Isomerization and redox tuning in ‘Maya yellow’ hybrids from flavonoid dyes plus palygorskite and kaolinite clays
Graphical abstract
Introduction
The Maya blue, a pigment widely used in wall paintings, pottery and sculptures by the Mayas and other ancient Mesoamerican peoples, has received considerable attention, since its discovery by Merwin [1], because of its intriguing durability and peculiar hue variability [2]. From the contemporary view, the Maya blue can be considered as a particular example of organic–inorganic hybrid materials [3], resulting from the association between indigotin or indigo (3H-indol-3-one-2-(1,3-dihydro-3-oxo-2H-indol-2-ylidene)-1,2-dihydro), a blue dye extracted from leaves of añil or xiuquitlitl (Indigofera suffruticosa) in Mesoamerica and a phyllosilicate clay, palygorskite, of ideal formula Si8(Mg2Al2)O20(OH)2(H2O)4·4H2O.
Apart from the still remaining controversy on the nature of the clay-dye association and the location of dye molecules in the clay framework [4], [5], [6], [7], [8], [9], [10], [11], the Maya blue has challenged to scientists due to the high symbolic value in the Maya culture contrasting with the absence of historical sources describing its preparation procedure. The studies of Gettens [12], Van Olphen [13], Shepard [14] and Kleber et al. [15] prompted the aforementioned view of the pigment as an organic–inorganic hybrid material. In parallel, Arnold discovered several locations in Yucatan peninsula where palygorskite has been found [16], [17] and, recently, has reported the first direct evidence of pre-Columbian sources of palygorskite for Maya blue [18].
The most extended view on the Maya blue, expanded to similar hybrid materials prepared from the dye and other clays [19], [20], [21] consider them as constituted by the original dye molecules distributed externally and/or inside pores and channels of the clay, with no other accompanying organic components [4], [5], [6], [7], [8], [9], [10], [11]. Based on solid state electrochemistry and spectral techniques, we proposed that, contrary to this dominating view, dehydroindigo, the oxidized form of indigo, accompanied the parent pigment in the clay and contributed significantly to the pigment hue and its variability [22], [23]. In this view, these hybrid materials can be described as a polyfunctional nanostructured systems where different dyes can be attached to the inorganic support in different sites [24], [25] the dye attachment to the clay determining the appearance of isomerization and redox tuning reactions [26], [27].
In this context, combination of electrochemical and spectroscopic data permitted to propose that the Maya blue pigment experienced local variations and evolved in time following a ramified scheme [23], [28] thus in agreement with the idea, expressed by Magaloni [29], that different technical schools existed. Additionally, recent archaeological discoveries suggested the existence of other associations between clays and indigoid dyes such as dehydroindigo and indirubin in the area Maya [30], [31], [32] so that leucoindigo [33] or isatin [30] could be present in several Mayan yellow pigments while dehydroindigo would be the majority component in remaining of a greenish plaster found in the site of La Blanca (Guatemala) [31], [32].
These results suggest a series of questions: is it possible to prepare other dye plus clay hybrid materials with stability comparable to that of the Maya blue?, or is Maya blue a unique material with regard to its significant redox tuning? Our more recent data on hybrids prepared from lapachol (2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone), a yellow dye extracted from guachupin plant (Diphysa robinoides, fam. Fabaceae) and porous phyllosilicates (palygorskite, sepiolite), reveals that isomerization, cyclization and redox tuning occurs accompanying the thermally assisted association of the dye to the clay, thus suggesting that there was a ‘Maya chemistry’ no limited to Maya blue [26], [27], [34].
In this report, we present a study on several dye-clay hybrid materials which could be used as yellow pigments in pre-Columbian civilizations [35]. Several yellow dyes were reported to be used on some Colonial Mexican documents [36]. Interestingly, the presence of yellow dyes associated to clays in the Codex Colombinus was reported by Torres et al. [37] and, more recently, in the Cospi Codex by Miliani et al. [38], thus suggesting the possibility of other than Maya blue dye-clay associations. Four species of dyes used in Mexico in pre-Columbian times [35], [38] have been selected for attaching to kaolinite (KA), a layered aluminosilicate (Al2Si2O5(OH)4), where only ‘external’ dye adsorption would be accessible and palygorskite (PL), which enables external attachment and inside channels or pores. Table 1 summarizes the chosen dyes with their nahuatl, Spanish and English names, botanic species of plants from which the dyes are extracted, and their main flavonoid chromophore molecules. The use of yellow dyes in molecular structure of the latter is illustrated in Fig. 1. Dyes will be labeled as zacatlaxcalli (ZAC), fustic (FUS), marigold (MAR) and cosmos (XOC). Analysis of the extracts from different dye plus clay complexes by high performance liquid chromatography with diode array detection (LC-DAD), and gas chromatography/mass spectrometry (GS–MS), combined with electron microscopy, visible and infrared spectroscopies reveals that, upon moderate thermal treatment, there is a significant modification in the composition of the guest dye. The chromatographic and spectroscopy study is combined with solid state electrochemistry of the hybrid materials in order to directly explore the possibility of dye redox tuning. Here, the voltammetry of microparticles (VMP), a methodology developed by Scholz et al. [39], [40] which provides analytical information on sparingly soluble solids attached to inert electrodes in contact with suitable electrolytes, has been applied. This technique is of application in a variety of fields [41] including archaeometry, conservation of heritage [42] and is complemented with scanning electrochemical microscopy (SECM) measurements. SECM is a technique used for characterizing surface properties providing an electrochemical topography image of surfaces, at the nanoscopic scale [43].
Section snippets
Reagents, reference products and Maya yellow-like specimens preparation
Methanol, acetonitrile, dimethylsulfoxide, acetone and formic acid (Carlo Erba), (HPLC grade). Sodium acetate (Fluka), chloroform (Sigma–Aldrich). N,O-Bis(trimethylsilyl)trifluoroacetamide (BSTFA, ⩾99.0% GC) and chlorotrimethylsilane (TMCS, ⩾99.0% GC) were purchased from Sigma–Aldrich (Madrid, Spain). Commercial pigments from natural sources, Cosmos (Couleur de Plantes, Rochefort, France), Cuscuta (Hunan Nat. Bioresources, Hunan, China), old fustic (Kremer) and Marigold (Changsha Natureway,
Materials characterization
ATR-FTIR spectra of dye-clay25 specimens were essentially identical to that of the corresponding clays, as expected in view of the low dye loading (see Supplementary information). Similarly, no significant differences were found between the TEM images of dye-clay25 and those of kaolinite and palygorskite crystals, the former consisting of hexagonal plates and the later forming aggregates of acicular crystals 0.5–1 μm sized having fine fiber structures, in agreement with previous reports [22],
Conclusions
Solid state electrochemical analysis of dye-clay specimens prepared upon attachment of zacatlaxcalli, fustic, marigold and cosmos to palygorskite and kaolinite at dye loadings ca. 1% wt provides well-defined voltammetric responses suggesting that a significant amount of the parent dye becomes oxidized when the material is submitted to heating between 100 and 180 °C. LC-DAD and GC–MS chromatographic analysis permits to identify hydroxyl benzoic acids (4-hydroxy benzoic acid, 2,4-dihydroxybenzoic
Acknowledgements
The authors wish to thank Prof. Costanza Miliani, who proposed the idea of studying flavonoid-clay hybrid materials, for their help in revising the manuscript. Financial support is gratefully acknowledged from the MEC Projects CTQ2011-28079-CO3-01 and 02 which are also supported with ERDF funds and “Grupo de análisis científico de bienes culturales y patrimoniales y estudios de ciencia de la conservación” Microcluster of the Excellence Campus of the University of Valencia.
References (77)
- et al.
Spectrochim. Acta B
(2004) - et al.
J. Archaeol. Sci.
(2012) - et al.
Microporous Mesoporous Mater.
(2011) - et al.
Spectrochim. Acta A
(2005) - et al.
J. Archaeol. Sci.
(2012) - et al.
Microchem. J.
(2007) - et al.
Electrochim. Acta
(2011) - et al.
Electrochim. Acta
(2013) Tetrahedron
(1977)- et al.
Microporous Mesoporous Mater.
(2013)
Microporous Mesoporous Mater.
Appl. Clay Sci.
Microporous Mesoporous Mater.
Am. J. Clin. Nutr.
Pharmacol. Ther.
De Bonampak al Templo Mayor: el azul Maya en Mesoamérica
New J. Chem.
Science
Clay. Clay Miner.
Anorg. Allgem. Chem.
J. Phys. Chem. B
J. Phys. Chem. C
J. Mater. Sci.
J. Mater. Sci.
Am. Antiq.
Science
Am. Antiq.
Stud. Conserv.
Am. Antiq.
Archaeology
Phys. Chem. Chem. Phys.
ACS Appl. Mater. Interface
J. Phys. Chem. B
Anal. Chem.
New J. Chem.
J. Phys. Chem. C
J. Mater. Sci.
Cited by (14)
Non-destructive and non-invasive methodology for the in situ identification of Mexican yellow lake pigments
2022, Microchemical JournalCitation Excerpt :Nevertheless, based only on the FORS spectra, as we have demonstrated in this work, it is difficult to confirm the presence of a marigold pigment. There are a very few works dealing with references prepared with marigold and s.s. marigold [24,65,66], for that reason, more references must be prepared and analyzed in order to gain a better understanding of these lakes and to refine the identification methods. From the lakes studied following this methodology, xochipalli presents the most unique characteristics: an “orange-red” color, a weak reddish UV fluorescence, a distinctive FORS spectrum (with both lake pigments falling into FORS group 3), and characteristic Raman bands at 1040 and 1123 cm−1.
Fibrous Clays in Dermopharmaceutical and Cosmetic Applications: Traditional and Emerging Perspectives
2022, International Journal of PharmaceuticsCitation Excerpt :The famous “Maya Blue (MB)” (Fig. 6A), developed by the ancient Mayas, is an organic–inorganic hybrid pigment consisting of natural indigo dye and palygorskite with strong resistance to acids, bases and organic solvents (Dong and Zhang, 2019). Inspired by MB, a range of similar hybrid pigments have been developed and applied in ceramics, painting, coating, printing, and luminescent materials, such as Maya Yellow (palygorskite/flavonoid or curcumin) (Domenech-Carbo et al., 2014; Li et al., 2021b), Maya Violet (palygorskite/methyl violet or alizarin) (Giustetto and Wahyudi, 2011; Szadkowski et al., 2022; Yamamoto et al., 2020; Zhang et al., 2015b) and Maya Red (palygorskite/methyl red) (Giustetto and Wahyudi, 2011). Many different methods have been reported to prepare the MB-like pigments, including adsorption-grinding (Giustetto and Wahyudi, 2011), self-adsorption assembly (Silva et al., 2018), one-step hydrothermal process (Lu et al., 2019; Tian et al., 2017a), microwave hydrothermal synthesis (Winum et al., 2021) and solid-state method (Ouellet-Plamondon et al., 2015).
Acid/base reversible allochroic anthocyanin/palygorskite hybrid pigments: Preparation, stability and potential applications
2019, Dyes and PigmentsCitation Excerpt :Therefore, it is indispensible to develop the natural, durable, and eco-friendly organic-inorganic hybrid pigments based on the natural colorants derived from natural plants. At present, the most common means of constructing hybrid pigments are realized by intercalating or encapsulating of organic dyes into inorganic carriers, which is in favor of significantly improving the stability of organic dyes, and the involved inorganic carriers are mainly focused on zeolite and clay minerals [12–16]. Among clay minerals, palygorskite (PAL) as a naturally hydrated magnesium aluminum phyllosilicate, is widely used as an inorganic carrier for constructing hybrid materials.
Learning from ancient Maya: Preparation of stable palygorskite/methylene blue@SiO<inf>2</inf> Maya Blue-like pigment
2015, Microporous and Mesoporous MaterialsCitation Excerpt :Different from other clays, PAL has a unique fibrous or rod-like microstructure due to inversion of oxygen atoms on the edge of silicon–oxygen tetrahedral layers, which results in discontinuous arrangement of the aluminum-oxide octahedral layers [14]. The large surface area, moderate cation exchange capacity and excellent adsorption property of PAL are of great benefit for its applications in various fields, especially in the adsorption of guest molecules [15,16] and ions [17], and the preparation of organic/inorganic nanocomposites [2,18,19]. A particularly fascinating property of Maya Blue is that it does not fade even in an environment of high humidity and high temperature for thousands of years.
Limits and perspectives of archaeometric analysis of archaeological metals: A focus on the electrochemistry for studying ancient bronze coins
2020, Journal of Cultural HeritageCitation Excerpt :Among these, square wave voltammetry (SWV) is one of the techniques widely used with VIMP methodology. The good results obtained in the first application of VIMP on mineral samples, allowed to introduce it in the archaeometric field, characterizing a variety of materials: pigments in oil, paintings and frescoes [94–101], dyes [102], minerals [86,103–106], plants [107–109], asphalts [110,111], ancient potteries [112,113], papers [114] and obviously archaeological metals and coins [19,56,59,82,115–121]. Domènech-Carbò introduced this archaeometric use of VIMP into the research in the early 2000s and it was immediately evident that this technique could be a valid tool for the analysis on ancient object.