Preparation and characterization of mesoporous silicon spheres directly from MCM-48 and their response to ammonia

The synthesis process of mesoporous silicon spheres directly from MCM-48 through a metal thermal reduction reaction is presented. The MCM-48 spheres were reduced in vacuum at 620 °C, with the spherical shape retained. The synthesized porous silicon spheres were confirmed as crystalline silicon by X-ray diffraction and transmission electron microscope. The silicon spheres have a microstructure different to those of etched silicon films by traditional method. The sample exhibited a slight red shift in PL spectrum after exposure to ammonia. This shift from 2.00 to 1.98 eV is ascribed to the Si–N adduct which disorder the space charge region in the semiconductor to weaken the quantum confinement effect. This design enables the syntheses of mesoporous nanocrystalline silicon spheres with multifarious three-dimensional shapes inherited from MCM-48 for sensor or optical applications.