Numerical Investigation of Plasma Generated Reactive Species in Formamide Solutions

The plasma-generated reactive species play a crucial role in plasma medicine. It is notable to investigate the mass transfer process of active species in liquid on the surface of biological tissues. As the simplest model of the peptide bond, formamide is added to the aqueous solution to simulate the protein’s peptide backbone. In this work, the process has been investigated using the numerical simulation based on a 1-D drift–diffusion model. The concentration and penetration depth of five main reactive oxygen species (ROS) (OH, OH2, O3,
$\text{O}_{2}^{-}$
, and H2O2) were analyzed in the formamide solution after 60 s of plasma treatment. The results show that formamide played an important role in the penetration of the OH, OH2, O3, and
$\text{O}_{2}^{-}$
species. The penetration depths of O3 and OH increase to a few tens of micrometers with the increase in formamide concentration. On the contrary, the concentration and penetration depth of
$\text{O}_{2}^{-}$
declined substantially, due to the drop in the yield of
$\text{O}_{2}^{-}$
produced by electrons reacting with oxygen. When the concentration of formamide ranges from 10−5 to 10−3 mol/L, the penetration depth of species is more affected. These results may be useful for evaluating ROS’ mass transfer in plasma drugs.