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In this paper, we compare the helium-based atmospheric pressure plasma jets (APPJs) with power-ground (PG) and power-floating (PF) configurations by using optical analysis. We find that the PG jet traps plasma between two electrodes (discharge region); thus, the hydroxyl radical intensity is significantly strong in discharge region; however, the plasma intensity in downstream region is relatively weak as compared with that of PF configuration. In contrast, using the APPJ with PF configuration, the hydroxyl radical and nitric oxide are approximately two and three times stronger, respectively, in the downstream region, even though the gas temperature and power consumption are lower. The PF jet successfully eradicates S. mutans and decreases water contact angle by ~40 within 15-s treatment, which demonstrates higher efficient than that of PG jet, and shows highly potential for dental filling demand. [ABSTRACT FROM PUBLISHER]

In this paper, we demonstrate that, by adding a small amount of \CF4 (2\%) into a compressed-air planar dielectric barrier discharge (DBD), one can effectively inactivate a B. subtilis spore up to 50 mm in width in the postdischarge jet region after ten passes of exposure of plasma plume (equivalent plasma exposure time of 1 s) for treatment distance of up to 14 mm for the spore concentration in the range of 10^5-10^7 CFU/mL. A possible mechanism is proposed, i.e., the chemically active F atoms and \CFn\ ({n} = 1 - 3) are generated through the help of abundant excited nitrogen molecules in the postdischarge region. [ABSTRACT FROM PUBLISHER]