Photolysis of Phenylalanine in the Presence of Oxidized Carbon Nanotubes

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• 作者：Eduardo Humeres ; Eduardo Pinheiro de Souza ; Nito Angelo Debacher ; Regina de F.P.M. Moreira ; Cristiane Nunes Lopes ; Mp>ap> Isabel Fern谩ndez ; J. Arturo Santaballa ; Mois茅s L. Canle ; Wido H. Schreiner ; Abil E. Aliev
• 刊名：Langmuir
• 出版年：2015
• 出版时间：January 13, 2015
• 年：2015
• 卷：31
• 期：1
• 页码：164-170
• 全文大小：286K
• ISSN：1520-5827

文摘

Photolyses at 254 nm of phenylalanine (Phe) in aqueous solutions, were carried out in the presence of oxidized carbon nanotubes modified by the reaction with SO₂ (mNTO). Kinetics of the photolyses were followed by UV spectrophotometry at 220 nm, and the products were characterized by HPLC, XPS, and p>13p>C-SSNMR. The ratio of the initial rates of photolysis in the presence and absence of mNTO, k*/k_o*, showed a systematic decrease. The photolytic decay of Phe occurs with minor formation of tyrosine. The mass of nanotubes produced an exponential attenuation of the photolytic decomposition of Phe. Total carbon analyses (TCA) showed no inorganic carbon formation after the photolyses. The first-order rate constant of photofunctionalization of mNTO by the insertion of phenylalanine onto the nanotube matrix was calculated from TCA to be k_in = 30.1 minp>鈥?p>. Comparison of the XPS spectra of the mNTO before and after the photolysis, using the atom inventory technique, suggests the insertion of Phe along with the extrusion of a sulfide radical anion (p>鈥?/sup>Sp>鈥?/sup>) which undergo subsequent oxidation to SO₄p>2鈥?/sup>. The obtained results show the effects of mNTO on the photolysis of Phe and provide a new method of photofunctionalization of carbon materials, modified by the intermediates of the reduction of SO₂, with an organic moiety.