碱性介质中L-赖氨酸在纳米金膜电极上的吸附和氧化过程

采用原位红外反射光谱(in situ FTIRS)和循环伏安法(CV)研究了碱性介质中L-赖氨酸在纳米金膜电极(nm-Au/GC)上的解离吸附和氧化过程. 研究结果表明, 在碱性溶液中以阴离子形式存在的赖氨酸-OOC—CH—NH2—(CH2)4—NH2]在低电位区间(-0.95~-0.80 V, vs. SCE)发生部分解离, 生成AuCN-物种(约2110 cm-1), 同时赖氨酸阴离子的羧基侧还可通过两个氧原子与金电极表面相互作用. 随着电位的升高, 吸附态CN-氧化产生NCO-, OCN-和AuCN, 其对应的红外吸收峰分别位于2254, 2168和2226 cm-1附近.

Adsorption and Oxidation of L-Lysine on Nanometer Scale Au Film Electrodes in Alkaline Solution

Amino acids are the building blocks of peptides and proteins. An amino acid molecule contains multi-functional groups such as —COOH, —NH2, —OH and —CHx, which leads to the amino acids to be used often as model reagents in surface electrochemistry and electrocatalysis, for the purpose of obtaining information about the interaction of different functional groups with electrocatalyst surfaces and the role of these functional groups in electrocatalysis of small organic fuels. Up to now, the reaction mechanism of amino acid electrooxidation is still far to be well understood. In this study, adsorption and oxidation of L-lysine on electrodes of nanometer scale thin film of gold in alkaline solutions were investigated using in situ FTIR reflection spectroscopy and electrochemical methods. The FTIRS result demonstrate that the dissociative adsorption of lysine on Au surface can occur in a low potential region, and the chemisorbed species were identified as adsorbed CN- species(cyanide, 2110 cm-1). Another reversibly(or loosely) adsorbed species may be the deprotonated amino acids, which were bound to the surface by both oxygen atoms of carboxyl group. When electrode potential is higher than 0.1 V, the adsorbed CN- can be oxidized to NCO-(2254 cm-1); when electrode potential is above 0.3 V, OCN-(cyanate, 2168 cm-1) appeared as oxidative species; and when the potential is increased further up to 0.5 V, another further oxidative species, the AuCN species(gold cyanide, 2226 cm-1) appeared. This study is of importance in understanding the interaction between amino acids and Au film electrodes.