Characterization of Nd-MCM41 obtained by impregnation

Abstract

Silica mesoporous molecular sieves (MCM-41), prepared by using micelles as template, were functionalized by means of incipient wetness method. Evidence for the neodymium presence in the silica matrix was obtained by means of EDX. SEM micrographs showed that impregnation does not change significantly MCM-41 morphology. The maintenance of the hexagonal structure was confirmed by XRD pattern analysis. However, the observed loss of long-range ordering, the cell parameter increase and the surface area decrease, observed by gas adsorption technique, were attributed to the introduction of neodymium oxide inside the MCM-41 mesochannels. By FT-IR and Raman spectra it was found that the main features of the silica framework are maintained. As consequence of impregnation, Raman technique displayed the disappearance of silica non-interacting silanols groups and the appearance of a new band that can be attributed to the Si-O-Nd linkages. The 29Si{1H} CP-MAS NMR and 29Si{1H} MAS NMR spectra analysis indicated a decrease of silicon atoms bearing one hydroxyl group and an increase of silicon atoms without hydroxyl groups confirming Raman hypothesis.