Figure 2.

(a) Visual observation for generation of OH^• species inside the DI water and PBS when the UV mercury lamp has been irradiated onto their surface; (b) Visual confirmation for generation of H₂O₂, inside the DI water either by irradiation of UV or plasma bombardment onto the water surface with quartz filter located just below the DI surface; (c) OH^• density vs the external H₂O₂ concentrations in DI water at 4 mm depth position, when the Ar plasma jet has been bombarded; (d)Density of OH^• vs the depth positions of the DI water and PBS solutions, generated by Ar plasma jet operated in Ar glove box, under the low electrical power of 4.9 W and driving frequency of 35 kHz.