Photochemical Reactivity between Graphene and Organic Peroxides

• Main Authors: Ya-lan Chu, 朱雅蘭
• Other Authors: Chao-Ming Chiang
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/22870470013634774187

碩士 === 國立中山大學 === 化學系研究所 === 104 === Graphene is a two-dimensional material composed of carbon atoms that are arranged in a single-layer hexagonal crystal lattice form. Due to its complete conjugated  system, graphene is chemically stable and thus has high potential in a variety of applications. Therefore, research on graphene has become popular and challenging in recent years. Previous studies have indicated that organic peroxides could undergo photolysis upon irradiation. In this research, we select di-tert butyl peroxide (DTBP) and tert-butyl peroxybenzoate (TBPB) as the radical initiator, respectively, and 365 nm LED as the light source to investigate the thermochemistry and photochemistry between graphene and adsorbed peroxides. Experiments were carried out in our ultrahigh vacuum system and in situ surface analytic techniques, including temperature programmed desorption (TPD) and reflection adsorption infrared spectroscopy (RAIRS), were employed. The interaction of DTBP with the surface of graphene showed that only the monolayer desorption was observed at 194 K. Neither thermochemistry nor photochemistry reactions happened.The results of reacting TBPB with the surface of graphene showed that TBPB was found to be depleted by 1 hour UV irradiation in the PITPD measurement. RAIR spectra showed that both carbonyl stretching vibration at 1765 cm-1 and peroxyl stretching vibration at 835 cm-1 almost disappeared after 1 hour irradiation, but two new peaks (1210 and 930 cm -1) simultaneously emerged. Hence, we confirmed TBPB underwent photolysis along with the formation of radical intermediates. Since all IR features faded out above 300 K, covalent bond formation between the expected photochemically generated phenyl or methyl radicals and the graphene carbons didn’t occurred. Instead, these radicals underwent disproportionation and thus formed benzene, tert-butanol and isobutylene epoxide as the final products. All products generated desorbed from the graphene surface before 200 K. TBPB itself does not absorb 365 nm wavelength of light but graphene does. Photoexcited graphene serves as a photosensitizer responsible for delivering hot electrons to the LUMO of TBPB. Meanwhile, an electron within the TBPB HOMO transferred to graphene, the energy transfer resulted from the electron-exchange triggered formation of ground state graphene and excited state TBPB. The excited state TBPB was decomposed via homolytic cleavage of O-O bond to render radicals.