Fluorescence enhancement in rare earth doped sol-gel glass by N,N dimethylformamide as a drying control chemical additive

Studies of terbium fluorescence intensity as a function of annealing temperature reveal the cause of increased fluorescence yields observed in rare earth doped sol-gel silicates prepared using N,N-dimethylformamide (DMF) as a drying control chemical additive (DCCA). While gels prepared with DMF actually have lower fluorescence yields than gels prepared without DMF at lower annealing temperatures, DMF gels can be annealed at much higher temperatures while retaining high optical quality. At these higher temperatures, terbium fluorescence yields increase dramatically as the sol-gel network undergoes densification, closing the pores of the network and eliminating the fluorescence quenching silanols on pore surfaces. DMF is therefore found to enhance the fluorescence properties of rare earth sol-gel glasses by reducing micro-fracturing and facilitating network densification. Further investigations are underway to determine the effectiveness of other promising DCCAs, such as glycerol, and to explore the possibility of exploiting the solubility properties of DCCAs to improve rare earth dopant dispersion.