Effect of alcohol addition on radical production*

Atmospheric pressure plasma can produce many kinds of reactive oxygen radicals, which make important role in plasma application in technological, chemical and biological field. Radical production occurs mainly in discharge gas and in the gas-liquid interface. Discharge performance depends on the composition of discharge gas. Reduction of the breakdown voltage is reported to become smaller by adding ethanol. In this work, effect of alcohol addition to argon gas on this radical production. Radical monitering methods with heat flux measurement and chemical probe will also reported.

Compared with pure argon case, plasma jet length shrinks but plasma heat flux becomes larger by ethanol addition. This means heat flux is carried by radicals produced and released on the target surface through the recombination process. So this results indicates radical enhancement occurs.

Our group has proposed that polyvinyl alcohol(PVA) - iodine potassium (KI) could be a new chemical probe. Color change of PVA-KI is enhanced by small amount of alcohol addition. There is an optimum value of alcohol for radical production. Although decompose of alcohol becomes source of oxygen radicals, alcohol itself works as radical scavenger.