Plasma-activated water (PAW) represents a promising green antibacterial agent for biomedical and agricultural applications. In this study, a novel AC multi-needle-to-water discharge device was developed to investigate the effects of gas flow on the generation and chemical composition of PAW. It is shown that the concentrations of NO 3 − and N(III) ( NO 2 − and HN O 2 ) in the PAW both increased with an extension of the plasma-processing time and a reduction of the gas-flow rate. The absorption of gas-phase products carried by the gas flow from the discharge chamber was found to be beneficial for the generation of both NO 3 − and N(III) in the PAW at a gas flow rate of 20–60 L h−1, yet their concentrations were still lower than those without any feeding gas. As opposed to NO 3 − or N(III), the H 2 O 2 concentration in the plasma-activated phosphate buffer solution (PAPBS) increased under stronger gas flows and was almost unaffected by absorption in PAPBS. The pH value of PAW increased at higher gas flow rates. A comparison of the N(III) in PAW and PAPBS reflects the effects of the reactions of NO 2 − and H 2 O 2 in the two different working liquids. To quantify the effects of gas flow on the discharge characteristics, gas temperatures were calculated from the optical emission spectra and were proven to be flow-independent near the discharge channel. Fourier transform infrared (FTIR) measurements of the gaseous products during the discharge, and further analysis of possible reaction pathways indicated that by controlling the gas flow in the multi-needle-to-water discharge system, the concentration of long-lived species in PAW could be tuned, which might favor the generation of ONOOH . These findings contribute to a better understanding of effective electric discharge-related mechanisms for enhancing the biochemical and chemical activities of PAW.

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Detecting the light from different freedom is of great significance to gain more information. Two-dimensional (2D) materials with low intrinsic carrier concentration and highly tunable electronic structure have been considered as the promising candidate for future room-temperature multi-functional photodetectors. However, current investigations mainly focus on intensity-sensitive detection; the multi-dimensional photodetection such as polarization-sensitive photodetection is still in its early stage. Herein, the intensity-and polarization-sensitive photodetection based on α-In 2 Se 3 is studied. By using angle-resolved polarized Raman spectroscopy, it is demonstrated that α-In 2 Se 3 shows an anisotropic phonon vibration property indicating its asymmetric structure. The α-In 2 Se 3 -based photodetector has a photoelectric performance with a responsivity of 1936 A/W and a specific detectivity of 2.1 × 10 13 Jones under 0.2 mW/cm 2 power density at 400 nm. Moreover, by studying the polarized angleresolved photoelectrical effect, it is found that the ratio of maximum and minimum photocurrent (dichroic ratio) reaches 1.47 at 650 nm suggesting good polarization-sensitive detection. After post-annealing, α-In 2 Se 3 in situ converts to β-In 2 Se 3 which has similar inplane anisotropic crystallinity and exhibits a dichroic ratio of 1.41. It is found that the responsivity of β-In 2 Se 3 is 6 A/W, much lower than that of α-In 2 Se 3 . The high-performance light intensity-and polarization-detection of α-In 2 Se 3 enlarges the 2D anisotropic materials family and provides new opportunities for future dual-mode photodetection.

Memory device is an important part of electronic equipment. 2D transition metal dichalcogenides that exhibit novel electrical characteristics hold promise in developing new types of memory device. Here, the memory effect in 2D mica/WSe2 heterostructure is investigated. Under applying constant bias voltage and gate voltage, the K+ ions in mica will migrate in the direction of the electric field and be trapped to enable the memory function. The gradient K+ ions work as long‐range scatters to electrostatically dope the WSe2 channel. The shift of the threshold voltage indicates an electrostatic doping concentration up to 2.11 × 1012 cm−2. The operating voltage is as low as 10 V and the on/off ratio is estimated to be 104. To determine the mechanism, the dynamic behavior of the device is discussed and a model is proposed which reveals the correlation between the programming/erasing process and the device performance. Moreover, through defining and studying the effective charge trapping rate, θ, it is found that the trapped charge is proportional to the charge flowing through the channel which means that the device performance can be finely tuned by the programming process.

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