Plasma interactions with l-alaine have been studied as a basis of fundamental processes in plasma medicine. The plasma interactions with l-alaine have been examined for investigations of molecular degradations induced by direct exposures with Ar plasma and exposures with UV-VUV photons emitted from the Ar plasma via chemical bonding states analyses using X-ray photoelectron spectroscopy (XPS). The direct Ar-plasma exposure resulted in significant degradations of COOH group and CNH2 group. Separate experiments via irradiation with photons in UV and VUV regions from the Ar plasma showed that the molecular degradation via irradiation with photons in VUV region was much more significant than via irradiation with photons in UV region. These experiments have indicated that the causality of the molecular degradation of the l-alanine during the Ar plasma exposure is considered to be significant in the following order; ions > VUV photons > UV photons ∼ meta-stable radicals. Furthermore, the exposure with Ar-O2 mixture plasma resulted in insignificant change in the XPS C1s spectra for variation of the exposure time ranging from 30 s to 300 s, indicating that the surface etching process is much more considerable than the chemical degradation process.
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