A double-layer (DL) nozzle device mounted on a dielectric tube for expanding the range of atmospheric pressure plasma jet is designed. Using the hierarchical structure of the nozzle, multiple discrete currents are obtained to form multiple discharge channels. The results show that the discrete flow can be divided into three categories: upper jet, middle jet and lower jet. For media tubes that are not equipped with the nozzle, the range of active substances of the DL nozzle device can be expanded to 5 times, the area can reach 1017 mm2, and the treatment of Escherichia coli (E. coli) for 120 s can achieve 100 % inactivation. A numerical model is established to analyze the distribution of the air flow field and helium mass fraction of the DL nozzle device. The DL nozzle device was used to treat deionized water (DIW), and plasma activated water (PAW) with better physical and chemical properties was obtained. In particular, the PH value was reduced from 7.39 before treatment to 4.16 after 180 s treatment. The concentration of H2O2 increased significantly from 23.5 to 64.56 mu M in 90 s.
