In order to obtain a single-host white-light phosphor, a series of KCaPO4 powder samples tri-doped with Eu2＋, Tb3＋ and Mn2＋ were synthesized via high-temperature solid-state reaction method. Their structural and lu...In order to obtain a single-host white-light phosphor, a series of KCaPO4 powder samples tri-doped with Eu2＋, Tb3＋ and Mn2＋ were synthesized via high-temperature solid-state reaction method. Their structural and luminescence properties were investigated. Under proper ultraviolet excitation （255-405 urn）, white light was obtained, consisting of blue, green and red emissions stemming from Eu2＋, Th3＋, Mn2＋ ions respectively. The temperature stability of our sample was analyzed by studying the variation tendeney of CIE chromaticity coordinates at different temperatures. The results indicated that this phosphor could yield good color stability when utilized in WLED.展开更多
Perovskite quantum dots(PQDs)have demonstrated great promise in bioimaging applications owing to their outstanding photophysical properties.Nonetheless,their practicality is seriously limited by the instability of PQD...Perovskite quantum dots(PQDs)have demonstrated great promise in bioimaging applications owing to their outstanding photophysical properties.Nonetheless,their practicality is seriously limited by the instability of PQDs against moisture.Here we develop a post-synthetic ligand exchange strategy to construct silica-coated PQD(PQD@SiO_(2))nanocrystals,which results in the simultaneous improvement of photoluminescence efficiency and moisture stability.More importantly,compared to the classical in-situ ligand exchange method of fabricating PQD@SiO_(2),the issues of chemical etching and resultant photoluminescence degradation are judiciously overcome.Employing the proposed PQD@SiO_(2),we showcase their robust usefulness in labeling chlorella,paving the way for PQD-based in-vivo photoluminescence bioimaging methodology.展开更多
A series of Tb^3＋ mono-doped and Ce^3＋-Tb^3＋ co-doped Sr3Gd2（Si3O9）2 phosphors with high thermal stability and quantum yields were successfully prepared via the solid state reaction. The as-prepared Sr3Gd2（Si3O9...A series of Tb^3＋ mono-doped and Ce^3＋-Tb^3＋ co-doped Sr3Gd2（Si3O9）2 phosphors with high thermal stability and quantum yields were successfully prepared via the solid state reaction. The as-prepared Sr3Gd2（Si3O9）2：Tb^3＋ samples showed broad excitation spectrum from 250 to 400 nm and presented characteristic emission transitions ^5D4→^7FJ（J=6, 5, 4, 3） of Tb^3＋ under 313 nm excitation, which were located at about 488, 541, 584 and 620 nm. The emission intensities of Tb^3＋ rose steadily in Sr3Gd2（Si3O9）2 host with the increase of Tb^3＋ concentration even though Gd^3＋ ions were completely replaced by Tb^3＋ ions. The Ce^3＋ ion as a sensitizer could efficiently improve the performance of Tb^3＋ ion. First, with Ce^3＋ co-doping, the excitation spectrum of Tb^3＋ monitored at 541 nm showed a similar band that responds to the violet emission of Ce^3＋ monitored at 416 nm. Second, the quantum yields of Sr3Gd2（Si3O9）2：Tb^3＋ phosphors could be enhanced from 26.6% to 80.2% by co-doping Ce^3＋. Finally, the co-doping of Ce^3＋ was also effective to improve the thermal stability of Sr3Gd2（Si3O9）2：Tb^3＋. As the temperature rose to 150 oC, the emission intensity of Tb^3＋ remained at about 83.6% of that measured at room temperature, which was better than the commercial YAG：Ce phosphor in terms of their thermal quenching properties. These results indicated that the as-prepared Sr3Gd2（Si3O9）2：Tb^3＋,Ce^3＋ samples could be used as green emission phosphors for possible applications in near ultraviolet based WLEDs.展开更多
Three novel coordination polymers, [Ni2(tib)2(btec)]·2H2O (1), [Co2(tib)2(btec)]·2H2O (2) and [Zn4(tib)2(btec)Cl4]·2H2O (3), have been synthesized by using mixed ligands of 1,3,5-tris(1-imidazolyl)benze...Three novel coordination polymers, [Ni2(tib)2(btec)]·2H2O (1), [Co2(tib)2(btec)]·2H2O (2) and [Zn4(tib)2(btec)Cl4]·2H2O (3), have been synthesized by using mixed ligands of 1,3,5-tris(1-imidazolyl)benzene (tib) and 1,2,4,5-benzenetetracarboxylic acid (H4btec) under hydrothermal conditions. Complexes 1 and 2 have the same structure and are rare three-dimensional (3D) self-penetrating (3,4,5)-connected nets, while complex 3 is an unprecedented (3,4)-connected 3D net. The different structures of 1 (2) and 3 are ascribed to the distinct coordination geometry of the metal centers. The thermal stability and photoluminescence property of the complexes were investigated.展开更多
The fabrication of heterostructures of two-dimensional semiconductors with specific bandgaps is an important approach to realizing the full potential of these materials in electronic and optoelectronic devices. Severa...The fabrication of heterostructures of two-dimensional semiconductors with specific bandgaps is an important approach to realizing the full potential of these materials in electronic and optoelectronic devices. Several groups have recently reported the direct growth of lateral and vertical heterostructures based on monolayers of typical semiconducting transition metal dichalcogenides （TMDCs） such as WSe2, MoSe2, WS2, and MoS2. Here, we demonstrate the single-step direct growth of lateral and vertical heterostructures based on bandgap-tunable Mo1-xWxS2 alloy monolayers by the sulfurization of patterned thin films of WO3 and MoO3. These patterned films are capable of generating a wide variety of concentration gradients by the diffusion of transition metals during the crystal growth phase. Under high temperatures, this leads to the formation of monolayer crystals of Mo1-xWxS2 alloys with various compositions and bandgaps, depending on the positions of the crystals on the substrates. Heterostructures of these alloys are obtained through stepwise changes in the ratio of W/Mo within a single domain during low-temperature growth. The stabilization of the monolayer Mo1-xWxS2 alloys, which often degrade even under gentle conditions, was accomplished by coating the alloys with other monolayers. The present findings demonstrate an efficient means of both studying and optimizing the optical and electrical properties of TMDC-based heterostructures to allow use of the materials in future device applications.展开更多
Herein,double-perovskite Ba_(2)LaTaO_(6) Eu-doped orange-red phosphors were successfully synthesized using a high-temperature solid-phase method.The phosphor phase purity was investigated using X-ray diffraction and m...Herein,double-perovskite Ba_(2)LaTaO_(6) Eu-doped orange-red phosphors were successfully synthesized using a high-temperature solid-phase method.The phosphor phase purity was investigated using X-ray diffraction and microscopic morphology analyses.Their luminescence properties were investigated using absorption,emission,excitation,and temperature-dependent spectra.The transition mechanism mainly involves a magnetic-dipole transition with an energy transfer mode featuring multipole-multipole interactions,and concentration quenching is achieved via dipole-dipole interactions.In addition,the intensity of the temperature-dependent spectrum increases abnormally between 298 and 373 K,with the luminous intensity at 373 K increasing to 110%of that observed at room temperature.This phenomenon can be attributed to lattice defects in Ba_(2)LaTaO_(6):Eu^(3+),and the phosphor luminous intensity at473 K remains at 80.62%of that at room temperature.In addition,white-light-emitting diode devices based on this novel Ba_(2)LaTaO_(6):0.35Eu^(3+)phosphor were fabricated to evaluate the potential applications of the as-prepared phosphor.展开更多
The development of deep-red emitting lead-free metal-halide perovskites with high photoluminescence quantum yields (PLQYs) and outstanding stability remains a major challenge for displays and deep-tissue bioimaging.In...The development of deep-red emitting lead-free metal-halide perovskites with high photoluminescence quantum yields (PLQYs) and outstanding stability remains a major challenge for displays and deep-tissue bioimaging.In this work,we report a facile and convenient solvothermal method to synthesize metal halides Cs_(2)Zn X_(4)(X=Cl,Br) that however is PL innert at room temperature.Upon composition engineering utilizing Sn^(2+) as the dopant,the resulting Cs_(2)Zn Cl_(4):Sn not only emits strong deep-red PL peaked at700 nm with the highest 99.4%PLQY among the similar materials so far,but also exhibits excellent structure stability in air (PLQY remains 96%after one year exposure to the atmosphere).Detailed experimental characterizations and theoretical calculations reveal that the deep-red emission stems from self-trapped excitons induced by the Sn^(2+) dopant.Particularly,triplet emission (^(3)P_(2)→^(1)S_(0)) from Sn-5s^(2) orbitals has been observed at low temperature due to the break of parity-forbidden transition.This work provides an important guidance for the development of deep-red light-emitting materials with low price,high efficiency and excellent stability.展开更多
基金supported by National Key Basic Research Program of China(2013CB921800)the National Natural Science Foundation of China(11374291,11204292,11274299,11311120047)+1 种基金the Fundamental Research Funds for the Central Universities(WK2030020021)Anhui Provincial Natural Science Foundation(1308085QE75)
文摘In order to obtain a single-host white-light phosphor, a series of KCaPO4 powder samples tri-doped with Eu2＋, Tb3＋ and Mn2＋ were synthesized via high-temperature solid-state reaction method. Their structural and luminescence properties were investigated. Under proper ultraviolet excitation （255-405 urn）, white light was obtained, consisting of blue, green and red emissions stemming from Eu2＋, Th3＋, Mn2＋ ions respectively. The temperature stability of our sample was analyzed by studying the variation tendeney of CIE chromaticity coordinates at different temperatures. The results indicated that this phosphor could yield good color stability when utilized in WLED.
基金supported by the National Natural Science Foundation of China(Nos.22373114,22103096,and 22273119)Beijing Natural Science Foundation,China(No.2232008)and the Research Funds of Renmin University of China(No.22XNKJ08).
文摘Perovskite quantum dots(PQDs)have demonstrated great promise in bioimaging applications owing to their outstanding photophysical properties.Nonetheless,their practicality is seriously limited by the instability of PQDs against moisture.Here we develop a post-synthetic ligand exchange strategy to construct silica-coated PQD(PQD@SiO_(2))nanocrystals,which results in the simultaneous improvement of photoluminescence efficiency and moisture stability.More importantly,compared to the classical in-situ ligand exchange method of fabricating PQD@SiO_(2),the issues of chemical etching and resultant photoluminescence degradation are judiciously overcome.Employing the proposed PQD@SiO_(2),we showcase their robust usefulness in labeling chlorella,paving the way for PQD-based in-vivo photoluminescence bioimaging methodology.
基金Project supported by National Natural Science Foundation of China(21571162)the Guangdong Province Enterprise-University-Academy Collaborative Project(2012B091100474)
文摘A series of Tb^3＋ mono-doped and Ce^3＋-Tb^3＋ co-doped Sr3Gd2（Si3O9）2 phosphors with high thermal stability and quantum yields were successfully prepared via the solid state reaction. The as-prepared Sr3Gd2（Si3O9）2：Tb^3＋ samples showed broad excitation spectrum from 250 to 400 nm and presented characteristic emission transitions ^5D4→^7FJ（J=6, 5, 4, 3） of Tb^3＋ under 313 nm excitation, which were located at about 488, 541, 584 and 620 nm. The emission intensities of Tb^3＋ rose steadily in Sr3Gd2（Si3O9）2 host with the increase of Tb^3＋ concentration even though Gd^3＋ ions were completely replaced by Tb^3＋ ions. The Ce^3＋ ion as a sensitizer could efficiently improve the performance of Tb^3＋ ion. First, with Ce^3＋ co-doping, the excitation spectrum of Tb^3＋ monitored at 541 nm showed a similar band that responds to the violet emission of Ce^3＋ monitored at 416 nm. Second, the quantum yields of Sr3Gd2（Si3O9）2：Tb^3＋ phosphors could be enhanced from 26.6% to 80.2% by co-doping Ce^3＋. Finally, the co-doping of Ce^3＋ was also effective to improve the thermal stability of Sr3Gd2（Si3O9）2：Tb^3＋. As the temperature rose to 150 oC, the emission intensity of Tb^3＋ remained at about 83.6% of that measured at room temperature, which was better than the commercial YAG：Ce phosphor in terms of their thermal quenching properties. These results indicated that the as-prepared Sr3Gd2（Si3O9）2：Tb^3＋,Ce^3＋ samples could be used as green emission phosphors for possible applications in near ultraviolet based WLEDs.
基金supported by the National Natural Science Foundation of China (20731004 and 20721002)the National Basic Research Program of China (2007CB925103 and 2010CB923303)
文摘Three novel coordination polymers, [Ni2(tib)2(btec)]·2H2O (1), [Co2(tib)2(btec)]·2H2O (2) and [Zn4(tib)2(btec)Cl4]·2H2O (3), have been synthesized by using mixed ligands of 1,3,5-tris(1-imidazolyl)benzene (tib) and 1,2,4,5-benzenetetracarboxylic acid (H4btec) under hydrothermal conditions. Complexes 1 and 2 have the same structure and are rare three-dimensional (3D) self-penetrating (3,4,5)-connected nets, while complex 3 is an unprecedented (3,4)-connected 3D net. The different structures of 1 (2) and 3 are ascribed to the distinct coordination geometry of the metal centers. The thermal stability and photoluminescence property of the complexes were investigated.
文摘The fabrication of heterostructures of two-dimensional semiconductors with specific bandgaps is an important approach to realizing the full potential of these materials in electronic and optoelectronic devices. Several groups have recently reported the direct growth of lateral and vertical heterostructures based on monolayers of typical semiconducting transition metal dichalcogenides （TMDCs） such as WSe2, MoSe2, WS2, and MoS2. Here, we demonstrate the single-step direct growth of lateral and vertical heterostructures based on bandgap-tunable Mo1-xWxS2 alloy monolayers by the sulfurization of patterned thin films of WO3 and MoO3. These patterned films are capable of generating a wide variety of concentration gradients by the diffusion of transition metals during the crystal growth phase. Under high temperatures, this leads to the formation of monolayer crystals of Mo1-xWxS2 alloys with various compositions and bandgaps, depending on the positions of the crystals on the substrates. Heterostructures of these alloys are obtained through stepwise changes in the ratio of W/Mo within a single domain during low-temperature growth. The stabilization of the monolayer Mo1-xWxS2 alloys, which often degrade even under gentle conditions, was accomplished by coating the alloys with other monolayers. The present findings demonstrate an efficient means of both studying and optimizing the optical and electrical properties of TMDC-based heterostructures to allow use of the materials in future device applications.
基金Project supported by the National Natural Science Foundation of China (52262020)the Science and Technology Foundation of Guizhou Province (ZK[2021]yiban 328)。
文摘Herein,double-perovskite Ba_(2)LaTaO_(6) Eu-doped orange-red phosphors were successfully synthesized using a high-temperature solid-phase method.The phosphor phase purity was investigated using X-ray diffraction and microscopic morphology analyses.Their luminescence properties were investigated using absorption,emission,excitation,and temperature-dependent spectra.The transition mechanism mainly involves a magnetic-dipole transition with an energy transfer mode featuring multipole-multipole interactions,and concentration quenching is achieved via dipole-dipole interactions.In addition,the intensity of the temperature-dependent spectrum increases abnormally between 298 and 373 K,with the luminous intensity at 373 K increasing to 110%of that observed at room temperature.This phenomenon can be attributed to lattice defects in Ba_(2)LaTaO_(6):Eu^(3+),and the phosphor luminous intensity at473 K remains at 80.62%of that at room temperature.In addition,white-light-emitting diode devices based on this novel Ba_(2)LaTaO_(6):0.35Eu^(3+)phosphor were fabricated to evaluate the potential applications of the as-prepared phosphor.
基金the financial supports from National Natural Science Foundation of China (Nos. 91741105, 22109130)Chongqing Municipal Natural Science Foundation (Nos. cstc2018jcyj AX0625, cstc2021jcyj-msxm X1180)Program for Innovation Team Building at Institutions of Higher Education in Chongqing (No. CXTDX201601011)。
文摘The development of deep-red emitting lead-free metal-halide perovskites with high photoluminescence quantum yields (PLQYs) and outstanding stability remains a major challenge for displays and deep-tissue bioimaging.In this work,we report a facile and convenient solvothermal method to synthesize metal halides Cs_(2)Zn X_(4)(X=Cl,Br) that however is PL innert at room temperature.Upon composition engineering utilizing Sn^(2+) as the dopant,the resulting Cs_(2)Zn Cl_(4):Sn not only emits strong deep-red PL peaked at700 nm with the highest 99.4%PLQY among the similar materials so far,but also exhibits excellent structure stability in air (PLQY remains 96%after one year exposure to the atmosphere).Detailed experimental characterizations and theoretical calculations reveal that the deep-red emission stems from self-trapped excitons induced by the Sn^(2+) dopant.Particularly,triplet emission (^(3)P_(2)→^(1)S_(0)) from Sn-5s^(2) orbitals has been observed at low temperature due to the break of parity-forbidden transition.This work provides an important guidance for the development of deep-red light-emitting materials with low price,high efficiency and excellent stability.
