The Role of Interfaces and Charge for Chemical Reactivity in Microdroplets

TL;DR

This paper reviews recent experimental and theoretical progress in understanding how interfaces and charge influence chemical reactivity in microdroplets, highlighting mechanisms and opportunities for future research.

Contribution

It provides a comprehensive perspective on the roles of interfaces and charge in microdroplet chemistry, emphasizing the importance of electric fields and surface phenomena.

Findings

Microdroplet interfaces facilitate solute adsorption and influence reactivity.

Droplet charge is crucial for thermodynamically enabling certain reactions.

Theoretical models and experiments are advancing understanding of microdroplet chemistry.

Abstract

A wide variety of reactions are reported to be dramatically accelerated in aqueous microdroplets, making them a promising platform for environmentally clean chemical synthesis. However to fully utilize the microdroplets for accelerating chemical reactions requires a fundamental understanding of how microdroplet chemistry differs from that of a homogeneous phase. Here we provide our perspective on recent progress to this end both experimentally and theoretically. We begin by reviewing the many ways in which microdroplets can be prepared, creating water/hydrophobic interfaces which have been frequently implicated in microdroplet reactivity due to preferential surface adsorption of solutes, persistent electric fields, and their acidity or basicity. These features of the interface interplay with specific mechanisms proposed for microdroplet reactivity, including partial solvation and possible gas phase channels. We especially highlight the role of droplet charge, which appears key to understanding how certain reactions, like the formation of hydrogen peroxide and reduced transition metal complexes, are thermodynamically possible in microdroplets. Lastly, we emphasize opportunities for theoretical advances in the microdroplet field generally, and to suggest experiments which would greatly enhance our understanding of this fascinating and emerging subject.