Room temperature blue-green photoluminescence of MCM-41, MCM-48 and SBA-15 mesoporous silicas in different conditions

The photoluminescence (PL) properties of siliceous MCM (MCM-41 and MCM-48) and SBA-15, no Na-containing MCM-41, and modified SBA-15 by silylation were comparatively investigated in dry and damp conditions, displaying the highest PL intensity of MCM-48. The PL intensity of MCM-41 is lower than that of SBA-15 in dry conditions, but reverse in damp conditions. In comparison with that of Na-containing MCM-41, the PL intensity of MCM-41 without Na⁺ is stronger. The PL intensity of modified SBA-15 by silylation is decreased in dry conditions, and however, against moisture and degradation in damp conditions. Twofold coordinated silicon centers in the tested samples are responsible for the blue-green bands at 440 nm. The shoulder peaks around 460–490 nm occurred in damp conditions are assigned to peroxy free radicals.