| dc.description.abstract | The characterization of monolayer-protected metal nanoparticles (NPs) is crucial to the advancement of biological, optical, and electronic applications. However, full characterization requires time and expertise with a number of analytical platforms. This dissertation presents the development of a novel characterization methodology based on ion mobility-mass spectrometry (IM-MS), with the goal of eventually replacing multiple spectroscopic and microscopic techniques. This is expected to reduce the amount of time, effort, and expertise required to characterize NPs, and to enable a more thorough characterization than previously achievable.
Using a two-dimensional gas-phase separation platform, the surfaces of monolayer-protected metal NPs are quickly and effectively characterized through the fragmentation, ionization, and observation of the metal-thiolate complexes that form the protecting shell of the NPs. The two-dimensions of separation facilitate the isolation of metal-thiolate ion signal from isobaric organic ions, permitting more sensitive measurements of monolayer characteristics. Applying this strategy, the use of IM-MS for fundamental studies of the properties of the protecting monolayer is explored. The ubiquity of metal-thiolate protection schemes on monolayer-protected metal NPs is illustrated by the observation of metal-thiolate complexes on NPs for which the nature of the core-shell interface has not been fully established. Furthermore, the existence of supramolecular structure in protecting monolayers is explored, yielding insight into the factors which contribute to the type and degree of supramolecular structure formation.
The development and application of mixed-ligand metal NPs, i.e., those with a mixture of thiolate ligands in the monolayer, is a very active field of study with few effective analytical characterization approaches. By observing the heteroleptic gold-thiolate ions generated from mixed-ligand AuNP surfaces, the relative abundances of each ligand as well as the presence of supramolecular structure can be determined. The results of these experiments illustrate the power of IM-MS to serve as a versatile characterization platform for fundamental studies or routine analysis of homoligand and heteroligand metal NPs. | |
