Investigating the origin of laser-induced fluorescence in mannan-rich Phytelephas macrocarpa seeds before and after thermal aging.

Autor: Ferreira da Silva Y; Department of Metallurgical and Materials Engineering, Federal University of Rio de Janeiro, P.O. Box: 68505, 21945-970 Rio de Janeiro, RJ, Brazil. Electronic address: yuri@metalmat.ufrj.br., Alencastro FS; Department of Metallurgical and Materials Engineering, Federal University of Rio de Janeiro, P.O. Box: 68505, 21945-970 Rio de Janeiro, RJ, Brazil. Electronic address: felipesa@metalmat.ufrj.br., de Souza ND; Department of Forest Products, Federal Rural University of Rio de Janeiro, Km 7 BR 465, 23890-000 Seropédica, RJ, Brazil., Oliveira RN; Department of Chemical Engineering, Federal Rural University of Rio de Janeiro, Km 7 BR 465, 23890-000 Seropédica, RJ, Brazil., Simao RA; Department of Metallurgical and Materials Engineering, Federal University of Rio de Janeiro, P.O. Box: 68505, 21945-970 Rio de Janeiro, RJ, Brazil. Electronic address: renata@metalmat.ufrj.br.
Jazyk: angličtina
Zdroj: Carbohydrate polymers [Carbohydr Polym] 2023 May 15; Vol. 308, pp. 120632. Date of Electronic Publication: 2023 Feb 03.
DOI: 10.1016/j.carbpol.2023.120632
Abstrakt: Natural polysaccharides, e.g., starch, cellulose and sodium alginate have been highlighted as unconventional chromophores owing to their chain structures containing clustered electron-rich groups and the rigidification imposed by inter/intramolecular interactions. On account of the abundant hydroxyl groups and dense packing of low-substituted (< 5 %) mannan chains, we have investigated the laser-induced fluorescence of mannan-rich vegetable ivory seeds (Phytelephas macrocarpa), both in the native state and after thermal aging. The untreated material emitted fluorescence at 580 nm (yellow-orange) when excited at 532 nm (green). This luminescence is intrinsic to the polysaccharide matrix abundant in crystalline homomannan, as demonstrated by lignocellulosic analyses, fluorescence microscopy, NMR, Raman, FTIR and XRD. Thermal aging at 140 °C and above intensified the yellow-orange fluorescence and caused the material to fluoresce when excited by a near-infrared laser (785 nm). In view of the clustering-triggered emission mechanism, the fluorescence of the untreated material can be attributed to hydroxyl clusters and the conformational rigidification in mannan I crystals. On the other hand, thermal aging caused dehydration and oxidative degradation of mannan chains, inducing the substitution of hydroxyl groups by carbonyls. These physicochemical changes may have affected cluster formation and increased conformational rigidification, enhancing fluorescence emission.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023 Elsevier Ltd. All rights reserved.)
Databáze: MEDLINE
Externí odkaz: