The Pennsylvania State University The Graduate School Department of Chemistry MECHANOCHEMICAL SYNTHESIS OF CARBON AND CARBON NITRIDE NANOTHREAD SINGLE CRYSTALS A Dissertation in Chemistry by Xiang Li 2018 Xiang Li Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy August 2018 The dissertation of Xiang Li was reviewed and approved* by the following: John V. Badding Professor of Chemistry, Physics and Materials Science and Engineering Dissertation Advisor Chair of Committee Vincent H. Crespi Professor of Physics, Materials Science and Engineering, and Chemistry Paul S. Cremer Professor of Chemistry and Biochemistry and Molecular Biology Mauricio Terrones Professor of Physics, Chemistry and Materials Science and Engineering Thomas E. Mallouk Professor of Chemistry, Biochemistry and Molecular Biology, Physics, and Engineering Science and Mechanics Head of the Department of Chemistry *Signatures are on file in the Graduate School iii 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 iv 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. v TABLE OF CONTENTS List of Figures .......................................................................................................................... vii List of Tables ........................................................................................................................... xiv Acknowledgements .................................................................................................................. xv Chapter 1 Carbon Materials and High-Pressure Chemistry ..................................................... 1 1.1 Natural Carbon Allotropes: Graphite and Diamond .................................................. 2 1.1.1 Bonding Environments and Crystal Structures ............................................... 3 1.1.2 Structural Properties and Applications ............................................................ 5 1.2 Era of Synthetic Carbon Allotropes: Nanocarbons .................................................... 8 1.3 Molecular Crystals under High Pressure .................................................................... 11 1.3.1 Introduction of Pressure Effects ...................................................................... 11 1.3.2 Pressure Dependence of Chemical Equilibrium and Reaction Rates .............. 15 1.3.3 Pressure Effects on Electronic Structure ......................................................... 17 1.4 Goals of the Dissertation ............................................................................................ 20 References ........................................................................................................................ 22 Chapter 2 Instrumentation and Characterization Techniques .................................................. 26 2.1 High Pressure Cells .................................................................................................... 26 2.1.1 Diamond Anvil Cell ........................................................................................ 26 2.1.2 Paris-Edinburgh Cell ....................................................................................... 28 2.2 Pressure Control System ............................................................................................ 30 2.3 High Pressure X-ray Diffraction ................................................................................ 33 2.3.1 Single Crystal Crystallography under Pressure ............................................... 34 2.3.2 Determine the Pressure in Diamond Anvil Cell .............................................. 36 2.3.3 High Pressure Single Crystal Diffraction at Synchrotron Beamline ............... 38 2.4 Vibrational Spectroscopy ........................................................................................... 40 2.4.1 Principles of Infrared Spectroscopy ................................................................ 40 2.4.2 Principles of Raman Spectroscopy .................................................................. 42 2.4.3 Application of Polarized Raman Spectroscopy ............................................... 45 2.4.4 Ultra-low Frequency Raman Spectroscopy with Volume Bragg Gratings as Optical Filter ................................................................................................ 47 References ........................................................................................................................ 52 Chapter 3 Mechanochemical Synthesis of Carbon Nanothread Single Crystals ..................... 55 3.1 Introduction ................................................................................................................ 55 3.2 Materials and Methods ............................................................................................... 58 3.3 Results and Discussion ............................................................................................... 60 3.4 Conclusions ................................................................................................................ 70 3.5 Insights and Future Consideration ............................................................................. 71 3.5.1 Sign of Reaction .............................................................................................. 71 vi 3.5.2 Polarized Raman Spectroscopy of Carbon Nanothread .................................. 73 3.5.3 Preliminary Ultra-Low Frequency Raman Study ............................................ 75 References ........................................................................................................................ 77 Chapter 4 Carbon Nitride Nanothread Crystals Derived from Pyridine .................................. 79 4.1 Introduction ................................................................................................................ 79 4.2 Materials and Methods ............................................................................................... 83 4.2.1 Synthesis ......................................................................................................... 83 4.2.2 X-ray Diffraction ............................................................................................. 84 4.2.3 Infrared Spectroscopy (IR) .............................................................................. 84 4.2.4 X-ray Photoelectron Spectroscopy (XPS) ....................................................... 85 4.2.5 Nuclear Magnetic Resonance (NMR) Spectroscopy ....................................... 85 4.2.6 Fluorescence Microscopy ................................................................................ 85 4.2.7 Photoluminescence Spectroscopy ................................................................... 86 4.2.8 Combustion Elemental Analysis ..................................................................... 86 4.3 Results and