Ion Hydration and Nanocalorimetry in Mass Spectrometry

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

With support from the Chemical Measurement and Imaging (CMI) Program and the Chemical Structure, Dynamics and Mechanisms (CSDM-A) Program in the Division of Chemistry, Professor Evan Williams at University of California, Berkeley, and his group will be developing thermochemical tools that will enable novel measurements that can lead to both detailed insights into ion-water interactions as well as an accurate new way to measure energetics of challenging chemical reactions. Ions play important roles in chemistry and biology, and can affect a wide range of physical properties, including structures of biomolecules, such as proteins and DNA. Although much is known about ion chemistry, the origins of some ion-induced effects are still hotly debated. The accuracy of a method developed by this group called nanocalorimetry will be calibrated using laser-generated light at precise frequencies. This method will then be applied to understanding how water solvates ions and to measure energetics of chemical reactions. These state-of-the-art measurements should make it possible to obtain information about the electrochemical properties of ions that have not been measured using conventional methods, such as one-electron reduction potentials of some ions. From measurements of absolute reduction potentials of single ions in aqueous nanodrops, an accurate absolute electrochemical scale and absolute ion solvation scale could be established. Because the sizes of the nanodrops are so small, a significant fraction of the water molecules in these droplets are at the surface. Infrared photodissociation spectroscopy will be used to investigate how ions affect the hydrogen-bonding network of water molecules, both in the interior of the nanodrop as well as at the surface. Ions at surfaces have been extensively investigated with computation chemistry, but the water surface can be difficult to characterize with conventional spectroscopic methods owing to the overwhelming number of water molecules below the surface of bulk samples. This research bridges many traditional disciplines in science, and data obtained in these studies provide stringent benchmarks that can be used by others to improve the accuracy of computational methods, which are being increasingly applied to solving important problem in chemistry. Both graduate and undergraduate students who participate in this research, as well as those who enroll in a related undergraduate course on chemical instrumentation or a dedicated graduate course on mass spectrometry learn about the newest developments in mass spectrometry, a method that is used in many fields of science with applications ranging from drug discovery, molecular characterization of cellular contents, chemical imaging, and petroleum characterization. Prior NSF funded research has lead to international collaborations, which exposes students to different cultures and approaches to science, and this NSF funded project will enable continued opportunities to do so.