Treatment of Glycine and Proline in Late Ar‐O₂ Afterglow

Abstract

Glycine and proline have been treated in Ar-O 2 afterglows at low temperature to study their modification in highly reactive non-equilibrium media. These two amino-acids can be efficiently etched in suited conditions. In the case of glycine, O( 3 P) is the main reactive species responsible for the etching mechanism. It reacts preferentially with the -CH 2 -group instead of the amine group -NH 2 . Further oxidation processes are observed but they are not rate-limiting. Etching of proline is a multi-step process, probably initiated by O( 3 P) and then followed by reactions which control the etch-rate, the opening of the non-aromatic ring of proline being a probable route.

Influence of applied plasma power on degradation of L-proline in an inductively coupled RF plasma reactor

“…Previous works that used Ar/O 2 mixture under different conditions (such as pressure, temperature and source power) [2,5,6,35,38] analyzed the residual products directly in the sample (after treatment) and evidenced the formation of products with lower molecular mass than that of L-proline [6]. This result corroborates with Figure 3, where the formation of volatile products of lower molar mass occurs from fragmentation of L-proline.…”

“…This result is corroborated by the shorter time required for degradation in the applied power of 200 W (Figure 2). According to some works [4,6,33], degradation of organic molecules occurs through chemical reactions with species generated in the plasma like singlet oxygen, reactive oxygen atoms and even ozone molecules. Oxygen molecules are also responsible for the degradation of amino acid molecules in aqueous environment.…”

“…As an alternative technique, there is the plasma cleaning technology, which has been the object of study of several works [2][3][4][5][6][7] and shown to be an efficient technique in degradation of compounds with different organic functions. Plasma cleaning technologies are already being used in the cleaning of inputs in the semiconductor sectors [8], food industry [9], medical [10,11], sputtering printed circuit boards [12], surface modification [13][14][15][16] and nitriding [17,18].…”

“…Aiming for a better understanding on the degradation mechanisms of organic functions by plasma, different compounds were studied: Hexatriacontane (C 36 H 74 ), which has only C-C and C-H bonds in its structure [6]; stearic acid (C 18 H 36 O 2 ) which has an acidic function (Carboxyl) [4] and bi-phenil (C 12 H 10 ) which has an aromatic ring [24]. In these works, argon (Ar) and argon-oxygen (Ar-O 2 ) plasma were used to study the degradation, functionalization and branching.…”

“…In NOMINÉ'S work and co-workers [6], authors treated L-proline and glycine samples in an Ar/O 2 plasma (10% V), generated by microwave. The authors verified that the proline engraving process occurs in multiple steps, probably initiating the reaction with oxygen [O ( 3 P)] and subsequent disruption of the nonaromatic ring.…”