Atomization by Acoustic Levitation Facilitates Contactless Microdroplet Reactions.

Microdroplet chemistry is now well-known to be able to remarkably accelerate otherwise slow reactions and trigger otherwise impossible reactions. The uniqueness of the microdroplet is attributable to either the air-water interface or solid-liquid interface, depending on the medium that the microdroplet is in contact with. To date, the importance of the solid-liquid interface might have been confirmed, but the contribution from the air-water interface seems to be elusive due to the lack of method for generating contactless microdroplets.

Harnessing the High Interfacial Electric Fields on Water Microdroplets to Accelerate Menshutkin Reactions.

Even though it is still an emerging field, the application of a high external electric field (EEF) as a green and efficient catalyst in synthetic chemistry has recently received significant attention for the ability to deliver remarkable control of reaction selectivity and acceleration of reaction rates. Here, we extend the application of the EEF to Menshutkin reactions by taking advantage of the spontaneous high electric field at the air-water interfaces of sprayed water microdroplets. Experimentally, a series of Menshutkin reactions were accelerated by 7 orders of magnitude.

Spontaneous Reduction of Transition Metal Ions by One Electron in Water Microdroplets and the Atmospheric Implications.

Freshman chemistry teaches that Fe and Cu ions are stable in water solutions, but their reduced forms, Fe and Cu, cannot exist in water as the major oxidation state due to the fast oxidation by O and/or disproportionation. Contrary to these well-known facts, significant fractions of dissolved Fe and Cu species exist in their reduced oxidation states in atmospheric water such as deliquesced aerosols, clouds, and fog droplets. Current knowledge attributes these phenomena to the stabilization of the lower oxidation states by the complexation of ligands and the various photochemical or thermal pathways that can reduce the higher oxidation states.

Spontaneous oxidation of I in water microdroplets and its atmospheric implications.

Atomic and molecular iodine, I˙ and I, play important roles in the atmosphere, such as the catalytic depletion of ozone and the oxidation of gaseous elemental mercury. It is known that the major source of I˙ and I in the atmosphere is the photodissociation of organoiodine molecules released by algae in the sea. In this study, we show the striking results of the spontaneous and ultrafast oxidation of I into I˙, which further evolves into I and I in water microdroplets, presenting a previously unknown source of I˙ and I in atmospheric water, such as the sea spray or cloud microdroplets.

An Am Plasma Desorption Ionization (AmDI) Source Scavenged from Smoke Detectors for Ambient Mass Spectrometry Sampling.

The development of efficient, low-cost, easy-to-use ambient ionization methods has been a major goal of modern mass spectrometry. In this Letter, we present a gas-free, voltage-free, economic, and safe desorption ionization method using the plasma generated by a radioactive element, americium-241, scavenged from smoke detectors that equip almost every household. No other energy sources, such as laser, discharge, fast-moving carrier gas, solvent droplet, ultrasound, or heat are needed.