Two-dimensional(2D)transition metal dichalcogenides(TMDs)and their heterostructures(HSs)exhibit unique optical properties and show great promise for developing next-generation optoelectronics.However,the photo-lumines...Two-dimensional(2D)transition metal dichalcogenides(TMDs)and their heterostructures(HSs)exhibit unique optical properties and show great promise for developing next-generation optoelectronics.However,the photo-luminescence(PL)quantum yield of monolayer(1L)TMDs is still quite low at room temperature,which severely lim-its their practical applications.Here we report a PL enhancement effect of 1L WS_(2) at room temperature when con-structing it into 1L-WS_(2)/hBN/1L-MoS_(2) vertical HSs.The PL enhancement factors(EFs)can be up to 4.2.By using transient absorption(TA)spectroscopy,we demonstrate that the PL enhancement effect is due to energy transfer from 1L MoS_(2) to 1L WS_(2).The energy transfer process occurs on a picosecond timescale and lasts more than one hundred picoseconds which indicates a prominent contribution from exciton-exciton annihilation.Furthermore,the PL en-hancement effect of 1L WS_(2) can be observed in 2L-MoS_(2)/hBN/1L-WS_(2) and 3L-MoS_(2)/hBN/1L-WS_(2) HSs.Our study provides a comprehensive understanding of the energy transfer process in the PL enhancement of 2D TMDs and a fea-sible way to optimize the performance of TMD-based optoelectronic devices.展开更多
Broadband near-infrared(NIR)luminescent materials have shown great promise in applications such as optical communication,biomedicine,and optoelectronic devices.However,the current research is focused on phos⁃phors and...Broadband near-infrared(NIR)luminescent materials have shown great promise in applications such as optical communication,biomedicine,and optoelectronic devices.However,the current research is focused on phos⁃phors and glasses,and it is important to develop broadband NIR luminescent nanomaterials.Here,we report an erbi⁃um-sensitized core-shell nanocrystal design for broadband NIR emission.Based on the structural design with suitable dopings of Tm^(3+)and Ho^(3+),the broadband NIR emission covering 1.5-2.1μm region is achieved under 980 nm and 808 nm excitations.Moreover,the emission intensity is further enhanced by introducing Yb^(3+)and Nd^(3+)into the sam⁃ple,respectively,and the energy transfer processes between them are systematically discussed.Our results present a novel approach for developing broadband NIR luminescent materials and devices.展开更多
4-Nonylphenol(NP)is a kind of estrogen belonging to the endocrine disrupter,widely used in various agricultural and industrial goods.However,extensive use of NP with direct release to environment poses high risks to b...4-Nonylphenol(NP)is a kind of estrogen belonging to the endocrine disrupter,widely used in various agricultural and industrial goods.However,extensive use of NP with direct release to environment poses high risks to both human health and ecosystems.Herein,for the first time,we developed near-infrared(NIR)responsive upconversion luminescence nanosensor for NP detection.The Förster resonance energy transfer based upconversion nanoparticles(UCNPs)-graphene oxide sensor offers highly selective and sensitive detection of NP in linear ranges of 5−200 ng/mL and 200−1000 ng/mL under 980 nm and 808 nm excitation,respectively,with LOD at 4.2 ng/mL.The sensors were successfully tested for NP detection in real liquid milk samples with excellent recovery results.The rare-earth fluoride based upconversion luminescence nanosensor with NIR excitation wavelength,holds promise for sensing food,environmental,and biological samples due to their high sensitivity,specific recognition,low LOD,negligible autofluorescence,along with the deep penetration of NIR excitation sources.展开更多
While three-dimensional perovskites have high defect tolerance and an adjustable bandgap,their charges tend to be free rather than forming excitons,making them unsuitable for use in efficient light-emitting diodes(LED...While three-dimensional perovskites have high defect tolerance and an adjustable bandgap,their charges tend to be free rather than forming excitons,making them unsuitable for use in efficient light-emitting diodes(LEDs).Rather,quasi-two-dimensional(Q-2D)perovskites offer high photoluminescence quantum yield along with the advantages of bulk perovskites,making them ideal for high-performance LEDs.In Q-2D perovskites,the structure(which includes factors like crystal orientation,phase distribution,and layer thickness)directly influences how excitons and charge carriers behave within the material.Growth control techniques,such as varying the synthesis conditions or employing methods,allow for fine-tuning the structural characteristics of these materials,which in turn affect exciton dynamics and charge transport.This review starts with a description of the basic properties of Q-2D perovskites,examines crystal growth in solution,explains how structure affects energy transfer behavior,and concludes with future directions for Q-2D perovskite LEDs.By understanding and optimizing the structure-dependent behavior,researchers can better control exciton dynamics and charge transport,which are crucial for enhancing the performance of optoelectronic devices like solar cells and LEDs.展开更多
Eu^(2+) and Mn^(2+) co-activated CaAlSiN_(3) red phosphors were produced using the solid-state reaction tech⁃nique in a N2 environment.Excitation spectra,emission spectra,and diffuse reflection spectra were used to st...Eu^(2+) and Mn^(2+) co-activated CaAlSiN_(3) red phosphors were produced using the solid-state reaction tech⁃nique in a N2 environment.Excitation spectra,emission spectra,and diffuse reflection spectra were used to study the luminescence characteristics,energy gap,and thermal stability in detail.CaAlSiN_(3)∶Eu^(2+) exhibits an extended emission band when stimulated with 450 nm blue light,which is caused by the 4f65d to 4f7 transition of Eu^(2+).Similar⁃ly,CaAlSiN_(3)∶Mn^(2+) displays a wide emission band centered at 628 nm,which results from Mn^(2+)’s transition from 4T1(4G) to 6A1(6S).When the ions of Mn^(2+)were combined into CaAlSiN_(3)∶Eu^(2+),the photoluminescence intensity of Eu^(2+ )was greatly boosted because there was energy transfer and co-emission between Mn^(2+) and Eu^(2+).Beyond that,CaAlSiN_(3)∶Eu^(2+),Mn^(2+) emerges with splendid thermostability and high quantum efficiency,the quenching temperature surpasses 300℃,and the internal quantum efficiency is determined to be around 84.9%.The white LED was pack⁃aged with a combination of CaAlSiN_(3)∶Eu^(2+),Mn^(2+),LuAG∶Ce3+ and a blue chip.At a warm white-light corresponding color temperature(3009 K) with CIE coordinates(0.4223,0.3748),the color rendering index Ra has reached 93.2.CaAlSiN_(3)∶Eu^(2+),Mn^(2+) would have great application potential as a red-emitting phosphor for white LEDs.展开更多
A new functionalized heteroleptic iridium complex coordinated with 1-phenylisoquinoline （1-piq） and a functionalized fl-diketone （G1）, Ir（1-piq）2G1, was synthesized and characterized by 1H-NMR, mass spectrometry...A new functionalized heteroleptic iridium complex coordinated with 1-phenylisoquinoline （1-piq） and a functionalized fl-diketone （G1）, Ir（1-piq）2G1, was synthesized and characterized by 1H-NMR, mass spectrometry and elemental analysis. The larger conjugation of the replacement of acetylacetone （acac） by a functionalizedβ-diketonate ligand led to a significant decrease in the HOMO level toward vacuum level, while Ir（1-piq）2G1 and Ir（1-piq）2（acac） showed red phosphorescent emissions of about 620 nm in dichloromethane solution. The phosphorescent polymer light-emitting devices were achieved, with the complexes incorporated with polyfluorene （PFO） as a host polymer doped with 30% of 5-（4-biphenylyl）-2-（4-tert-butylphenyl）-1,3,4-oxadiazole （PBD） as electron transport material. The energy transfer mechanism of the devices was also discussed. The lower EL performance of Ir（1-piq）2G1 is ascribed to the inter-ligand energy transfer, indicating that it is important to control the energy level of the cyclometalated and ancillary ligands.展开更多
In this paper,the single crystals of GdP 5O 14 :Sm 3+ ,Pr 3+ (GdPP: Sm,Pr)were grown by the hydrothermal method.The process of growing crystal is th e formation and grown up of new phase. Whether new phase can appear ...In this paper,the single crystals of GdP 5O 14 :Sm 3+ ,Pr 3+ (GdPP: Sm,Pr)were grown by the hydrothermal method.The process of growing crystal is th e formation and grown up of new phase. Whether new phase can appear and how can occur,which is driven by the force of phase transformation.It is necessary to co ntrol this process by the concentration in the hydrothermal solution.In the syst em of cohesive phosphoric acid growing crystal is a process of complex chemical reaction,in which nucleation depends on the stability of small cluster and on ho w many of them form,so the number of controllable nucleation is very complex sta tistical problem.The natural face and high optical quality of single crystal can be preserved by adding a seed which is cut from large crystal. The crystal structure of GdPP:Sm,Pr,isotypic with monoclinic (space group PZ 1/ c )GdPP,has been checked by X ray powder diffraction and emission and em is sion spectrum were measured and analyzed in the range from ultraviolet to visibl e at room temperature.The dependence of containg different Pr 3+ ion concent rations on the emission intensities of 4 G 5/2 → 6 H 7/2 tran sition of Sm 3+ ion have been discussed in the GdPP:Sm,Pr crystals.The energ y transfer between Sm 3+ and Pr 3+ ions have been investigated.展开更多
The energy transfer and upconversion of Er 3+ /Yb 3+ co-doped TeO2-TiO2-K2O glasses upon excitation with 976nm lasers diode were studied. The tellurite glasses were prepared by conventional melting methods. Their opti...The energy transfer and upconversion of Er 3+ /Yb 3+ co-doped TeO2-TiO2-K2O glasses upon excitation with 976nm lasers diode were studied. The tellurite glasses were prepared by conventional melting methods. Their optical properties and sensitization upconversion spectra were performed. The dependence of green upconversion luminescence intensity on the mole ratio of Yb 3+ to Er 3+ and Er 3+ concentration were discussed in detail. When the mole ratio of Yb 3+ to Er 3+ is 25/1 and Er 3+ concentration is 0.1% （mole fraction）, or when the mole ratio of Yb 3+ to Er 3+ is 10/1 and Er 3+ concentration is 0.15%, the optimal upconversion luminescence intensity is obtained. The obtained glasses can be one of the potential candidates for lasers-diode pumping microchip solid-state lasers.展开更多
Eu^(2+)-doped Na_(3)Sc_(2)(PO_(4))_(3)ionic conductor possesses superior thermal quenching(TQ)resistance,which is considered as a promising phosphor for high-power lighting applications.Yet the underlying mechanism of...Eu^(2+)-doped Na_(3)Sc_(2)(PO_(4))_(3)ionic conductor possesses superior thermal quenching(TQ)resistance,which is considered as a promising phosphor for high-power lighting applications.Yet the underlying mechanism of negative thermal quenching(NTQ)is not fully understood.In this study,we focus on upconversion(UC)and downshifting(DS)luminescence of Yb^(3+)/Er^(3+)with f-f transition rather than susceptible d-f transition of Eu^(2+)in Na_(3)Sc_(2)(PO_(4))_(3),aiming to get a more insightful view.The results show that thermally accelerated dynamic defects/ions contributes to the significant negative thermal quenching(NTQ)of UC luminescence and thermally stabilized DS luminescence by promoting the radiative transition and suppressing the non-radiative transition.The UC process with slow population rate is more susceptible to perturbation of Na+migration process with time scale equivalent to that of the former,resulting in evident NTQ of UC luminescence.This research opens an avenue for understanding the NTQ mechanism of luminescence via dynamic defects/ions.展开更多
OBJECTIVE The chemokine-like receptor 1(CMKLR1,Chem R23) is a functional receptor for chemerin,the chemerin-derived nonapeptide(C9),and the amyloid β peptide 1-42(Aβ_(42)).Because these peptides share little sequenc...OBJECTIVE The chemokine-like receptor 1(CMKLR1,Chem R23) is a functional receptor for chemerin,the chemerin-derived nonapeptide(C9),and the amyloid β peptide 1-42(Aβ_(42)).Because these peptides share little sequence homology,studies were conducted to investigate their pharmacological properties and regulation at CMKLR1.METHODS Cells expressing CMKLR1 were incubated with Aβ_(42) before stimulation with a strong agonist,the C9 peptide.Calcium mobilization,c AMP inhibition and MAP kinase activation were measured.Intramolecular FRET were determined using CMKLR1 constructs with an ECFP attached to the C-terminus and a Fl As H binding motif embedded in the first intracellular loop(IL1).RESULTS Binding of both Aβ_(42) and the C9 peptide induced CMKLR1 internalization,but only the Aβ_(42)-induced receptor internalization involved clathrin-coated pits.Likewise,Aβ_(42) but not C9 stimulated β-arrestin 2 translocation to plasma membranes.A robust Ca^(2+)flux was observed following C9 stimulation,whereas Aβ_(42) was ineffective even at micromolar concentrations.Despite its low potency in calcium mobilization assay,Aβ_(42) was able to alter C9-induced Ca^(2+) flux in dose-dependent manner:a potentiation effect at 100 pmol·L^(-1) of Aβ_(42) was followed by a suppression at 10 nmol·L^(-1) and further potentiation at 1 μmol·L^(-1).This unusual and biphasic modulatory effect was also seen in the C9-induced ERK phosphorylation but the dose curve was opposite to that of Ca^(2+) flux and c AMP inhibition,suggesting a reciprocal regulatory mechanism.Intramolecular FRET assay confirmed that Aβ_(42) modulates CMKLR1 rather than its downstream signaling pathways.CONCLUSION These findings suggest Aβ_(42) as an allosteric modulator that can both positively and negatively regulate the activation state of CMKLR1 in a manner that differs from existing allosteric modulatory mechanisms.展开更多
OBJECTIVE To identify the mechanisms by which the formyl peptide receptor 2(FPR2)mediates both inflammatory and anti-inflammatory signaling in an agonist-dependent manner.METHODS Cells expressing FPR2 were incubated w...OBJECTIVE To identify the mechanisms by which the formyl peptide receptor 2(FPR2)mediates both inflammatory and anti-inflammatory signaling in an agonist-dependent manner.METHODS Cells expressing FPR2 were incubated with weak agonists,Aβ42 and Ac2-26,before stimulation with a strong agonist,WKYMVm.Calcium mobilization,c AMP inhibition and MAP kinase activation were measured.Intramolecular FRET were determined using FPR2 constructs with an ECFP attached to the C-terminus and a Fl As H binding motif embedded in the first or third intracellular loop(IL1 or IL3,respectively).RESULTS Aβ42 did not induce significant Ca^(2+) mobilization,but positively modulated WKYMVm-induced Ca^(2+) mobilization and c AMP reduction in a dose-variable manner within a narrow range of ligand concentrations.Treating FPR2-expressing cells with Ac2-26,a peptide with anti-inflammatory activity,negatively modulated WKYMVm-induced Ca^(2+) mobilization and c AMP reduction.Intramolecular FRET assay showed that stimulation of the receptor constructs with Aβ42 brought the C-terminal domain closer to IL1 but away from IL3.An opposite conformational change was induced by Ac2-26.The FPR2 conformation induced by Aβ42 corresponded to enhanced ERK phosphorylation and attenuated p38 MAPK phosphorylation,whereas Ac2-26 induced FPR2 conformational change corresponding to elevated p38 MAPK phosphorylation and reduced ERK phosphorylation.CONCLUSION Aβ42 and Ac2-26 induce different conformational changes in FPR2.These findings provide a structural basis for FPR2 mediation of inflammatory vs anti-inflammatory functions and identify a type of receptor modulation that differs from the classic positive and negative allosteric modulation.展开更多
文摘Two-dimensional(2D)transition metal dichalcogenides(TMDs)and their heterostructures(HSs)exhibit unique optical properties and show great promise for developing next-generation optoelectronics.However,the photo-luminescence(PL)quantum yield of monolayer(1L)TMDs is still quite low at room temperature,which severely lim-its their practical applications.Here we report a PL enhancement effect of 1L WS_(2) at room temperature when con-structing it into 1L-WS_(2)/hBN/1L-MoS_(2) vertical HSs.The PL enhancement factors(EFs)can be up to 4.2.By using transient absorption(TA)spectroscopy,we demonstrate that the PL enhancement effect is due to energy transfer from 1L MoS_(2) to 1L WS_(2).The energy transfer process occurs on a picosecond timescale and lasts more than one hundred picoseconds which indicates a prominent contribution from exciton-exciton annihilation.Furthermore,the PL en-hancement effect of 1L WS_(2) can be observed in 2L-MoS_(2)/hBN/1L-WS_(2) and 3L-MoS_(2)/hBN/1L-WS_(2) HSs.Our study provides a comprehensive understanding of the energy transfer process in the PL enhancement of 2D TMDs and a fea-sible way to optimize the performance of TMD-based optoelectronic devices.
文摘Broadband near-infrared(NIR)luminescent materials have shown great promise in applications such as optical communication,biomedicine,and optoelectronic devices.However,the current research is focused on phos⁃phors and glasses,and it is important to develop broadband NIR luminescent nanomaterials.Here,we report an erbi⁃um-sensitized core-shell nanocrystal design for broadband NIR emission.Based on the structural design with suitable dopings of Tm^(3+)and Ho^(3+),the broadband NIR emission covering 1.5-2.1μm region is achieved under 980 nm and 808 nm excitations.Moreover,the emission intensity is further enhanced by introducing Yb^(3+)and Nd^(3+)into the sam⁃ple,respectively,and the energy transfer processes between them are systematically discussed.Our results present a novel approach for developing broadband NIR luminescent materials and devices.
文摘4-Nonylphenol(NP)is a kind of estrogen belonging to the endocrine disrupter,widely used in various agricultural and industrial goods.However,extensive use of NP with direct release to environment poses high risks to both human health and ecosystems.Herein,for the first time,we developed near-infrared(NIR)responsive upconversion luminescence nanosensor for NP detection.The Förster resonance energy transfer based upconversion nanoparticles(UCNPs)-graphene oxide sensor offers highly selective and sensitive detection of NP in linear ranges of 5−200 ng/mL and 200−1000 ng/mL under 980 nm and 808 nm excitation,respectively,with LOD at 4.2 ng/mL.The sensors were successfully tested for NP detection in real liquid milk samples with excellent recovery results.The rare-earth fluoride based upconversion luminescence nanosensor with NIR excitation wavelength,holds promise for sensing food,environmental,and biological samples due to their high sensitivity,specific recognition,low LOD,negligible autofluorescence,along with the deep penetration of NIR excitation sources.
文摘While three-dimensional perovskites have high defect tolerance and an adjustable bandgap,their charges tend to be free rather than forming excitons,making them unsuitable for use in efficient light-emitting diodes(LEDs).Rather,quasi-two-dimensional(Q-2D)perovskites offer high photoluminescence quantum yield along with the advantages of bulk perovskites,making them ideal for high-performance LEDs.In Q-2D perovskites,the structure(which includes factors like crystal orientation,phase distribution,and layer thickness)directly influences how excitons and charge carriers behave within the material.Growth control techniques,such as varying the synthesis conditions or employing methods,allow for fine-tuning the structural characteristics of these materials,which in turn affect exciton dynamics and charge transport.This review starts with a description of the basic properties of Q-2D perovskites,examines crystal growth in solution,explains how structure affects energy transfer behavior,and concludes with future directions for Q-2D perovskite LEDs.By understanding and optimizing the structure-dependent behavior,researchers can better control exciton dynamics and charge transport,which are crucial for enhancing the performance of optoelectronic devices like solar cells and LEDs.
文摘Eu^(2+) and Mn^(2+) co-activated CaAlSiN_(3) red phosphors were produced using the solid-state reaction tech⁃nique in a N2 environment.Excitation spectra,emission spectra,and diffuse reflection spectra were used to study the luminescence characteristics,energy gap,and thermal stability in detail.CaAlSiN_(3)∶Eu^(2+) exhibits an extended emission band when stimulated with 450 nm blue light,which is caused by the 4f65d to 4f7 transition of Eu^(2+).Similar⁃ly,CaAlSiN_(3)∶Mn^(2+) displays a wide emission band centered at 628 nm,which results from Mn^(2+)’s transition from 4T1(4G) to 6A1(6S).When the ions of Mn^(2+)were combined into CaAlSiN_(3)∶Eu^(2+),the photoluminescence intensity of Eu^(2+ )was greatly boosted because there was energy transfer and co-emission between Mn^(2+) and Eu^(2+).Beyond that,CaAlSiN_(3)∶Eu^(2+),Mn^(2+) emerges with splendid thermostability and high quantum efficiency,the quenching temperature surpasses 300℃,and the internal quantum efficiency is determined to be around 84.9%.The white LED was pack⁃aged with a combination of CaAlSiN_(3)∶Eu^(2+),Mn^(2+),LuAG∶Ce3+ and a blue chip.At a warm white-light corresponding color temperature(3009 K) with CIE coordinates(0.4223,0.3748),the color rendering index Ra has reached 93.2.CaAlSiN_(3)∶Eu^(2+),Mn^(2+) would have great application potential as a red-emitting phosphor for white LEDs.
基金Project(50803008) supported by the National Natural Science Foundation of ChinaProject(2002CB613403) supported by the Ministry of Science and Technology (MOST) of China+1 种基金Project(09JJ6085) supported by the Natural Science Foundation of Hunan Province,ChinaProject(08hjyh02) supported by the Open Project Program of Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education,China
文摘A new functionalized heteroleptic iridium complex coordinated with 1-phenylisoquinoline （1-piq） and a functionalized fl-diketone （G1）, Ir（1-piq）2G1, was synthesized and characterized by 1H-NMR, mass spectrometry and elemental analysis. The larger conjugation of the replacement of acetylacetone （acac） by a functionalizedβ-diketonate ligand led to a significant decrease in the HOMO level toward vacuum level, while Ir（1-piq）2G1 and Ir（1-piq）2（acac） showed red phosphorescent emissions of about 620 nm in dichloromethane solution. The phosphorescent polymer light-emitting devices were achieved, with the complexes incorporated with polyfluorene （PFO） as a host polymer doped with 30% of 5-（4-biphenylyl）-2-（4-tert-butylphenyl）-1,3,4-oxadiazole （PBD） as electron transport material. The energy transfer mechanism of the devices was also discussed. The lower EL performance of Ir（1-piq）2G1 is ascribed to the inter-ligand energy transfer, indicating that it is important to control the energy level of the cyclometalated and ancillary ligands.
基金This project was supported by the National Natural Sciences Foundation of China
文摘In this paper,the single crystals of GdP 5O 14 :Sm 3+ ,Pr 3+ (GdPP: Sm,Pr)were grown by the hydrothermal method.The process of growing crystal is th e formation and grown up of new phase. Whether new phase can appear and how can occur,which is driven by the force of phase transformation.It is necessary to co ntrol this process by the concentration in the hydrothermal solution.In the syst em of cohesive phosphoric acid growing crystal is a process of complex chemical reaction,in which nucleation depends on the stability of small cluster and on ho w many of them form,so the number of controllable nucleation is very complex sta tistical problem.The natural face and high optical quality of single crystal can be preserved by adding a seed which is cut from large crystal. The crystal structure of GdPP:Sm,Pr,isotypic with monoclinic (space group PZ 1/ c )GdPP,has been checked by X ray powder diffraction and emission and em is sion spectrum were measured and analyzed in the range from ultraviolet to visibl e at room temperature.The dependence of containg different Pr 3+ ion concent rations on the emission intensities of 4 G 5/2 → 6 H 7/2 tran sition of Sm 3+ ion have been discussed in the GdPP:Sm,Pr crystals.The energ y transfer between Sm 3+ and Pr 3+ ions have been investigated.
基金Projects(2004Z2-D0131 and 2004A10602002) supported by the Science and Technology Programof Guangzhou , Guang-dong Province project(60307004 and 50472053) supported by the National Natural Science Foundation of China project(04200036) sup-ported by the Natural Foundation of Guangdong Province
文摘The energy transfer and upconversion of Er 3+ /Yb 3+ co-doped TeO2-TiO2-K2O glasses upon excitation with 976nm lasers diode were studied. The tellurite glasses were prepared by conventional melting methods. Their optical properties and sensitization upconversion spectra were performed. The dependence of green upconversion luminescence intensity on the mole ratio of Yb 3+ to Er 3+ and Er 3+ concentration were discussed in detail. When the mole ratio of Yb 3+ to Er 3+ is 25/1 and Er 3+ concentration is 0.1% （mole fraction）, or when the mole ratio of Yb 3+ to Er 3+ is 10/1 and Er 3+ concentration is 0.15%, the optimal upconversion luminescence intensity is obtained. The obtained glasses can be one of the potential candidates for lasers-diode pumping microchip solid-state lasers.
文摘Eu^(2+)-doped Na_(3)Sc_(2)(PO_(4))_(3)ionic conductor possesses superior thermal quenching(TQ)resistance,which is considered as a promising phosphor for high-power lighting applications.Yet the underlying mechanism of negative thermal quenching(NTQ)is not fully understood.In this study,we focus on upconversion(UC)and downshifting(DS)luminescence of Yb^(3+)/Er^(3+)with f-f transition rather than susceptible d-f transition of Eu^(2+)in Na_(3)Sc_(2)(PO_(4))_(3),aiming to get a more insightful view.The results show that thermally accelerated dynamic defects/ions contributes to the significant negative thermal quenching(NTQ)of UC luminescence and thermally stabilized DS luminescence by promoting the radiative transition and suppressing the non-radiative transition.The UC process with slow population rate is more susceptible to perturbation of Na+migration process with time scale equivalent to that of the former,resulting in evident NTQ of UC luminescence.This research opens an avenue for understanding the NTQ mechanism of luminescence via dynamic defects/ions.
基金supported by National Natural Science Foundation of China(31470856 to RDY)the Science and Technology Development Fund of Macao(FDCT 072/2015/A2)the University of Macao(SRG2015-00047-ICMS-QRCM)
文摘OBJECTIVE The chemokine-like receptor 1(CMKLR1,Chem R23) is a functional receptor for chemerin,the chemerin-derived nonapeptide(C9),and the amyloid β peptide 1-42(Aβ_(42)).Because these peptides share little sequence homology,studies were conducted to investigate their pharmacological properties and regulation at CMKLR1.METHODS Cells expressing CMKLR1 were incubated with Aβ_(42) before stimulation with a strong agonist,the C9 peptide.Calcium mobilization,c AMP inhibition and MAP kinase activation were measured.Intramolecular FRET were determined using CMKLR1 constructs with an ECFP attached to the C-terminus and a Fl As H binding motif embedded in the first intracellular loop(IL1).RESULTS Binding of both Aβ_(42) and the C9 peptide induced CMKLR1 internalization,but only the Aβ_(42)-induced receptor internalization involved clathrin-coated pits.Likewise,Aβ_(42) but not C9 stimulated β-arrestin 2 translocation to plasma membranes.A robust Ca^(2+)flux was observed following C9 stimulation,whereas Aβ_(42) was ineffective even at micromolar concentrations.Despite its low potency in calcium mobilization assay,Aβ_(42) was able to alter C9-induced Ca^(2+) flux in dose-dependent manner:a potentiation effect at 100 pmol·L^(-1) of Aβ_(42) was followed by a suppression at 10 nmol·L^(-1) and further potentiation at 1 μmol·L^(-1).This unusual and biphasic modulatory effect was also seen in the C9-induced ERK phosphorylation but the dose curve was opposite to that of Ca^(2+) flux and c AMP inhibition,suggesting a reciprocal regulatory mechanism.Intramolecular FRET assay confirmed that Aβ_(42) modulates CMKLR1 rather than its downstream signaling pathways.CONCLUSION These findings suggest Aβ_(42) as an allosteric modulator that can both positively and negatively regulate the activation state of CMKLR1 in a manner that differs from existing allosteric modulatory mechanisms.
基金supported by National Natural Science Foundation of China(31470856 to RDY)the Science and Technology Development Fund of Macao(FDCT 072/2015/A2)the University of Macao(SRG2015-00047-ICMS-QRCM)
文摘OBJECTIVE To identify the mechanisms by which the formyl peptide receptor 2(FPR2)mediates both inflammatory and anti-inflammatory signaling in an agonist-dependent manner.METHODS Cells expressing FPR2 were incubated with weak agonists,Aβ42 and Ac2-26,before stimulation with a strong agonist,WKYMVm.Calcium mobilization,c AMP inhibition and MAP kinase activation were measured.Intramolecular FRET were determined using FPR2 constructs with an ECFP attached to the C-terminus and a Fl As H binding motif embedded in the first or third intracellular loop(IL1 or IL3,respectively).RESULTS Aβ42 did not induce significant Ca^(2+) mobilization,but positively modulated WKYMVm-induced Ca^(2+) mobilization and c AMP reduction in a dose-variable manner within a narrow range of ligand concentrations.Treating FPR2-expressing cells with Ac2-26,a peptide with anti-inflammatory activity,negatively modulated WKYMVm-induced Ca^(2+) mobilization and c AMP reduction.Intramolecular FRET assay showed that stimulation of the receptor constructs with Aβ42 brought the C-terminal domain closer to IL1 but away from IL3.An opposite conformational change was induced by Ac2-26.The FPR2 conformation induced by Aβ42 corresponded to enhanced ERK phosphorylation and attenuated p38 MAPK phosphorylation,whereas Ac2-26 induced FPR2 conformational change corresponding to elevated p38 MAPK phosphorylation and reduced ERK phosphorylation.CONCLUSION Aβ42 and Ac2-26 induce different conformational changes in FPR2.These findings provide a structural basis for FPR2 mediation of inflammatory vs anti-inflammatory functions and identify a type of receptor modulation that differs from the classic positive and negative allosteric modulation.
