The ultrafast carrier relaxation processes in CdTe quantum dots are investigated by femtosecond fluorescence upconversion spectroscopy.Photo-excited hole relaxing to the edge of the forbidden gap takes a maximal time ...The ultrafast carrier relaxation processes in CdTe quantum dots are investigated by femtosecond fluorescence upconversion spectroscopy.Photo-excited hole relaxing to the edge of the forbidden gap takes a maximal time of ～ 1.6 ps with exciting at 400 nm,depending on the state of the photo-excited hole.The shallow trapped states and deep trap states in the forbidden gap are confirmed for CdTe quantum dots.In addition,Auger relaxation of trapped carriers is observed to occur with a time constant of ～ 5 ps.A schematic model of photodynamics is established based on the results of the spectroscopy studies.Our work demonstrates that femtosecond fluorescence up-conversion spectroscopy is a suitable and effective tool in studying the transportation and conversion dynamics of photon energy in a nanosystem.展开更多
Carbazole-core multi-branched chromophores 9-ethyl- 3, 6-bis （ 2- { 4- [ 5- （4-tert-butyl-phenyl） - [ 1, 3, 4 ] oxadiazol-2-yl ] - phenyl }-vinyl） -carbazole（3） and 9-ethyl-3-（ 2- {4-[ 5-（4-tert-butyl- phenyl...Carbazole-core multi-branched chromophores 9-ethyl- 3, 6-bis （ 2- { 4- [ 5- （4-tert-butyl-phenyl） - [ 1, 3, 4 ] oxadiazol-2-yl ] - phenyl }-vinyl） -carbazole（3） and 9-ethyl-3-（ 2- {4-[ 5-（4-tert-butyl- phenyl） -[ 1, 3, 4 ] oxadiazol-2-yl ] -phenyl }-vinyl ） -carbazole （ 2 ） are synthesized through Wittig reaction and characterized by nuclear magnetic resonance（NMR）and infrared（IR）. The two- photon absorption properties of chromophores are investigated. These chromophores exhibit large two-photon absorption crosssections and strong blue two-photon excited fluorescence. The cooperative enhancement of two-photon absorption（TPA） in the multi-branched structures is observed. This enhancement is partly attributed to the electronic coupling between the branches. The electronic push-pull structures in the arm and their cooperative effects help the extended charge transfer for TPA.展开更多
Two new bithiophene derivatives named as 5, 5-bis(p-N,N-dimethylaminostyryl)-2, 2 -bithiophene (BMSBT), and 5, 5-bis(p-N,N-diethylaminostyryl)-2, 2-bithiophene (BESBT) have been synthesized. Both compounds can emit s...Two new bithiophene derivatives named as 5, 5-bis(p-N,N-dimethylaminostyryl)-2, 2 -bithiophene (BMSBT), and 5, 5-bis(p-N,N-diethylaminostyryl)-2, 2-bithiophene (BESBT) have been synthesized. Both compounds can emit strong single-photon excited fluorescence (SPEF) and two-photon excited fluorescence (TPEF) with the emission peaks around ~560 nm and with the lifetime of ~1ns.展开更多
Apoptosis is very important for the maintenance of cellular homeostasis and is closely related to the occurrence and treatment of many diseases.Mitochondria in cells play a crucial role in programmed cell death and re...Apoptosis is very important for the maintenance of cellular homeostasis and is closely related to the occurrence and treatment of many diseases.Mitochondria in cells play a crucial role in programmed cell death and redox processes.Nicotinamide adenine dinucleotide(NAD(P)H)is the primary producer of energy in mitochondria,changing NAD(P)H can directly reflect the physiological state of mitochondria.Therefore,NAD(P)H can be used to evaluate metabolic response.In this paper,we propose a noninvasive detection method that uses two-photon fluorescence lifetime imaging microscopy(TP-FLIM)to characterize apoptosis by observing the binding kinetics of cellular endogenous NAD(P)H.The result shows that the average fluorescence lifetime of NAD(P)H and the fluorescence lifetime of protein-bound NAD(P)H will be affected by the changing pH,serum content,and oxygen concentration in the cell culture environment,and by the treatment with reagents such as H2O2 and paclitaxel.Taxol(PTX).This noninvasive detection method realized the dynamic detection of cellular endogenous substances and the assessment of apoptosis.展开更多
An electron donor-π-bridge-electron acceptor(D-π-A) optical functional organic compound comprising a triphenylamine moiety as the electron donor and pyridine moiety as the electron acceptor was synthesized. The stru...An electron donor-π-bridge-electron acceptor(D-π-A) optical functional organic compound comprising a triphenylamine moiety as the electron donor and pyridine moiety as the electron acceptor was synthesized. The structure of the compound was solved by single-crystal X-ray diffraction analysis. It crystallizes in monoclinic, space group P21, with a = 9.753(5), b = 8.815(5), c = 25.554(5) ?, β = 96.315(5)°, V = 2184(2) ?~3, Z = 2, D_c = 1.136 g/m^3, F(000) = 792, Μr = 746.92, μ = 0.069 mm^(-1), the final R = 0.0658 and wR = 0.1730 for 6790 observed reflections with I > 2(I). Study of nonlinear optical properties shows that the compound exhibits excellent two-photon excited fluorescence with the two-photon absorption cross-section value of 116 GM. The structure-property relationship was researched in detail through X-ray crystallography and quantum chemical calculation. Result of living cell imaging experiment shows its potential in fluorescence microscopy bioimaging.展开更多
Efficient Ti-catalyzed reductive coupling methodology was first employed to synthesize the symmetrical bis-donor stilbene, trans-4, 4'-bis[diphenyl amino] stilbene (BDPAS). X-ray diffraction analyses reveal that t...Efficient Ti-catalyzed reductive coupling methodology was first employed to synthesize the symmetrical bis-donor stilbene, trans-4, 4'-bis[diphenyl amino] stilbene (BDPAS). X-ray diffraction analyses reveal that this new crystal belongs to the triclinic crystal system of centro-symmetric P-1 space group. The DBPAS solution, with the linear transmission at wavelength of greater than or equal to 450 nm, possesses large two-photon absorption cross section as high as 39.4x10(-48) cm(4).s/photon resulting in strong two-photon induced blue fluorescence of 460 nm, pumped by 740 nm laser irradiation.展开更多
Two new compounds involving a thiophene moiety named as 2,5-bis[4-(N,N- diphenyl- amino)styryl]thiophene (BPST) and 2,5-bis[4-(N,N-diethylamino)styryl]thiophene (BEST) have been synthesized. The two-photon absorptio...Two new compounds involving a thiophene moiety named as 2,5-bis[4-(N,N- diphenyl- amino)styryl]thiophene (BPST) and 2,5-bis[4-(N,N-diethylamino)styryl]thiophene (BEST) have been synthesized. The two-photon absorption cross section of BPST was measured as large as 256 × 10-50 cm4·s/photon, when it was excited by 800 nm femtosecond laser.展开更多
Three dye-doped polymer rods in different matrices were synthesized in which weak hydrogen bond, strong hydrogen bond and covalent bond existed between the dye and the polymer chain. And the two-photon up-conversion...Three dye-doped polymer rods in different matrices were synthesized in which weak hydrogen bond, strong hydrogen bond and covalent bond existed between the dye and the polymer chain. And the two-photon up-conversion luminescent properties of HMASPS and HEASPS1 in three different microenvironments were studied.展开更多
The synthesis and upconverted fluorescent properties of a series of organic compounds with the structure: donor/bridge/acceptor, and different side-chains are reported. The results show that the compounds with differe...The synthesis and upconverted fluorescent properties of a series of organic compounds with the structure: donor/bridge/acceptor, and different side-chains are reported. The results show that the compounds with different side-chains exhibit different two-photon induced fluorescent properties, although they have the same main donor/bridge/acceptor structure.展开更多
Two new D--A type compounds, where electron-donor D is tertiary amino group, electron-acceptor A is 2-benzothiazolyl and ?is two conjugated styryl units, have been synthesized. They are named as trans, trans-2-{4-[4-(...Two new D--A type compounds, where electron-donor D is tertiary amino group, electron-acceptor A is 2-benzothiazolyl and ?is two conjugated styryl units, have been synthesized. They are named as trans, trans-2-{4-[4-(N, N-diethylamino)styryl]styryl}-1, 3-benzothiazole and trans, trans-2-{4-[4-(N, N-diphenylamino)styryl]styryl}-1, 3-benzothiazole. Both compounds show strong two-photon excited fluorescence in yellow-orange region when excited by a femtosecond laser at 800 nm.展开更多
The synthesis and upconverted fluorescent properties of three novel organic compoundswith the structure: donor/bridge/acceptor are reported. The dyes show strong upconvertedfluorescence.
The two-photon fluorescence properties and ultrafast responses of a hyperbranched polyyne （hb-DPP-J2） with triphenylamine as the central core, Diketo-Pyrrolo-Pyrrole as the connecting unit and electron acceptor are ...The two-photon fluorescence properties and ultrafast responses of a hyperbranched polyyne （hb-DPP-J2） with triphenylamine as the central core, Diketo-Pyrrolo-Pyrrole as the connecting unit and electron acceptor are studied. The polymer has a D-π-A-π-D conjugated structure along the extended polyyne w-bridge systems, and the effective condugated unit repeats itself in the whole hyperbranehed polymer chain. The polymer exhibits a large two-photon absorption cross section and high fluorescence quantum yields. The ultrafast dynamic results give a deep understanding of the excited energy transfer processes under excitation, and reveal a long relaxation lifetime of the intramolecular charge transfer （ICT） state.展开更多
Ischemic stroke is one of the most common causes of mortality and disability worldwide.However,treatment efficacy and the progress of research remain unsatisfactory.As the critical support system and essential compone...Ischemic stroke is one of the most common causes of mortality and disability worldwide.However,treatment efficacy and the progress of research remain unsatisfactory.As the critical support system and essential components in neurovascular units,glial cells and blood vessels(including the bloodbrain barrier)together maintain an optimal microenvironment for neuronal function.They provide nutrients,regulate neuronal excitability,and prevent harmful substances from entering brain tissue.The highly dynamic networks of this support system play an essential role in ischemic stroke through processes including brain homeostasis,supporting neuronal function,and reacting to injuries.However,most studies have focused on postmortem animals,which inevitably lack critical information about the dynamic changes that occur after ischemic stroke.Therefore,a high-precision technique for research in living animals is urgently needed.Two-photon fluorescence laser-scanning microscopy is a powerful imaging technique that can facilitate live imaging at high spatiotemporal resolutions.Twophoton fluorescence laser-scanning microscopy can provide images of the whole-cortex vascular 3D structure,information on multicellular component interactions,and provide images of structure and function in the cranial window.This technique shifts the existing research paradigm from static to dynamic,from flat to stereoscopic,and from single-cell function to multicellular intercommunication,thus providing direct and reliable evidence to identify the pathophysiological mechanisms following ischemic stroke in an intact brain.In this review,we discuss exciting findings from research on the support system after ischemic stroke using two-photon fluorescence laser-scanning microscopy,highlighting the importance of dynamic observations of cellular behavior and interactions in the networks of the brain’s support systems.We show the excellent application prospects and advantages of two-photon fluorescence laser-scanning microscopy and predict future research developments and directions in the study of ischemic stroke.展开更多
Oxy-fluoride glasses with composition of 25SiO2-65PbF2-9.4AlF3-0.1HoF3-0.5YbF3 were prepared. Their up-conversion fluorescence characteristics were investigated by 980 nm laser. Two emission peaks were observed at 540...Oxy-fluoride glasses with composition of 25SiO2-65PbF2-9.4AlF3-0.1HoF3-0.5YbF3 were prepared. Their up-conversion fluorescence characteristics were investigated by 980 nm laser. Two emission peaks were observed at 540 and 650 nm. The up-conversion mechanism and processes were analyzed. The relationship between pumping power and relative intensity of emissions was discussed. From the dependence, it is known that the emissions centered at 540 and 650 nm are both attributed to two-photon process.展开更多
The green and red up-conversion emissions centred at about 534, 549 and 663 nm of wavelength, corresponding respectively to the ^2H11/2 → ^4I15/2, ^4S3/2 → ^4I15/2 and ^4F9/2 → ^4I15/2 transitions of Er^3＋ ions, h...The green and red up-conversion emissions centred at about 534, 549 and 663 nm of wavelength, corresponding respectively to the ^2H11/2 → ^4I15/2, ^4S3/2 → ^4I15/2 and ^4F9/2 → ^4I15/2 transitions of Er^3＋ ions, have been observed for the Er^3＋-doped silicate glass excited by a 978 nm semiconductor laser beam. Excitation power dependent behaviour of the up-conversion emission intensity indicates that a two-photon absorption up-conversion process is responsible for the green and red up-conversion emissions. The temperature dependence of the green up-conversion emissions is also studied in a temperature range of 296-673 K, which shows that Er^3＋-doped silicate glass can be used as a sensor in high-temperature measurement.展开更多
The up-conversion luminescence tuning of rare-earth ions is an important research topic for understanding luminescence mechanisms and promoting related applications. In this paper, we experimentally study the up-conve...The up-conversion luminescence tuning of rare-earth ions is an important research topic for understanding luminescence mechanisms and promoting related applications. In this paper, we experimentally study the up-conversion luminescence tuning of Er3+-doped ceramic glass excited by the unshaped, V-shaped and cosine-shaped femtosecond laser field with different laser powers. The results show that green and red up-conversion luminescence can be effectively tuned by varying the power or spectral phase of the femtosecond laser field. We further analyze the up-conversion luminescence tuning mechanism by considering different excitation processes, including single-photon absorption(SPA), two-photon absorption(TPA), excited state absorption(ESA), and energy transfer up-conversion(ETU). The relative weight of TPA in the whole excitation process can increase with the increase of the laser power, thereby enhancing the intensity ratio between green and red luminescence(I547/I656). However, the second ETU(ETU2) process can generate red luminescence and reduce the green and red luminescence intensity ratio I547/I656, while the third ESA(ESA3) process can produce green luminescence and enhance its control efficiency. Moreover, the up-conversion luminescence tuning mechanism is further validated by observing the up-conversion luminescence intensity, depending on the laser power and the down-conversion luminescence spectrum under the excitation of 400-nm femtosecond laser pulse. These studies can present a clear physical picture that enables us to understand the up-conversion luminescence tuning mechanism in rare-earth ions, and can also provide an opportunity to tune up-conversion luminescence to promote its related applications.展开更多
To improve two-photon absorption(TPA)response of a newly synthesized probe,a series of ratiometric two-photon fluorescent Zn^(2+) sensors based on quinoline and DPA moieties have been designed.The one-photon absorptio...To improve two-photon absorption(TPA)response of a newly synthesized probe,a series of ratiometric two-photon fluorescent Zn^(2+) sensors based on quinoline and DPA moieties have been designed.The one-photon absorption,TPA,and emission properties of the experimental and designed probes before and after coordination with Zn^(2+) are investigated employing the density functional theory in combination with response functions.The design consists of two levels.In the first level of design,five probes are constructed through using several electron acceptors or donors to increase accepting or donating ability of the fluorophores.It shows that all the designed probes have stronger TPA intensities at longer wavelengths with respect to the experimental probe because of the increased intra-molecular charge transfer.Moreover,it is found that the probe 4 built by adding an acyl unit has the largest TPA cross section among the designed structures due to the form of longer conjugated length and more linear backbone.One dimethylamino terminal attached along the skeleton can improve TPA intensity more efficiently than two side amino groups.Therefore,in the second level of design,a new probe 7 is formed by both an acyl unit and a dimethylamino terminal.It exhibits that the TPA cross sections of probe 7 and its zinc complex increase dramatically.Furthermore,the fluorescence quantum yields of the designed probes4 and 7 are calculated in a new way,which makes use of the relation between the computed difference of dipole moment and the measured fluorescence quantum yield.The result shows that our design also improves the fluorescence quantum yield considerably.All in all,the designed probes 4 and 7 not only possess enhanced TPA intensities but also have large differences of emission wavelength upon Zn^(2+) coordination and strong fluorescence intensity,which demonstrates that they are potential ratiometric two-photon fluorescent probes.展开更多
Fluorescent probe is an important tool for investigation of biological events in plant tissues.However,the research on small-molecule based fluorescent probe for plant imaging still stays at the initial stage.In order...Fluorescent probe is an important tool for investigation of biological events in plant tissues.However,the research on small-molecule based fluorescent probe for plant imaging still stays at the initial stage.In order to noninvasively achieve the subcellular information of Arabidopsis thaliana,a two-photon and fluorene based fluorophore with a bi-oligo(ethylene glycol)functional group was synthesized.Under the laser's irradiation at 750 nm,the subcellular structures of Arabidopsis thaliana including stomata and root tips were clearly observed without slicing,which displayed significant superiorities over traditional single-photon excitation microscopy.Subsequently,the above functionalized fluorophore was further modified with a recognition group(dipicolylamine)to form a smart fluorescent probe(LJTP1).As results,LJTP1 not only can sensitively detect Cu^(2+)/S^(2-)with fluorescence“on-off-on”response in vitro and in vivo,but also can achieve noninvasive imaging in Arabidopsis thaliana tissues under two-photon microscopy.We believe this study will open up a new mind for noninvasive imaging in plant tissues.展开更多
A non-polar organic dye, E, E-1, 4-bis[4＇-（N,N-dibutylamino）styryl]-2,5-dimethoxybenzene （DBASDMB）, has been synthesized and characterized, and its structure has been determined. Pumped with a 200fs pulse this dy...A non-polar organic dye, E, E-1, 4-bis[4＇-（N,N-dibutylamino）styryl]-2,5-dimethoxybenzene （DBASDMB）, has been synthesized and characterized, and its structure has been determined. Pumped with a 200fs pulse this dye showed the up-conversion laser properties. The influences of various organic solvents and different pumping wavelength on the laser properties have been demonstrated.展开更多
The properties of one-photon absorption(OPA),emission and two-photon absorption(TPA)of a bipyridine-based zinc ion probe are investigated employing the density functional theory in combination with response functions....The properties of one-photon absorption(OPA),emission and two-photon absorption(TPA)of a bipyridine-based zinc ion probe are investigated employing the density functional theory in combination with response functions.The responsive mechanism and coordination mode effect are explored.The structural fluctuation is illustrated by molecular dynamics simulation.The calculated OPA and emission wavelengths of the probe are consistent with the experimental data.It is found that the red-shift of OPA wavelength and the enhancement of TPA intensity are induced by the increased intra-molecular charge transfer mechanism upon metal binding.The structural fluctuation could result in the blue-shift of TPA wavelength and the decrease of the TPA cross section.The TPA properties are quite different among the zinc complexes with different coordination modes.The TPA wavelength of the complexes with two ligands is close to that of the probe,which is in agreement with the experimental observation.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11074003 and 20973001)the Key Program of Educational Commission of Anhui Province of China (Grant No. KJ2010A132)
文摘The ultrafast carrier relaxation processes in CdTe quantum dots are investigated by femtosecond fluorescence upconversion spectroscopy.Photo-excited hole relaxing to the edge of the forbidden gap takes a maximal time of ～ 1.6 ps with exciting at 400 nm,depending on the state of the photo-excited hole.The shallow trapped states and deep trap states in the forbidden gap are confirmed for CdTe quantum dots.In addition,Auger relaxation of trapped carriers is observed to occur with a time constant of ～ 5 ps.A schematic model of photodynamics is established based on the results of the spectroscopy studies.Our work demonstrates that femtosecond fluorescence up-conversion spectroscopy is a suitable and effective tool in studying the transportation and conversion dynamics of photon energy in a nanosystem.
基金The National Natural Science Foundation of China(No.60678042)the Natural Science Foundation of Jiangsu Province(No.BK2006553)the Pre-Research Project of the National Natural Science Foundation supported by Southeast University(No.9207041399)
文摘Carbazole-core multi-branched chromophores 9-ethyl- 3, 6-bis （ 2- { 4- [ 5- （4-tert-butyl-phenyl） - [ 1, 3, 4 ] oxadiazol-2-yl ] - phenyl }-vinyl） -carbazole（3） and 9-ethyl-3-（ 2- {4-[ 5-（4-tert-butyl- phenyl） -[ 1, 3, 4 ] oxadiazol-2-yl ] -phenyl }-vinyl ） -carbazole （ 2 ） are synthesized through Wittig reaction and characterized by nuclear magnetic resonance（NMR）and infrared（IR）. The two- photon absorption properties of chromophores are investigated. These chromophores exhibit large two-photon absorption crosssections and strong blue two-photon excited fluorescence. The cooperative enhancement of two-photon absorption（TPA） in the multi-branched structures is observed. This enhancement is partly attributed to the electronic coupling between the branches. The electronic push-pull structures in the arm and their cooperative effects help the extended charge transfer for TPA.
基金This work is supported by the National Natural Science Foundation of China(No.20172034)grant for State Key Program of China.
文摘Two new bithiophene derivatives named as 5, 5-bis(p-N,N-dimethylaminostyryl)-2, 2 -bithiophene (BMSBT), and 5, 5-bis(p-N,N-diethylaminostyryl)-2, 2-bithiophene (BESBT) have been synthesized. Both compounds can emit strong single-photon excited fluorescence (SPEF) and two-photon excited fluorescence (TPEF) with the emission peaks around ~560 nm and with the lifetime of ~1ns.
基金supported in part by the National Key R&D Program of China(2017YFA0700402)National Natural Science Foundation of China(61961136005/61935012/62175163/61835009)+1 种基金Shenzhen Key projects(JCYJ20200109105404067)Shenzhen International Cooperation Project(GJHZ 20190822095420249).
文摘Apoptosis is very important for the maintenance of cellular homeostasis and is closely related to the occurrence and treatment of many diseases.Mitochondria in cells play a crucial role in programmed cell death and redox processes.Nicotinamide adenine dinucleotide(NAD(P)H)is the primary producer of energy in mitochondria,changing NAD(P)H can directly reflect the physiological state of mitochondria.Therefore,NAD(P)H can be used to evaluate metabolic response.In this paper,we propose a noninvasive detection method that uses two-photon fluorescence lifetime imaging microscopy(TP-FLIM)to characterize apoptosis by observing the binding kinetics of cellular endogenous NAD(P)H.The result shows that the average fluorescence lifetime of NAD(P)H and the fluorescence lifetime of protein-bound NAD(P)H will be affected by the changing pH,serum content,and oxygen concentration in the cell culture environment,and by the treatment with reagents such as H2O2 and paclitaxel.Taxol(PTX).This noninvasive detection method realized the dynamic detection of cellular endogenous substances and the assessment of apoptosis.
基金supported by the Major Project of Natural Science Research in Universities of Anhui Province(KJ2018ZD037,KJ2018A0333)Key Project of Youth Talents in Universities of Anhui Province(gxyqZD2017067)+5 种基金National Natural Science Foundation of China(21401024)Natural Science Foundation of Anhui Province(1508085MB21)National Students Research Training Program(201810371028)Research Innovation Team of Fuyang Normal University(kytd201710)Horizontal Cooperation Project of Fuyang Municipal Government and Fuyang Normal University(XDHX2016011,XDHX2016004)Anhui University Research Innovation Platform Team Project(201549)
文摘An electron donor-π-bridge-electron acceptor(D-π-A) optical functional organic compound comprising a triphenylamine moiety as the electron donor and pyridine moiety as the electron acceptor was synthesized. The structure of the compound was solved by single-crystal X-ray diffraction analysis. It crystallizes in monoclinic, space group P21, with a = 9.753(5), b = 8.815(5), c = 25.554(5) ?, β = 96.315(5)°, V = 2184(2) ?~3, Z = 2, D_c = 1.136 g/m^3, F(000) = 792, Μr = 746.92, μ = 0.069 mm^(-1), the final R = 0.0658 and wR = 0.1730 for 6790 observed reflections with I > 2(I). Study of nonlinear optical properties shows that the compound exhibits excellent two-photon excited fluorescence with the two-photon absorption cross-section value of 116 GM. The structure-property relationship was researched in detail through X-ray crystallography and quantum chemical calculation. Result of living cell imaging experiment shows its potential in fluorescence microscopy bioimaging.
文摘Efficient Ti-catalyzed reductive coupling methodology was first employed to synthesize the symmetrical bis-donor stilbene, trans-4, 4'-bis[diphenyl amino] stilbene (BDPAS). X-ray diffraction analyses reveal that this new crystal belongs to the triclinic crystal system of centro-symmetric P-1 space group. The DBPAS solution, with the linear transmission at wavelength of greater than or equal to 450 nm, possesses large two-photon absorption cross section as high as 39.4x10(-48) cm(4).s/photon resulting in strong two-photon induced blue fluorescence of 460 nm, pumped by 740 nm laser irradiation.
基金supported by the National Natural Science Foundation of China(No.20172034)the Ph.D.programs Foundation of Ministry of Education of China
文摘Two new compounds involving a thiophene moiety named as 2,5-bis[4-(N,N- diphenyl- amino)styryl]thiophene (BPST) and 2,5-bis[4-(N,N-diethylamino)styryl]thiophene (BEST) have been synthesized. The two-photon absorption cross section of BPST was measured as large as 256 × 10-50 cm4·s/photon, when it was excited by 800 nm femtosecond laser.
基金This work was supported by the grant for State Key Program of China.
文摘Three dye-doped polymer rods in different matrices were synthesized in which weak hydrogen bond, strong hydrogen bond and covalent bond existed between the dye and the polymer chain. And the two-photon up-conversion luminescent properties of HMASPS and HEASPS1 in three different microenvironments were studied.
基金This work was supported by thc grant for State Key Program of Chinaby the National Natural Science Foundation of China.
文摘The synthesis and upconverted fluorescent properties of a series of organic compounds with the structure: donor/bridge/acceptor, and different side-chains are reported. The results show that the compounds with different side-chains exhibit different two-photon induced fluorescent properties, although they have the same main donor/bridge/acceptor structure.
文摘Two new D--A type compounds, where electron-donor D is tertiary amino group, electron-acceptor A is 2-benzothiazolyl and ?is two conjugated styryl units, have been synthesized. They are named as trans, trans-2-{4-[4-(N, N-diethylamino)styryl]styryl}-1, 3-benzothiazole and trans, trans-2-{4-[4-(N, N-diphenylamino)styryl]styryl}-1, 3-benzothiazole. Both compounds show strong two-photon excited fluorescence in yellow-orange region when excited by a femtosecond laser at 800 nm.
文摘The synthesis and upconverted fluorescent properties of three novel organic compoundswith the structure: donor/bridge/acceptor are reported. The dyes show strong upconvertedfluorescence.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11404048,61205154 and 11375034the Fundamental Research Funds for the Central Universities under Grant Nos 3132015233,3132013104,3132014337,3132015144 and3132015152+1 种基金the State Key Laboratory of Fine Chemicals(KF1409)the Program for Liaoning Excellent Talents in University under Grant No LJQ2014051
文摘The two-photon fluorescence properties and ultrafast responses of a hyperbranched polyyne （hb-DPP-J2） with triphenylamine as the central core, Diketo-Pyrrolo-Pyrrole as the connecting unit and electron acceptor are studied. The polymer has a D-π-A-π-D conjugated structure along the extended polyyne w-bridge systems, and the effective condugated unit repeats itself in the whole hyperbranehed polymer chain. The polymer exhibits a large two-photon absorption cross section and high fluorescence quantum yields. The ultrafast dynamic results give a deep understanding of the excited energy transfer processes under excitation, and reveal a long relaxation lifetime of the intramolecular charge transfer （ICT） state.
基金supported by grants from the National Natural Science Foundation of China,Nos.92148206,82071330(to ZPT)82201745(to HN)the Natural Science Foundation of Hubei Province,China,Nos.2021BCA109(to ZPT)and 2021CFB067(to HN)。
文摘Ischemic stroke is one of the most common causes of mortality and disability worldwide.However,treatment efficacy and the progress of research remain unsatisfactory.As the critical support system and essential components in neurovascular units,glial cells and blood vessels(including the bloodbrain barrier)together maintain an optimal microenvironment for neuronal function.They provide nutrients,regulate neuronal excitability,and prevent harmful substances from entering brain tissue.The highly dynamic networks of this support system play an essential role in ischemic stroke through processes including brain homeostasis,supporting neuronal function,and reacting to injuries.However,most studies have focused on postmortem animals,which inevitably lack critical information about the dynamic changes that occur after ischemic stroke.Therefore,a high-precision technique for research in living animals is urgently needed.Two-photon fluorescence laser-scanning microscopy is a powerful imaging technique that can facilitate live imaging at high spatiotemporal resolutions.Twophoton fluorescence laser-scanning microscopy can provide images of the whole-cortex vascular 3D structure,information on multicellular component interactions,and provide images of structure and function in the cranial window.This technique shifts the existing research paradigm from static to dynamic,from flat to stereoscopic,and from single-cell function to multicellular intercommunication,thus providing direct and reliable evidence to identify the pathophysiological mechanisms following ischemic stroke in an intact brain.In this review,we discuss exciting findings from research on the support system after ischemic stroke using two-photon fluorescence laser-scanning microscopy,highlighting the importance of dynamic observations of cellular behavior and interactions in the networks of the brain’s support systems.We show the excellent application prospects and advantages of two-photon fluorescence laser-scanning microscopy and predict future research developments and directions in the study of ischemic stroke.
文摘Oxy-fluoride glasses with composition of 25SiO2-65PbF2-9.4AlF3-0.1HoF3-0.5YbF3 were prepared. Their up-conversion fluorescence characteristics were investigated by 980 nm laser. Two emission peaks were observed at 540 and 650 nm. The up-conversion mechanism and processes were analyzed. The relationship between pumping power and relative intensity of emissions was discussed. From the dependence, it is known that the emissions centered at 540 and 650 nm are both attributed to two-photon process.
基金Project supported by the National Natural Science Foundation of China (Grant No 60477023)the Natural Science Foundation of Science and Technology Commission of Liaoning Province, China (Grant No 20062137)
文摘The green and red up-conversion emissions centred at about 534, 549 and 663 nm of wavelength, corresponding respectively to the ^2H11/2 → ^4I15/2, ^4S3/2 → ^4I15/2 and ^4F9/2 → ^4I15/2 transitions of Er^3＋ ions, have been observed for the Er^3＋-doped silicate glass excited by a 978 nm semiconductor laser beam. Excitation power dependent behaviour of the up-conversion emission intensity indicates that a two-photon absorption up-conversion process is responsible for the green and red up-conversion emissions. The temperature dependence of the green up-conversion emissions is also studied in a temperature range of 296-673 K, which shows that Er^3＋-doped silicate glass can be used as a sensor in high-temperature measurement.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51132004,11474096,11604199,U1704145,and 11747101)the Fund from the Science and Technology Commission of Shanghai Municipality,China(Grant No.14JC1401500)+1 种基金the Henan Provincial Natural Science Foundation,China(Grant No.182102210117)the Higher Educational Key Program of Henan Province of China(Gant Nos.17A140025 and 16A140030)
文摘The up-conversion luminescence tuning of rare-earth ions is an important research topic for understanding luminescence mechanisms and promoting related applications. In this paper, we experimentally study the up-conversion luminescence tuning of Er3+-doped ceramic glass excited by the unshaped, V-shaped and cosine-shaped femtosecond laser field with different laser powers. The results show that green and red up-conversion luminescence can be effectively tuned by varying the power or spectral phase of the femtosecond laser field. We further analyze the up-conversion luminescence tuning mechanism by considering different excitation processes, including single-photon absorption(SPA), two-photon absorption(TPA), excited state absorption(ESA), and energy transfer up-conversion(ETU). The relative weight of TPA in the whole excitation process can increase with the increase of the laser power, thereby enhancing the intensity ratio between green and red luminescence(I547/I656). However, the second ETU(ETU2) process can generate red luminescence and reduce the green and red luminescence intensity ratio I547/I656, while the third ESA(ESA3) process can produce green luminescence and enhance its control efficiency. Moreover, the up-conversion luminescence tuning mechanism is further validated by observing the up-conversion luminescence intensity, depending on the laser power and the down-conversion luminescence spectrum under the excitation of 400-nm femtosecond laser pulse. These studies can present a clear physical picture that enables us to understand the up-conversion luminescence tuning mechanism in rare-earth ions, and can also provide an opportunity to tune up-conversion luminescence to promote its related applications.
基金Project supported by the Shandong Provincial Natural Science Foundation,China(Grant No.ZR2020MA078)。
文摘To improve two-photon absorption(TPA)response of a newly synthesized probe,a series of ratiometric two-photon fluorescent Zn^(2+) sensors based on quinoline and DPA moieties have been designed.The one-photon absorption,TPA,and emission properties of the experimental and designed probes before and after coordination with Zn^(2+) are investigated employing the density functional theory in combination with response functions.The design consists of two levels.In the first level of design,five probes are constructed through using several electron acceptors or donors to increase accepting or donating ability of the fluorophores.It shows that all the designed probes have stronger TPA intensities at longer wavelengths with respect to the experimental probe because of the increased intra-molecular charge transfer.Moreover,it is found that the probe 4 built by adding an acyl unit has the largest TPA cross section among the designed structures due to the form of longer conjugated length and more linear backbone.One dimethylamino terminal attached along the skeleton can improve TPA intensity more efficiently than two side amino groups.Therefore,in the second level of design,a new probe 7 is formed by both an acyl unit and a dimethylamino terminal.It exhibits that the TPA cross sections of probe 7 and its zinc complex increase dramatically.Furthermore,the fluorescence quantum yields of the designed probes4 and 7 are calculated in a new way,which makes use of the relation between the computed difference of dipole moment and the measured fluorescence quantum yield.The result shows that our design also improves the fluorescence quantum yield considerably.All in all,the designed probes 4 and 7 not only possess enhanced TPA intensities but also have large differences of emission wavelength upon Zn^(2+) coordination and strong fluorescence intensity,which demonstrates that they are potential ratiometric two-photon fluorescent probes.
基金supported by the National Natural Science Foundation of China(21806048,21801086 and 22071072).
文摘Fluorescent probe is an important tool for investigation of biological events in plant tissues.However,the research on small-molecule based fluorescent probe for plant imaging still stays at the initial stage.In order to noninvasively achieve the subcellular information of Arabidopsis thaliana,a two-photon and fluorene based fluorophore with a bi-oligo(ethylene glycol)functional group was synthesized.Under the laser's irradiation at 750 nm,the subcellular structures of Arabidopsis thaliana including stomata and root tips were clearly observed without slicing,which displayed significant superiorities over traditional single-photon excitation microscopy.Subsequently,the above functionalized fluorophore was further modified with a recognition group(dipicolylamine)to form a smart fluorescent probe(LJTP1).As results,LJTP1 not only can sensitively detect Cu^(2+)/S^(2-)with fluorescence“on-off-on”response in vitro and in vivo,but also can achieve noninvasive imaging in Arabidopsis thaliana tissues under two-photon microscopy.We believe this study will open up a new mind for noninvasive imaging in plant tissues.
基金the State Key Program of China,the National Natural Science Foundation of China(50173015)NSFC/RGC(50218001)+1 种基金the Foundation for University Key Teacher by the Ministry of EducationChina Postdoctoral Foundation.
文摘A non-polar organic dye, E, E-1, 4-bis[4＇-（N,N-dibutylamino）styryl]-2,5-dimethoxybenzene （DBASDMB）, has been synthesized and characterized, and its structure has been determined. Pumped with a 200fs pulse this dye showed the up-conversion laser properties. The influences of various organic solvents and different pumping wavelength on the laser properties have been demonstrated.
基金the Natural Science Foundation of Shandong Province,China(Grant No.ZR2014AM026).
文摘The properties of one-photon absorption(OPA),emission and two-photon absorption(TPA)of a bipyridine-based zinc ion probe are investigated employing the density functional theory in combination with response functions.The responsive mechanism and coordination mode effect are explored.The structural fluctuation is illustrated by molecular dynamics simulation.The calculated OPA and emission wavelengths of the probe are consistent with the experimental data.It is found that the red-shift of OPA wavelength and the enhancement of TPA intensity are induced by the increased intra-molecular charge transfer mechanism upon metal binding.The structural fluctuation could result in the blue-shift of TPA wavelength and the decrease of the TPA cross section.The TPA properties are quite different among the zinc complexes with different coordination modes.The TPA wavelength of the complexes with two ligands is close to that of the probe,which is in agreement with the experimental observation.
