November 4^th, 2015

Dr. Zare is developing a method which exploits the use of electrospray ionization (ESI) to watch reaction kinetics on the microdroplet scale. In this set-up, two ESI sources are angled towards each other to efficiently mix two reactants into a single droplet. The short distance between the collision point (droplet formation point) and the mass spectrometer (MS) inlet makes it possible to look at reaction intermediates that are theoretically only available for a few milliseconds or less. By changing the distance between the collision point and the MS inlet, different intermediates can be detected for complex multistep reactions.

Encouraged by these results, the Zare lab decided to use this intermediate information to study previously published reactions and determine kinetic information from running these microdroplet reactions at different distances. A high speed camera was used to determine the speed at which the microdroplets traveled. An interesting observation after the study of multiple reactions showed that reaction rates were increased by about 1000 times the previously published bulk reaction rates. Having found a peculiar trend, Dr. Zare’s lab continued to study previously published slow chemical reactions to compare the reaction rate on the microdroplet scale versus bulk scale. Interestingly enough reactions which took multiple days in bulk solution were accelerated to the span of a few seconds. Further studies were conducted to determine that evaporation was not the leading cause of the acceleration. Dr. Zare speculates that this phenomenon might revolutionize the field of chemistry and how scientist think of reaction kinetics on the microdroplet scale.