Date of Award
Ph.D. in Chemistry
Chemistry and Biochemistry
Gregory S. Tschumper
Chapter 1 gives a brief introduction to the field of gold nanomolecules. Various synthetic protocols and analytical techniques used through out this dissertation are discussed in detail. Size dependent properties of the gold nanomolecules are described. The structure of gold nanomolecules is explained based on the crystal structure of Au25(SCH2CH2Ph)18. The theoretical basis for the stability of the gold nanomolecules is explained using the super atom complex model and geometric parameters. Chapter 2 includes ligand exchange experiments on gold nanomolecules. Ligand exchange experiments are used to modify the monolayer of nanomolecules after synthesis. Ligand exchange reactions are monitored by mass spectrometry. Exploiting the mass difference of various ligands to monitor ligand exchange reactions is explained. Ligand exchange with dithiols is covered in this chapter. Interstaple vs intrastaple dithiol binding, optimum chain length for bidentate binding and effect on optical properties are studied in this project. Ligand exchange with other chalcogenide ligands like tellurides is discussed briefly. Chapter 3 covers the core size conversion reactions in gold nanomolecules. When gold nanomolecules are etched in excess thiols at elevated temperatures, some of the gold nanomolecules convert to a different size. Such change in core size is called core size conversion. Core size conversion in the larger and smaller sizes is studied in this project. Etching reactions are similar to ligand exchange except that they are more rigorous and performed at elevated temperatures. The use of core size conversion reactions as high yield synthetic protocols is explained. Some mechanistic details based on the mass spectrometric results are discussed. Chapter 4 covers the electrochemical properties of gold nanomolecules. The electrochemical behavior of gold nanomolecules is probed by voltammetry experiments. Cyclic voltammetry and differential pulse voltammetry are the primary techniques used for this purpose. The size dependence of electrochemical properties is demonstrated with different sizes. Solvent effects and the effect of alloying are also covered in detail. Chapter 5 covers mass spectrometry of gold nanomolecules. MALDI MS and ESI MS are the primary analytical techniques used to find the composition of gold nanomolecules. These techniques are increasingly used for studying synthesis, ligand exchange, alloying and fragmentation of gold nanomolecules. These techniques have several advantages and disadvantages for various applications. Applications of mass spectrometry tools for different applications are discussed with several case studies. Chapter 6 covers separation of gold nanomolecules by size exclusion chromatography. Size exclusion chromatography is the most efficient technique for separation of gold nanomolecules. Separation of different gold nanomolecules using size exclusion chromatography is described in this chapter. Advantages of size exclusion chromatography over conventional solvent fractionation techniques are demonstrated with examples. Chapter 7 highlights the contributions of this dissertation work to the field of gold nanomolecule research. Possible improvements and future directions of this research are presented.
Jupally, Vijay Bhaskar Reddy, "Synthesis, Characterization and Electrochemical Properties of Gold Nanomolecules" (2014). Electronic Theses and Dissertations. 1365.