Optomagnetic multifunctional composite based on upconversion luminescence nanomaterial is regarded as a promising strategy for bioimaging,disease diagnosis and targeted delivery of drugs.To explore a mesoporous nanost...Optomagnetic multifunctional composite based on upconversion luminescence nanomaterial is regarded as a promising strategy for bioimaging,disease diagnosis and targeted delivery of drugs.To explore a mesoporous nanostructure with excellent water dispersibility and high drug-loading capacity,a novel nanorattle-structured Fe3O4@SiO2@NaYF4:Yb,Er magnetic upconversion nanorattle(MUCNR)was successfully designed by using Fe3O4 as core and NaYF4:Yb,Er nanocrystals as shell.The microstructures and crystal phase of the as-prepared MUCNRs were evaluated by transmission electron microscopy,Xray powder diffraction and N2 adsorption/desorption isotherms.The Kirkendall effect was adapted to explain the formation mechanism of the MUCNRs.The loading content and encapsulation efficiency of doxorubicin hydrochloride(DOX)could reach as high as 18.2%and 60.7%,respectively.Moreover,the DOX loading MUCNR(DOX-MUCNR)system showed excellent sustained drug release and strong p Hdependent performance,which was conducive to drug release at the slightly acidic microenvironment of tumor.Microcalorimetry was used to quantify the interactions between the carrier structure and drug release rate directly.The heat release rates in the heat-flow diagrams are basically consistent with the DOX release rate,thereby showing that microcalorimetry assay not only provides a unique thermodynamic explanation for the structure–activity relationship of Fe3O4@SiO2@NaYF4:Yb,Er MUCNRs but also provides powerful guidance to avoid the blind selection or design of drug carriers.Therefore,our work firmly provided a comprehensive perspective for using Fe3O4@SiO2@NaYF4:Yb,Er MUCNRs as a remarkable magnetic targeted drug carrier.展开更多
A series of Yb:Tm:LiNbO_3 crystals doped with x mol% Hf^(4+)ions(x = 2, 4, and 6) were grown by the Czochralski method. The dopant occupancy and defect structure of Hf:Yb:Tm:LiNbO_3 crystals were investigated by x-ray...A series of Yb:Tm:LiNbO_3 crystals doped with x mol% Hf^(4+)ions(x = 2, 4, and 6) were grown by the Czochralski method. The dopant occupancy and defect structure of Hf:Yb:Tm:LiNbO_3 crystals were investigated by x-ray diffraction and infrared transmission spectra. The influence of Hf^(4+)ions concentration on UV–VIS–NIR absorption spectra of Hf:Yb:Tm:LiNbO_3 crystals was discussed. The upconversion luminescence of Hf:Yb:Tm:LiNbO_3 crystals was obtained under 980 nm excitation. Strong emissions were observed at 475 nm in the blue wavelength range and 651 nm in the red wavelength range. Remarkably, enhancement of the red and blue upconversion luminescence was achieved by tridoping Hf^(4+)ions.展开更多
LaF_3:Yb^(3 +),Er^(3 +) nanoparticles were successfully synthesized using solvothermal treatment,and LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 core /shell nanoparticles were also prepared with reverse microemulsion technique.The...LaF_3:Yb^(3 +),Er^(3 +) nanoparticles were successfully synthesized using solvothermal treatment,and LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 core /shell nanoparticles were also prepared with reverse microemulsion technique.The crystal structure,morphology and photoluminescence properties of as-prepared core /shell nanoparticles were investigated by X-ray diffraction,transmission electron microscopy and fluorescence spectrophotometer.The results showed that LaF_3:Yb^(3 +),Er^(3 +) nanoparticles are of hexagonal structure and SiO_2 shell is amorphous.The size of LaF_3:Yb^(3 +),Er^(3 +) nanoparticles is 13 nm and the LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 nanoparticles present clearly a core /shell structure with 12 nm shell thickness.The solubility of LaF_3:Yb^(3 +),Er^(3 +) nanocrystals in water and the biocompatibility are both improved by the SiO_2 shell.The upconversion luminescence spectra suggested that the SiO_2 shell has small effect on the upconversion luminescence properties of the LaF_3:Yb^(3 +),Er^(3 +) nanocrystals.The core /shell structure LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 nanoparticles are expected to be used in biological applications.展开更多
A new upconversion luminescence agent, 40CdF2·60BaF2·0.8Er2O3, was synthesized and its fluorescent spectra were determined. This upconversion luminescence agent can emit five upconversion fluorescent peaks s...A new upconversion luminescence agent, 40CdF2·60BaF2·0.8Er2O3, was synthesized and its fluorescent spectra were determined. This upconversion luminescence agent can emit five upconversion fluorescent peaks shown in the fluorescent spectra whose wavelengths are all below 387 nm under the excitation of 488 nm visible light. This upconversion luminescence agent was mixed into nano rutile TiO2 powder by ultrasonic and boiling dispersion and the novel doped nano TiO2 photocatalyst utilizing visible light was firstly prepared. The doped TiO2 powder was charactered by XRD and TEM and its photocatalytic activity was tested through the photocatalytic degradation of methyl orange as a model compound under the visible light irradiation emitted by six three basic color lamps. In order to compare the photocatalytic activities, the same experiment was carried out for undoped TiO2 powder. The degradation ratio of methyl orange in the presence of doped nano TiO2 powder reached 32.5% under visible light irradiation at 20 h which was obviously higher than the corresponding 1.64% in the presence of undoped nano TiO2 powder, which indicate the upconversion luminescence agent prepared as dopant can effectively turn visible lights to ultraviolet lights that are absorbed by nano TiO2 particles to produce the electron-cavity pairs. All the results show that the nano rutile TiO2 powder doped with upconversion luminescence agent is a promising photocatalyst using sunlight for treating the industry dye wastewater in great force.展开更多
Cubic NaYF4:Yb3+(20%) /Er3+(1%) microspheres were synthesized by EDTA-assisted hydrothermal method. Under 980 nm excitation,ultraviolet(4G11/2→4I15/2) ,violet(2H9/2→4I15/2) ,green(4F7/2→4I15/2,2H11/2→4I15/2,and 4S...Cubic NaYF4:Yb3+(20%) /Er3+(1%) microspheres were synthesized by EDTA-assisted hydrothermal method. Under 980 nm excitation,ultraviolet(4G11/2→4I15/2) ,violet(2H9/2→4I15/2) ,green(4F7/2→4I15/2,2H11/2→4I15/2,and 4S3/2→4I15/2) ,and red(4F9/2→4I15/2) upconversion fluorescence were observed. The number of laser photons absorbed in one upconversion excitation process,n,was determined to be 3.89,1.61,2.55,and 1.09 for the ultraviolet,violet,green,and red emissions,respectively. Obviously,n=3.89 indicated that a four-photon process was involved in populating the 4G11/2 state,and n=2.55 indicated that a three-photon process was involved in populating the 4F7/2/2H11/2/4S3/2 levels. For the violet and red emissions,the population of the states 2H9/2 and 4F9/2 separately came from three-photon and two-photon processes. The decrease of n was well explained by the mechanism of competition between linear decay and upconversion processes for the depletion of the intermediate excited states.展开更多
Y2O3: Er3+, Yb3+ nanoparticles were synthesized by a homogeneous precipitation method without and with different concentrations of EDTA 2Na. Upconversion luminescence spectra of the samples were studied under 980 nm l...Y2O3: Er3+, Yb3+ nanoparticles were synthesized by a homogeneous precipitation method without and with different concentrations of EDTA 2Na. Upconversion luminescence spectra of the samples were studied under 980 nm laser excitation. The results of XRD showed that the obtained Y2O3:Er3+,Yb3+ nanoparticles were of a cubic structure. The average crystallite sizes calculated were in the range of 28-40 nm. Green and red upconversion emission were observed, and attributed to 2H11/ 2,4S3/ 2→4I15/ 2 and 4F9/ 2→4I15/2 transitions of the Er3+ ion, respectively. The ratio of the intensity of green emission to that of red emission drastically changed with a change in the EDTA 2Na concentration. In the sample synthesized without EDTA, the relative intensity of the green emission was weaker than that of the red emission. The relative intensities of green emission increased with the increased amount of EDTA 2Na used. The possible upconversion luminescence mechanisms were discussed.展开更多
Cubic YAG:Yb3+, Ho3+ pure phase nanocrystals were synthesized by using coprecipition nitrate and ammonium hydrogen carbonate as raw materials.After calcining the precipitates at 800 °C, the resultant YAG:Yb3+, Ho...Cubic YAG:Yb3+, Ho3+ pure phase nanocrystals were synthesized by using coprecipition nitrate and ammonium hydrogen carbonate as raw materials.After calcining the precipitates at 800 °C, the resultant YAG:Yb3+, Ho3+ nanocrystals were nearly spheric and the particle size was about 40 nm.Intense upconversion spectra were observed on the powder compact pumped by a 980 nm continuous wave diode laser, and green emission centered at 549 nm, red emission centered at 667 nm, and NIR centered at 760 nm were all due to two photons process, which originated from 5S2(5F4)→5I8, 5F5→5I8, and 5S2(5F4)→5I7 transitions, respectively.展开更多
Y2O3:Er3+ ultrafine phosphors with a varying Yb3+ ion concentration were prepared by a urea homogeneous precipitation method. The results of XRD show that all the samples are of a pure cubic structure and the average ...Y2O3:Er3+ ultrafine phosphors with a varying Yb3+ ion concentration were prepared by a urea homogeneous precipitation method. The results of XRD show that all the samples are of a pure cubic structure and the average crystallite sizes can be calculated as 45, 34, and 28 nm for Y2O3:Er3+ ultrafine phosphors with Yb3+ ion concentrations of 0, 10%, and 20%, respec- tively. The lattice constant and cell volume of the ultrafine phosphors decrease with enhancing Yb3+ ion concentration. The upconversion luminescence spectra of all the samples were studied under 980 nm laser excitation. The strong green and red upconversion emission were observed, and attributed to the 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+, respectively. The intensity of red emission increases with increasing Yb3+ ion concentration. The effect of Yb3+ ion concentra- tion on the structures and upconversion luminescence mechanism were discussed.展开更多
The effects of a Mg2+ ion on the dopant occupancy and upconversion luminescence of a Ho3+ ion in LiNbO3 crystal are reported. The birefringence gradient of the crystal is measured to investigate the optical homogeneit...The effects of a Mg2+ ion on the dopant occupancy and upconversion luminescence of a Ho3+ ion in LiNbO3 crystal are reported. The birefringence gradient of the crystal is measured to investigate the optical homogeneity. The X-ray powder diffraction spectrum and the upconversion luminescence are used to investigate defect structure and spectroscopic properties of Mg,Ho:LiNbO3 . Under 808-nm excitation, blue, red, and very intense yellow-green bands are observed. Based on the energy levels of Ho3+ in LiNbO3 , and the pump intensity dependence of the observed emission, an excitation scheme is presented. The upconversion emission spectra reveal an enhancement of upconversion intensity when the Mg2+ ions are introduced into Ho:LiNbO3 . The main upconversion mechanism is discussed in this work.展开更多
YLiF4∶Er 3+ was synthesized by hydrothermal method. Concentration of Er 3+ is changed from 0 to 5%. The absorption of Er 3+ in all samples from 200 to 1200 nm was measured at room temperature. The J-O parameters calc...YLiF4∶Er 3+ was synthesized by hydrothermal method. Concentration of Er 3+ is changed from 0 to 5%. The absorption of Er 3+ in all samples from 200 to 1200 nm was measured at room temperature. The J-O parameters calculated from absorption spectrum are Ω2=1.05×10 -20 cm2, Ω4=1.25×10 -20 cm2 and Ω6=1.35×10 -20 cm2. Infrared-to-visible upconversion emission of YLiF4∶Er 3+ was observed when excited by 980 nm. The results show that the Er 3+ content is less than 1.5%, excite-state absorption is the main mechanism of upconversion emission. When Er 3+ content is larger than 1.5%, both of the excite-state absorption and energy transfer lead to the upconversion luminescence. The upconversion intensity was enhanced with the increasing of Er 3+ concentration. At room temperature, the lifetime of 2H 11/2 and 4S 3/2 is 205 μs while that of 4F 9/2 is 188 μs for sample Er-2. The transition rates and quantum efficiency were also calculated. The quantum efficiencies of 4S 3/2 and 4F 9/2 are 27.9% and 10.7%, respectively.展开更多
Nanocrystalline Gd 1.77 Yb 0.2 Er 0.03 O 3 samples were prepared by combustion and precipitation methods.Structures and upconversion luminescence properties of samples were studied.The results of XRD show that all sam...Nanocrystalline Gd 1.77 Yb 0.2 Er 0.03 O 3 samples were prepared by combustion and precipitation methods.Structures and upconversion luminescence properties of samples were studied.The results of XRD show that all samples are cubic structure,the average crystallite size could be calculated as 23 nm and 39 nm, respectively.The lattice constants were obtained.The FT-IR spectra were measured to investigate the vibrational feature of the samples.Upconversion luminescence spectra of samples under 980 nm laser excitation were investigated.The strong red emission of samples were observed,and attributed to 4F 9/2 →4I 15/2 transitions of Er3+ions,the emission intensity for sample synthesized by precipitation method is stronger compared to that of combustion method.The possible upconversion luminescence mechanisms in nanocrystalline Gd 1.77 Yb 0.2 Er 0.03 O 3 were discussed.展开更多
Tm 3+/Yb 3+-codoped oxychloride tellurite glasses were prepared. Thermal stability, Raman spectra and upconversion luminescence spectra were studied, and upconversion luminescence mechanisms were analyzed. The results...Tm 3+/Yb 3+-codoped oxychloride tellurite glasses were prepared. Thermal stability, Raman spectra and upconversion luminescence spectra were studied, and upconversion luminescence mechanisms were analyzed. The results show that the intense blue and relatively weak red emissions centered at 476 and 649 nm corresponding to the transitions 1G4→3H6 and 1G4→3H4 of Tm 3+, respectively, were simultaneously observed at room temperature under 980 nm LD excitation. With increasing while PbCl2 content, thermal stability of host glasses increases, phonon energy of host glasses decreases, and upconversion luminescence intensities increase, which indicate that Tm 3+/Yb 3+-codoped oxychloride tellurite glasses can be used as potential host materials for upconversion blue lasers.展开更多
YAG∶1% （atom fraction） Yb 3+ , 0.5% （atom fraction） Er 3+ transparent ceramics were fabricated by the solid state reaction method using high-purity Y2O3, Al2O3, Yb2O3, and Er2O3 powders as starting materials. The...YAG∶1% （atom fraction） Yb 3+ , 0.5% （atom fraction） Er 3+ transparent ceramics were fabricated by the solid state reaction method using high-purity Y2O3, Al2O3, Yb2O3, and Er2O3 powders as starting materials. The mixed powder compact was sintered at 1760 ℃ for 6 h in vacuum and annealed at 1500 ℃ for 10 h in an air atmosphere. The ceramics consisted of about 10 μm grains and exhibited a pore-free structure. The optical transmittance of the ceramics at 1064 nm was nearly 80%. Upconversion emissions were investigated on the ceramics pumped by a 980 nm continuous wave diode laser, and strong green emission centered at 523 and 559 nm and red emission centered at 669 nm were observed, which originated from the radiative transitions of 2H 11/2 →4I 15/2 , 4S 3/2 →4I 15/2 , and 4F 9/2 →4I 15/2 of Er 3+ ions, respectively.展开更多
A synthesis of LaF3:0.04Yb3+,0.01Er3+ nanocrystals with oleic acid as a capping ligand was presented. The X-Ray Diffraction (XRD) pattern indicated that the power was a single hexagonal phase. Transmission Electron Mi...A synthesis of LaF3:0.04Yb3+,0.01Er3+ nanocrystals with oleic acid as a capping ligand was presented. The X-Ray Diffraction (XRD) pattern indicated that the power was a single hexagonal phase. Transmission Electron Microscopy (TEM) demonstrated that the av- erage size of the nanocrystals was less than 10 nm, with a narrow size distribution. The nanocrystals were dispersible in nonpolar solvents and form a fully transparent colloidal solution, and the solution was stable for several months without any aggregates. The Yb3+-Er3+ codoped nanocrystal colloidal solution exhibited a bright green upconversion fluorescence under 980 nm excitation from a diode laser. The nanocrys- tals were potentially applicable in biolabeling and bioimaging.展开更多
LaF3: Yb3+, Er3+ microcrystals were synthesized by a hydrothermal method, and then, the LaF3: Yb3+, Er3+ microcrystals were coated with silica. Phase identification of LaF3: Yb3+, Er3+ and LaF3: Yb3+, Er3+/SiO2 was pe...LaF3: Yb3+, Er3+ microcrystals were synthesized by a hydrothermal method, and then, the LaF3: Yb3+, Er3+ microcrystals were coated with silica. Phase identification of LaF3: Yb3+, Er3+ and LaF3: Yb3+, Er3+/SiO2 was performed via XRD. The TEM image showed that the size of LaF3: Yb3+, Er3+ was 150 nm and LaF3: Yb3+, Er3+/SiO2 presented clearly a core/shell structure with 20 nm shell thickness. The upconversion spectra of LaF3: Yb3+, Er3+ and LaF3: Yb3+, Er3+/SiO2 in solid state and in ethanol were studied with a 980 nm diode laser as the excitation source. The upconversion spectra showed that the silica shell had little effect on the properties of fluorescence of the LaF3: Yb3+, Er3+ microcrystals. At the same time, the green luminescence photo of LaF3: Yb3+, Er3+/SiO2 in the PBS buffer was obtained, which indicated that the LaF3: Yb3+, Er3+/SiO2 could be used in biological applications.展开更多
Nd^(3+)-doped NaGdF_(4):Yb,Tm nanocrystals were synthesized by an improved high-temperature thermal decomposition method,and the effects of doping concentrations on the crystal structure,phase composition,and upconver...Nd^(3+)-doped NaGdF_(4):Yb,Tm nanocrystals were synthesized by an improved high-temperature thermal decomposition method,and the effects of doping concentrations on the crystal structure,phase composition,and upconverted fluorescence intensity were also investigated.The results reveal that the introduction of Nd^(3+) ions does not cause the transformation of the crystal phase,but induce the change of the unit cell parameters.Meanwhile,the fluorescence intensity of the synthesized nanocrystals when co-doped with 3 mol%Nd^(3+) is the strongest under the excitation of 980 nm laser,which is 3.9 times that of the Nd^(3+)-free doped nanoparticles,and the average size is 62.9 nm.And it is located in the blue area of the CIE coordinate diagram,and the corresponding color purity is 91.81%under the same experimental conditions.The resulting nanocrystals show the potential as excellent fluorescence labeling and in vivo imaging probes.展开更多
基金supported by the Key Research and Development Plan of Shaanxi Province(2020GY-313)the Specialized Research Fund of Education Department of Shaanxi Province(19JK0255)+1 种基金the Specialized Scientific Research Fund Projects of Academician Shengyong Zhang(18YSZX001)the Science and Technology Innovation Team of Shangluo University(20SCX02)。
文摘Optomagnetic multifunctional composite based on upconversion luminescence nanomaterial is regarded as a promising strategy for bioimaging,disease diagnosis and targeted delivery of drugs.To explore a mesoporous nanostructure with excellent water dispersibility and high drug-loading capacity,a novel nanorattle-structured Fe3O4@SiO2@NaYF4:Yb,Er magnetic upconversion nanorattle(MUCNR)was successfully designed by using Fe3O4 as core and NaYF4:Yb,Er nanocrystals as shell.The microstructures and crystal phase of the as-prepared MUCNRs were evaluated by transmission electron microscopy,Xray powder diffraction and N2 adsorption/desorption isotherms.The Kirkendall effect was adapted to explain the formation mechanism of the MUCNRs.The loading content and encapsulation efficiency of doxorubicin hydrochloride(DOX)could reach as high as 18.2%and 60.7%,respectively.Moreover,the DOX loading MUCNR(DOX-MUCNR)system showed excellent sustained drug release and strong p Hdependent performance,which was conducive to drug release at the slightly acidic microenvironment of tumor.Microcalorimetry was used to quantify the interactions between the carrier structure and drug release rate directly.The heat release rates in the heat-flow diagrams are basically consistent with the DOX release rate,thereby showing that microcalorimetry assay not only provides a unique thermodynamic explanation for the structure–activity relationship of Fe3O4@SiO2@NaYF4:Yb,Er MUCNRs but also provides powerful guidance to avoid the blind selection or design of drug carriers.Therefore,our work firmly provided a comprehensive perspective for using Fe3O4@SiO2@NaYF4:Yb,Er MUCNRs as a remarkable magnetic targeted drug carrier.
基金Project supported by Special Funds of Harbin Innovation Talents in Science and Technology Research,China(Grant No.2015RQQXJ045)Science Funds for the Young Innovative Talents of HUST,China
文摘A series of Yb:Tm:LiNbO_3 crystals doped with x mol% Hf^(4+)ions(x = 2, 4, and 6) were grown by the Czochralski method. The dopant occupancy and defect structure of Hf:Yb:Tm:LiNbO_3 crystals were investigated by x-ray diffraction and infrared transmission spectra. The influence of Hf^(4+)ions concentration on UV–VIS–NIR absorption spectra of Hf:Yb:Tm:LiNbO_3 crystals was discussed. The upconversion luminescence of Hf:Yb:Tm:LiNbO_3 crystals was obtained under 980 nm excitation. Strong emissions were observed at 475 nm in the blue wavelength range and 651 nm in the red wavelength range. Remarkably, enhancement of the red and blue upconversion luminescence was achieved by tridoping Hf^(4+)ions.
文摘LaF_3:Yb^(3 +),Er^(3 +) nanoparticles were successfully synthesized using solvothermal treatment,and LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 core /shell nanoparticles were also prepared with reverse microemulsion technique.The crystal structure,morphology and photoluminescence properties of as-prepared core /shell nanoparticles were investigated by X-ray diffraction,transmission electron microscopy and fluorescence spectrophotometer.The results showed that LaF_3:Yb^(3 +),Er^(3 +) nanoparticles are of hexagonal structure and SiO_2 shell is amorphous.The size of LaF_3:Yb^(3 +),Er^(3 +) nanoparticles is 13 nm and the LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 nanoparticles present clearly a core /shell structure with 12 nm shell thickness.The solubility of LaF_3:Yb^(3 +),Er^(3 +) nanocrystals in water and the biocompatibility are both improved by the SiO_2 shell.The upconversion luminescence spectra suggested that the SiO_2 shell has small effect on the upconversion luminescence properties of the LaF_3:Yb^(3 +),Er^(3 +) nanocrystals.The core /shell structure LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 nanoparticles are expected to be used in biological applications.
基金The National Natural Science Foundation of China (No.20371023)
文摘A new upconversion luminescence agent, 40CdF2·60BaF2·0.8Er2O3, was synthesized and its fluorescent spectra were determined. This upconversion luminescence agent can emit five upconversion fluorescent peaks shown in the fluorescent spectra whose wavelengths are all below 387 nm under the excitation of 488 nm visible light. This upconversion luminescence agent was mixed into nano rutile TiO2 powder by ultrasonic and boiling dispersion and the novel doped nano TiO2 photocatalyst utilizing visible light was firstly prepared. The doped TiO2 powder was charactered by XRD and TEM and its photocatalytic activity was tested through the photocatalytic degradation of methyl orange as a model compound under the visible light irradiation emitted by six three basic color lamps. In order to compare the photocatalytic activities, the same experiment was carried out for undoped TiO2 powder. The degradation ratio of methyl orange in the presence of doped nano TiO2 powder reached 32.5% under visible light irradiation at 20 h which was obviously higher than the corresponding 1.64% in the presence of undoped nano TiO2 powder, which indicate the upconversion luminescence agent prepared as dopant can effectively turn visible lights to ultraviolet lights that are absorbed by nano TiO2 particles to produce the electron-cavity pairs. All the results show that the nano rutile TiO2 powder doped with upconversion luminescence agent is a promising photocatalyst using sunlight for treating the industry dye wastewater in great force.
基金supported by the National Natural Science Foundation of China (10474096 and 50672030)
文摘Cubic NaYF4:Yb3+(20%) /Er3+(1%) microspheres were synthesized by EDTA-assisted hydrothermal method. Under 980 nm excitation,ultraviolet(4G11/2→4I15/2) ,violet(2H9/2→4I15/2) ,green(4F7/2→4I15/2,2H11/2→4I15/2,and 4S3/2→4I15/2) ,and red(4F9/2→4I15/2) upconversion fluorescence were observed. The number of laser photons absorbed in one upconversion excitation process,n,was determined to be 3.89,1.61,2.55,and 1.09 for the ultraviolet,violet,green,and red emissions,respectively. Obviously,n=3.89 indicated that a four-photon process was involved in populating the 4G11/2 state,and n=2.55 indicated that a three-photon process was involved in populating the 4F7/2/2H11/2/4S3/2 levels. For the violet and red emissions,the population of the states 2H9/2 and 4F9/2 separately came from three-photon and two-photon processes. The decrease of n was well explained by the mechanism of competition between linear decay and upconversion processes for the depletion of the intermediate excited states.
基金the Foundation for the University by Educational Department of Liaoning (05L337)Key Laboratory of Rare Earth Chemistry and Physics, Chinese Academy of Sciences
文摘Y2O3: Er3+, Yb3+ nanoparticles were synthesized by a homogeneous precipitation method without and with different concentrations of EDTA 2Na. Upconversion luminescence spectra of the samples were studied under 980 nm laser excitation. The results of XRD showed that the obtained Y2O3:Er3+,Yb3+ nanoparticles were of a cubic structure. The average crystallite sizes calculated were in the range of 28-40 nm. Green and red upconversion emission were observed, and attributed to 2H11/ 2,4S3/ 2→4I15/ 2 and 4F9/ 2→4I15/2 transitions of the Er3+ ion, respectively. The ratio of the intensity of green emission to that of red emission drastically changed with a change in the EDTA 2Na concentration. In the sample synthesized without EDTA, the relative intensity of the green emission was weaker than that of the red emission. The relative intensities of green emission increased with the increased amount of EDTA 2Na used. The possible upconversion luminescence mechanisms were discussed.
基金supported by the National Natural Science Foundation of China (50372075)Shanghai Light-Tech Project (036105021)Singapore AStar SERC (052 101 0039)
文摘Cubic YAG:Yb3+, Ho3+ pure phase nanocrystals were synthesized by using coprecipition nitrate and ammonium hydrogen carbonate as raw materials.After calcining the precipitates at 800 °C, the resultant YAG:Yb3+, Ho3+ nanocrystals were nearly spheric and the particle size was about 40 nm.Intense upconversion spectra were observed on the powder compact pumped by a 980 nm continuous wave diode laser, and green emission centered at 549 nm, red emission centered at 667 nm, and NIR centered at 760 nm were all due to two photons process, which originated from 5S2(5F4)→5I8, 5F5→5I8, and 5S2(5F4)→5I7 transitions, respectively.
基金financially supported by the Foundation for Universities by the Educational Department of Liaoning Province, China (No. 05L337)
文摘Y2O3:Er3+ ultrafine phosphors with a varying Yb3+ ion concentration were prepared by a urea homogeneous precipitation method. The results of XRD show that all the samples are of a pure cubic structure and the average crystallite sizes can be calculated as 45, 34, and 28 nm for Y2O3:Er3+ ultrafine phosphors with Yb3+ ion concentrations of 0, 10%, and 20%, respec- tively. The lattice constant and cell volume of the ultrafine phosphors decrease with enhancing Yb3+ ion concentration. The upconversion luminescence spectra of all the samples were studied under 980 nm laser excitation. The strong green and red upconversion emission were observed, and attributed to the 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+, respectively. The intensity of red emission increases with increasing Yb3+ ion concentration. The effect of Yb3+ ion concentra- tion on the structures and upconversion luminescence mechanism were discussed.
基金Project supported by the National Natural Science Foundation of China （Grant No 10074020）.Acknowledgement The authors would like to thank Professor Siyuan Zhang for providing Er^3＋：YAG crystal.
基金Project supported by the Shanghai ＂Post-Qi-Ming-Xing plan＂ for Young Scientists, China （Grant No 04QMX1448） and the National Natural Science Foundation of China （Grant No 60207006）.The author would like to thank Wen L,Shen Y H and Zhao Y for their help in machining and measuring.
基金supported by the China Postdoctoral Science Foundation (Grant No. 2012M520759 )the Science and Technology Research Project of Education Bureau of Heilongjiang Province, China (Grant No. 12531098)
文摘The effects of a Mg2+ ion on the dopant occupancy and upconversion luminescence of a Ho3+ ion in LiNbO3 crystal are reported. The birefringence gradient of the crystal is measured to investigate the optical homogeneity. The X-ray powder diffraction spectrum and the upconversion luminescence are used to investigate defect structure and spectroscopic properties of Mg,Ho:LiNbO3 . Under 808-nm excitation, blue, red, and very intense yellow-green bands are observed. Based on the energy levels of Ho3+ in LiNbO3 , and the pump intensity dependence of the observed emission, an excitation scheme is presented. The upconversion emission spectra reveal an enhancement of upconversion intensity when the Mg2+ ions are introduced into Ho:LiNbO3 . The main upconversion mechanism is discussed in this work.
基金supported by the National Natural Science Foundation of China (60508014 and 50772102)Program for New Century Excellent Talents in University (NCET-07-0786)the Natural Science Foundation of Zhejiang Province (R406007)
文摘YLiF4∶Er 3+ was synthesized by hydrothermal method. Concentration of Er 3+ is changed from 0 to 5%. The absorption of Er 3+ in all samples from 200 to 1200 nm was measured at room temperature. The J-O parameters calculated from absorption spectrum are Ω2=1.05×10 -20 cm2, Ω4=1.25×10 -20 cm2 and Ω6=1.35×10 -20 cm2. Infrared-to-visible upconversion emission of YLiF4∶Er 3+ was observed when excited by 980 nm. The results show that the Er 3+ content is less than 1.5%, excite-state absorption is the main mechanism of upconversion emission. When Er 3+ content is larger than 1.5%, both of the excite-state absorption and energy transfer lead to the upconversion luminescence. The upconversion intensity was enhanced with the increasing of Er 3+ concentration. At room temperature, the lifetime of 2H 11/2 and 4S 3/2 is 205 μs while that of 4F 9/2 is 188 μs for sample Er-2. The transition rates and quantum efficiency were also calculated. The quantum efficiencies of 4S 3/2 and 4F 9/2 are 27.9% and 10.7%, respectively.
基金the Foundation for University by Educational Department of Liaoning(No.05L337)
文摘Nanocrystalline Gd 1.77 Yb 0.2 Er 0.03 O 3 samples were prepared by combustion and precipitation methods.Structures and upconversion luminescence properties of samples were studied.The results of XRD show that all samples are cubic structure,the average crystallite size could be calculated as 23 nm and 39 nm, respectively.The lattice constants were obtained.The FT-IR spectra were measured to investigate the vibrational feature of the samples.Upconversion luminescence spectra of samples under 980 nm laser excitation were investigated.The strong red emission of samples were observed,and attributed to 4F 9/2 →4I 15/2 transitions of Er3+ions,the emission intensity for sample synthesized by precipitation method is stronger compared to that of combustion method.The possible upconversion luminescence mechanisms in nanocrystalline Gd 1.77 Yb 0.2 Er 0.03 O 3 were discussed.
文摘Tm 3+/Yb 3+-codoped oxychloride tellurite glasses were prepared. Thermal stability, Raman spectra and upconversion luminescence spectra were studied, and upconversion luminescence mechanisms were analyzed. The results show that the intense blue and relatively weak red emissions centered at 476 and 649 nm corresponding to the transitions 1G4→3H6 and 1G4→3H4 of Tm 3+, respectively, were simultaneously observed at room temperature under 980 nm LD excitation. With increasing while PbCl2 content, thermal stability of host glasses increases, phonon energy of host glasses decreases, and upconversion luminescence intensities increase, which indicate that Tm 3+/Yb 3+-codoped oxychloride tellurite glasses can be used as potential host materials for upconversion blue lasers.
基金This work was supported by the Department of Education of Zhejiang Province （No.20060496） and the Natural Science Foundation of Zhejiang Province （No.Y406309）.
基金Project supported bythe National Natural Science Foundation of China (50372075)
文摘YAG∶1% （atom fraction） Yb 3+ , 0.5% （atom fraction） Er 3+ transparent ceramics were fabricated by the solid state reaction method using high-purity Y2O3, Al2O3, Yb2O3, and Er2O3 powders as starting materials. The mixed powder compact was sintered at 1760 ℃ for 6 h in vacuum and annealed at 1500 ℃ for 10 h in an air atmosphere. The ceramics consisted of about 10 μm grains and exhibited a pore-free structure. The optical transmittance of the ceramics at 1064 nm was nearly 80%. Upconversion emissions were investigated on the ceramics pumped by a 980 nm continuous wave diode laser, and strong green emission centered at 523 and 559 nm and red emission centered at 669 nm were observed, which originated from the radiative transitions of 2H 11/2 →4I 15/2 , 4S 3/2 →4I 15/2 , and 4F 9/2 →4I 15/2 of Er 3+ ions, respectively.
基金Project supported by the National Natural Science Foundation of China (10474096 50672030)
文摘A synthesis of LaF3:0.04Yb3+,0.01Er3+ nanocrystals with oleic acid as a capping ligand was presented. The X-Ray Diffraction (XRD) pattern indicated that the power was a single hexagonal phase. Transmission Electron Microscopy (TEM) demonstrated that the av- erage size of the nanocrystals was less than 10 nm, with a narrow size distribution. The nanocrystals were dispersible in nonpolar solvents and form a fully transparent colloidal solution, and the solution was stable for several months without any aggregates. The Yb3+-Er3+ codoped nanocrystal colloidal solution exhibited a bright green upconversion fluorescence under 980 nm excitation from a diode laser. The nanocrys- tals were potentially applicable in biolabeling and bioimaging.
基金Project supported by the National Natural Science Foundation of China (10474096 and 50672030)
文摘LaF3: Yb3+, Er3+ microcrystals were synthesized by a hydrothermal method, and then, the LaF3: Yb3+, Er3+ microcrystals were coated with silica. Phase identification of LaF3: Yb3+, Er3+ and LaF3: Yb3+, Er3+/SiO2 was performed via XRD. The TEM image showed that the size of LaF3: Yb3+, Er3+ was 150 nm and LaF3: Yb3+, Er3+/SiO2 presented clearly a core/shell structure with 20 nm shell thickness. The upconversion spectra of LaF3: Yb3+, Er3+ and LaF3: Yb3+, Er3+/SiO2 in solid state and in ethanol were studied with a 980 nm diode laser as the excitation source. The upconversion spectra showed that the silica shell had little effect on the properties of fluorescence of the LaF3: Yb3+, Er3+ microcrystals. At the same time, the green luminescence photo of LaF3: Yb3+, Er3+/SiO2 in the PBS buffer was obtained, which indicated that the LaF3: Yb3+, Er3+/SiO2 could be used in biological applications.
文摘Nd^(3+)-doped NaGdF_(4):Yb,Tm nanocrystals were synthesized by an improved high-temperature thermal decomposition method,and the effects of doping concentrations on the crystal structure,phase composition,and upconverted fluorescence intensity were also investigated.The results reveal that the introduction of Nd^(3+) ions does not cause the transformation of the crystal phase,but induce the change of the unit cell parameters.Meanwhile,the fluorescence intensity of the synthesized nanocrystals when co-doped with 3 mol%Nd^(3+) is the strongest under the excitation of 980 nm laser,which is 3.9 times that of the Nd^(3+)-free doped nanoparticles,and the average size is 62.9 nm.And it is located in the blue area of the CIE coordinate diagram,and the corresponding color purity is 91.81%under the same experimental conditions.The resulting nanocrystals show the potential as excellent fluorescence labeling and in vivo imaging probes.
