MECHANOCHEMICAL SYNTHESIS OF CARBON AND CARBON NITRIDE NANOTHREAD SINGLE CRYSTALS
Open Access
- Author:
- Li, Xiang
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 06, 2018
- Committee Members:
- John V Badding, Dissertation Advisor/Co-Advisor
John V Badding, Committee Chair/Co-Chair
Vincent Henry Crespi, Committee Member
Paul S Cremer, Committee Member
Mauricio Terrones Maldonado, Outside Member - Keywords:
- High pressure
Solid state
Nanocarbon
Single crystal - Abstract:
- Carbon nanomaterials such as fullerenes, nanotubes, and graphene have been widely studied in recent decades. Benefitting from their unique bonding, they possess extraordinary physical and chemical properties. Compared with sp2 hybridized carbon allotropes, there are significantly fewer new carbon materials dominated by sp3 bonding that have been developed. Adamantane and graphane represent the smallest unit and thinnest sheet of diamond possible, respectively. One-dimensional, mostly sp3 hybridized nanocarbon, did not yet exist in 2013, when the first synthesis of carbon nanothreads finally filled up the last remaining entry in the matrix of dimensionality and hybridization of carbon nanomaterials that year. Carbon nanothread was first made by compressing benzene to ~25 GPa in a large-volume anvil cell and slowly decompressing back to ambient pressure by an alumnus of the Badding group. Background about high-pressure chemistry will be introduced in Chapter 1. An overview of basic principles and the core instrumental techniques employed in this dissertation will be provided in Chapter 2. In Chapter 3, I will present the progress of carbon nanothread synthesis since 2013. Before my thesis work, only polycrystalline quality carbon nanothreads had been made. With my optimized synthetic protocol, a single crystal carbon nanothread has been successfully synthesized both in large-scale and in standard high-pressure apparatuses. High-pressure x-ray diffraction illustrating the first direct in situ observation of nanothread formation during compression will be presented in this chapter as well. The result of this experiment demonstrates that the transformation from benzene to carbon nanothread is a unique non-topochemical solid state reaction. In Chapter 4, I will report the synthesis and structural characterization of the second member in the nanothread family. Carbon nitride nanothread has been obtained by compressing pyridine with the same slow compression/decompression method, suggesting that this mechanochemical synthetic approach is possibly quite general. The shift of the fluorescence emission wavelength compared with carbon nanothread indicates that tuning the physical properties of nanothreads can be realized by introducing heteroatoms or functional groups to the benzene precursor. A new high-pressure phase of pyridine has been discovered from the in situ diffraction study of the carbon nitride nanothread reaction pathway. Preliminary analysis and provisional crystal structures will be presented in Chapter 5. Chapter 6 includes a concluding summary as well as an outlook, with a broader picture than the insight sections at the end of Chapters 3, 4 and 5 provided.