Microdroplet Chemistry with Unactivated Droplets.

Microdroplet chemistry has attracted much attention owing to its ability to accelerate otherwise slow reactions and to trigger thermodynamically forbidden reactions. The cause of this unique behavior is the intrinsic properties of the droplets, such as the spontaneously generated electric field on the droplet surface. However, some have argued that the droplet generation methods provided energy to the reactions, and the different interfaces that the droplets contact also played important roles; therefore, it is the droplet activation or the environment, not the intrinsic properties, that is responsible for the observed chemistry. In this study, we used adiabatic expansion and dry ice in water to generate homogeneous, contactless, supercooled, and unactivated microdroplets. A large variety of reactions were successfully tested. We opine that it is the intrinsic properties, and not droplet activation, that are responsible for microdroplet chemistry.