New amino-functionalized monodispersed mesoporous silica spheres (MMSS) were synthesized directly by co-condensation of 3-ammopropyltrimethoxysilane (AP-TMS), [3-(2-aminoethylamino)propyl]trimethoxysilane (AEAP-TMS) or 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane (AEA-EAP-TMS) with tetramethoxysilane. By changing the methanol ratio or adding extra silica source, amino-functionalized MMSS with different particle diameter (310-780 nm) and the same mesopore size were successfully synthesized. TEM observations revealed that the mesopores were aligned radially from the center towards the outside of the spheres even in the amino-functionalized MMSS. The effect of particle diameter on base catalytic activity was investigated using the amino-functionalized MMSS. In addition, the amino-functionalized MMSS were found to be excellent base catalysts in the nitroaldol condensation reactions. The effectiveness factor was evaluated to be 0.8-0.82 and improved substantially compared with MMSS prepared by grafting method. (c) 2007 Elsevier B.V. All rights reserved.