Interparticle Delivery and Detection of Volatile Singlet Oxygen at Air/Solid Interfaces

Abstract

An interparticle system has been devised, allowing airborne singlet oxygen to transfer between particle surfaces. Singlet oxygen is photogenerated on a sensitizer particle, where it then travels through air to a second particle bearing an oxidizable compounda particulate-based approach with some similarities to reactive oxygen quenching in the atmosphere. In atmospheric photochemistry, singlet oxygen is generated by natural particulate matter, but its formation and quenching between particles has until now not been determined. Determining how singlet oxygen reacts on a second surface is useful and was developed by a three-phase system (particle–air–particle) interparticulate photoreaction with tunable quenching properties. We identify singlet oxygen quenching directly by near-IR phosphorescence in the airborne state and at the air/particle interface for total quenching rate constants (k T) of adsorbed anthracene trapping agents. The air/solid interface k T of singlet oxygen by anthracene-coated particles was (2.8 ± 0.8) × 107 g mol–1 s–1 for 9,10-dimethylanthracene and (2.1 ± 0.9) × 107 g mol–1 s–1 for 9,10-anthracene dipropionate dianion, and the lifetime of airborne singlet oxygen was measured to be 550 μs. These real-time interactions and particle-induced quenching steps open up new opportunities for singlet oxygen research of atmospheric and particulate processes.

Singlet Oxygen Seasonality in Aqueous PM10 is Driven by Biomass Burning and Anthropogenic Secondary Organic Aerosol

“…On the other hand, extrapolating from our dilute, aqueous extracts to concentrated OA systems likely does not follow a linear scale but could reach a plateau at a maximum [ 1 O 2 ] SS given by the increasing competing strength of the chemical sinks. (2) The sensitization experiments were conducted in bulk solutions, influencing reaction kinetics and absorption behavior compared to faster reaction rates in droplets. − It is also likely that 1 O 2 production is enhanced if the chromophore is at the surface of the OA. (3) Our extracts were not buffered and were thus at pH 6, potentially influencing the concentrations of protonated chromophores .…”

Probing the Transition State-to-Intermediate Continuum: Mechanistic Distinction between a Dry versus Wet Perepoxide in the Singlet Oxygen “Ene” Reaction at the Air–Water Interface

“…Effect of the Chain Length on k T . With the advent of a technique to monitor the quenching of 1 O 2 at the air−D 2 O and air−solid interfaces, 16,51 the rate constants k T can show the removal of 1 O 2 by the surfactants. In the present k T experiments, the use of D 2 O was preferred because of a longer lifetime in D 2 O (τ Δ = 66 μs) than in H 2 O (τ Δ = 4.5 μs), 52 thereby facilitating the time-resolved measurements.…”

“…Previous studies have also examined 1 O 2 transfer in silicas, zeolites, supramolecular systems, and superhydrophobic surfaces. − Flow reactors for 1 O 2 generation and reactions in water are emerging and show good potential, as well as surfactants − in reactive oxygen species (ROS) reactions at the air–water interface. − A study of Singleton et al on the reaction of cis- 2-butene and tetramethylethylene with 1 O 2 proposed a two-step no-intermediate pathway and laid the groundwork for potential bifurcations on the 1 O 2 reaction surface. The trans -cyclooctene/ 1 O 2 “ene” reaction − is unique in that its allylic hydrogens are inaccessible so that a minimum develops on the potential energy surface (PES) for the perepoxide.…”

Potentiation Effect of Iodine Species on the Antimicrobial Capability of Surfaces Coated with Electroactive Phthalocyanines

“…These values are slightly higher than those found for DMA, probably because this substrate reacts selectively with 1 O 2 . Interestingly, the total (physical + chemical) quenching rate constants ( k T ) of 1 O 2 by Trp and DMA are 7.1 × 10 7 and 9.44 × 10 7 M –1 s –1 , respectively, , suggesting that values for k obs should present similarities when the same surface is compared. Indeed, values are of the same order of magnitude, being in both surfaces, the rate constants, k obs DMA and k obs Trp , are 1 order of magnitude higher for ZnPc-PEDOT.…”