Synthesis of Spherical SBA-15 Particles under Mixed and Dilute Electrolyte Conditions

Spherical SBA-15 particles were synthesized by co-addition of dilute but strong electrolytes (NH4F and Cu(NO3)(2)) under classical acidic conditions without an organic solvent or another template. These materials were characterized by low angle X-ray diffraction (XRD ), N-2 sorption isotherms, and scanning electron microscopy (SEM). Separated uniform hexagonal SBA-15 particles form in strong acidic media while an appropriate content of fluoride anions favors the synthesis of a sphere-like and highly pored ordered structure. Effects of different electrolytes on the morphology and the mesostructure of the resulting materials were discussed. We found that fluoride played the main role in the formation of sphere-like SBA-15 while the presence of the Cu2+ was beneficial for the formation of separated spherical SBA-15 particles. When the concentration of Cu2+ increases, a part of the silica does not contribute to the formation of SBA-15. This phenomenon is probably due to the formation of a PEO (polyoxyethylene)/Cu2+ head-group at the hybrid interface which affects the normal coordination and condensation of the silica source.