Luminescence enhancement by energy transfer in melamine-Y2O3:Tb3+ nanohybrids

Abstract

The phenomenon of luminescence enhancement was studied in melamine-Y2O3:Tb hybrids. Terbium doped Y2O3 mesoporous nanowires were synthesized by hydrothermal method. X-ray diffraction patterns and Raman scattering spectra testified the realization of a cubic crystal phase. Organic-inorganic melamine-Y2O3:Tb3+ hybrid system was successfully obtained by vapour deposition method. Vibration Raman active modes of the organic counterpart were investigated in order to verify the achievement of hybrid system. Photoluminescence excitation and photoluminescence spectra, preformed in the region between 250 and 350 nm, suggest a strong interaction among melamine and Terbium ions. In particular, a remarkable improvement of 5D4→ FJ Rare Earth emission (at about 542 nm) of about 102 fold was observed and attributed to an efficient organic-Tb energy transfer. The energy transfer mechanism was studied by the use of time resolved photoluminescence measurements. The melamine lifetime undergoes to a significant decrease when adsorbed to oxide surfaces and it was connected to a sensitization mechanism. The detailed analysis of time decay profile of Terbium radiative recombination shows a variation of double exponential law toward a single exponential one. Its correlation with surface defects and non-radiative recombination was thus discussed

Role of Ce in Manipulating the Photoluminescence of Tb Doped Y2Zr2O7

“…This phenomenon of luminescence quenching with Ce doping was corroborated from the lifetimes of the 5 D 4 – 7 F 5 transition in YZO:Tb,Ce codoped NPs and comparable to a Y 2 O 3 reference (Table ). The Tb 3+ lifetimes were extracted using a second order exponential decay function and showed a decreasing trend with increasing Ce concentration (Figure c). Introducing up to 2 mol % Ce into the YZO:Tb (2 mol %) system decreases the Tb lifetime, indicating no effective energy transfer from Ce to Tb .…”

“… a Tb 3+ -doped Y 2 O 3 and Eu 3+ -doped La 2 Zr 2 O 7 are included as references. The asymmetry ratio ( R ) was calculated from the Eu 3+ I ED (607 nm)/ I MD (590 nm) and Tb 3+ I ED (542 nm)/ I MD (488 nm) transitions. …”

“…PL Lifetimes of the Tb 3+5 D 4 − 7 F 5 (542 nm) and Eu 3+5 D 0 − 7 F 2 (608 nm) Transitions of Doped YZO:Tb/ Eu 3+ ,Ce NPs a Tb 3+ -doped Y 2 O 356 and Eu 3+ -doped La 2 Zr 2 O 761 are included as references. The asymmetry ratio (R) was calculated from the Eu 3+ I ED (607 nm)/I MD (590 nm) and Tb 3+ I ED (542 nm)/I MD (488 nm) transitions.…”

Photophysics and Photocatalysis of Melem: A Spectroscopic Reinvestigation

“…Therefore, it is reasonable to conclude that the fluorescence emission of a 0.003 mg mL −1 aqueous solution of melamine (Figure B) originates from the fluorescence emission of the melem impurity contained in melamine. Thus, previous reports on the fluorescence characteristics of melamine should be carefully interpreted . Additionally, the fluorescence decay lifetime of a 0.003 mg mL −1 aqueous melem is much longer than that of melem powder (Table ); this is due to stronger molecular interactions in the condensed phase of melem.…”

“…Thus, previous reports on the fluorescence characteristicso fm elamine should be carefully interpreted. [29,30] Additionally,t he fluorescence decay lifetime of a 0.003 mg mL À1 aqueous melem is much longert han that of melem powder (Table 2);t his is due to stronger molecular interactions in the condensed phase of melem.…”