Non‐OH‐driven liquid‐phase chemistry in water microdroplets

Abstract

Water microdroplets containing organic and fluorinated compounds, such as formate, perfluorooctanoic acid (PFOA) and triflic acid, were exposed to a radiofrequency glow discharge plasma with a droplet residence time on the order of milliseconds. Triflic acid remained unaffected by any plasma condition while >75% decomposition of formate and PFOA could be achieved. In situ hydroxyl (OH)‐laser‐induced fluorescence measurements near the droplets confirmed that the conversion was independent of the OH flux to the droplet. A series of control experiments suggest that the contribution of vacuum UV photons in such decomposition of aqueous compounds can be significant for He and He + 17% Ar plasmas and can also explain unexpected decomposition trends as a function of droplet residence time in the plasma.

Mechanisms of controlled stabilizer-free synthesis of gold nanoparticles in liquid aerosol containing plasma

“…With a total gas ow rate of 1 to 3 slm, the average gas velocity varied from 0.5 to 1.4 m s −1 , corresponding to droplet residence times of 5.6-10.9 ms and 4.9-10.2 ms measured in He/Ar and He/Ar/H 2 O plasmas, respectively. 51,52 The electron properties determined from continuum radiation as a function of total gas ow rate and plasma power are shown in Fig. S2 in ESI.…”

“…where n e , D a , R p and L s , are the electron density, the ambipolar diffusion coefficient, the droplet radius and the sheath thickness respectively. We assumed similarly to Nayak et al 51 that the dominant ion was (H 3 O + $H 2 O) with a reduced zero-eld mobility (m 0 ) of 17.3 ± 0.9 cm 2 V −1 s −1 (ref. 54) and the sheath thickness was ∼100 mm.…”

“…It has been previously shown that for similar conditions photolysis can contribute to reactivity in the droplet. 51 Furthermore, in acidic solution (the pH of 1 mM precursor is ∼3.0), the H radicals could also be produced within the droplet via scavenging of e aq − or injected ions by a proton as…”

“…The plasmamicrodroplet reactor used in this study provides a controlled environment, and has previously been used for the investigation of plasma conversion of organic and uorinated compounds in water droplets. [49][50][51] We not only show that we can produce stabilizer-free AuNPs with a narrow size distribution, but we also investigate the effect of plasma-produced short-lived species (electrons and VUV photolysis) and H 2 O 2 by proposing a reaction-diffusion model consisting of fast reduction processes and particle growth mechanism that is able to describe the experiment. The model analysis provides a picture of overall process of AuNPs formation consisting of steps with different timescales.…”

Plasma Electrochemistry for Carbon–Carbon Bond Formation via Pinacol Coupling

“…A decrease in faradaic efficiency was observed upon increasing the NaClO 4 concentration, albeit substantially less than for NaNO 3 , which was verified by the reactiondiffusion model (see SI for details). The potential role of vacuum-ultraviolet (VUV) radiation, which has recently been shown to be important in plasma-assisted degradation of organic compounds in liquids, 45 was investigated by exposing MFB to a VUV lamp, and replacing Ar with He in our plasmaliquid process. The lamp was found to produce very little pinacol product (Figure S9), and changing to He, which should produce lower wavelengths than Ar, had minimal effect on the pinacol product yield (Figure S10).…”