Photosensitive Self-assembled Membrane Of Amino Acidic Compounds Against Copper Corrosion

Copper and its alloys are widely used in heating and cooling systems, because of their good thermal conductivity and mechanical properties. Nevertheless, they react easily in ordinary environment containing oxygen. Thus, the study of their corrosion inhibition has attracted much attention. One of the most important methods in the corrosion protection of copper is the use of organic inhibitors. The amino-acid compounds are cheap, non-toxic and easily bio-degradable. They have opened the new domain for the safe and highly effective use of corrosion inhibitors. Self-assembled monolayers (SAMs) formed spontaneously by chemical adsorption and self-organization on the surface of the metal offers great flexibility for the control of surface structure and interfacial properties. The SAMs is the ideal technology of studying metal corrosion, having broad application prospect and important theory value. New methods of expressing the SAMs face with new request. The organic illumination compounds with fluorescence emission have gained much attentions. They are important functional materials, can be used for the fluorescent probe, the sensor and the fluorescence analysis, and so on.In this dissertation, three amino acid compounds including cystein(Cys), methionine(Met) and glutathione(Gsh) are assembled on the copper surface, respectively. Their protection effect are investigated by electrochemical measurement. The SEM and EDS analysis of the SAMs are conducted. It shows that the adsorption of the amino acids and their derivatives on copper surface obeys the Langmuir isotherm. The free energy of adsorption△Gads is -31.49 kJ·mol-1 for Cys,-29.69 kJ·mol-1 for Met,and -30.89kJ·mol-1 for Gsh. The best assemble condition is 1h immersion at 10-2 mM concentration for Cys, 3h immersion at 10mM concentration for Met, and 6h immersion at 1mM concentration for Gsh. The results also show that the Cys film formed on the electrode at pH=3 is more stable than that at other pH values. And protection efficiency of Met SAMs formed at pH =9 is the best.The bilayer membrane of NADA/amino acid/Cu is assembled on Cu electrode by the electrostatic interaction between the fluorescence regent 1-naphthylamine diacetate acid(NADA) and amino acid compounds. The protection properties of the bilayer membrane on copper in 0.5 M NaCl solution are examined by electrochemical impedance spectroscopy (EIS) and their fluorescence spectrum are also measured. The correlation between the fluorescence intensity and the impedance is investigated. The correlation coefficient R is 0.98336 for NADA/Cys/Cu bilayer membrane, 0.9468 for NADA/Met/Cu bilayer membrane, and 0.86829 for NADA/Gsh/Cu bilayer membrane, respectively. A photosensitive measurement is established to evaluate the protection of the inhibitive self-assembled monolayers.