Silica spheres doped with Eu （TTFA）3 and/or Sm（TTFA）3 were synthesized by using the modified Stober method. The transmission electron microscope image reveals that the hybrid spheres have smooth surfaces and an av...Silica spheres doped with Eu （TTFA）3 and/or Sm（TTFA）3 were synthesized by using the modified Stober method. The transmission electron microscope image reveals that the hybrid spheres have smooth surfaces and an average diameter of about 210 nm. Fluorescence spectrometer was used to analyze the fluorescence properties of hybrid spheres. The results show that multiple energy transfer processes are simultaneously achieved in the same samples co-doped with Eu （TTFA）3 and Sm（TTFA）3, namely between the ligand and Eu^3＋ ion, the ligand and Sm^3＋ ion, and Sm^3＋ ion and Eu^3＋ ion. Energy transfer of Sm^3＋→Eu^3＋ in the hybrid spheres leads to fluorescence enhancement of Eu^3＋ emission by approximately an order of magnitude. The lifetimes of the hybrid spheres were also measured.展开更多
A series of Eu0.5Tb0.5（TTA）3Phen/PMMA （TTA=thenoyltrifluoroacetone,Phen=phenanthroline） and Eu0.5Tb0.5（TTA）3Dipy/PMMA （Dipy=2,2’-dipyridyl） were prepared by in-situ polymerization.The structures of the compos...A series of Eu0.5Tb0.5（TTA）3Phen/PMMA （TTA=thenoyltrifluoroacetone,Phen=phenanthroline） and Eu0.5Tb0.5（TTA）3Dipy/PMMA （Dipy=2,2’-dipyridyl） were prepared by in-situ polymerization.The structures of the composites were characterized by IR spectra and electron spectrum.Photoluminescence properties were investigated by UV-Vis spectra and fluorescence spectra.Meanwhile,the energy transfer models were set up.The results indicated that polymer parts were attached with the rare-earth molecular parts in the composite luminescent materials.Eu0.5Tb0.5（TTA）3Phen/PMMA and Eu0.5Tb0.5（TTA）3Dipy/PMMA emitted mostly characteristic fluorescence of europium ion and intense red fluorescence with peak wavelength at 611.8 nm and bandwidth of 10.4 nm under UV excitation at 365 nm.Fluorescence intensity of Eu0.5Tb0.5（TTA）3Phen/PMMA was found to be influenced with the content of MMA.The fluorescence emission of europium ions was greatly sensitized by terbium ions and the enhancement of red emission was most likely due to the energy transfer enhancement from Tb3＋ to Eu3＋.展开更多
A series of CaMoO4：xTb3＋ （x=0.01, 0.03, 0.05, 0.07, 0.09, 0.15 and 0.20） phosphors in pure phase were prepared via high temperature solid-state reaction approach. The crystal structure of the phosphors was investi...A series of CaMoO4：xTb3＋ （x=0.01, 0.03, 0.05, 0.07, 0.09, 0.15 and 0.20） phosphors in pure phase were prepared via high temperature solid-state reaction approach. The crystal structure of the phosphors was investigated by X-ray diffraction （XRD）, and the optical properties were investigated by Fourier transform infrared spectroscopy （FT-IR）, ultraviolet-visible spectroscopy （UV-Vis） and photoluminescence （PL） spectroscopy. The PL spectra illustrated that these phosphors could be efficiently excited by the charge transfer band of the host and the energy transfer efficiency from the host to the doped activator reached 60% when the doping con- centration of the activator Th3＋ was 20 mol.%. The concentration quenching occurred at x= 10 mol.%, from which the critical distance of activator was calculated to be about 1.14 nm. The CIE coordinates were estimated to be close to the standard green value. The host sensitized samples had potential application as green phosphors.展开更多
Rare earth doped upconversion nanoparticles can be considered as the spice of research in the field of luminescence nanomaterials due to their unique optical properties such as near-infrared excitation.Enormous works ...Rare earth doped upconversion nanoparticles can be considered as the spice of research in the field of luminescence nanomaterials due to their unique optical properties such as near-infrared excitation.Enormous works have been reported about biomedical applications of 980 nm excited and Yb^3+-sensitized upconversion nanoparticles.However,980 nm excitation wavelength overlaps with the absorption band of water molecules in the biological environment,leading to overheating effect that can induce thermal damages of normal cells and tissues.Recently,Nd^3+-sensitized upconversion nanoparticles which can be excited with 808 nm has been widely investigated as alternative nanoparticles that can surmount this issue of overheating effect.Even though Nd^3+-sensitized upconversion nanoparticles can reduce the overheating effect by 20 fold as compared to Yb^3+-sensitized counterpart,there are several factors that reduce the upconversion luminescence intensity.In this review article,photon energy harvesting and transferring mechanisms in Nd^3+,Yb^3+and emitter ions co-doped upconversion nanoparticles under 808 nm excitation are briefly discussed.Factors that affect upconversion luminescence intensity and quantum yield of Nd^3+-sensitized upconversion nanoparticles are also addressed.Besides,some of the important strategies that have been recently utilized to boost upconversion luminescence intensity of Nd^3+sensitized upco nversion nanoparticles are tho roughly summarized.Lastly,the future challenges in the area and our perspectives are in sight.展开更多
A reactive Tb（III） complex with 2-aminobenzoic acid（2-ABAH） and acrylonitrile（AN） as ligands was synthesized.The structure of the complex was characterized by elemental analysis and Fourier transform infrared sp...A reactive Tb（III） complex with 2-aminobenzoic acid（2-ABAH） and acrylonitrile（AN） as ligands was synthesized.The structure of the complex was characterized by elemental analysis and Fourier transform infrared spectrometry（FT-IR）.The results indicated that the ligands were coordinated with Tb（III） ion.Thermal gravity-derivative thermogravimetric（TG-DTG） analysis indicated that the complex kept stable up to 198 oC.Luminescence properties were investigated by UV-vis absorption spectra and fluorescence spectra.The results suggested that being excited at 361 nm,the complex exhibited characteristic emission of Tb（III） ion,revealing that the complex could be excited by 365 nm ultraviolet chip.The HOMO and LUMO,ΔE（HOMO-LUMO）,molecular frontier orbital,and the singlet state and triplet energy state levels of the ligands were calculated at the B3LYP/6-31＋G（d） level.The results indicated that intramolecular energy transfer mechanism followed Dexter exchange energy transfer theory.Both the calculation for excited state of ligand and energy transfer mechanism could provide the theoretical basis for the design of high luminescent materials of rare earth complexes with organic ligands.展开更多
Lanthanide doped NaYF4 microcrystals were synthesized via a facile hydrothermal method. Multicolor upconversion luminescence was observed in NaYF4 microcrystals doped with yb^3＋/Er^3＋, yb^3＋/Tm^3＋, and yb^3＋/Er^3...Lanthanide doped NaYF4 microcrystals were synthesized via a facile hydrothermal method. Multicolor upconversion luminescence was observed in NaYF4 microcrystals doped with yb^3＋/Er^3＋, yb^3＋/Tm^3＋, and yb^3＋/Er^3＋/Zm^3＋ under the excitation of 980 nm infrared light. Importantly, the excitation power density dependence of upconversion emission intensity indicated clearly the energy transfer from Tm^3＋ to Er^3＋ ions under the excitation of low power density （5× 10^2× 10^2 W/cm^2）. Meanwhile, the inverse energy transfer from Er^3＋ to Tm^3＋ ions under the excitation of relatively higher power density （4.1 × 10^4.9× 10^4 W/cm^2） was also revealed. This was a direct evidence for reversible energy transfer between Er^3＋ and Tm^3＋ ions. Under the excitation of high power density （4.1 ×10^4-4.9× 10^4 W/cm^2）, dark sensitizers were also motivated so that the bottleneck effect of high concentration Yb^3＋ ion doping was broken. This was the main reason for realizing high upconversion efficiency of the samples with heavy doping of Yb^3＋ ion.展开更多
Nanopowder of Cr：GGG and nanopowder of Cr,Nd：GGG with different concentrations of Cr3＋ ranging from 0.1 at.% to 1.5 at.% were synthesized by the sol-gel method using acetic acid and ethylene glycol. Thermal gravime...Nanopowder of Cr：GGG and nanopowder of Cr,Nd：GGG with different concentrations of Cr3＋ ranging from 0.1 at.% to 1.5 at.% were synthesized by the sol-gel method using acetic acid and ethylene glycol. Thermal gravimetric analysis and differential scanning calorimetry （TGA-DSC）, X-ray diffraction （XRD） and photoluminescence spectroscopy were used to characterize the powder. The crystallite size was about 58 nm when treated at 1000 oC for 2 h. Cr3＋ photoluminescence spectrum in GGG showed a broad band emission around 730 nm. The intensity of this band decreased when co-doped with Nd, indicating an efficient energy transfer from Cr3＋ to Nd3＋. Photoluminescence intensity of Nd in Cr,Nd：GGG at 1.06μm showed that the optimum concentration of Cr3＋ was about 1 at.% （more or less） for 1 at.% Nd3＋. This result was also confirmed by chromium fluorescence decay rate analysis. Energy transfer efficiency was found to be about 84% for 1 at.% concentration of each chromium and neodymium.展开更多
The Langmuir-Blodgett (LB) technique was used for studying enhanced lumines-cence of Eu (TTA)3 Phen (acceptor) by La (TTA)3 Phen (donor). LB films studied here are:(1) [0. 5% Eu (TTA)3 Phen + 99. 5% La (TTA)3 Phen]: A...The Langmuir-Blodgett (LB) technique was used for studying enhanced lumines-cence of Eu (TTA)3 Phen (acceptor) by La (TTA)3 Phen (donor). LB films studied here are:(1) [0. 5% Eu (TTA)3 Phen + 99. 5% La (TTA)3 Phen]: AA = 1: 1; (2) [0. 5%Eu(TTA)3 Phen+99. 5%AA]: AA= 1: 1; (3) La(TTA)3 Phen: AA= 1: 1. These filmscould form stable monolayers at air/water surface. The fluorescence intensity of LB 1 was 65times stronger than that of LB2. This signifies that the luminescence intensity ofEu(TTA)3 Phen could be enhanced by La (TTA)3 Phen clearly. Low angle X-ray diffrac-tog ram of LB1 showed that the film has a period layered structure. To study the intermolec-ular energy transfer, different structures of the multilayer were designed by combining LB2(layer of acceptor) with LB3(layer of donor). The results indicated that the intermolecularenergy transfer occurred in a short-range (<3 nm) and at the position of head-head in Y-typemodel. The influence of the interface on the energy transfer was prominent. The process ofenergy transfer was carried out via the triplet state of TTA.展开更多
文摘Silica spheres doped with Eu （TTFA）3 and/or Sm（TTFA）3 were synthesized by using the modified Stober method. The transmission electron microscope image reveals that the hybrid spheres have smooth surfaces and an average diameter of about 210 nm. Fluorescence spectrometer was used to analyze the fluorescence properties of hybrid spheres. The results show that multiple energy transfer processes are simultaneously achieved in the same samples co-doped with Eu （TTFA）3 and Sm（TTFA）3, namely between the ligand and Eu^3＋ ion, the ligand and Sm^3＋ ion, and Sm^3＋ ion and Eu^3＋ ion. Energy transfer of Sm^3＋→Eu^3＋ in the hybrid spheres leads to fluorescence enhancement of Eu^3＋ emission by approximately an order of magnitude. The lifetimes of the hybrid spheres were also measured.
基金Funded by the National Natural Science Foundation of China(No.20671068)the Science Foundation of North University of China
文摘A series of Eu0.5Tb0.5（TTA）3Phen/PMMA （TTA=thenoyltrifluoroacetone,Phen=phenanthroline） and Eu0.5Tb0.5（TTA）3Dipy/PMMA （Dipy=2,2’-dipyridyl） were prepared by in-situ polymerization.The structures of the composites were characterized by IR spectra and electron spectrum.Photoluminescence properties were investigated by UV-Vis spectra and fluorescence spectra.Meanwhile,the energy transfer models were set up.The results indicated that polymer parts were attached with the rare-earth molecular parts in the composite luminescent materials.Eu0.5Tb0.5（TTA）3Phen/PMMA and Eu0.5Tb0.5（TTA）3Dipy/PMMA emitted mostly characteristic fluorescence of europium ion and intense red fluorescence with peak wavelength at 611.8 nm and bandwidth of 10.4 nm under UV excitation at 365 nm.Fluorescence intensity of Eu0.5Tb0.5（TTA）3Phen/PMMA was found to be influenced with the content of MMA.The fluorescence emission of europium ions was greatly sensitized by terbium ions and the enhancement of red emission was most likely due to the energy transfer enhancement from Tb3＋ to Eu3＋.
基金Project supported by National Natural Science Foundation of China(20903123)Key Project of Chinese Ministry of Education(211154)Natural Science Foundation Project of Chongqing(KJ110532,CSTCjjA1425)
文摘A series of CaMoO4：xTb3＋ （x=0.01, 0.03, 0.05, 0.07, 0.09, 0.15 and 0.20） phosphors in pure phase were prepared via high temperature solid-state reaction approach. The crystal structure of the phosphors was investigated by X-ray diffraction （XRD）, and the optical properties were investigated by Fourier transform infrared spectroscopy （FT-IR）, ultraviolet-visible spectroscopy （UV-Vis） and photoluminescence （PL） spectroscopy. The PL spectra illustrated that these phosphors could be efficiently excited by the charge transfer band of the host and the energy transfer efficiency from the host to the doped activator reached 60% when the doping con- centration of the activator Th3＋ was 20 mol.%. The concentration quenching occurred at x= 10 mol.%, from which the critical distance of activator was calculated to be about 1.14 nm. The CIE coordinates were estimated to be close to the standard green value. The host sensitized samples had potential application as green phosphors.
基金Projects supported by the National Natural Science Foundation of China(21571125,51872183,51672171)National Key R&D Program of China(2016YFE0114800)
文摘Rare earth doped upconversion nanoparticles can be considered as the spice of research in the field of luminescence nanomaterials due to their unique optical properties such as near-infrared excitation.Enormous works have been reported about biomedical applications of 980 nm excited and Yb^3+-sensitized upconversion nanoparticles.However,980 nm excitation wavelength overlaps with the absorption band of water molecules in the biological environment,leading to overheating effect that can induce thermal damages of normal cells and tissues.Recently,Nd^3+-sensitized upconversion nanoparticles which can be excited with 808 nm has been widely investigated as alternative nanoparticles that can surmount this issue of overheating effect.Even though Nd^3+-sensitized upconversion nanoparticles can reduce the overheating effect by 20 fold as compared to Yb^3+-sensitized counterpart,there are several factors that reduce the upconversion luminescence intensity.In this review article,photon energy harvesting and transferring mechanisms in Nd^3+,Yb^3+and emitter ions co-doped upconversion nanoparticles under 808 nm excitation are briefly discussed.Factors that affect upconversion luminescence intensity and quantum yield of Nd^3+-sensitized upconversion nanoparticles are also addressed.Besides,some of the important strategies that have been recently utilized to boost upconversion luminescence intensity of Nd^3+sensitized upco nversion nanoparticles are tho roughly summarized.Lastly,the future challenges in the area and our perspectives are in sight.
基金Project supported by the Program for Changjiang Scholar and Innovative Research Team in University (IRT0972)the International Cooperation Program of Shanxi Province (2009081046)the Postgraduate Innovation Program of Shanxi Province (20103023)
文摘A reactive Tb（III） complex with 2-aminobenzoic acid（2-ABAH） and acrylonitrile（AN） as ligands was synthesized.The structure of the complex was characterized by elemental analysis and Fourier transform infrared spectrometry（FT-IR）.The results indicated that the ligands were coordinated with Tb（III） ion.Thermal gravity-derivative thermogravimetric（TG-DTG） analysis indicated that the complex kept stable up to 198 oC.Luminescence properties were investigated by UV-vis absorption spectra and fluorescence spectra.The results suggested that being excited at 361 nm,the complex exhibited characteristic emission of Tb（III） ion,revealing that the complex could be excited by 365 nm ultraviolet chip.The HOMO and LUMO,ΔE（HOMO-LUMO）,molecular frontier orbital,and the singlet state and triplet energy state levels of the ligands were calculated at the B3LYP/6-31＋G（d） level.The results indicated that intramolecular energy transfer mechanism followed Dexter exchange energy transfer theory.Both the calculation for excited state of ligand and energy transfer mechanism could provide the theoretical basis for the design of high luminescent materials of rare earth complexes with organic ligands.
基金Project supported by the National Natural Science Foundation of China(21301058,61274026)Innovation Foundation of Hunan University of Science and Technology(S140036)
文摘Lanthanide doped NaYF4 microcrystals were synthesized via a facile hydrothermal method. Multicolor upconversion luminescence was observed in NaYF4 microcrystals doped with yb^3＋/Er^3＋, yb^3＋/Tm^3＋, and yb^3＋/Er^3＋/Zm^3＋ under the excitation of 980 nm infrared light. Importantly, the excitation power density dependence of upconversion emission intensity indicated clearly the energy transfer from Tm^3＋ to Er^3＋ ions under the excitation of low power density （5× 10^2× 10^2 W/cm^2）. Meanwhile, the inverse energy transfer from Er^3＋ to Tm^3＋ ions under the excitation of relatively higher power density （4.1 × 10^4.9× 10^4 W/cm^2） was also revealed. This was a direct evidence for reversible energy transfer between Er^3＋ and Tm^3＋ ions. Under the excitation of high power density （4.1 ×10^4-4.9× 10^4 W/cm^2）, dark sensitizers were also motivated so that the bottleneck effect of high concentration Yb^3＋ ion doping was broken. This was the main reason for realizing high upconversion efficiency of the samples with heavy doping of Yb^3＋ ion.
文摘Nanopowder of Cr：GGG and nanopowder of Cr,Nd：GGG with different concentrations of Cr3＋ ranging from 0.1 at.% to 1.5 at.% were synthesized by the sol-gel method using acetic acid and ethylene glycol. Thermal gravimetric analysis and differential scanning calorimetry （TGA-DSC）, X-ray diffraction （XRD） and photoluminescence spectroscopy were used to characterize the powder. The crystallite size was about 58 nm when treated at 1000 oC for 2 h. Cr3＋ photoluminescence spectrum in GGG showed a broad band emission around 730 nm. The intensity of this band decreased when co-doped with Nd, indicating an efficient energy transfer from Cr3＋ to Nd3＋. Photoluminescence intensity of Nd in Cr,Nd：GGG at 1.06μm showed that the optimum concentration of Cr3＋ was about 1 at.% （more or less） for 1 at.% Nd3＋. This result was also confirmed by chromium fluorescence decay rate analysis. Energy transfer efficiency was found to be about 84% for 1 at.% concentration of each chromium and neodymium.
文摘The Langmuir-Blodgett (LB) technique was used for studying enhanced lumines-cence of Eu (TTA)3 Phen (acceptor) by La (TTA)3 Phen (donor). LB films studied here are:(1) [0. 5% Eu (TTA)3 Phen + 99. 5% La (TTA)3 Phen]: AA = 1: 1; (2) [0. 5%Eu(TTA)3 Phen+99. 5%AA]: AA= 1: 1; (3) La(TTA)3 Phen: AA= 1: 1. These filmscould form stable monolayers at air/water surface. The fluorescence intensity of LB 1 was 65times stronger than that of LB2. This signifies that the luminescence intensity ofEu(TTA)3 Phen could be enhanced by La (TTA)3 Phen clearly. Low angle X-ray diffrac-tog ram of LB1 showed that the film has a period layered structure. To study the intermolec-ular energy transfer, different structures of the multilayer were designed by combining LB2(layer of acceptor) with LB3(layer of donor). The results indicated that the intermolecularenergy transfer occurred in a short-range (<3 nm) and at the position of head-head in Y-typemodel. The influence of the interface on the energy transfer was prominent. The process ofenergy transfer was carried out via the triplet state of TTA.
