Dynamic Self-Assembly Of Macrocycles;Structural Investigations By Using TEM

Everyone knows that the data needed to solve a problem quickly are more important than ever. Transmission electron microscopy is one of the main tools for the characterization of nanostructure, which can be used to approach the structural information and spatial distribution. In this paper, I describe by using transmission electron microscopy for characterization of nanostructures. Successful TEM requires the analyst to bring considerable knowledge to the microscope and even to the specimen preparation protocols. In the first and third chapter, I will describe how the surface treatment influence our experiments result. As we all know, there are numerous reported sample preparation methods for different samples. So I need to try different sample preparation methods for our own system. There still have some effectors in dry state TEM. So here we suggest cryogenic transmission electron microscopy. Cryo-TEM plays a very important role in approaching a native result. Cryo-TEM and dry-TEM results should be complementary. To analysis the real morphology I need to combine these two results. To get high contrast image sometimes we need to introduce the contrast agent, even it will also make some artifacts but it is still a very useful technology. There are many kinds of contrast agents can be used. In the second chapter I will describe the contrast agent effects based on my experiments experience. These self-assembled nanostructures constructed through secondary forces such as hydrogen bonding, electrostatic, van der Waals interaction, and hydrophobic interaction can be a powerful tool to develop specific functional supramolecular materials. In order to understand further about the principle of self-assembled process, transmission electron microscopy(TEM) becomes a vitally important research tool, and it allows us to be more intuitive to see the process and results of the assembly. The combination with the property, conformational stability, software simulation analysis, spectroscopy and other data of the aromatic amphiphiles, then to reasonable explain the assembly principle and responsible behavior. On the basis of understanding the structural properties of the nanomaterial and its responsible behavior to environmental changes, it has profound significance for the development of its application value. This article includes three chapters, in each result and discussion part, I will focus on the scientific problems which solved by transmission electron microscopy.The work in the first chapter was published in Nature Commun. 2015, through TEM investigation, firstly we can construct highly uniform millimeter-long tubular structure based on aromatic macrocycle amphiphiles, the diameter of each tube is ~9 nm, and the tubular pore is ~2 nm. With the dilution of the tube solution, we found that the nanotube separates to fibrils; the diameter of each fiber is ~4 nm. By outside thermal trigger, this nanotube will shrink and close the tubular pore completely, and change to a fibril-like structure which diameter is ~6 nm. This fibril-like structure will reopen when we cooling back to room temperature. Then after heating and cooling several cycles we confirm that this open and close behavior is reversible. We realized highly dynamic tubular pores that are quickly switching between open and closed states triggered by a thermal signal, by using the self-assembly of disc-shaped aromatic macrocycle amphiphiles.The work in the second chapter was published in Angew. Chem. Int. Ed. 2016, the results demonstrate that the self-assembly of the disc-shaped aromatic amphiphile generates long columnar fibrils that laterally associate to form planar ribbons. The ribbons have 8 laterally associated elementary fibrils, and are 28 nm wide and 3.5 nm thick. Remarkably, these planar structures spontaneously curve into closed tubules with an outer diameter of 8 nm through lengthwise folding and then zipping driven by fructose addition.The work in the third chapter is ongoing. Through TEM observations, until now we constructed a toroid structure which is sensitive to the concentration change. The diameter of each toroid is ~12 nm, and the pore of the toroid is ~2 nm. When dilute this toroid solution we can get the left-handed helical fiber with a diameter of 9 nm. After introduced 1eq of coronene into the helical fiber solution, we found that the helical fiber changes back to the toroid. Besides by addition of guest molecule hexahelicene at toroid condition we can get helical spring. The diameter is ~12 nm. These phenomena are consistent with our conceptions. We need to study more about this work in a systematical way.