technique. Interestingly, many guests including polymers, water-soluble or oil-soluble organic molecules can be encapsulated into the nanotubes and further spread on a water subphase. Through elaborate control, large-scale parallel alignment of self-assembled organic nanotubes encapsulated by guests was also realized. This study implies that 2D hierarchical alignment of one-dimensional organic nanostructures can be realized using a simple method. ■ INTRODUCTION The orderly arrangement of materials at various scales from atomic, molecular, and nanoscale levels is very important to realize the material performance and to deepen our fundamental understanding of the physical, chemical, and even biological effects of the materials. 1−6 Many of the materials can be arranged through the top−down 7−9 or bottom−up 10−13 technique. Although two- and three-dimen- sional periodic arrays of molecules can be easily realized via self- assembly, engineering nanosized materials into rational arrange- ments remains challenging. Numerous studies have been devoted to achieve large-scale alignment of one-dimensional nanostructures for their application as nanodevices. 14−17 Various techniques and methods, such as microfluidic net- work, 18,19 microcontact printing technique, 20 electrospinning, 13 flow, 4,21 magnetic field, 22 and template method, 1,23 have been developed to arrange one-dimensional nanomaterials into desired arrays. Among various techniques, Langmuir−Blodgett (LB) method has been attracting great interest owing to its ease of use and regulative properties. Originally, this technique is used for arranging amphiphilic molecules. 24−28 This technique recently has also been found to be effective in aligning inorganic nanomaterials such as carbon nanotubes, 29,30 metal nanowires, 15,31−33 and nanoparticles. 34−38 However, unlike the rapid progress in the alignment of inorganic nanomaterials, patterning of organic nanostructures is still far behind, partially because of their fragile nature. Among all one-dimensional nanostructures, organic nano- tubes are quite special and very appealing owing to their hollow inner space, which can be used as a carrier for drugs 39−41 and catalysts. 42 Obtaining organic nanotubes is not so easy; normally, the formation relies on specific molecules in specific solvents under harsh conditions. 43 During our previous study on glutamic acid derivatives, we have found a supergelator, which can self-assemble into hexagonal nanotubes in almost all kinds of common solvents. 44 More interestingly, gelation can even instantly occur at room temperature by mixing different kinds of solvents, which endows the organic nanotubes with great power for the encapsulation of functional molecules. Moreover, these nanotubes can be easily dispersed in several Received: October 9, 2016 Revised: November 15, 2016 Published: November 17, 2016 Article pubs.acs.org/Langmuir © 2016 American Chemical Society 13065 DOI: 10.1021/acs.langmuir.6b03680 Langmuir 2016, 32, 13065−13072