Erbium-doped BaTiO3 films on LaNiO3/Si substrates were fabricated by sol-gel method. The crystalline structure, morphologies and upconversion （UC） luminescence properties of films were respectively investigated by X...Erbium-doped BaTiO3 films on LaNiO3/Si substrates were fabricated by sol-gel method. The crystalline structure, morphologies and upconversion （UC） luminescence properties of films were respectively investigated by X-ray diffraction （XRD）, atomic force microcopy （AFM） and photoluminescence （PL）. The results indicate that both of the microstructure and luminescence are found to be dependent on Er^3＋ substituting sites. The samples with A-site substitution have smaller lattice constants, larger grains and smoother surface than those with B-site substitution. The photoluminescence spectra show that both of the samples have two stronger green emission bands centered at 528 and 548 nm and a weak red emission band centered at 673 nm, which correspond to the relaxation of Er^3＋ from ^2H11/2, ^4S3/2, and ^4F9/2 levels to the ground level ^4I15/2, respectively. Compared with B-site doped films, A-site doped films have a stronger integrated intensity of green emissions and a weaker relative intensity of red emissions. The differences could be explained by the crystalline quality and cross relaxation （CR） process.展开更多
By using metal nitrates as starting materials and citric acid as a complexing agent, Y2Si207：Re3＋ （Re=Eu, Tb） phosphors were prepared by a sol-gel method. X-ray diffraction was employed to characterize the resulti...By using metal nitrates as starting materials and citric acid as a complexing agent, Y2Si207：Re3＋ （Re=Eu, Tb） phosphors were prepared by a sol-gel method. X-ray diffraction was employed to characterize the resulting samples. The results of XRD indicate that the α-Y2Si2O7 nanocrystal with size of 27 nm is obtained at 1000 ℃ and the doping ion content does not influence the structure. The excitation spectra in the UV and VUV ranges and the emission spectra of Re^3＋ doped samples were measured. The excitation spectra in the VUV range is due to absorption of host, that in the UV range is ascribed to absorption transitions from 4f to 5d state of the Tb^3＋ and the charge transfer in the En^3＋-O^2- bond. The spectral energy distribution of the Tb^3＋ emission depends strongly on the Tb3＋ concentration. The dependence of photolumineseenee intensity on Re^3＋ concentration is also discussed in detail. The fluorescent decay curves at room temperature were measured and analyzed.展开更多
Europium-doped yttrium aluminum garnet nanopowders were synthesized through an aqueous sol-gel method. The structure, morphology and luminescence spectra were investigated by using X-ray diffraction, thermogravimetric...Europium-doped yttrium aluminum garnet nanopowders were synthesized through an aqueous sol-gel method. The structure, morphology and luminescence spectra were investigated by using X-ray diffraction, thermogravimetric and differential thermal analysis, scanning electron microscopy, transmission electron microscopy and photoluminescence spectroscopy measurements. The results show that YAG：Eu with an average particle size of 50 nm is formed. The activation energy of YAG：Eu nanocrystallite growth during calcination is 24.1 kJ/mol. The crystalline YAG：Eu nanopowders show an orange-red emission with 5D0–7F1 as the most prominent group.展开更多
Europium ternary complex of Eu(NNA) 3(NNA=α-naphthylacetic acid) was embedded in silica matrix at different ratios by sol-gel method. The luminescence properties of silica composites were studied by comparing them wi...Europium ternary complex of Eu(NNA) 3(NNA=α-naphthylacetic acid) was embedded in silica matrix at different ratios by sol-gel method. The luminescence properties of silica composites were studied by comparing them with those of corresponding pure complex by means of excitation, emission spectra and lifetimes. The fluorescence lifetime was prolonged when the pure complex was incorporated in silica matrix. The relative fluorescence intensity and fluorescence lifetimes increased simultaneously with the increase of (Eu(NNA) 3.)展开更多
Thiol-stabilized PbS quantum dots （QDs） with dimensions 3-5 nm capped with a mixture of 1-thioglycerol/dithioglycerol （TGL/DTG） were coUoidally prepared at room temperature. Room temperature photoluminescence quan...Thiol-stabilized PbS quantum dots （QDs） with dimensions 3-5 nm capped with a mixture of 1-thioglycerol/dithioglycerol （TGL/DTG） were coUoidally prepared at room temperature. Room temperature photoluminescence quantum efficiency of freshly prepared PbS QDs （7%-11%） remained higher than 5% upon aging for three weeks when the nanocrystals （NCs） were stored in an ice-bath in the dark, and higher than 5%for at least five weeks when extra DTG ligands were introduced into the nanocrystal solution followed by stirring every two weeks. Poly（N-isopropyl acrylamide） （PNIPAM） microgels were produced via precipitation polymerization with dimensions of ca. 230 nm and polydispersity of 3-5%. Incorporation of PbS QDs into PNIPAM microgels indicated that PbS can be incorporated into the interior of microgel particles and not at the microgel interface. The combination of reasonable room temperature quantum efficiency and strong, efficient luminescence covering the 1.3-1.55 μm telecommunication window makes these nanoparticles promising materials in optical devices and telecommunications.展开更多
Er^3- / Yb^3＋ co - doped silica - alumina monolithic xerogels were prepared with the same concentration on 2 000 Er/Si ppm and 6 000 AI/Si ppm. The Yb/Si content was varied from 0 to 4 000 ppm. Densification of the s...Er^3- / Yb^3＋ co - doped silica - alumina monolithic xerogels were prepared with the same concentration on 2 000 Er/Si ppm and 6 000 AI/Si ppm. The Yb/Si content was varied from 0 to 4 000 ppm. Densification of the samples was achieved by thermal treatment in air at 950 ~C for 120 hours with a heating rate 0.1 ~C / min. Photoluminescence spectroscopy was used to obtain information about the effective excitation efficiency of Er^3＋ ions by co-doping with Yb^3- ions. The infrared-to-visible up-conversion luminescence has been investigated upon continuous wave excitation at 980 nm. The samples exhibit red, green and blue upconversion emission. It is found that the intensity of up-conversion luminescence increases with increasing Yb3- doping concentration. An opposite behavior is observed for the 4 I13/2 luminescence of the Er^3＋ ions.展开更多
Mn^2＋ doped Zn2SiO4 phosphors were synthesized by sol-gel method, and the influence of zinc source, Mn^2＋ dopant concentration and annealing temperature were investigated. Results show that zinc nitrate based precur...Mn^2＋ doped Zn2SiO4 phosphors were synthesized by sol-gel method, and the influence of zinc source, Mn^2＋ dopant concentration and annealing temperature were investigated. Results show that zinc nitrate based precursor with strong green emission intensities is better than zinc acetate based precursor. The intensity of green light emission reaches a peak at 254 nm when the Mn^2＋ dopant concentration is about 5%（ molar percentage）. Structural details of the phosphors were examined through X-ray diffractometry, thermogravimetric and differential thermal analysis. The result indicates that they are both rhombohedral structures, which remain amorphous below 700 ℃ and crystallize completely around 1000 ℃. The luminescent properties of Zn2SiO4/Mn^2＋ phosphors were characterized by excitation and emission spectra.展开更多
It is difficult to directly dope europium complexes in gel because the excessive water or high acidic condition may lead to their decomposition. We prepared a novel homogeneous TiO2 gel containing Eu-phen complexes by...It is difficult to directly dope europium complexes in gel because the excessive water or high acidic condition may lead to their decomposition. We prepared a novel homogeneous TiO2 gel containing Eu-phen complexes by using an in-situ synthesis method. The formation of Eu-phen complexes in sol-gel derived TiO2 was confirmed by luminescence excitation spectra. The effects of temperature and aging time on in-situ synthesis are discussed. The luminescence spectra of gel containing europium complexes were also compared with the pure Eu-phen complexes.展开更多
Stretchable ionic conductors with high transparency and excellent resilience are highly desired for flexible electronics,but traditional ionic conductive hydrogels are easy to dry and freeze.Herein,a newly hybrid cros...Stretchable ionic conductors with high transparency and excellent resilience are highly desired for flexible electronics,but traditional ionic conductive hydrogels are easy to dry and freeze.Herein,a newly hybrid crosslinking strategy is presented for preparing a stretchable and transparent hydrogel by using sodium alginate(SA)and acrylamide based on the unique physically and covalently hybrid crosslinking mechanism,which is transformed into organohydrogel by simple solvent replacement.Due to the combination of hybrid crosslinking double network and hydrogen bond interactions introduced by the glycerin-water binary solvent,the SA-poly(acrylamide)-organohydrogel(SPOH)demonstrates excellent anti-freezing(-20℃)property,stability(>2 days),transparency,stretchability(~1600%)and high ionic conductivity(17.1 mS cm^(-1)).Thus,a triboelectric nanogenerator made from SPOH(O-TENG)shows an instantaneous peak power density of 262 mW m^(-2)at a load resistance of 10 MΩand efficiently harvests biomechanical energy to drive an electronic watch and light-emitting diode.Moreover,The O-TENG exhibits favorable long-term stability(2 weeks)and temperature tolerance(-20℃).In addition,the raw materials can be prepared into SPOH fibers by a simple tubular mold method,exhibiting high transparency,which can be used for laser transmission.The various abilities of the SPOH promise the application of energy harvesting and laser transmission for wearable electronics and biomedical field.展开更多
CdS nanocrystals have been successfully grown on porous silicon(PS) by sol-gel method. The plan-view field emission scanning electron microscopy(FESEM) shows that the pore size of PS is smaller than 5 μm in diameter ...CdS nanocrystals have been successfully grown on porous silicon(PS) by sol-gel method. The plan-view field emission scanning electron microscopy(FESEM) shows that the pore size of PS is smaller than 5 μm in diameter and the agglomerates of Cd S are broadly distributed on the surface of PS substrate. With the increase of annealing time, the Cd S nanoparticles grow in both length and diameter along the preferred orientation. The cross-sectional FESEM images of Zn O/PS show that Cd S nanocrystals are uniformly penetrated into all PS layers and adhere to them very well. photoluminescence(PL) spectra demonstrate that the intensity of PL peak located at about 425 nm has almost no change after the annealing time increases. The range of emission wavelength of Cd S/PS is from 425 nm to 455 nm and the PL intensity is decreasing with the annealing temperature increasing from 100 °C to 200 °C.展开更多
基金Project (2009AA035002) supported by the High-tech Research and Development Program of China
文摘Erbium-doped BaTiO3 films on LaNiO3/Si substrates were fabricated by sol-gel method. The crystalline structure, morphologies and upconversion （UC） luminescence properties of films were respectively investigated by X-ray diffraction （XRD）, atomic force microcopy （AFM） and photoluminescence （PL）. The results indicate that both of the microstructure and luminescence are found to be dependent on Er^3＋ substituting sites. The samples with A-site substitution have smaller lattice constants, larger grains and smoother surface than those with B-site substitution. The photoluminescence spectra show that both of the samples have two stronger green emission bands centered at 528 and 548 nm and a weak red emission band centered at 673 nm, which correspond to the relaxation of Er^3＋ from ^2H11/2, ^4S3/2, and ^4F9/2 levels to the ground level ^4I15/2, respectively. Compared with B-site doped films, A-site doped films have a stronger integrated intensity of green emissions and a weaker relative intensity of red emissions. The differences could be explained by the crystalline quality and cross relaxation （CR） process.
文摘By using metal nitrates as starting materials and citric acid as a complexing agent, Y2Si207：Re3＋ （Re=Eu, Tb） phosphors were prepared by a sol-gel method. X-ray diffraction was employed to characterize the resulting samples. The results of XRD indicate that the α-Y2Si2O7 nanocrystal with size of 27 nm is obtained at 1000 ℃ and the doping ion content does not influence the structure. The excitation spectra in the UV and VUV ranges and the emission spectra of Re^3＋ doped samples were measured. The excitation spectra in the VUV range is due to absorption of host, that in the UV range is ascribed to absorption transitions from 4f to 5d state of the Tb^3＋ and the charge transfer in the En^3＋-O^2- bond. The spectral energy distribution of the Tb^3＋ emission depends strongly on the Tb3＋ concentration. The dependence of photolumineseenee intensity on Re^3＋ concentration is also discussed in detail. The fluorescent decay curves at room temperature were measured and analyzed.
基金Project supported by the Islamic Azad University,Najafabad Branch,Iran
文摘Europium-doped yttrium aluminum garnet nanopowders were synthesized through an aqueous sol-gel method. The structure, morphology and luminescence spectra were investigated by using X-ray diffraction, thermogravimetric and differential thermal analysis, scanning electron microscopy, transmission electron microscopy and photoluminescence spectroscopy measurements. The results show that YAG：Eu with an average particle size of 50 nm is formed. The activation energy of YAG：Eu nanocrystallite growth during calcination is 24.1 kJ/mol. The crystalline YAG：Eu nanopowders show an orange-red emission with 5D0–7F1 as the most prominent group.
文摘Europium ternary complex of Eu(NNA) 3(NNA=α-naphthylacetic acid) was embedded in silica matrix at different ratios by sol-gel method. The luminescence properties of silica composites were studied by comparing them with those of corresponding pure complex by means of excitation, emission spectra and lifetimes. The fluorescence lifetime was prolonged when the pure complex was incorporated in silica matrix. The relative fluorescence intensity and fluorescence lifetimes increased simultaneously with the increase of (Eu(NNA) 3.)
基金NSFC(No.50543007)Scientific Research Foundation for the Returned Overseas Chinese Scholars (State Education Ministry)+1 种基金NSF of Guangdong Province (No.07006838)Tianhe Bureau of Sci. & Techno., Guangzhou.
文摘Thiol-stabilized PbS quantum dots （QDs） with dimensions 3-5 nm capped with a mixture of 1-thioglycerol/dithioglycerol （TGL/DTG） were coUoidally prepared at room temperature. Room temperature photoluminescence quantum efficiency of freshly prepared PbS QDs （7%-11%） remained higher than 5% upon aging for three weeks when the nanocrystals （NCs） were stored in an ice-bath in the dark, and higher than 5%for at least five weeks when extra DTG ligands were introduced into the nanocrystal solution followed by stirring every two weeks. Poly（N-isopropyl acrylamide） （PNIPAM） microgels were produced via precipitation polymerization with dimensions of ca. 230 nm and polydispersity of 3-5%. Incorporation of PbS QDs into PNIPAM microgels indicated that PbS can be incorporated into the interior of microgel particles and not at the microgel interface. The combination of reasonable room temperature quantum efficiency and strong, efficient luminescence covering the 1.3-1.55 μm telecommunication window makes these nanoparticles promising materials in optical devices and telecommunications.
基金This research is performed in the context of the Italy-Vietnamre-search project 6 BS 2 MAE2006-2008 .MIUR-FIRB RBNE012N3X,PAT FAPVU2004-2006 ,MIUR-PRIN2004-2006 .
文摘Er^3- / Yb^3＋ co - doped silica - alumina monolithic xerogels were prepared with the same concentration on 2 000 Er/Si ppm and 6 000 AI/Si ppm. The Yb/Si content was varied from 0 to 4 000 ppm. Densification of the samples was achieved by thermal treatment in air at 950 ~C for 120 hours with a heating rate 0.1 ~C / min. Photoluminescence spectroscopy was used to obtain information about the effective excitation efficiency of Er^3＋ ions by co-doping with Yb^3- ions. The infrared-to-visible up-conversion luminescence has been investigated upon continuous wave excitation at 980 nm. The samples exhibit red, green and blue upconversion emission. It is found that the intensity of up-conversion luminescence increases with increasing Yb3- doping concentration. An opposite behavior is observed for the 4 I13/2 luminescence of the Er^3＋ ions.
文摘Mn^2＋ doped Zn2SiO4 phosphors were synthesized by sol-gel method, and the influence of zinc source, Mn^2＋ dopant concentration and annealing temperature were investigated. Results show that zinc nitrate based precursor with strong green emission intensities is better than zinc acetate based precursor. The intensity of green light emission reaches a peak at 254 nm when the Mn^2＋ dopant concentration is about 5%（ molar percentage）. Structural details of the phosphors were examined through X-ray diffractometry, thermogravimetric and differential thermal analysis. The result indicates that they are both rhombohedral structures, which remain amorphous below 700 ℃ and crystallize completely around 1000 ℃. The luminescent properties of Zn2SiO4/Mn^2＋ phosphors were characterized by excitation and emission spectra.
基金Project (No. 2004C210023) supported by Science Planning Project of Zhejiang Province, China
文摘It is difficult to directly dope europium complexes in gel because the excessive water or high acidic condition may lead to their decomposition. We prepared a novel homogeneous TiO2 gel containing Eu-phen complexes by using an in-situ synthesis method. The formation of Eu-phen complexes in sol-gel derived TiO2 was confirmed by luminescence excitation spectra. The effects of temperature and aging time on in-situ synthesis are discussed. The luminescence spectra of gel containing europium complexes were also compared with the pure Eu-phen complexes.
基金financially supported by the National Natural Science Foundation of China(52002059 and 51872204)the Belt&Road Young Scientist Exchanges Project of Science and Technology Commission Foundation of Shanghai(20520741000)+1 种基金the Fundamental Research Funds for the Central Universities(20D110631)the State Key Laboratory for Modification of Chemical Fibers and Polymer Materials(DonghuaUniversity,KF2019)。
文摘Stretchable ionic conductors with high transparency and excellent resilience are highly desired for flexible electronics,but traditional ionic conductive hydrogels are easy to dry and freeze.Herein,a newly hybrid crosslinking strategy is presented for preparing a stretchable and transparent hydrogel by using sodium alginate(SA)and acrylamide based on the unique physically and covalently hybrid crosslinking mechanism,which is transformed into organohydrogel by simple solvent replacement.Due to the combination of hybrid crosslinking double network and hydrogen bond interactions introduced by the glycerin-water binary solvent,the SA-poly(acrylamide)-organohydrogel(SPOH)demonstrates excellent anti-freezing(-20℃)property,stability(>2 days),transparency,stretchability(~1600%)and high ionic conductivity(17.1 mS cm^(-1)).Thus,a triboelectric nanogenerator made from SPOH(O-TENG)shows an instantaneous peak power density of 262 mW m^(-2)at a load resistance of 10 MΩand efficiently harvests biomechanical energy to drive an electronic watch and light-emitting diode.Moreover,The O-TENG exhibits favorable long-term stability(2 weeks)and temperature tolerance(-20℃).In addition,the raw materials can be prepared into SPOH fibers by a simple tubular mold method,exhibiting high transparency,which can be used for laser transmission.The various abilities of the SPOH promise the application of energy harvesting and laser transmission for wearable electronics and biomedical field.
基金supported by the Xinjiang Science and Technology Project(No.2015211C275)
文摘CdS nanocrystals have been successfully grown on porous silicon(PS) by sol-gel method. The plan-view field emission scanning electron microscopy(FESEM) shows that the pore size of PS is smaller than 5 μm in diameter and the agglomerates of Cd S are broadly distributed on the surface of PS substrate. With the increase of annealing time, the Cd S nanoparticles grow in both length and diameter along the preferred orientation. The cross-sectional FESEM images of Zn O/PS show that Cd S nanocrystals are uniformly penetrated into all PS layers and adhere to them very well. photoluminescence(PL) spectra demonstrate that the intensity of PL peak located at about 425 nm has almost no change after the annealing time increases. The range of emission wavelength of Cd S/PS is from 425 nm to 455 nm and the PL intensity is decreasing with the annealing temperature increasing from 100 °C to 200 °C.
