%0 Journal Article
%A Sánchez del Río, Manuel
%A Boccaleri, Enrico
%A Milanesio, Marco
%A Croce, Gianluca
%A Beek, Wouter van
%A Tsiantos, Constantinos
%A Chyssikos, Georgios D.
%A Gionis, Vassilis
%A Kacandes, Georges H.
%A Súarez Barrios, Mercedes
%A García Romero, Emilia
%T A combined synchrotron powder diffraction and vibrational studyof the thermal treatment of palygorskite–indigo to produce Mayablue
%D 2009
%@ 0022-2461
%U https://hdl.handle.net/20.500.14352/49753
%X The heating process (30–200 ºC) of a palygorskite-indigo mixture has been monitored in situ andsimultaneously by synchrotron powder diffraction andRaman spectroscopy. During this process, the dye and theclay interact to form Maya blue (MB), a pigment highlyresistant to degradation. It is shown that the formation of avery stable pigment occurs in the 70–130 ºC interval; i.e.,when palygorskite starts to loose zeolitic water, and isaccompanied by a reduction of the crystallographic aparameter, as well as by alterations in the C=C and C=Obonds of indigo. Mid- and near-infrared spectroscopicwork and microporosity measurements, employed to studythe rehydration process after the complex formation, provideevidence for the inhibition of the rehydration of MB ascompared with palygorskite. These results are consistentwith the blocking of the palygorskite tunnel entrance byindigo molecules with a possible partial penetration insidethe tunnels. The surface silanols of palygorskite are notperturbed by indigo, suggesting that MB is not a surfacecomplex.
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