Search results for "indigo"

‘Maya chemistry’ of organic–inorganic hybrid materials: isomerization, cyclicization and redox tuning of organic dyes attached to porous silicates

2013

[EN] Association of indigo and lapachol dyes to aluminosilicate clays yields polyfunctional organic – inorganic hybrid materials forming Maya Blue-like systems. Upon partial removing of clay's zeolitic water by moderate thermal treatment, abundant isomerization, cyclicization and oxidation reactions occur defining a‘ Maya chemistry whose complexity could explain the versatile use of such materials in the pre-Columbian cultures and permits the preparation of polyfunctional materials potentially usable for therapeutic and catalytic purposes.

All-organic device with integrated chemical filter dedicated to the selective measurement of NO2 in air

2010

Abstract An original organic semiconductor gas sensor devoted to the selective monitoring of nitrogen dioxide in air has been successfully developed. This device combines the great sensitivity and the partial selectivity toward oxidizing gases of a molecular organic semiconductor, copper phthalocyanine, with the O3 filtering selectivity of an organic material, indigo. Experimental measurements highlight filtering yield of indigo close to 100% toward O3 and lower than 10% for NO2. Nanometric indigo layers were realized for the first time by thermal evaporation and characterized by FT-IR spectroscopy. Such all-organic device exhibits a high NO2 sensitivity for low concentrations, a resolution…

Insights into the Maya Blue technology: greenish pellets from the ancient city of La Blanca.

2011

Financial support is gratefully acknowledged from the MEC Projects CTQ2011-28079-CO3-01 and 02 which are also supported with ERDF funds. Research was conducted within the "Grupo de anlisis cientifico de bienes culturales y patrimoniales y estudios de ciencia de la conservacion" Microcluster of the University of Valencia Excellence Campus. The authors would like to thank Dr. Isabel Solana (SCSIE, UV), Dr. Jose Luis Moya Lopez, and Manuel Planes Insausti (Microscopy Service UPV) for their technical support.

From Maya Blue to “Maya Yellow”: A Connection between Ancient Nanostructured Materials from the Voltammetry of Microparticles

2011

The yellow hue of a series of samples from wall paintings in several Mayan archaeological sites can be attributed to the presence of indigoid compounds, including isatin and dehydroindigo, attached to palygorskite, a local phyllosilicate clay. SEM/EDX, TEM, UV/Vis spectroscopy, and voltammetry of microparticles show that the ancient Mayas could prepare indigo, Maya Blue, and "Maya Yellow" during successive stages. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Les exilés et l'enseignement de l'espagnol en France

2006

International audience; Au moment où la France accorde l’asile au demi million d’Espagnols qui fuient Franco, la langue espagnole n’intéressait qu’une minorité restreinte d’élèves. Au début des années cinquante, alors que l’anglais et même l’allemand connaissaient les faveurs accrues de la jeunesse, l’espagnol continuait de végéter au sein d’un système éducatif où rien n’était entrepris pour le rendre plus attractif. Au cours des années qui suivirent, l’arrivée au lycée des enfants des exilés républicains, et d’une façon plus localisée, le souvenir du rôle joué par les républicains-résistants dans la libération des certaines villes du sud, modifièrent sensiblement cette situation. Les desce…

Endoscopic surveillance in ulcerative colitis: smart biopsies do it better.

2007

Patients with ulcerative colitis (UC) have a significantly higher risk for the development of colitisassociated colorectal cancer. Endoscopic surveillance is recommended. The growth pattern of dysplastic tissue is often multifocal and flat. Thus, significant lesions might be overlooked. Multiple random biopsies are recommended, but cannot eliminate the possibility of missed cancers with severe consequences for the patient. Chromoendoscopy with methylene blue or indigo carmine can unmask flat lesions and may solve this problem. In addition, confocal laser endomicroscopy enables in vivo histology with subcellular resolution during ongoing colonoscopy and leads to highly selected mucosal biops…

Chromoendoscopy and intravital staining techniques.

2000

Chromoendoscopy and intravital staining techniques are synonymous methods for the endoscopic early detection of malignant changes in the intestinal tract. Endoscopic intravital staining involves the use of absorptive stains (methylene blue and Lugol's solution), contrast stains (indigo carmine) and reactive stains (Congo red). Lugol's iodine solution is used to identify superficial carcinomas in the squamous epithelium of the oesophagus. Methylene blue stains the specialized intestinal epithelium in Barrett's oesophagus and, in addition to this, is helpful in the diagnosis of dysplasia. Intravital staining with indigo carmine contributes to contrasting and accentuating changed mucosal proce…

Identification of indigoid compounds present in archaeological Maya blue by pyrolysis-silylation-gas chromatography–mass spectrometry

2014

Abstract A study based on the use of pyrolysis-silylation-gas chromatograpy–mass spectrometry (Py-GC–MS), which aimed to identify indigoid compounds and to clarify the multicomponent composition of Maya blue (MB) pigment, has been carried out. A series of reference compounds and synthetic MB specimens prepared in the laboratory have been analysed by this technique. An analysis of archaeological MB samples from 14 Maya archaeological sites from Mexico and Guatemala has also been performed. The obtained results demonstrate that, in addition to indigo, oxidised species such as dehydroindigo, which is formed as a result of redox processes taking place while preparing the pigment, are present in…

The Maya Blue Pigment

2011

Abstract Maya blue is an artificial pigment fabricated by the Maya in the early first millennium AD. The pigment was used in Prehispanic times from the southern Maya region to most Mesoamerican cultures. Maya blue is made from indigotin mixed with palygorskite. This light blue pigment is surprisingly resistant to degradation in adverse environmental conditions, as it is unaffected by the attack of acids, alkalis, oxidants, reducing agents and organic solvents. Scientists do not fully agree in the mechanism of this organoclay interaction. The fabrication and distribution of this pigment probably required a sophisticated technical and commercial infrastructure. This chapter reviews the presen…

2004

Analysis of extracts from two woad species (Isatis tinctoria and Isatis indigotica) and Polygonum tinctorium revealed that only one indigo precursor (indican) was present in Polygonum, but two precursors were found in Isatis spp. This was done using high performance liquid chromatography (HPLC), coupled to an evaporative light scattering detector (ELSD). In Isatis spp., the indigo precursors indican and a fraction representing isatan B were identified. The proportion of indican and isatan B was different between the two Isatis spp. tested. For the first time, it was possible to quantify the precursors in woad plant species, and the results were found to be in good agreement with those made …