Sousa Micaela M, Miguel Catarina, Rodrigues Isa, Parola A Jorge, Pina Fernando, Seixas de Melo J Sérgio, Melo Maria J
Department of Conservation and Restoration, New University Lisbon, Campus da Caparica, Portugal.
Photochem Photobiol Sci. 2008 Nov;7(11):1353-9. doi: 10.1039/b809578g. Epub 2008 Sep 1.
The degradation of indigo and its water soluble derivative indigo carmine was investigated under light excitation in the presence and absence of molecular oxygen in solution (homogeneous) and gels (heterogeneous) media. Collagen and carboxymethylcellulose (CMC) aqueous gels were chosen to simulate a natural textile environment, wool and cotton, respectively. Isatin was found to be the major degradation product of indigo. In solution, the photodegradation quantum yields (Phi(R)) were in the order of 10(-4), with the exception of aqueous media (Phi(R) = 9 x 10(-6)), and dependent on the irradiation wavelength. In the case of indigo carmine the Phi(R) values were found to suffer a 2-fold increase upon going from water to gels. The results indicate the absence of degradation products involving singlet oxygen and suggest peroxides, or other oxygen based radicals, to have a key role in the degradation of indigo. Finally, the relevance of the simulation is discussed by comparing the main degradation products to those found in the blues of millenary Andean textiles.
在溶液（均相）和凝胶（非均相）介质中，在有和没有分子氧存在的情况下，研究了靛蓝及其水溶性衍生物靛蓝胭脂红在光激发下的降解情况。分别选择胶原蛋白和羧甲基纤维素（CMC）水凝胶来模拟天然纺织环境羊毛和棉花。发现异吲哚酮是靛蓝的主要降解产物。在溶液中，光降解量子产率（Phi(R)）约为10^(-4)，水性介质除外（Phi(R) = 9×10^(-6)），且依赖于照射波长。对于靛蓝胭脂红，发现从水到凝胶时Phi(R)值增加了2倍。结果表明不存在涉及单线态氧的降解产物，并表明过氧化物或其他氧自由基在靛蓝降解中起关键作用。最后，通过将主要降解产物与在安第斯千年纺织品蓝色中发现的降解产物进行比较，讨论了模拟的相关性。
