Kinetics in Colliding Microdroplets: Accelerated Synthesis of Azamonardine from Dopamine and Resorcinol

EMILY BROWN, Grazia Rovelli, Kevin R. Wilson, Lawrence Berkeley National Laboratory

     Abstract Number: 450
     Working Group: Aerosol Chemistry

Abstract
Micron-sized compartments have become a recent focus of study as strong electric fields, pH effects, and surface confinement among other properties have been revealed to lead to unique reaction acceleration. Micron-sized compartments are ubiquitous in the environment including aerosols, rock pores, and biological compartments which makes understanding their chemistry a priority. The reaction of dopamine with resorcinol to form the fluorescent product azamonardine is used as a model system to examine how droplet interfaces accelerate reaction kinetics. This reaction is initiated in a branched quadrupole trap (BQT) by colliding two droplets and observing the formation of azamonardine. The BQT allows for observation of single droplets with control over droplet size, concentration, and charge. The reaction was observed to be accelerated in droplets from 9 to 35 micron in radius by as much as 7.4 times. Kinetic modeling suggests that the acceleration can be attributed to rapid diffusion of oxygen into the droplet and increased reagent concentrations at the air-water interface.