Photoluminescence tuning and energy transfer process from Tb3+ to Eu3+ in GPTMS/TEOS-derived organic/silica hybrid films

In this work the photoluminescence study and energy transfer from Tb3+ to Eu3+-beta-diketonate complexes incorporated into organic/Silica hybrid films derived from 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetraethylorthosilicate (TEOS) alkoxysilanes were investigated. Highly homogeneous and transparent films of Ln(3+)-doped GPTMS/TEOS-derived organic/silica hybrids were obtained from the organic/silica sols prepared by sol-gel. Tb3+: Eu3+-doped GPTMS/TEOS-derived films showed very intense luminescence when excited with UV light. Films co-doped with Tb3+ concentration fixed at 40.0x10(18) ions/cm(3) and Eu3+ concentrations of 0, 0.03, 0.05, 0.1, 0.3, 0.5, 1.0, 1.5, and 2.0x10(18) ions/cm(3) were studied. The films presented characteristic transitions D-5(4)-F-7(6-3) of Tb3+ ions and D-5(0)-F-7(0-4) of Eu3+ ions measured on the visible spectrum region. Energy transfer from Terbium to Europium was studied through emission decay time measurements of D-5(4)-F-7(5) transition of Tb3+ (547 nm) which showed an accentuated decrease (from 1329 to 55 mu s) due to the co-doping with Eu3+ ions concentrations varied from 0.03 to 1.5x10(18) ions/cm(3). Energy transfer rate (WET) of 17.4x10(3) s(-1) and relative energy transfer efficiency (eta(T)) of 96% were observed for films samples co-doped with 40x10(18) ions/cm(3) of Tb3+ and 1.5x10(18) ions/cm(3) of Eu3+. Due to the variation in WET and eta(T) from Tb3+ to Eu3+, the intensity ratios of Tb3+ band at 547 nm (D-5(4)-F-7(5)) and Eu3+ band at 617 nm (D-5(0)-F-7(2)) vary remarkably making the co-doped film samples exhibit different luminescence colors varying from green to orange and red which can be tuned by the Tb3+/Eu3+ ratio incorporated into the samples.