Ca3Sc2Si3O12:Ce3+ phosphors with single-phase were successfully synthesized by a gel-combustion method.Annealing atmosphere greatly affected the luminescent properties of the phosphor.The intensity of absorption band ...Ca3Sc2Si3O12:Ce3+ phosphors with single-phase were successfully synthesized by a gel-combustion method.Annealing atmosphere greatly affected the luminescent properties of the phosphor.The intensity of absorption band at 450 nm was greatly increased with a reducing atmosphere,which was very suitable as a color converter in white LED.The absorption at 243 and 311 nm was gradually enhanced with a stronger reducing atmosphere and a new absorption peak at 362 nm appeared in N2+H2 mixing gas.The emission intensit...展开更多
A novel method of codoping the Er^3＋, Yb^3＋, and Ho^3＋ ions in tellurite glasses is demonstrated to obtain a high efficiency of infrared-to-visible upconversion. Three intense emission bands observed in Er^3＋, Yb^...A novel method of codoping the Er^3＋, Yb^3＋, and Ho^3＋ ions in tellurite glasses is demonstrated to obtain a high efficiency of infrared-to-visible upconversion. Three intense emission bands observed in Er^3＋, Yb^3＋, and Ho^3＋ codoped tellurite glasses centred at 525, 547, and 657nm correspond to Er^3＋： ^2H11/2 -4 ^4I15/2, Er^3＋： ^4S3/2 →^4I15/2＋Ho^3＋： ^5S2（^5F4） → ^5Is, and Er^3＋： ^4Sa/2 → ^4I15/2＋Ho^3＋： ^5F5 → ^5Is transitions, respectively. No visible upconversion quenching phenomenon is observed when three rare-earth ions are codoped together in tellurite glasses. In contrast, the upconversion intensity of red and green emissions in Er^3＋, Yb^3＋, and Ho^3＋ codoped glasses is enhanced largely when compared with Er^3＋ /Yb^3＋-codoped glasses. The dependence of upconversion intensities on excitation power and the possible upconversion mechanisms are evaluated. The three emissions are based on two-photon absorption processes.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
The Zn1-xAl2 O4：xEu2＋ phosphor powders were synthesized by the solid-state reaction method.The synthesis temperature for ZnAl2 O4 was optimized,whereas the phase structure,TEM images,photoluminescence（PL） properti...The Zn1-xAl2 O4：xEu2＋ phosphor powders were synthesized by the solid-state reaction method.The synthesis temperature for ZnAl2 O4 was optimized,whereas the phase structure,TEM images,photoluminescence（PL） properties,the concentration quenching mechanism,the fluorescence decay curves,as well as the CIE chromaticity coordinates of the samples were investigated in details.Under the excitation at 379 nm,the phosphor exhibits an asymmetric broad-band green emission with a peak at 532 nm,which is ascribed to the 5 d-4 f transition of Eu2＋.When the doping concentration of Eu2＋ ions is 0.01,the luminescence intensity of the sample reaches the maximum value.It is further proved that the exchange interaction results in the concentration quenching of Eu2＋ in the Zn1-xAl2 O4：xEu2＋ phosphor powders.The thermal quenching property of ZnAl2 O4：Eu2＋phosphor was investigated and the quantum efficiency（QE） values of the selected Zn0.99Al2 O4：0.01 Eu2＋ phosphor was measured and determined as 54.85%.The lifetime of the optimized sample Zn0.99Al2 O4：0.01 Eu2＋ is 3.0852 μs and the CIE coordinate of the sample was calculated as（0.3323,0.5538） with high-color-purity green emission.All properties indicate that the green-emitting ZnAl2 O4：Eu2＋ phosphor powder has potential application in white LEDs.展开更多
A novel green phosphor,Sr2MgB2O6：Tb3＋,Li＋ for white light-emitting diodes was prepared by solid-state reactions,and its structure and luminescence properties were investigated.The excitation and emission spectra in...A novel green phosphor,Sr2MgB2O6：Tb3＋,Li＋ for white light-emitting diodes was prepared by solid-state reactions,and its structure and luminescence properties were investigated.The excitation and emission spectra indicated that this as-prepared phosphor could be effectively excited by ultraviolet 368 nm,and exhibited bright green emission centered at 545 nm corresponding to the^5D_4→~7F_5 transition.9 mol.%of Tb^（3＋） was shown to be optimal.Good green emissions with the CIE chromaticity coordinates（0.262,0.583） could be achieved.Furthermore,the integrated emission intensity of Sr_2MgB_2O_6：0.09Tb^（3＋）,0.09Li~＋ phosphor decreased continuously to 72.1%at 300 ℃ with increasing temperature,and the activation energy of thermal quenching（E_a） was calculated to be0.175 eV,moreover,the quantum yield excited by 368 nm was measured as 11.1%.A green emission LED was made by coating Sr_2MgB_2O_6：0.09Tb^（3＋）,0.09Li~＋ phosphor on a NUV（365-370 nm） chip.Our results showed that Sr_2MgB_2O_6：Tb^（3＋）,Li~＋ is a kind of potential green-emitting phosphor and features good thermal stability.展开更多
Rare-earth doped upconversion nanophosphors(UCNPs), which convert low energy near-infrared(NIR) photons into high energy photons such as ultraviolet, visible light and NIR light, have found various applications in opt...Rare-earth doped upconversion nanophosphors(UCNPs), which convert low energy near-infrared(NIR) photons into high energy photons such as ultraviolet, visible light and NIR light, have found various applications in optical bioimaging. In this review article, we summarize recent advances in the synthesis and applications of UCNPs achieved by us and other groups in the past few years. The approaches for the synthesis of UCNPs are presented,with an emphasis on the role of green chemistry in the advancement of this field, followed by a focused overview on their latest applications in optical bioimaging from subcellular structures through cells to living animals. Challenges and opportunities for the use of UCNPs in biomedical diagnosis and therapy are discussed.展开更多
基金supported by the Ministry of Science and Technology of China (2006CB601104,2006AA03A133)
文摘Ca3Sc2Si3O12:Ce3+ phosphors with single-phase were successfully synthesized by a gel-combustion method.Annealing atmosphere greatly affected the luminescent properties of the phosphor.The intensity of absorption band at 450 nm was greatly increased with a reducing atmosphere,which was very suitable as a color converter in white LED.The absorption at 243 and 311 nm was gradually enhanced with a stronger reducing atmosphere and a new absorption peak at 362 nm appeared in N2+H2 mixing gas.The emission intensit...
基金Supported by the Science and Technology Department of Zhejiang Province under Grant No 2006C21082, the Natural Science Foundation of Zhejiang Province under Grant No 601011.
文摘A novel method of codoping the Er^3＋, Yb^3＋, and Ho^3＋ ions in tellurite glasses is demonstrated to obtain a high efficiency of infrared-to-visible upconversion. Three intense emission bands observed in Er^3＋, Yb^3＋, and Ho^3＋ codoped tellurite glasses centred at 525, 547, and 657nm correspond to Er^3＋： ^2H11/2 -4 ^4I15/2, Er^3＋： ^4S3/2 →^4I15/2＋Ho^3＋： ^5S2（^5F4） → ^5Is, and Er^3＋： ^4Sa/2 → ^4I15/2＋Ho^3＋： ^5F5 → ^5Is transitions, respectively. No visible upconversion quenching phenomenon is observed when three rare-earth ions are codoped together in tellurite glasses. In contrast, the upconversion intensity of red and green emissions in Er^3＋, Yb^3＋, and Ho^3＋ codoped glasses is enhanced largely when compared with Er^3＋ /Yb^3＋-codoped glasses. The dependence of upconversion intensities on excitation power and the possible upconversion mechanisms are evaluated. The three emissions are based on two-photon absorption processes.
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Project supported by the National Natural Science Foundation of China(51472222,51372232)the Fundamental Research Fund for the Central Universities(2652017362)
文摘The Zn1-xAl2 O4：xEu2＋ phosphor powders were synthesized by the solid-state reaction method.The synthesis temperature for ZnAl2 O4 was optimized,whereas the phase structure,TEM images,photoluminescence（PL） properties,the concentration quenching mechanism,the fluorescence decay curves,as well as the CIE chromaticity coordinates of the samples were investigated in details.Under the excitation at 379 nm,the phosphor exhibits an asymmetric broad-band green emission with a peak at 532 nm,which is ascribed to the 5 d-4 f transition of Eu2＋.When the doping concentration of Eu2＋ ions is 0.01,the luminescence intensity of the sample reaches the maximum value.It is further proved that the exchange interaction results in the concentration quenching of Eu2＋ in the Zn1-xAl2 O4：xEu2＋ phosphor powders.The thermal quenching property of ZnAl2 O4：Eu2＋phosphor was investigated and the quantum efficiency（QE） values of the selected Zn0.99Al2 O4：0.01 Eu2＋ phosphor was measured and determined as 54.85%.The lifetime of the optimized sample Zn0.99Al2 O4：0.01 Eu2＋ is 3.0852 μs and the CIE coordinate of the sample was calculated as（0.3323,0.5538） with high-color-purity green emission.All properties indicate that the green-emitting ZnAl2 O4：Eu2＋ phosphor powder has potential application in white LEDs.
基金supported by Natural Science Foundation of Fujian Province(2014J01209)Fujian Provincial Department of Science&Technology(2015H0036)the President Fund of Xiamen University(20720160087)
文摘A novel green phosphor,Sr2MgB2O6：Tb3＋,Li＋ for white light-emitting diodes was prepared by solid-state reactions,and its structure and luminescence properties were investigated.The excitation and emission spectra indicated that this as-prepared phosphor could be effectively excited by ultraviolet 368 nm,and exhibited bright green emission centered at 545 nm corresponding to the^5D_4→~7F_5 transition.9 mol.%of Tb^（3＋） was shown to be optimal.Good green emissions with the CIE chromaticity coordinates（0.262,0.583） could be achieved.Furthermore,the integrated emission intensity of Sr_2MgB_2O_6：0.09Tb^（3＋）,0.09Li~＋ phosphor decreased continuously to 72.1%at 300 ℃ with increasing temperature,and the activation energy of thermal quenching（E_a） was calculated to be0.175 eV,moreover,the quantum yield excited by 368 nm was measured as 11.1%.A green emission LED was made by coating Sr_2MgB_2O_6：0.09Tb^（3＋）,0.09Li~＋ phosphor on a NUV（365-370 nm） chip.Our results showed that Sr_2MgB_2O_6：Tb^（3＋）,Li~＋ is a kind of potential green-emitting phosphor and features good thermal stability.
基金Supported by the National Key Research and Development Program of China(2016YFA0201701/2016YFA0201700)the Beijing Natural Science Foundation(2182051)+2 种基金the National Natural Science Foundation of China(21622601)the Fundamental Research Funds for the Central Universities of China(BUCTRC201601)the "111" project of China(B14004)
文摘Rare-earth doped upconversion nanophosphors(UCNPs), which convert low energy near-infrared(NIR) photons into high energy photons such as ultraviolet, visible light and NIR light, have found various applications in optical bioimaging. In this review article, we summarize recent advances in the synthesis and applications of UCNPs achieved by us and other groups in the past few years. The approaches for the synthesis of UCNPs are presented,with an emphasis on the role of green chemistry in the advancement of this field, followed by a focused overview on their latest applications in optical bioimaging from subcellular structures through cells to living animals. Challenges and opportunities for the use of UCNPs in biomedical diagnosis and therapy are discussed.
