Novel Nano Boehmite prepared by Solvothermal reaction of aluminum hydroxide gel in Monoethanolamine

Solvothermal reaction of aluminum hydroxide gel (AHG) in monoethanolamine (MEA) was studied at several temperatures (100, 120, 150, and 200 °C) in several reaction times (2, 3, 4, 5, 6, and 13 h). The reaction product prepared at a low temperature of 120 °C in the reaction time more than 6 h gave a blue photoluminescence nanoboehmite intercalated with monoethanolamine derivatives (BM-MEA) in the colloidal solution, which showed a photoluminescence emission centered at 420 nm with an excitation of 360 nm. The powdery samples recovered from the reaction products were characterized by using elemental analysis, XRD analysis, IR spectroscopy, thermogravimetric (TG)-DTA, ¹³C and ²⁷Al CP/MAS NMR spectroscopies, N₂ gas adsorption/desorption isotherm, SEM and TEM images, and photoluminescence spectroscopy. The X-ray diffraction revealed that the basal space in BM-MEA was expanded from 0.61 to 1.2 nm by intercalation of MEA derivatives to boehmite, and the IR and ¹³C CP/MAS NMR spectra determined that the intercalated MEA derivatives are protonated- and carbamate-substituted MEAs, which are formed in the layers through a covalent bond with Al–OH groups on boehmite surface. The empirical formula of BM-MEA was estimated to be AlO(OH)_0.82(OCH₂CH₂NH₃⁺)_0.05(OCH₂CH₂NHCOO⁻)_0.13 on the basis of the elemental TG-DTA and IR spectral analyses. We discuss the reaction mechanism of a unique blue photoluminescence BM-MEA formed by proceeding in CO₂–H₂O–alkanolamine system. .