title: A hybrid material assembled by anthocyanins from açaí fruit intercalated between niobium lamellar oxide.
abstract: Organic-inorganic hybrid materials can be prepared dispersing organic species into well-defined inorganic nanoblocks. This paper describes the immobilization of natural dyes from the extract of the Brazilian açaí-fruit into two types of layered hexaniobate precursors derived from H(2)K(2)Nb(6)O(17): (i) colloidal dispersion of niobate exfoliated nanoparticles and (ii) niobate pre-intercalated with tetraethylammonium cations (TEA(+)). The restacking of exfoliated particles in the presence of açaí anthocyanins promotes their intercalation and produces stacked layers showing large basal spacing (ca. 50 A). The TEA(+) pre-intercalated niobate provides particles with lower content of dye species than the exfoliated precursor but with higher degree of organization and regularity according to X-ray diffraction data and images obtained by electron microscopies. Vibrational (FTIR and Raman) and (13)C NMR spectroscopies indicate the presence of flavylium cations in the hybrid materials and spectral profiles characteristic of glycosylated anthocyanidins. According to thermal analysis results, the purplish hybrids materials are more stable than the free açaí-dyes. One hybrid sample was heated under air up to 170 degrees C and maintained at this temperature for 240 min. No weight loss events were observed and the sample retained its original color, indicating that the intercalation of anthocyanin into hexaniobate increases its thermal stability. Considering the structural, chemical, optical and thermal properties of the synthesized hybrid materials, they might be good candidates to be investigated for future specialized applications.
authors.affiliation: Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, CEP 05508-000, São Paulo-SP, Brazil.
authors.forename: Angela Albuquerque
authors.initials: AA
authors.lastname: Teixeira-Neto
authors.forename: Ana Lucia
authors.initials: AL
authors.lastname: Shiguihara
authors.forename: Celly M S
authors.initials: CM
authors.lastname: Izumi
authors.forename: Marcos Augusto
authors.initials: MA
authors.lastname: Bizeto
authors.forename: Fabrice
authors.initials: F
authors.lastname: Leroux
authors.forename: Marcia L Arruda
authors.initials: ML
authors.lastname: Temperini
authors.forename: Vera R Leopoldo
authors.initials: VR
authors.lastname: Constantino
mesh_terms: D000872:Anthocyanins / Q000737:chemistry*; D028023:Arecaceae / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry; D005638:Fruit / Q000737:chemistry*; D008854:Microscopy, Electron; D009556:Niobium / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry; D013057:Spectrum Analysis; D013696:Temperature; D019789:Tetraethylammonium / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D000872:Anthocyanins; D004396:Coloring Agents; D010087:Oxides; D010936:Plant Extracts; D009556:Niobium; D019789:Tetraethylammonium