Papers by Keyword: Energy Transfer

Abstract: Cd_1-xZn_xSiO₃:0.01 Mn²⁺ phosphor was synthesized by sol-gel method. It was characterized by excitation, emission spectra and XRD. The luminescent properties show the phenomenon of energy transfer from the tetrahedral coordinated Mn²⁺ ion to the octahedral coordinated Mn²⁺ ion after exciting by ultraviolet light, which boost the performance of the phosphor. With the increasing of Zn²⁺ in Cd_1-xZn_xSiO₃:0.01 Mn²⁺ phosphor, it was observed the excitation spectra broadened and a red shift in the emission spectra, which emission peak moved from 580nm to 589nm.

Abstract: In this letter, γ-Zn₃(PO₄)₂: Mn²⁺ phosphors have only one emission band centered at 620 nm while two emission bands are observed in γ-Zn₃(PO₄)₂: Mn²⁺, Ga³⁺, which are respectively centered at 507 nm and 620 nm. The spectral overlap between the green emission band and the excitation band monitored at 620 nm, which supports the occurrence of the energy transfer from Mn²⁺ (CN=4) to Mn²⁺ (CN=6), has been studied. The influence of Ga3+ ions on luminescence and long lasting phosphorescence properties of Mn²⁺ in phosphor γ-Zn₃(PO₄)₂: Mn²⁺, Ga³⁺ are also investigated. It is found that the green/red phosphorescence performance of Mn²⁺ ion such as brightness and duration is largely improved when Ga³⁺ ion is co-doped into the matrix in which Mn²⁺ ion acts as luminescent center and Ga³⁺ ion plays an important role of electron trap.

Abstract: This work studies the two-photon luminescence spectra of a Yb³⁺ doped YAG crystal grown using the Czochralski method. To study the spectral performance of a 50 at.% Yb:YAG crystal, intense green light (centered at about 544nm) was generated by the crystal upon excitation using a 973nm InGaAs LD pump source. The luminescence spectra were obtained for various Yb concentrations and the emission intensity were plotted versus Yb³⁺ concentration. The green emission light attributed to Yb³⁺ two-photon transition.

Abstract: YVO₄ co-doped with Tm³⁺/Ho³⁺/Yb³⁺ were synthesized by the high temperature solid state method and the optical properties of phosphors were characterized. Intense visible emissions centered at around 475, 541 and 649 nm, originated from the transitions of Tm³⁺:¹G₄→³H₆, Ho³:⁵S₂/>:⁵F₄ →⁵I₈, Tm³⁺:⁵G₄→3F₄ and Ho³⁺:⁵F₅→⁵I₈, respectively, have been observed in samples upon excitation with a 980 nm laser diode, and the involved mechanisms have been explained.

Abstract: The visible and near infrared emission spectra of Er³⁺/Tm³⁺-doped Ga₂O₃-Bi₂O₃-PbO-GeO₂ (GBPG) glasses excited at 808 nm are experimentally investigated. The results reveal that 1.53 µm emission were enhanced with an increase of Er³⁺ concentration. Furthermore, the incorporation of Er³⁺ into Tm³⁺-doped systems has also resulted in intense 522, 545 and 693nm upconversion emission intensity and an weak 660 nm red emission. The possible mechanism and related discussions on this phenomenon have been presented. The results show that Er³⁺/Tm³⁺-codoped GBPG glass may be a promising materials for developing laser and fiber optical devices.

Abstract: Spectroscopic properties and energy transfer (ET) in Er³⁺/Eu³⁺-doped Ga2O3-GeO2 glass have been investigated. Effects of alkali metal and alkaline earth metals ions on thermal stability of Er³⁺-doped gallate-germanium glass have been investigated. Simultaneously influences of Eu³⁺ codoping on the optical properties of Er³⁺-doped Ga₂O₃-GeO₂-Na₂O (GN) glass have been investigated and the possible ET mechanisms involved have also been discussed. Significant enhancement of the 1.53 µm emission intensity and decrease of upconversion (UC) fluorescence with increasing Eu3+ concentration have been observed. The results indicate that the incorporation of Eu³⁺ into Er³⁺-doped GN glass can effectively improve 1.53-μm and lower UC luminescence, which makes GN glass more attractive for their use in C-band optical fiber amplifiers.

Abstract: The phosphors Sr₃B₂O₆: Ce³⁺, Sr₃B₂O₆: Tb³⁺ and Sr₃B₂O₆: Ce³⁺, Tb³⁺ were synthesized by the solid-state reaction method at high temperature. For the phosphor Sr₃B₂O₆: Ce³⁺, the lowest 5d levels, the emission and the Stokes shifts of Ce³⁺ in the host lattice were identified. In addition, its concentration quenching process was also studied. For the phosphor Sr₃B₂O₆: Tb³⁺, the f-d transitions of Tb³⁺ in the host lattice were assigned and discussed. Moreover, the energy transfer phenomenon between Ce³⁺ and Tb³⁺ in Sr₃B₂O₆: Ce³⁺, Tb³⁺ was discussed. The emission of Tb³⁺ is significantly enhanced due to energy transfer from Ce³⁺ to Tb³⁺ when Ce³⁺, Tb³⁺ dopants were used together in Sr₃B₂O₆.

Abstract: Using constant temperature hot-wire anemometer IFA300, we measured the wall turbulence on different normal location of the boundary layer in the wind tunnel experiment section. The wind tunnel is of low turbulence intensity. We have applied Fourier transform, Wavelet transform and Hilbert-Huang transform to analyze the turbulent fluctuating velocity obtained by measurement and have compared turbulent energy transfer law in different wall distance. This article quantitatively analyzed on the eddy motion process for different wall distance in wall turbulence from the energy point of view. It also discussed the energy transfer law based on eddy combination theory and the inertial sub-range.

Abstract: The different concentrations C-phycocyanin (C-PC), Allophycocyanin (APC) or R-phycoerythrin(R-PE) solution can reconstitute with thylakoid to synthesize different donor-acceptor complexes. The energy transfer efficiencies of those complexes are studied, where C-PC, APC and R-PE are donor, the thylakoid are acceptor. The results show excitation energy can be transfered to thylakoid from C-PC or APC. However, the energy transfer process of R-PE to thylakoid membrane does not happen. The energy transfer process of the APC to thylakoid membrane shows the highest efficiency. Those results also indicate that the linkage between phycobiliproteins and thylakoid does not have specificity. It can be concluded that the energy transfer efficiencies not only strongly depend on the relative positions of donor and acceptor but also on spectral matching relation between phycobiliproteins and Chla molecules in thylakoid membrane.

Abstract: Novel single-phase Ca2-xBO3Cl:xDy3+ phosphors were synthesized at 900 oC in an activated carbon reducing atmosphere, and their luminescent properties were investigated by photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The optimal doping concentration of Dy3+ ions is found to be x=0.03 mol, and the nature of resonance energy transfer for Dy3+ ions is also discussed. Generation of white-light excited by 390 near-ultraviolet (n-UV) light shows that all the investigated phosphors lie within white region and the colour coordinate of Ca1.95BO3Cl:0.05Dy3+ (0.272, 0.326) is closer to the equal-energy white light point, which is potentially a good candidate as an n-UV-converted phosphor for white light-emitting diodes (LEDs).