FTIR spectroscopy of NH3 on acidic and ionotropic alginate aerogels.
The acidity of alginate aerogel films has been investigated by infrared spectroscopy of adsorbed NH(3). Supercritical drying of the alginate provided samples with a surface area of several hundred square meters per gram, in which the probe molecule could reach all acidic sites. Free carboxylic groups were studied on acid-gelled alginates and were found to behave as effective Brønsted acid sites. Ionotropic alginate gels formed by alkaline earth cations presented only the Lewis acidity of the cations. Ionotropic gels formed by transition metal cations presented both Lewis and Brønsted sites, because of the presence of a fraction of free carboxylic groups. The incomplete salification was correlated to the pH of the gelling solutions.
Valentin
Romain
R
Laboratoire de Matériaux Catalytiques et Catalyse en Chimie Organique, UMR 5618 CNRS-ENSCM-UM1, Institut C. Gerhardt, FR 1878, 8 rue de l'Ecole Normale, 34296 Montpellier Cedex 5, France.
Horga
Raluca
R
Bonelli
Barbara
B
Garrone
Edoardo
E
Di Renzo
Francesco
F
Quignard
Françoise
F
D000327:Adsorption; D000438:Alcohols / Q000737:chemistry; D000464:Alginates / Q000737:chemistry*; D000641:Ammonia / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry; D002412:Cations; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D009584:Nitrogen / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013057:Spectrum Analysis
D000438:Alcohols; D000464:Alginates; D001672:Biocompatible Materials; D002264:Carboxylic Acids; D002412:Cations; D046911:Macromolecular Substances; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D000641:Ammonia; D009584:Nitrogen