2.4. Characterization methods
2.4.1. N2 adsorption–desorption isotherms
The textural properties of the mesoporous matrices were determined
from the nitrogen adsorption isotherms recorded at 77 K
with a Micromeritics TriStar 3000 apparatus. The samples were
previously degassed at 423 K for 24 h under a vacuum (104 mbar)
to ensure a clean, dry surface, free of any loosely bound adsorbed
species. The specific areas of the samples were calculated according
to standard BET procedure using nitrogen adsorption data collected
in the relative equilibrium pressure interval of 0.03 < P/
P0 < 0.3. Pore size distributions were calculated from the adsorption
and desorption branches of the corresponding nitrogen isotherm
using the BJH method. The total pore volume (Vtotal) was
estimated from the amount of nitrogen adsorbed at a relative pressure
of 0.99.
2.4.2. High resolution transmission electron microscopy (HRTEM)
Transmission electron microscopy (TEM) study of a dried aminefunctionalized
SBA-15 sample was carried out using a JEOL JEM
2000FX microscope operating at 200 kV with very low illumination
in order to avoid the destruction of material under the electron
beam. The adsorbent was crushed and dispersed ultrasonically in
acetone at room temperature and then spread onto a perforated
carbon–copper micro grid.