Preparative mass spectrometry applications in nanomaterials and organic synthesis
Preparative mass spectrometry was traditionally a vacuum based experiment where mass selected ion beams were deposited onto surfaces; however, recently ions have been manipulated in the open air to perform accelerated synthesis. The work of this dissertation focuses on the generation of charged ions from microdroplets and their use in organic synthesis and the preparation of atomically precise metal nanoclusters. First the mechanism for charging in the zero volt paper spray will be presented. This works builds a computational model based on the statistical fluctuation of positive and negative charges based on the theory of Dodd. It is found through experiment and simulation that in zero volt paper spray and presumably other zero volt methods the most surface active species are preferentially ionized. Charged microdroplets are exploited in this dissertation for two very different applications but in seemingly similar ways. First metal salts are electrosprayed, heated, and subjected to harsh in-source conditions to cause the reduction of the metal salts into atomically precise metal clusters. This method is capable of producing atomically precise silver cluster cations and anions as well as bimetallic silver-palladium complexes. Microdroplets are also exploited to screen chemical pathways to common pharmaceutical including atropine and diphenhydramine. The two step synthesis of diphenhydramine from benzhydrol was performed in charged microdroplets and confirmed in microfluidics. While the fundamental mechanism of reaction in microdroplets and microfluidics might differ useful connections were found in the cases of atropine, diphenhydramine, and diazepam. It is envisioned that this methodology could impact drug discovery as a rapid platform for the screening of chemical pathways to both old and new molecules. The droplet reaction was extended to a “super reagent” form where a reagent of choice is sprayed onto a variety of substrate contained in a well plate or on paper. This method allows for rapid screening with hopes of screening 1000’s of reaction conditions per hour.
Cooks, Purdue University.
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