Ultralong-lasting plasma-activated water: production and control mechanisms

Abstract

Despite the rapidly growing interest stemming from the broad-spectrum, high inactivation capacity, and environmental friendliness of the plasma-activated water (PAW), practical applications are limited because of the PAW’s short lifetime. While low-temperature storage can extend the lifetime, but the freezing and thawing processes are energy- and labor-intense and are generally not suitable for large-scale applications such as environmental and biomedical disinfection. This work addresses this issue by developing the ultra-long-life PAW at room temperature. The innovative approach is based on using DC needle-water discharges, wherein the gaseous products are blown out and absorbed separately by a gas flow. By simply adjusting the voltage and gas flow rates, two distinctive types of PAW with acidic hydrogen peroxide and nitrite as the main products are produced and separated in the discharge chamber and gas bubbling bottle. Intentional mixing of these two PAWs causes a chain chemical reaction dominated by peroxynitrite (ONOOH). This reaction can generate a variety of short-lived reactive species, thereby achieving the ultralong-lasting PAW with very stable inactivation ability. This study further demonstrates the ability to effectively control the reaction products in both chambers and provides insights into the secondary activation mechanism of short-lived reactive species stimulated by ONOOH.

Insights into the mechanisms of plasma physicochemical characteristics on ultralong-lasting plasma-activated water: the influence of DC power polarity on RONS generation

“…As evident from the above results, the alternation of power polarity significantly influences the preparation of ultralong-lasting PAW. Considering the crucial role of pH value and long-lived RONS such as H 2 O 2 and NO 2 − in the preparation of ultralong-lasting PAW as elucidated in our recent study, 17 the detection of pH, H 2 O 2 and NO 2 − was imperative. As shown in Fig.…”

“…29–31 Additionally, ONOO − , ˙OH and NO˙ all play roles in realizing the ultralong-lasting property as demonstrated in our recent study. 17 In summary, H + derived from the NO 3 − generation pathway might have a contributing effect on ultralong-lasting PAW, while the role of NH 4 + is more complex. The effect of NO 3 − and NH 4 + on the preparation of ultralong-lasting PAW warrants investigation in future experimental research.…”

“…To tackle this challenge, we designed an in-built DC power source-derived pin-water discharge device with a gas bubbling chamber in our recent work. This device facilitates the absorption of gas-phase discharge products 17 and enables the generation of ultralong-lasting PAW at room temperature. Depending on the activation method (direct or indirect), there were significant differences in RONS content and pH value between the discharge chamber PAW and the absorption chamber PAW.…”

“…1). 17 Recent studies have highlighted the significance of various process parameters, especially power polarity, in regulating RONS and pH value. 18–28 However, the impact of power polarity on the preparation method of ultralong-lasting PAW, including key long-lived RONS content and plasma characteristics, remains poorly understood.…”