Room-temperature metal-activator-free phosphorescence from mesoporous silica.

Room-temperature phosphorescence has been observed and studied on metal-activator-free mesoporous silica. The mesoporous silica was prepared using a nonionic triblock copolymer as the mesostructure-directing agent. The as-calcined products have a well-ordered porous structure and exhibit strong phosphorescence under ultraviolet light excitation. The luminescence spectra are featured with several peaks in the visible region. The luminescence intensity is found to vary as a function of the calcination temperature and reach a maximum around 500-600 °C, but the peak positions remain nearly unchanged. The average luminescence lifetime is several hundred microseconds, and the luminescence can persist for seconds after the excitation is switched off. In addition, due to the moderate calcination temperature, phosphorescent mesoporous silica monoliths with controllable sizes and shapes have been fabricated. Such mesoporous silica materials, including both powders and monoliths, with strong phosphorescence could find promising applications as low-density and eco-friendly phosphors and optically detectable drug carriers.