To fit a specific application, a cheap and effective manner of measurement of chemistries in plasma‐activated water (PAW) is in demand. We propose a digital colorimetry‐based method of quantifying the long‐lived species in PAW using only smartphones and specialized software. Pin−plate discharge and surface microdischarge were used to generate the PAWs. H2O2 and NO2− were selected as representatives for the test. Various color parameters were extracted from images of a solution consisting of testing species and colorimetric reagent. Specialized curve‐fitting strategies were developed during data processing. The results were consistent with those measured by UV–Vis spectrometry, but they provided better performance and simplified operation. Additionally, the proposed PAW generator design can be integrated with the detecting module based on this method.

This study investigated NH4NO3 formation by air plasma and NH3 in three different reaction modes for nitrogen fixation and environmental protection. A DC‐driven needle–needle discharge was used. We found that NH4NO3 could be effectively formed by directly mixing NO x (generated by air discharge) and NH3 in Mode 1. In Mode 3, when discharging in the air/NH3 mixture, no NH4NO3 was detected. However, in Mode 2, when discharging in the NO x /air/NH3 mixture, NH4NO3 was first formed and then subsequently decreased as the discharging time increased. NH4NO3 was identified by white smoke observation and gas/aqueous‐phase Fourier‐transform infrared spectroscopy (FTIR) analysis. Stable NH4NO3 formation may be affected by self‐thermal decomposition and NH3 decomposition through discharge.

Despite becoming increasingly established as a treatment technique, the mechanism underlying the plasma treatment of onychomycosis has yet to be elucidated. Here, we focus on the interactions between the nail plate and a surface microdischarge plasma, including penetration, uptake, and chemical reactions. Results show that long‐lived gaseous species from plasma can penetrate the nail plate effectively and are primarily responsible for the instantaneous antionychomycosis effect. The amount of uptake far exceeded that of penetration. Attenuated total reflection‐Fourier‐transform infrared spectroscopy and X‐ray photoelectron spectroscopy results show that antimicrobial compounds form on the nail surface. Combined with the uptake of active species in the nail plate, these antimicrobial compounds may inhibit microorganism growth, thereby promoting long‐term protection against onychomycosis.

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