The excited state dynamics and critically regulated factors of reverse intersystem crossing(RISC)in through-space charge transfer(TSCT)molecules have received insufficient attention.Here,five molecules of through spac...The excited state dynamics and critically regulated factors of reverse intersystem crossing(RISC)in through-space charge transfer(TSCT)molecules have received insufficient attention.Here,five molecules of through space/bond charge transfer inducing thermally activated delayed fluorescence(TADF)are prepared,and their excited state charge transfer processes are studied by ultrafast transient absorption and theoretical calculations.DM-Z has a largerΔEST,leading to a longer lifetime of intersystem crossing(ISC),resulting in the lowest photoluminescence quantum yield(PLQY).Oppositely,ISC and RISC are demonstrated to take place with shorter lifetimes for TSCT molecules.The face-to-faceπ-πstacking interactions and electron communication enable DM-B and DM-BX to have an efficient RISC,increasing the weight coefficient of RISC from 1.7%(DM-X)to close to 50%(DM-B and DM-BX)in the solvents,which make DM-BX and DM-B to have a high PLQY.However,partial local excitation in the donor center is observed and the charge transfer is decreased for DM-G and DM-X.The triplet excited state(DM-G)or singlet excited state(DM-X)mainly undergoes inactivation through a non-radiative relaxation process,resulting in less RISC and low PLQY.This work provides theoretical hints to enhance the RISC process in the TADF materials.展开更多
First-principles calculations are applied for investigating influence of electron donating ability of donor groups in eight thermally activated delayed fluorescence（TADF） molecules on their geometrical structures an...First-principles calculations are applied for investigating influence of electron donating ability of donor groups in eight thermally activated delayed fluorescence（TADF） molecules on their geometrical structures and transition properties as well as reverse intersystem crossing（RISC） processes. Results show that the diphenylamine substitution in the donor part can slightly change the bond angle but decrease bond length between donor and acceptor unit except for the lowest triplet state（Ti） of carbazole-xanthone molecule. As the electron donating ability of donor groups is increased, the overlap between the highest occupied molecular orbital（HOMO） and the lowest unoccupied molecular orbital（LUMO） is decreased. As the diphenylamine groups are added in donor part, the delocalization of HOMO is enlarged,which brings a decreased energy gap(△ES1-T1) between the lowest singlet excited state（S1）and T1 state. Furthermore, with the calculated spin-orbit coupling coefficient(HSO), one finds that the larger value of ■ is, the faster the RISC is. The results show that all investigated molecules are promising candidates as TADF molecules. Overall, a wise molecular design strategy for TADF molecules,in which a small △ES1-T1 can be achieved by enlarging the delocalization of frontier molecular orbitals with large separation between HOMO and LUMO, is proposed.展开更多
Recently, an effective exciton diffusion length L exceeding 100μm has been reported for organic- inorganic halide perovskites owing to both the high mobility and ultra-long lifetime of the excitons; however, the orig...Recently, an effective exciton diffusion length L exceeding 100μm has been reported for organic- inorganic halide perovskites owing to both the high mobility and ultra-long lifetime of the excitons; however, the origin of ultra-long L is still unclear in nature. In some photoelectric materials, reverse intersystem crossing （RISC） from the triplet to the singlet state can enhance the quantum yield of pho- toluminescence greatly. In this study, our theoretical investigation indicated that the energy difference △E_st between the singlet state and the triplet state of CH_3NH_3Pbl_3 was less than 0.1 eV, which represents one crucial prerequisite for the occurrence of RISC. Meanwhile, the experimental results showed that the photoluminescence lifetime increased with the increasing temperature, a typical feature of RISC. Based on this study, we put forward the hypothesis that the ultra-long lifetime of excitons in organic-inorganic halide perovskite might be caused by the RISC process. This may provide a new insight into the important photophysical properties of such novel photovoltaic materials.展开更多
2016年11月8日,近日,医疗信息技术领域全球领导者Inter Systems与荣科科技股份有限公司正式签署战略合作伙伴协议。双方将共享先进技术、本土经验与市场资源,基于Inter Systems Health Share互联互通解决方案进行开发,联合打造智慧工作...2016年11月8日,近日,医疗信息技术领域全球领导者Inter Systems与荣科科技股份有限公司正式签署战略合作伙伴协议。双方将共享先进技术、本土经验与市场资源,基于Inter Systems Health Share互联互通解决方案进行开发,联合打造智慧工作流程、标准化及可共享的医疗信息、临床数据中心等多种集成的、互联互通的医疗应用,满足中国医疗机构对全面医疗信息化的需求,帮助中国医疗机构优化业务流程、提升医疗效率、改进医疗服务质量。展开更多
Circularly polarized luminescence(CPL)materials with delayed fluorescence have attracted much attention due to their ability to efficiently trap triplet state excitons,thereby improving the photoluminescence quantum y...Circularly polarized luminescence(CPL)materials with delayed fluorescence have attracted much attention due to their ability to efficiently trap triplet state excitons,thereby improving the photoluminescence quantum yields of CPL materials.However,much effort has been normally focused on the utilization of T1 excitons but seldom on the utilization of higher excited triplet state T_(n)(n>1)excitons.Rational manipulation of higher excited triplet state T_(n)(n>1)excitons and suppression of Kasha’s rule of CPL materials remains a major challenge.Herein,two gold complex enantiomers((R/S)-BPAuBC)based on axially chiral binaphthyls and 3,6-Di-tert-butylcarbazole groups are synthesized and systematically investigated.These materials exhibit aggregation-induced circularly polarized delayed fluorescence.Circularly polarized delayed fluorescence was found to be enabled by activating high-level reverse intersystem crossing(hRISC).The anti-Kasha phosphorescence at 77 K proves that the exciton has a large population in the high-lying triplet state T_(2),which allows the effective hRISC process to cross back to the singlet state S_(1)and emit delayed fluorescence.In addition,CPL“on-off”switching is further achieved in nanoparticles by acid-base stimulus,showing its potential as an acid-base responsive material.展开更多
Organic scintillators that efficiently generate bright triplet excitons are of critical importance for highperformance X-ray-excited luminescence in radiation detection.However,the nature of triplet-singlet spinforbid...Organic scintillators that efficiently generate bright triplet excitons are of critical importance for highperformance X-ray-excited luminescence in radiation detection.However,the nature of triplet-singlet spinforbidden transitions in these materials often result in long-lived phosphorescence,which is undesirable for ultrafast X-ray detection and imaging.Here we demonstrate that the effect of hybridized local and charge-transfer(HLCT)excited states enables organic scintillators to exhibit highly efficient and fast radioluminescence(RL)in response to X-ray irradiation.Our experimental and theoretical investigation shows that the oxidized 1,8-naphthalimide-phenothiazine dyad(OMNI-PTZ 2)with HLCT-excited states has an enhanced overlap integral of the highest occupied molecular orbital(HOMO)and lowest unoccupied molecular orbital(LUMO)on MNIπ-orbitals,and moderate donor–acceptor electron interactions.As a result,the RL of these crystals exhibits a 61-fold increase and its monoexponential decay lifetime is three orders of magnitude faster compared to its corresponding thermally activated delayed fluorescence(TADF)molecule MNI-PTZ 1.We further demonstrate the practical utility of the OMNI-PTZ 2(G)in high-performance X-ray detection and imaging,achieving an X-ray dose sensitivity of 97 nGy s−1 and an exceptional spatial resolution of 20 lp/mm.Our study provides a promising molecular design principle for utilizing triplet excitons to develop high-efficiency and fast X-ray scintillators for the development of next-generation flexible and stretchable X-ray imaging detectors.展开更多
The global navigation satellite system(GNSS) has become an important space infrastructure. Following GPS and GLONASS, Europe and China have been building their own global navigation satellite system, respectively, GAL...The global navigation satellite system(GNSS) has become an important space infrastructure. Following GPS and GLONASS, Europe and China have been building their own global navigation satellite system, respectively, GALILEO and Compass. In order to consolidate the leadership of GPS in the globe, United States is gradually upgrading the traditional GPS. Simultaneously, Russia is also intensively restoring full performance of GLONASS. With the advancement of international satellite navigation system, satellite navigation frequency resources are already in short supply, and the design and use of the navigation signals are more sophisticated and complex due to commercial, disaster relief and other reasons. Since there may be many navigation signals in the same basic bandwidth, the coexistence of multiple systems and the combined application make intersystem mutual interference become the focus research. Under this background, the satellite navigation system mutual interference evaluation system needs to be established urgently to meet and support the compatibility and interoperability of the GNSS system. In the paper, through the performance analysis of the GNSS signal acquisition, carrier tracking, data demodulation and code tracking, the equivalent carrier to noise ratio model based on spectrum isolation coefficient is established, and the theoretical system of the GNSS signal mutual interference is proposed according to the mechanism, and the mutual interference of GPS, GALILEO and Compass system is analyzed and assessed.展开更多
The intersystem crossing channels of gaseous 4H-pyran-4-thione were investigated using the CASSCF//TD-B3LYP methods and group theory. Using the effective one-electron spin-orbit Harniltonian, the strengths of spin-orb...The intersystem crossing channels of gaseous 4H-pyran-4-thione were investigated using the CASSCF//TD-B3LYP methods and group theory. Using the effective one-electron spin-orbit Harniltonian, the strengths of spin-orbit coupling were estimated, which plays an essential role in the spin transitions between different spin states. Calculated results show that phosphorescence and non-radiative decay via intersystem crossing to the So state are concurrent processes occurring at the T1 state. A rapid depletion of the S1 state via intersystem crossing to the T1 state can be mediated by the T2 state, if spin relaxation is fast within the triplet levels. Our calculated results are in close agreement with experimental observations.展开更多
Development of new photosensitizers(PSs)with high singlet oxygen quantumyield and minimal side effects is of great interest in photodynamic therapy(PDT).Herein,a facile strategy to significantly improve photosensitiza...Development of new photosensitizers(PSs)with high singlet oxygen quantumyield and minimal side effects is of great interest in photodynamic therapy(PDT).Herein,a facile strategy to significantly improve photosensitization has been demonstrated for the first time with two pentamethine dyes connected by a varying alkyl chain resulting in a series of cyanine dimers.The photophysical properties of the dimerswere studied with steady-state optical spectroscopies,a timecorrelated single photon counting technique,and laser flash photolysis spectrometry.X-ray crystallography confirmed that the molecular packing modes of Cy-Bu-D and Cy-He-D were dominated by H-aggregation.The H-aggregation by dimerization suppresses the radiative singlet decay,which helps to stabilize the highly efficient triplet excitation state.Moreover,the dimers show more intensewavelength absorption in the nearinfrared(ɛ1.5-2.0 times more than monomer Cy-H at 650 nm),better singlet oxygen quantum yield,and a longer triplet-state lifetime than monomer Cy-H,providing excellent performance as a triplet PS.In vivo experiments demonstrated that Cy-He-D successfully suppresses tumor growth after PDT treatment.This work is beneficial to the design of novel heavy atom free PSs for PDT-based theranostic systems.展开更多
We report for the first time a practical and simple supramolecular approach to turn fluorophores into photosensitizers(PSs).Using boron dipyrromethene(BODIPY)as a proof-of-concept,eight BODIPY derivatives manifest bri...We report for the first time a practical and simple supramolecular approach to turn fluorophores into photosensitizers(PSs).Using boron dipyrromethene(BODIPY)as a proof-of-concept,eight BODIPY derivatives manifest bright fluorescence and generate negligible singlet oxygen in solution.In contrast,aggregation fails to emit fluorescence and enhances singlet oxygen generation.Experimentally,these aggregates have excellent photodynamic therapy(PDT)performance,and one even exhibits much stronger photocytotoxicity than the commercialized PS Ce6 under identical conditions.Theoretical studies show that this property originated from significantly reduced energy gaps between relevant excited singlet and triplet states,leading to considerably improved intersystem-crossing efficiency.Importantly,a simple disaggregation recovers the original properties of the fluorophores.This reversible switching property between fluorophores and PSs assists the development of smart PDT systems,in which singlet oxygen generation in tumors can be controlled in an intelligent manner after PDT treatment.The present work provides a novel strategy to design heavy-atom-free PSs and may pave the way to the development of smart PDT systems.展开更多
A general formula for the multi-dimensional Monte Carlo microcanonical nonadiabatic rate constant expressed in configuration space is applied to calculate the rate of intersystem crossing(ISC) between the ground(S0) a...A general formula for the multi-dimensional Monte Carlo microcanonical nonadiabatic rate constant expressed in configuration space is applied to calculate the rate of intersystem crossing(ISC) between the ground(S0) and first excited triplet(T1) states for isocyanic acid.One-,two-and three-dimensional potential energy surfaces are constructed by coupled-cluster single-double CCSD calculations,which are used for Monte Carlo sampling.The calculated S0→T1 ISC rate is in good agreement with experimental findings,which gives us a reason to believe that the multi-dimensional Monte Carlo microcanonical nonadiabatic rate theory is a very effective method for calculating nonadiabatic transition rate of a polyatomic molecule.展开更多
Clinical phototheranostic agents suffer from low absorption in near-infrared(NIR)region,decreasing singlet oxygen quantum yield(^(1)O_(2)QY)caused by aggregation in water,and low photothermal conversion efficiency(PCE...Clinical phototheranostic agents suffer from low absorption in near-infrared(NIR)region,decreasing singlet oxygen quantum yield(^(1)O_(2)QY)caused by aggregation in water,and low photothermal conversion efficiency(PCE),all of which are factors weakening their phototheranostic efficacy.Herein,we designed and synthesized a donor-acceptor-donor(D-A-D)structured boron-dipyrromethene derivative(B-2TPA)which exhibited NIR absorption and fluorescence.After being encapsulated in amphiphilic distearoyl phosphoethanolamine polyethyleneglycol 2000(DSPE-PEG-2000),the water-soluble B-2TPA nanoparticles(NPs)had increasing^(1)O_(2)QY(6.7%)due to the intermolecular aggregation-induced decrease in the energy gap between singlet and triplet excited states.Moreover,the quenched fluorescence and stable twisted intramolecular charge transfer in aggregates further increased the PCE of B-2TPA NPs to 60.1%.In vitro and in vivo studies confirmed that B-2TPA NPs could be used in NIR fluorescence and photoacoustic imagingguided synergistic photodynamic and photothermal therapy in tumor treatment.展开更多
Efficient yield of^(1)O_(2)determines the photocatalytic degradation rate of antibiotics,but the regulatory mechanism for^(1)O_(2)selective generation in O_(2)activation is still lacking exploration.Herein,oxygen vaca...Efficient yield of^(1)O_(2)determines the photocatalytic degradation rate of antibiotics,but the regulatory mechanism for^(1)O_(2)selective generation in O_(2)activation is still lacking exploration.Herein,oxygen vacancy(OV)modification strategy of MIL-125 was successfully practiced to promote the selective generation of^(1)O_(2).Multiple characterizations including extended X-ray absorption fine structure(EXAFS)and electron paramagnetic resonance spectra(EPR)confirmed the formation of oxygen vacancy in OV-MIL-125.The synthesized OV-MIL-125 exhibited greatly enhanced^(1)O_(2)selective(~90%)and antibiotics removal rate in water with high mineralization rate.Dynamics analysis of excitons by transient-steady state fluorescence and phosphorescence,transient absorption spectra(TAS)revealed that oxygen vacancy greatly enhanced the intersystem crossing(ISC)of singlet exciton,promoting triplet exciton generation.Density functional theoretical(DFT)calculation also proved the reduced gap of intersystem(ΔE_(ST))and the modulated highest occupied molecular orbital(HOMO)-lowest unoccupied molecular orbital(LUMO)population which was conducive to intersystem crossing process.Calculation of transition state further confirmed the lower energy barrier forπ^(*)orbital spin flip of O_(2)adsorbed on OV-MIL-125.The Dexter energy transfer involving triplet annihilation dominated the O_(2)activation mechanism to generate^(1)O_(2)instead of the charge transfer to generate O_(2)^(·-)which happened in MIL-125.This study provides new thinking for photocatalytic activation of molecular oxygen and is expected to guide the design of MOF-based catalysts for water treatment.展开更多
基金supported by the National Natural Science Foundation of China(No.22273057)the Universities Joint Laboratory of Guangdong,Hong Kong and Macao(No.2021LSYS009)+2 种基金the Natural Science Foundation of Guangdong Province(Nos.2022A1515011661,2023A1515012631)the Chemistry and Chemical Engineering Guangdong Laboratory(No.1922003)Guangdong Major Project of Basic and Applied Basic Research(No.2019B030302009)。
文摘The excited state dynamics and critically regulated factors of reverse intersystem crossing(RISC)in through-space charge transfer(TSCT)molecules have received insufficient attention.Here,five molecules of through space/bond charge transfer inducing thermally activated delayed fluorescence(TADF)are prepared,and their excited state charge transfer processes are studied by ultrafast transient absorption and theoretical calculations.DM-Z has a largerΔEST,leading to a longer lifetime of intersystem crossing(ISC),resulting in the lowest photoluminescence quantum yield(PLQY).Oppositely,ISC and RISC are demonstrated to take place with shorter lifetimes for TSCT molecules.The face-to-faceπ-πstacking interactions and electron communication enable DM-B and DM-BX to have an efficient RISC,increasing the weight coefficient of RISC from 1.7%(DM-X)to close to 50%(DM-B and DM-BX)in the solvents,which make DM-BX and DM-B to have a high PLQY.However,partial local excitation in the donor center is observed and the charge transfer is decreased for DM-G and DM-X.The triplet excited state(DM-G)or singlet excited state(DM-X)mainly undergoes inactivation through a non-radiative relaxation process,resulting in less RISC and low PLQY.This work provides theoretical hints to enhance the RISC process in the TADF materials.
基金This work was supported by the National Natural Science Foundation of China(No.11374195 and No.21403133),the Taishan Scholar Project of Shandong Province,the Promotive Research Fund for Excellent Young and Middle-aged Scientists of Shandong Province(No.BS2014CL001),and the General Financial Grant from the China Postdoctoral Science Foundation(No.2014M560571).
文摘First-principles calculations are applied for investigating influence of electron donating ability of donor groups in eight thermally activated delayed fluorescence（TADF） molecules on their geometrical structures and transition properties as well as reverse intersystem crossing（RISC） processes. Results show that the diphenylamine substitution in the donor part can slightly change the bond angle but decrease bond length between donor and acceptor unit except for the lowest triplet state（Ti） of carbazole-xanthone molecule. As the electron donating ability of donor groups is increased, the overlap between the highest occupied molecular orbital（HOMO） and the lowest unoccupied molecular orbital（LUMO） is decreased. As the diphenylamine groups are added in donor part, the delocalization of HOMO is enlarged,which brings a decreased energy gap(△ES1-T1) between the lowest singlet excited state（S1）and T1 state. Furthermore, with the calculated spin-orbit coupling coefficient(HSO), one finds that the larger value of ■ is, the faster the RISC is. The results show that all investigated molecules are promising candidates as TADF molecules. Overall, a wise molecular design strategy for TADF molecules,in which a small △ES1-T1 can be achieved by enlarging the delocalization of frontier molecular orbitals with large separation between HOMO and LUMO, is proposed.
基金The financial supports of the National Natural Science Foundation of China (grant nos. 21373042, 21677029 and 51402036)the Fundamental Research Funds for the Central Universities (grant no. DUT15YQ109)
文摘Recently, an effective exciton diffusion length L exceeding 100μm has been reported for organic- inorganic halide perovskites owing to both the high mobility and ultra-long lifetime of the excitons; however, the origin of ultra-long L is still unclear in nature. In some photoelectric materials, reverse intersystem crossing （RISC） from the triplet to the singlet state can enhance the quantum yield of pho- toluminescence greatly. In this study, our theoretical investigation indicated that the energy difference △E_st between the singlet state and the triplet state of CH_3NH_3Pbl_3 was less than 0.1 eV, which represents one crucial prerequisite for the occurrence of RISC. Meanwhile, the experimental results showed that the photoluminescence lifetime increased with the increasing temperature, a typical feature of RISC. Based on this study, we put forward the hypothesis that the ultra-long lifetime of excitons in organic-inorganic halide perovskite might be caused by the RISC process. This may provide a new insight into the important photophysical properties of such novel photovoltaic materials.
文摘2016年11月8日,近日,医疗信息技术领域全球领导者Inter Systems与荣科科技股份有限公司正式签署战略合作伙伴协议。双方将共享先进技术、本土经验与市场资源,基于Inter Systems Health Share互联互通解决方案进行开发,联合打造智慧工作流程、标准化及可共享的医疗信息、临床数据中心等多种集成的、互联互通的医疗应用,满足中国医疗机构对全面医疗信息化的需求,帮助中国医疗机构优化业务流程、提升医疗效率、改进医疗服务质量。
基金support from the National Natural Science Foundation of China(52003298)the Natural Science Foundation of Jiangsu Province(BK20200578)+4 种基金funding from the Beijing University of Technology(049000513202 and 049000514123564)support of the Research Grants Council of Hong Kong(C6014-20W)the Innovation and Technology Commission(ITC-CNERC14SC01)Shenzhen Key Laboratory of Functional Aggregate Materials(ZDSYS20211021111400001)the Science Technology Innovation Commission of Shenzhen Municipality(KQTD20210811090142053 and JCYJ2022081810-3007014).
文摘Circularly polarized luminescence(CPL)materials with delayed fluorescence have attracted much attention due to their ability to efficiently trap triplet state excitons,thereby improving the photoluminescence quantum yields of CPL materials.However,much effort has been normally focused on the utilization of T1 excitons but seldom on the utilization of higher excited triplet state T_(n)(n>1)excitons.Rational manipulation of higher excited triplet state T_(n)(n>1)excitons and suppression of Kasha’s rule of CPL materials remains a major challenge.Herein,two gold complex enantiomers((R/S)-BPAuBC)based on axially chiral binaphthyls and 3,6-Di-tert-butylcarbazole groups are synthesized and systematically investigated.These materials exhibit aggregation-induced circularly polarized delayed fluorescence.Circularly polarized delayed fluorescence was found to be enabled by activating high-level reverse intersystem crossing(hRISC).The anti-Kasha phosphorescence at 77 K proves that the exciton has a large population in the high-lying triplet state T_(2),which allows the effective hRISC process to cross back to the singlet state S_(1)and emit delayed fluorescence.In addition,CPL“on-off”switching is further achieved in nanoparticles by acid-base stimulus,showing its potential as an acid-base responsive material.
基金supported by the National Key R&D Program of China(grant no.2020YFA0709900)the National Natural Science Foundation of China(grant nos.21971041,22201042,22027805,62134003,and 22104016)+2 种基金the Natural Science Foundation of Fujian Province(grant nos.2020J01447,2022J06008,and 2022J0121)the Research Foundation of Education Bureau of Fujian Province(grant no.JAT210001)the Fuzhou University Testing Fund of Precious Apparatus(grant no.2022T001).
文摘Organic scintillators that efficiently generate bright triplet excitons are of critical importance for highperformance X-ray-excited luminescence in radiation detection.However,the nature of triplet-singlet spinforbidden transitions in these materials often result in long-lived phosphorescence,which is undesirable for ultrafast X-ray detection and imaging.Here we demonstrate that the effect of hybridized local and charge-transfer(HLCT)excited states enables organic scintillators to exhibit highly efficient and fast radioluminescence(RL)in response to X-ray irradiation.Our experimental and theoretical investigation shows that the oxidized 1,8-naphthalimide-phenothiazine dyad(OMNI-PTZ 2)with HLCT-excited states has an enhanced overlap integral of the highest occupied molecular orbital(HOMO)and lowest unoccupied molecular orbital(LUMO)on MNIπ-orbitals,and moderate donor–acceptor electron interactions.As a result,the RL of these crystals exhibits a 61-fold increase and its monoexponential decay lifetime is three orders of magnitude faster compared to its corresponding thermally activated delayed fluorescence(TADF)molecule MNI-PTZ 1.We further demonstrate the practical utility of the OMNI-PTZ 2(G)in high-performance X-ray detection and imaging,achieving an X-ray dose sensitivity of 97 nGy s−1 and an exceptional spatial resolution of 20 lp/mm.Our study provides a promising molecular design principle for utilizing triplet excitons to develop high-efficiency and fast X-ray scintillators for the development of next-generation flexible and stretchable X-ray imaging detectors.
基金supported by the National Natural Science Foundation of China(Grant No.61203226)
文摘The global navigation satellite system(GNSS) has become an important space infrastructure. Following GPS and GLONASS, Europe and China have been building their own global navigation satellite system, respectively, GALILEO and Compass. In order to consolidate the leadership of GPS in the globe, United States is gradually upgrading the traditional GPS. Simultaneously, Russia is also intensively restoring full performance of GLONASS. With the advancement of international satellite navigation system, satellite navigation frequency resources are already in short supply, and the design and use of the navigation signals are more sophisticated and complex due to commercial, disaster relief and other reasons. Since there may be many navigation signals in the same basic bandwidth, the coexistence of multiple systems and the combined application make intersystem mutual interference become the focus research. Under this background, the satellite navigation system mutual interference evaluation system needs to be established urgently to meet and support the compatibility and interoperability of the GNSS system. In the paper, through the performance analysis of the GNSS signal acquisition, carrier tracking, data demodulation and code tracking, the equivalent carrier to noise ratio model based on spectrum isolation coefficient is established, and the theoretical system of the GNSS signal mutual interference is proposed according to the mechanism, and the mutual interference of GPS, GALILEO and Compass system is analyzed and assessed.
文摘The intersystem crossing channels of gaseous 4H-pyran-4-thione were investigated using the CASSCF//TD-B3LYP methods and group theory. Using the effective one-electron spin-orbit Harniltonian, the strengths of spin-orbit coupling were estimated, which plays an essential role in the spin transitions between different spin states. Calculated results show that phosphorescence and non-radiative decay via intersystem crossing to the So state are concurrent processes occurring at the T1 state. A rapid depletion of the S1 state via intersystem crossing to the T1 state can be mediated by the T2 state, if spin relaxation is fast within the triplet levels. Our calculated results are in close agreement with experimental observations.
基金This work was supported by National Natural Science Foundation of China(project 22090011)NSFCLiaoning United Fund(U1908202).
文摘Development of new photosensitizers(PSs)with high singlet oxygen quantumyield and minimal side effects is of great interest in photodynamic therapy(PDT).Herein,a facile strategy to significantly improve photosensitization has been demonstrated for the first time with two pentamethine dyes connected by a varying alkyl chain resulting in a series of cyanine dimers.The photophysical properties of the dimerswere studied with steady-state optical spectroscopies,a timecorrelated single photon counting technique,and laser flash photolysis spectrometry.X-ray crystallography confirmed that the molecular packing modes of Cy-Bu-D and Cy-He-D were dominated by H-aggregation.The H-aggregation by dimerization suppresses the radiative singlet decay,which helps to stabilize the highly efficient triplet excitation state.Moreover,the dimers show more intensewavelength absorption in the nearinfrared(ɛ1.5-2.0 times more than monomer Cy-H at 650 nm),better singlet oxygen quantum yield,and a longer triplet-state lifetime than monomer Cy-H,providing excellent performance as a triplet PS.In vivo experiments demonstrated that Cy-He-D successfully suppresses tumor growth after PDT treatment.This work is beneficial to the design of novel heavy atom free PSs for PDT-based theranostic systems.
基金This research was made possible as a result of generous grants from the National Natural Science Foundation of China(nos.22177014,21971023,21688102 and 21525206).
文摘We report for the first time a practical and simple supramolecular approach to turn fluorophores into photosensitizers(PSs).Using boron dipyrromethene(BODIPY)as a proof-of-concept,eight BODIPY derivatives manifest bright fluorescence and generate negligible singlet oxygen in solution.In contrast,aggregation fails to emit fluorescence and enhances singlet oxygen generation.Experimentally,these aggregates have excellent photodynamic therapy(PDT)performance,and one even exhibits much stronger photocytotoxicity than the commercialized PS Ce6 under identical conditions.Theoretical studies show that this property originated from significantly reduced energy gaps between relevant excited singlet and triplet states,leading to considerably improved intersystem-crossing efficiency.Importantly,a simple disaggregation recovers the original properties of the fluorophores.This reversible switching property between fluorophores and PSs assists the development of smart PDT systems,in which singlet oxygen generation in tumors can be controlled in an intelligent manner after PDT treatment.The present work provides a novel strategy to design heavy-atom-free PSs and may pave the way to the development of smart PDT systems.
基金Supported by the National Natural Science Foundation of China (Grant No. 20720102038)
文摘A general formula for the multi-dimensional Monte Carlo microcanonical nonadiabatic rate constant expressed in configuration space is applied to calculate the rate of intersystem crossing(ISC) between the ground(S0) and first excited triplet(T1) states for isocyanic acid.One-,two-and three-dimensional potential energy surfaces are constructed by coupled-cluster single-double CCSD calculations,which are used for Monte Carlo sampling.The calculated S0→T1 ISC rate is in good agreement with experimental findings,which gives us a reason to believe that the multi-dimensional Monte Carlo microcanonical nonadiabatic rate theory is a very effective method for calculating nonadiabatic transition rate of a polyatomic molecule.
基金supported by National Key Research and Development Program of China(No.2022YFA1207600)National Natural Science Foundation of China(Nos.62175262,62375289)+2 种基金The Science and Technology Innovation Program of Hunan Province(No.2022RC1201)The Climb Plan of Hunan Cancer Hospital(No.ZX2021005)The Hunan Provincial Natural Science Foundation of China(No.2023JJ60464)。
文摘Clinical phototheranostic agents suffer from low absorption in near-infrared(NIR)region,decreasing singlet oxygen quantum yield(^(1)O_(2)QY)caused by aggregation in water,and low photothermal conversion efficiency(PCE),all of which are factors weakening their phototheranostic efficacy.Herein,we designed and synthesized a donor-acceptor-donor(D-A-D)structured boron-dipyrromethene derivative(B-2TPA)which exhibited NIR absorption and fluorescence.After being encapsulated in amphiphilic distearoyl phosphoethanolamine polyethyleneglycol 2000(DSPE-PEG-2000),the water-soluble B-2TPA nanoparticles(NPs)had increasing^(1)O_(2)QY(6.7%)due to the intermolecular aggregation-induced decrease in the energy gap between singlet and triplet excited states.Moreover,the quenched fluorescence and stable twisted intramolecular charge transfer in aggregates further increased the PCE of B-2TPA NPs to 60.1%.In vitro and in vivo studies confirmed that B-2TPA NPs could be used in NIR fluorescence and photoacoustic imagingguided synergistic photodynamic and photothermal therapy in tumor treatment.
基金supported by the National Natural Science Foundation of China(Nos.22276086 and 21976078)the Natural Science Foundation of Jiangxi Province(Nos.20202ACB213001 and20232BAB213029)。
文摘Efficient yield of^(1)O_(2)determines the photocatalytic degradation rate of antibiotics,but the regulatory mechanism for^(1)O_(2)selective generation in O_(2)activation is still lacking exploration.Herein,oxygen vacancy(OV)modification strategy of MIL-125 was successfully practiced to promote the selective generation of^(1)O_(2).Multiple characterizations including extended X-ray absorption fine structure(EXAFS)and electron paramagnetic resonance spectra(EPR)confirmed the formation of oxygen vacancy in OV-MIL-125.The synthesized OV-MIL-125 exhibited greatly enhanced^(1)O_(2)selective(~90%)and antibiotics removal rate in water with high mineralization rate.Dynamics analysis of excitons by transient-steady state fluorescence and phosphorescence,transient absorption spectra(TAS)revealed that oxygen vacancy greatly enhanced the intersystem crossing(ISC)of singlet exciton,promoting triplet exciton generation.Density functional theoretical(DFT)calculation also proved the reduced gap of intersystem(ΔE_(ST))and the modulated highest occupied molecular orbital(HOMO)-lowest unoccupied molecular orbital(LUMO)population which was conducive to intersystem crossing process.Calculation of transition state further confirmed the lower energy barrier forπ^(*)orbital spin flip of O_(2)adsorbed on OV-MIL-125.The Dexter energy transfer involving triplet annihilation dominated the O_(2)activation mechanism to generate^(1)O_(2)instead of the charge transfer to generate O_(2)^(·-)which happened in MIL-125.This study provides new thinking for photocatalytic activation of molecular oxygen and is expected to guide the design of MOF-based catalysts for water treatment.
