Fisetin attracts intense attention not only due to its antioxidant and anticancer properties but also be-cause of wide applications in fluo-rescence probes and sensors,which are based on the dual fluorescence induced ...Fisetin attracts intense attention not only due to its antioxidant and anticancer properties but also be-cause of wide applications in fluo-rescence probes and sensors,which are based on the dual fluorescence induced by excited-state proton transfer(ESPT).However,to date,its ESPT dynamics remains unknown yet.In this study,we give a comprehensive investiga-tion on ESPT dynamics of fisetin in both protic methanol and aprot-ic acetonitrile by using femtosecond transient absorption spectroscopy combined with time-dependent density functional theory calculations.In acetonitrile,the ESPT time constant of fisetin is 1.2 ps.In methanol,two distinct intermolecular hydrogen bonding configurations contribute to a fast(<90 fs)and slow ESPT(11.1 ps),respectively.The slow ESPT in methanol explains the higher emission intensity of normal species than in acetonitrile.The ex-cited-state relaxation of fisetin involves two main vibrational modes:rotation between B and C rings and butterfly-like motion of C ring.Our results give insight into the effect of solvent-solute hydrogen bonding interaction on the dual fluorescence,providing a fundamental guide-line for the development of fluorescent probes and sensors based on ESPT.展开更多
The heavy-atom effect of halogen(Br and I)has been widely employed for boosting spin-crossover in organic molecules,while recent investigation indicated halogen-substitution can also enhance fluorescence and even lead...The heavy-atom effect of halogen(Br and I)has been widely employed for boosting spin-crossover in organic molecules,while recent investigation indicated halogen-substitution can also enhance fluorescence and even lead to aggregation-induced emission(AIE).In this work,we investigated ultrafast excited state dynamics of a halogen-substituted model system,i.e.squaryliums NSQ-R(R=H,Cl,Br,I),by using femtosecond spectroscopy and theoretical approach.Fast external reorganization(Ex-re,~3 ps)and slow internal reorganization(In-re,5-20 ps)were observed,while quantitative fitting indicated halogen-substitution leads to a slower non-radiative S1→S0 decay(k_(NR)^(s))and subsequently enhanced fluorescence emitting.By analyzing the extracted k_(NR)^(s)within theoretical framework of non-radiative transition in the strong coupling regime,a plausible AIE mechanism of NSQs was revealed.Our work provides a clear picture on non-radiative dynamics of halogen-substituted squaryliums,which might be useful for future development of organic dyes.展开更多
A correlation equation between the UV absorption wavenumbers of 1,4-disubstituted benzenes and the excited-state substituent constant was obtained. For 80 sorts of 1,4- disubstituted benzenes, the correlation coeffici...A correlation equation between the UV absorption wavenumbers of 1,4-disubstituted benzenes and the excited-state substituent constant was obtained. For 80 sorts of 1,4- disubstituted benzenes, the correlation coefficient was 0.9805, and the standard deviation was only 672.27 cm^-1. The results imply that the excited-state substituent constant can be used productively for research on UV energy of 1,4-disubstituted benzenes. The present method provides a new avenue to study the UV absorption spectra of aromatic systems with the excited-state substituent constant, and it is helpful to understand the effect of substituent electrostatic effects on the chemical and physical properties of conjugated compounds with multiple substituents in excited state.展开更多
Using DFT/TDDFT methods,the excited-state lifetimes of Ru（Ⅱ） polypyridyl complexes were computed accurately and the reason of Ru（Ⅱ） polypyridyl complexes with long excited-state lifetimes was explained by the el...Using DFT/TDDFT methods,the excited-state lifetimes of Ru（Ⅱ） polypyridyl complexes were computed accurately and the reason of Ru（Ⅱ） polypyridyl complexes with long excited-state lifetimes was explained by the electron-transfer distances and HOMO-LUMO gaps.Finally,the photovoltaic conversion efficiencies of complexes were predicted using DFT and docking methods.This work has provided methods of predicting the excited-state lifetimes and photovoltaic conversion efficiencies of Ru（Ⅱ） polypyridyl complexes.展开更多
Intracellular pH is a key parameter related to various biological and pathological processes.In this study,a ratiometric pH fluorescent sensor ABTT was developed harnessing the amino-type excited-state intramolecular ...Intracellular pH is a key parameter related to various biological and pathological processes.In this study,a ratiometric pH fluorescent sensor ABTT was developed harnessing the amino-type excited-state intramolecular proton transfer(ESIPT) process.Relying on whether the ESIPT proceeds normally or not,ABTT exhibited the yellow fluorescence in acidic media,or cyan fluorescence in basic condition.According to the variation,ABTT behaved as a promising sensor which possessed fast and reversible response to pH change without interference from the biological substances,and exported a steady ratiometric signal(I_(478)/I_(546)).Moreover,due to the ESIPT effect,large Stokes shift and high quantum yield were also exhibited in ABTT.Furthermore,ABTT was applied for monitoring the pH changes in living cells and visualizing the pH fluctuations under oxidative stress successfully.These results elucidated great potential of ABTT in understanding pH-dependent physiological and pathological processes.展开更多
Understanding the excited state dynamics of donor-acceptor(D-A)complexes is of fundamental importance both experimentally and theoretically.Herein,we have first explored the photoinduced dynamics of a recently synthes...Understanding the excited state dynamics of donor-acceptor(D-A)complexes is of fundamental importance both experimentally and theoretically.Herein,we have first explored the photoinduced dynamics of a recently synthesized paddle-wheel BODIPY-hexaoxatriphenylene(BODIPY is the abbreviation for BF_(2)-chelated dipyrromethenes)conjugates D-A complexes with the combination of both electronic structure calculations and nonadiabatic dynamics simulations.On the basis of computational results,we concluded that the BODIPY-hexaoxatriphenylene(BH)conjugates will be promoted to the local excited(LE)states of the BODIPY fragments upon excitation,which is followed by the ultrafast exciton transfer from LE state to charge transfer(CT).Instead of the photoinduced electron transfer process proposed in previous experimental work,such a exciton transfer process is accompanied with the photoinduced hole transfer from BODIPY to hexaoxatriphenylene.Additionally,solvent effects are found to play an important role in the photoinduced dynamics.Specifically,the hole transfer dynamics is accelerated by the acetonitrile solvent,which can be ascribed to significant influences of the solvents on the charge transfer states,i.e.the energy gaps between LE and CT excitons are reduced greatly and the non-adiabatic couplings are increased in the meantime.Our present work not only provides valuable insights into the underlying photoinduced mechanism of BH,but also can be helpful for the future design of novel donor-acceptor conjugates with better optoelectronic performance.展开更多
A Series of all-optical devices are proposed based on nonlinear excited-stateabsorption and working at non-resonant frequency. Experimental and theoretical results obtainedwith C_(60) and metal-organic materials using...A Series of all-optical devices are proposed based on nonlinear excited-stateabsorption and working at non-resonant frequency. Experimental and theoretical results obtainedwith C_(60) and metal-organic materials using ns and ps laser at 532nm are presented.展开更多
The excited-state double proton transfer(ESDPT)properties of 1,5-dihydroxyanthraquinone(1,5-DHAQ)in various solvents were investigated using femtosecond transient absorption spectroscopy and the DFT/TDDFT method.The s...The excited-state double proton transfer(ESDPT)properties of 1,5-dihydroxyanthraquinone(1,5-DHAQ)in various solvents were investigated using femtosecond transient absorption spectroscopy and the DFT/TDDFT method.The steady-state fluorescence spectra in toluene,tetrahydrofuran(THF)and acetonitrile(ACN)solvents presented that the solvent polarity has an effect on the position of the ESDPT fluorescence emission peak for the 1,5-DHAQ system.Transient absorption spectra show that the increasing polarity of the solvent accelerates the rate of excited state dynamics.Calculated potential energy curves analysis further verified the experimental results.The ESDPT barrier decreases gradually with the increase of solvent polarity from toluene,THF to ACN solvent.It is convinced that the increase of solvent polarity can promote the occurrence of the ESDPT dynamic processes for the 1,5-DHAQ system.This work clarifies the mechanism of the influence of solvent polarity on the ESDPT process of 1,5-DHAQ,which provides novel ideas for design and synthesis of new hydroxyanthraquinone derivatives.展开更多
Excited-state intramolecular proton transfer(ESIPT)is favored by researchers because of its unique optical properties.However,there are relatively few systematic studies on the effects of changing the electronegativit...Excited-state intramolecular proton transfer(ESIPT)is favored by researchers because of its unique optical properties.However,there are relatively few systematic studies on the effects of changing the electronegativity of atoms on the ESIPT process and photophysical properties.Therefore,we selected a series of benzoxazole isothiocyanate fluorescent dyes(2-HOB,2-HSB,and 2-HSe B)by theoretical methods,and systematically studied the ESIPT process and photophysical properties by changing the electronegativity of chalcogen atoms.The calculated bond angle,bond length,energy gap,and infrared spectrum analysis show that the order of the strength of intramolecular hydrogen bonding of the three molecules is 2-HOB<2-HSB<2-HSe B.Correspondingly,the magnitude of the energy barrier of the potential energy curve is 2-HOB>2-HSB>2-HSe B.In addition,the calculated electronic spectrum shows that as the atomic electronegativity decreases,the emission spectrum has a redshift.Therefore,this work will offer certain theoretical guidance for the synthesis and application of new dyes based on ESIPT properties.展开更多
Organic lasers that emit light in the deep-red and near-infrared(NIR)region are of essential importance in laser communication,night vision,bioimaging,and information-secured displays but are still challenging because...Organic lasers that emit light in the deep-red and near-infrared(NIR)region are of essential importance in laser communication,night vision,bioimaging,and information-secured displays but are still challenging because of the lack of proper gain materials.Herein,a new molecular design strategy that operates by merging two excited-state intramolecular proton transfer-active molecules into one excited-state double proton transfer(ESDPT)-active molecule was demonstrated.Based on this new strategy,three new materials were designed and synthesized with two groups of intramolecular resonance-assisted hydrogen bonds,in which the ESDPT process was proven to proceed smoothly based on theoretical calculations and experimental results of steady-state and transient spectra.Benefiting from the effective six-level system constructed by the ESDPT process,all newly designed materials showed low threshold laser emissions at approximately 720 nm when doped in PS microspheres,which in turn proved the existence of the second proton transfer process.More importantly,our well-developed NIR organic lasers showed high laser stability,which can maintain high laser intensity after 12000 pulse lasing,which is essential in practical applications.This work provides a simple and effective method for the development of NIR organic gain materials and demonstrates the ESDPT mechanism for NIR lasing.展开更多
Excited-state double proton transfer(ESDPT)is a controversial issue which has long been plagued with theoretical and experimental communities.Herein,we took 1,8-dihydroxy-2-naphthaldehyde(DHNA)as a prototype and used ...Excited-state double proton transfer(ESDPT)is a controversial issue which has long been plagued with theoretical and experimental communities.Herein,we took 1,8-dihydroxy-2-naphthaldehyde(DHNA)as a prototype and used combined complete active space selfconsistent field(CASSCF)and multi-state complete active-space second-order perturbation(MS-CASPT2)methods to investigate ESDPT and excited-state deactivation pathways of DHNA.Three different tautomer minima of S1-ENOL,S1-KETO-1,and S1-KETO-2 and two crucial conical intersections of S1 S0-KETO-1 and S1 S0-KETO-2 in and between the S0 and S1 states were obtained.S1-KETO-1 and S1-KETO-2 should take responsibility for experimentally observing dual-emission bands.In addition,two-dimensional potential energy surfaces(2 D-PESs)and linear interpolated internal coordinate paths connecting relevant structures were calculated at the MS-CASPT2//CASSCF level and confirmed a stepwise ESDPT mechanism.Specifically,the first proton transfer from S1-ENOL to S1-KETO-1 is barrierless,whereas the second one from S1-KETO-1 to S1-KETO-2 demands a barrier of ca.6.0 kcal/mol.The linear interpolated internal coordinate path connecting S1-KETO-1(S1-KETO-2)and S_(1) S0-KETO-1(S1 S0-KETO-2)is uphill with a barrier of ca.12.0 kcal/mol,which will trap DHNA in the S_(1) state while therefore enabling dual-emission bands.On the other hand,the S1/S0 conical intersections would also prompt the S_(1) system to decay to the S_(0) state,which could be to certain extent suppressed by locking the rotation of the C5-C8-C9-O10 dihedral angle.These mechanistic insights are not only helpful for understanding ESDPT but also useful for designing novel molecular materials with excellent photoluminescent performances.展开更多
Excited-states play a crucial role in the optical absorption and luminescence of solids and hence their accurate information is highly desired. Herein, we attempt to seize the excited-states information of Mn^(4+)ions...Excited-states play a crucial role in the optical absorption and luminescence of solids and hence their accurate information is highly desired. Herein, we attempt to seize the excited-states information of Mn^(4+)ions in K_(2)SiF_(6) microcrystals via measuring and calculating their variable-temperature photoluminescence excitation(PLE) spectra. At cryogenic temperatures, an unpredicted splitting of the high-excited-state is observed. Moreover, the two-split high-excited-state levels are further revealed to primarily couple with the two hyperfine split modes of quasi-localized ν2 vibration in the distorted Mn-F_(6) octahedral configuration,whereas the coupling strengths are found to be substantially different from each other. The slightly split vibrational mode is firmly supported by the low-temperature Raman spectra. Jahn-Teller lattice distortion is believed to be responsible for the observed splitting of the electronic high-excited-state and the quasi-localized vibrational mode.展开更多
Fluorogenic probes have shown great potential in imaging biological species as well as in diagnosing diseases,especially cancers.However,the fluorogenic mechanisms are largely limited to a few photophysical processes ...Fluorogenic probes have shown great potential in imaging biological species as well as in diagnosing diseases,especially cancers.However,the fluorogenic mechanisms are largely limited to a few photophysical processes to date,typically including photoinduced electron transfer(PeT),fluorescence resonant energy transfer(FRET),and intramolecular charge transfer(ICT).Herein,by calculations and experiments,we set forth that the inhibition of the excited-stateπ-conjugation in meso-ester Si-rhodamine SiR-COOM or the de-π-conjugation in meso-ester cyanine 5 Cy5-COOM via the“ester-to-carboxylate”conversion can operate as a general fluorogenic mechanism to fabricate fluorogenic probes.Based on the mechanism and considering the higher chemical stability of Cy5-COOM than that of SiR-COOM,we developed,as a proof-of-concept,three fluorogenic probes Cy5-APN,Cy5-GGT,and Cy5-NTR on the basis of the Cy5-COOM platform for sensing cancer biomarkers aminopeptidase N(APN),γ-glutamyltranspeptidase(GGT),and nitroreductase(NTR),respectively,and demonstrated their outstanding performances in distinguishing between cancerous and normal tissues with the high tumor-tonormal tissue ratios in the range of 9−14.展开更多
Luminescent metal halides doped with ns^(2-)metal ions such as 6s^(2-)metal Bi^(3+)have aroused reviving interest owing to their outstanding optical properties;however,the origin of the photoluminescence(PL)remains co...Luminescent metal halides doped with ns^(2-)metal ions such as 6s^(2-)metal Bi^(3+)have aroused reviving interest owing to their outstanding optical properties;however,the origin of the photoluminescence(PL)remains controversial and unclear.Herein,we report a strategy for the controlled synthesis of Bi^(3+)-doped vacancy-ordered double perovskite Cs_(2)SnCl_(6)nanocrystals(NCs)and unravel the triplet excited-state dynamics of Bi^(3+)through temperature-dependent PL and ultrafast femtosecond transient absorption spectroscopies.Owing to the aliovalent Bi^(3+)doping in the spatially confined zero-dimensional(0D)structure of Cs2SnCl6,Bi^(3+)ions experience an enhancive Jahn-Teller distortion in the excited state,which results in intense broadband blue PL originating from the inter-configurational 3P0,1→1S0 transitions of Bi^(3+)at 450 nm,with a large Stokes shift and a quantum yield of 35.2%.Specifically,an unusual thermal-enhanced Jahn-Teller splitting of the excitation band and a remarkable transition of the PL lifetime from ms at 10 K toμs at 300 K were observed,as solid evidence for the isolated Bi^(3+)emission.These findings clarify the controversy about the PL origin in ns^(2-)metal ion-doped lead-free luminescent metal halides,thereby paving the way for exploring their optoelectronic applications.展开更多
We review our recent work on the methodology development of the excited-state properties for the molecules in vacuum and liquid solution.The general algorithms of analytical energy derivatives for the specific propert...We review our recent work on the methodology development of the excited-state properties for the molecules in vacuum and liquid solution.The general algorithms of analytical energy derivatives for the specific properties such as the first and second geometrical derivatives and IR/Raman intensities are demonstrated in the framework of the time-dependent density functional theory(TDDFT).The performance of the analytical approaches on the calculation of excited-state energy Hessian has also been shown.It is found that the analytical approaches are superior to the finite-difference method on the computational accuracy and efficiency.The computational cost for a TDDFT excited-state Hessian calculation is only 2–3 times as that for the DFT ground-state Hessian calculation.With the low computational complexity of the developed analytical approaches,it becomes feasible to realize the large-scale numerical calculations on the excited-state vibrational frequencies,vibrational spectroscopies and the electronic-structure parameters which enter the spectrum calculations of electronic absorption and emission,and resonance Raman spectroscopies for medium-to large-sized systems.展开更多
Photo-induced excited-state dynamics within organic materials fundamentally determine their photophysical properties for various applications,and thus understanding the primary excited-state dynamics behavior is of fu...Photo-induced excited-state dynamics within organic materials fundamentally determine their photophysical properties for various applications,and thus understanding the primary excited-state dynamics behavior is of fundamental and practical significance.Until recently,the excited-state dynamics of organic materials towards biophotonics have been rarely studied,although numerous endeavors have been devoted to the design of organic materials for biophotonics.Herein,various spectroscopy technologies including femtosecond transient absorption(fs-TA)spectroscopy clearly reveal a totally different excited state dynamics behavior within Bodipy monomer(2B-BDP dye)and aggregates(2B-BDP NPs),indicating strongly morphology dependent character.2B-BDP dye undergoes an ultrafast conversion from S1 to intramolecular charge transfer(ICT)state for subsequent photoluminescence(PL)and nonradiative(NR)decay,while 2B-BDP NPs show an accelerated excited-state deactivation mainly through S1→S0 NR decay.The potential bioapplications based on the corresponding excited state dynamics behavior are discussed together with experimental results.Interestingly,the accelerated NR decay in 2B-BDP NPs does not yield a stronger photoacoustic(PA)signal than that in 2B-BDP dye,which violates the conventional wisdom that faster NR decay would benefit the photothermal effects for better photoacoustic imaging(PAI).These insightful and fundamental observations of the excited-state dynamics may contribute an alternative approach at the molecular level towards the future design of functional Bodipy-based organic molecules with desirable performances.展开更多
Doping foreign atom(s)in metal nanoclusters is an effective strategy to engineer the properties and functionalities of metal nanoclusters.However,until now,to dope Pd atom into Ag nanoclusters remains a huge challenge...Doping foreign atom(s)in metal nanoclusters is an effective strategy to engineer the properties and functionalities of metal nanoclusters.However,until now,to dope Pd atom into Ag nanoclusters remains a huge challenge.Here we develop a one-step rapid method to synthesize the Pd-doped Ag nanocluster with high yield.The prepared Pd1Ag28 nanocluster was characterized by mass spectroscopy,X-ray photoelectron spectroscopy,X-ray crystallography,fluorescence spectroscopy,ultraviolet-visible absorption spectroscopy and transient absorption spectroscopy.The nanocluster exhibits a perfect face-centered cubic(FCC)kernel structure with a tetrahedron-like shell.Of note,Pd1Ag28 nanocluster had an unexpectedly long excited-state lifetime of 3.3 microseconds,which is the longest excited-state lifetime for Ag-based nanoclusters S0 far.Meanwhile,the excellent near-infrared luminescence indicated the nanocluster has the potential in fluorescent bio-imaging.Besides,it was revealed that Pd1Ag28 nanocluster could be transformed into Au1Ag28 nanocluster via ion exchange reaction of AuPPhzCl with Pd1Ag28 nanocluster.This work provides an efficient synthetic protocol of alloy nanoclusters and wil contribute to study the effect of foreign atom on the properties of metal nanoclusters.展开更多
Recently, the spectroscopic signatures of a benzoselenadiazole derivative have been investigated in the framework of designing a new ratiometric fluoride sensor （Saravanan et al., Org Lett, 2014, 16： 354-357）. It w...Recently, the spectroscopic signatures of a benzoselenadiazole derivative have been investigated in the framework of designing a new ratiometric fluoride sensor （Saravanan et al., Org Lett, 2014, 16： 354-357）. It was suggested that this sensor is un- dergoing excited-state intramolecular proton transfer. In this work, we provide a new look at these experimental data, using a state-of-the-art time-dependent density fimctiona/theory approach to mimic the spectroscopic signatures. New insights about the nature of the excited-state processes are obtained.展开更多
In recent periods, some organic conjugated polymers with large nonlinear optical effectand fast responses are being studied widely. With them, people hope to produce ultrafastoptronic devices, such as optical switches...In recent periods, some organic conjugated polymers with large nonlinear optical effectand fast responses are being studied widely. With them, people hope to produce ultrafastoptronic devices, such as optical switches or optical modulators. However, up to now, fewpolymeric samples have been discovered to have enough large nonlinear optical effect orfast time responses to satisfy the practical applications. In this note, we report展开更多
The research results of the excited-state properties of asymmetric pentaazadentate ex-panded-porphyrins are reported. The results show that the emission spectra appear in the 770-820 nm region in accord with the diffe...The research results of the excited-state properties of asymmetric pentaazadentate ex-panded-porphyrins are reported. The results show that the emission spectra appear in the 770-820 nm region in accord with the different substituents on the benzene ring. The quantum yield of fluorescence is less than 0.02, and the lifetime of the first singlet excited state (S1) is shorter than 1ns. There are excellent linear relationships between the energy of the S1 and the Hammett constants as well as the quantum yield of fluorescence and the electrophilic substituent constants σ+. The energies of the lowest excited triplet state (T1) of the complexes are in the range of 94 -130kJ/mol. The lifetime of T 1 is as long as tens of microseconds. The T1-Tn transient absorption spectra appear in 450-550 nm region. And the quantum yield of title compounds for generating singlet oxygen is as high as 0.9.展开更多
基金supported by the National Natural Science Foundation of China(No.22003066)。
文摘Fisetin attracts intense attention not only due to its antioxidant and anticancer properties but also be-cause of wide applications in fluo-rescence probes and sensors,which are based on the dual fluorescence induced by excited-state proton transfer(ESPT).However,to date,its ESPT dynamics remains unknown yet.In this study,we give a comprehensive investiga-tion on ESPT dynamics of fisetin in both protic methanol and aprot-ic acetonitrile by using femtosecond transient absorption spectroscopy combined with time-dependent density functional theory calculations.In acetonitrile,the ESPT time constant of fisetin is 1.2 ps.In methanol,two distinct intermolecular hydrogen bonding configurations contribute to a fast(<90 fs)and slow ESPT(11.1 ps),respectively.The slow ESPT in methanol explains the higher emission intensity of normal species than in acetonitrile.The ex-cited-state relaxation of fisetin involves two main vibrational modes:rotation between B and C rings and butterfly-like motion of C ring.Our results give insight into the effect of solvent-solute hydrogen bonding interaction on the dual fluorescence,providing a fundamental guide-line for the development of fluorescent probes and sensors based on ESPT.
基金support by the National Key R&D Program of China(Nos.2020YFA0714603 and 2020YFA0714604)。
文摘The heavy-atom effect of halogen(Br and I)has been widely employed for boosting spin-crossover in organic molecules,while recent investigation indicated halogen-substitution can also enhance fluorescence and even lead to aggregation-induced emission(AIE).In this work,we investigated ultrafast excited state dynamics of a halogen-substituted model system,i.e.squaryliums NSQ-R(R=H,Cl,Br,I),by using femtosecond spectroscopy and theoretical approach.Fast external reorganization(Ex-re,~3 ps)and slow internal reorganization(In-re,5-20 ps)were observed,while quantitative fitting indicated halogen-substitution leads to a slower non-radiative S1→S0 decay(k_(NR)^(s))and subsequently enhanced fluorescence emitting.By analyzing the extracted k_(NR)^(s)within theoretical framework of non-radiative transition in the strong coupling regime,a plausible AIE mechanism of NSQs was revealed.Our work provides a clear picture on non-radiative dynamics of halogen-substituted squaryliums,which might be useful for future development of organic dyes.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.20772028 and No.20472019）, the Natural Science Foundation of Hunan Province （No.06JJ2002）, and the Scientific Research Fund of Hunan Provincial Education Commission.
文摘A correlation equation between the UV absorption wavenumbers of 1,4-disubstituted benzenes and the excited-state substituent constant was obtained. For 80 sorts of 1,4- disubstituted benzenes, the correlation coefficient was 0.9805, and the standard deviation was only 672.27 cm^-1. The results imply that the excited-state substituent constant can be used productively for research on UV energy of 1,4-disubstituted benzenes. The present method provides a new avenue to study the UV absorption spectra of aromatic systems with the excited-state substituent constant, and it is helpful to understand the effect of substituent electrostatic effects on the chemical and physical properties of conjugated compounds with multiple substituents in excited state.
基金supported by the Research Foundation of the National Natural Science Foundation of China(No.U1204209)the Major Program of the Natural Science of Anhui University(No.KJ2016SD52)+1 种基金the Key Program of the Natural Science of Anhui University for Young and Middle-aged Key Talent to Study in the Domestic(No.gxfx ZD2016097)Undergraduates Innovating Project(No.201510373083)
文摘Using DFT/TDDFT methods,the excited-state lifetimes of Ru（Ⅱ） polypyridyl complexes were computed accurately and the reason of Ru（Ⅱ） polypyridyl complexes with long excited-state lifetimes was explained by the electron-transfer distances and HOMO-LUMO gaps.Finally,the photovoltaic conversion efficiencies of complexes were predicted using DFT and docking methods.This work has provided methods of predicting the excited-state lifetimes and photovoltaic conversion efficiencies of Ru（Ⅱ） polypyridyl complexes.
基金the financial supports from National Natural Science Foundation of China (Nos.81971678 and 81671756)the Innovation Fund for Postgraduate Students of Central South University (No.2019zzts1019)。
文摘Intracellular pH is a key parameter related to various biological and pathological processes.In this study,a ratiometric pH fluorescent sensor ABTT was developed harnessing the amino-type excited-state intramolecular proton transfer(ESIPT) process.Relying on whether the ESIPT proceeds normally or not,ABTT exhibited the yellow fluorescence in acidic media,or cyan fluorescence in basic condition.According to the variation,ABTT behaved as a promising sensor which possessed fast and reversible response to pH change without interference from the biological substances,and exported a steady ratiometric signal(I_(478)/I_(546)).Moreover,due to the ESIPT effect,large Stokes shift and high quantum yield were also exhibited in ABTT.Furthermore,ABTT was applied for monitoring the pH changes in living cells and visualizing the pH fluctuations under oxidative stress successfully.These results elucidated great potential of ABTT in understanding pH-dependent physiological and pathological processes.
基金supported by the National Natural Science Foundation of China(No.22003043 for Xiang-Yang Liu)the National Natural Science Foundation of China(No.21688102,No.21590801,and No.21520102005 for Ganglong Cui)+1 种基金Sichuan Science and Technology Program(No.2020YJ0161 for Xiang-Yang Liu)the High Performance Computing Center of Sichuan Normal University。
文摘Understanding the excited state dynamics of donor-acceptor(D-A)complexes is of fundamental importance both experimentally and theoretically.Herein,we have first explored the photoinduced dynamics of a recently synthesized paddle-wheel BODIPY-hexaoxatriphenylene(BODIPY is the abbreviation for BF_(2)-chelated dipyrromethenes)conjugates D-A complexes with the combination of both electronic structure calculations and nonadiabatic dynamics simulations.On the basis of computational results,we concluded that the BODIPY-hexaoxatriphenylene(BH)conjugates will be promoted to the local excited(LE)states of the BODIPY fragments upon excitation,which is followed by the ultrafast exciton transfer from LE state to charge transfer(CT).Instead of the photoinduced electron transfer process proposed in previous experimental work,such a exciton transfer process is accompanied with the photoinduced hole transfer from BODIPY to hexaoxatriphenylene.Additionally,solvent effects are found to play an important role in the photoinduced dynamics.Specifically,the hole transfer dynamics is accelerated by the acetonitrile solvent,which can be ascribed to significant influences of the solvents on the charge transfer states,i.e.the energy gaps between LE and CT excitons are reduced greatly and the non-adiabatic couplings are increased in the meantime.Our present work not only provides valuable insights into the underlying photoinduced mechanism of BH,but also can be helpful for the future design of novel donor-acceptor conjugates with better optoelectronic performance.
文摘A Series of all-optical devices are proposed based on nonlinear excited-stateabsorption and working at non-resonant frequency. Experimental and theoretical results obtainedwith C_(60) and metal-organic materials using ns and ps laser at 532nm are presented.
基金supported by the National Basic Research Program of China(No.2019YFA0307701)the National Natural Science Foundation of China(No.11874180)the Young and Middle-aged Scientific and Technological Innovation leaders and Team Projects in Jilin Province(No.20200301020RQ)。
文摘The excited-state double proton transfer(ESDPT)properties of 1,5-dihydroxyanthraquinone(1,5-DHAQ)in various solvents were investigated using femtosecond transient absorption spectroscopy and the DFT/TDDFT method.The steady-state fluorescence spectra in toluene,tetrahydrofuran(THF)and acetonitrile(ACN)solvents presented that the solvent polarity has an effect on the position of the ESDPT fluorescence emission peak for the 1,5-DHAQ system.Transient absorption spectra show that the increasing polarity of the solvent accelerates the rate of excited state dynamics.Calculated potential energy curves analysis further verified the experimental results.The ESDPT barrier decreases gradually with the increase of solvent polarity from toluene,THF to ACN solvent.It is convinced that the increase of solvent polarity can promote the occurrence of the ESDPT dynamic processes for the 1,5-DHAQ system.This work clarifies the mechanism of the influence of solvent polarity on the ESDPT process of 1,5-DHAQ,which provides novel ideas for design and synthesis of new hydroxyanthraquinone derivatives.
基金supported by the National Natural Science Foundation of China(No.21773238)the Fundamental Research Funds of Shandong University(2019GN025)。
文摘Excited-state intramolecular proton transfer(ESIPT)is favored by researchers because of its unique optical properties.However,there are relatively few systematic studies on the effects of changing the electronegativity of atoms on the ESIPT process and photophysical properties.Therefore,we selected a series of benzoxazole isothiocyanate fluorescent dyes(2-HOB,2-HSB,and 2-HSe B)by theoretical methods,and systematically studied the ESIPT process and photophysical properties by changing the electronegativity of chalcogen atoms.The calculated bond angle,bond length,energy gap,and infrared spectrum analysis show that the order of the strength of intramolecular hydrogen bonding of the three molecules is 2-HOB<2-HSB<2-HSe B.Correspondingly,the magnitude of the energy barrier of the potential energy curve is 2-HOB>2-HSB>2-HSe B.In addition,the calculated electronic spectrum shows that as the atomic electronegativity decreases,the emission spectrum has a redshift.Therefore,this work will offer certain theoretical guidance for the synthesis and application of new dyes based on ESIPT properties.
基金We are grateful for financial supports from the National Natural Science Foundation of China(Nos.52173177,21971185,22105139)Fundação Universidade de Ciência e Tecnologia de Macao(No.0006/2021/AKP)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK20221362)the Science and Technology Support Program of Jiangsu Province(No.TJ-2022-002).This project is also funded by Suzhou Key Laboratory of Functional Nano&Soft Materials,Collaborative Innovation Center of Suzhou Nano Science&Technology,the 111 Project,Joint International Research Laboratory of Carbon-Based Functional Materials and Devices,and Soochow University Tang Scholar.
文摘Organic lasers that emit light in the deep-red and near-infrared(NIR)region are of essential importance in laser communication,night vision,bioimaging,and information-secured displays but are still challenging because of the lack of proper gain materials.Herein,a new molecular design strategy that operates by merging two excited-state intramolecular proton transfer-active molecules into one excited-state double proton transfer(ESDPT)-active molecule was demonstrated.Based on this new strategy,three new materials were designed and synthesized with two groups of intramolecular resonance-assisted hydrogen bonds,in which the ESDPT process was proven to proceed smoothly based on theoretical calculations and experimental results of steady-state and transient spectra.Benefiting from the effective six-level system constructed by the ESDPT process,all newly designed materials showed low threshold laser emissions at approximately 720 nm when doped in PS microspheres,which in turn proved the existence of the second proton transfer process.More importantly,our well-developed NIR organic lasers showed high laser stability,which can maintain high laser intensity after 12000 pulse lasing,which is essential in practical applications.This work provides a simple and effective method for the development of NIR organic gain materials and demonstrates the ESDPT mechanism for NIR lasing.
基金supported by the National Key Research and Development Program of China for BinBin Xie(No.2019YFA0709400)the National Natural Science Foundation of China for Bin-Bin Xie(No.21903068)+1 种基金Xiang-Yang Liu(No.22003043)Natural Science Foundation of Zhejiang Province for Bin-Bin Xie(No.LQ19B030007)。
文摘Excited-state double proton transfer(ESDPT)is a controversial issue which has long been plagued with theoretical and experimental communities.Herein,we took 1,8-dihydroxy-2-naphthaldehyde(DHNA)as a prototype and used combined complete active space selfconsistent field(CASSCF)and multi-state complete active-space second-order perturbation(MS-CASPT2)methods to investigate ESDPT and excited-state deactivation pathways of DHNA.Three different tautomer minima of S1-ENOL,S1-KETO-1,and S1-KETO-2 and two crucial conical intersections of S1 S0-KETO-1 and S1 S0-KETO-2 in and between the S0 and S1 states were obtained.S1-KETO-1 and S1-KETO-2 should take responsibility for experimentally observing dual-emission bands.In addition,two-dimensional potential energy surfaces(2 D-PESs)and linear interpolated internal coordinate paths connecting relevant structures were calculated at the MS-CASPT2//CASSCF level and confirmed a stepwise ESDPT mechanism.Specifically,the first proton transfer from S1-ENOL to S1-KETO-1 is barrierless,whereas the second one from S1-KETO-1 to S1-KETO-2 demands a barrier of ca.6.0 kcal/mol.The linear interpolated internal coordinate path connecting S1-KETO-1(S1-KETO-2)and S_(1) S0-KETO-1(S1 S0-KETO-2)is uphill with a barrier of ca.12.0 kcal/mol,which will trap DHNA in the S_(1) state while therefore enabling dual-emission bands.On the other hand,the S1/S0 conical intersections would also prompt the S_(1) system to decay to the S_(0) state,which could be to certain extent suppressed by locking the rotation of the C5-C8-C9-O10 dihedral angle.These mechanistic insights are not only helpful for understanding ESDPT but also useful for designing novel molecular materials with excellent photoluminescent performances.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12074324, and 11374247)the Science, Technology, and Innovation Commission of Shenzhen Municipality (Grant Nos. JCJY20180508163404043, and JCYJ20170818141709893)。
文摘Excited-states play a crucial role in the optical absorption and luminescence of solids and hence their accurate information is highly desired. Herein, we attempt to seize the excited-states information of Mn^(4+)ions in K_(2)SiF_(6) microcrystals via measuring and calculating their variable-temperature photoluminescence excitation(PLE) spectra. At cryogenic temperatures, an unpredicted splitting of the high-excited-state is observed. Moreover, the two-split high-excited-state levels are further revealed to primarily couple with the two hyperfine split modes of quasi-localized ν2 vibration in the distorted Mn-F_(6) octahedral configuration,whereas the coupling strengths are found to be substantially different from each other. The slightly split vibrational mode is firmly supported by the low-temperature Raman spectra. Jahn-Teller lattice distortion is believed to be responsible for the observed splitting of the electronic high-excited-state and the quasi-localized vibrational mode.
基金supported by the National Natural Science Foundation of China(Nos.22277070,22274091,22007061)the Youth Talent Support Program of Shanxi Province,the Program for the Top Young Academic Leaders of Higher Learning Institutions of Shanxi,and the fundamental research program of Shanxi province(20210302123445).
文摘Fluorogenic probes have shown great potential in imaging biological species as well as in diagnosing diseases,especially cancers.However,the fluorogenic mechanisms are largely limited to a few photophysical processes to date,typically including photoinduced electron transfer(PeT),fluorescence resonant energy transfer(FRET),and intramolecular charge transfer(ICT).Herein,by calculations and experiments,we set forth that the inhibition of the excited-stateπ-conjugation in meso-ester Si-rhodamine SiR-COOM or the de-π-conjugation in meso-ester cyanine 5 Cy5-COOM via the“ester-to-carboxylate”conversion can operate as a general fluorogenic mechanism to fabricate fluorogenic probes.Based on the mechanism and considering the higher chemical stability of Cy5-COOM than that of SiR-COOM,we developed,as a proof-of-concept,three fluorogenic probes Cy5-APN,Cy5-GGT,and Cy5-NTR on the basis of the Cy5-COOM platform for sensing cancer biomarkers aminopeptidase N(APN),γ-glutamyltranspeptidase(GGT),and nitroreductase(NTR),respectively,and demonstrated their outstanding performances in distinguishing between cancerous and normal tissues with the high tumor-tonormal tissue ratios in the range of 9−14.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.12074379,U1805252,21875250,12074380,11904365,and 12004384)the Chinese Academy of Sciences/State Administration of Foreign Experts Affairs(CAS/SAFEA)International Partnership Program for Creative Research Teams.
文摘Luminescent metal halides doped with ns^(2-)metal ions such as 6s^(2-)metal Bi^(3+)have aroused reviving interest owing to their outstanding optical properties;however,the origin of the photoluminescence(PL)remains controversial and unclear.Herein,we report a strategy for the controlled synthesis of Bi^(3+)-doped vacancy-ordered double perovskite Cs_(2)SnCl_(6)nanocrystals(NCs)and unravel the triplet excited-state dynamics of Bi^(3+)through temperature-dependent PL and ultrafast femtosecond transient absorption spectroscopies.Owing to the aliovalent Bi^(3+)doping in the spatially confined zero-dimensional(0D)structure of Cs2SnCl6,Bi^(3+)ions experience an enhancive Jahn-Teller distortion in the excited state,which results in intense broadband blue PL originating from the inter-configurational 3P0,1→1S0 transitions of Bi^(3+)at 450 nm,with a large Stokes shift and a quantum yield of 35.2%.Specifically,an unusual thermal-enhanced Jahn-Teller splitting of the excitation band and a remarkable transition of the PL lifetime from ms at 10 K toμs at 300 K were observed,as solid evidence for the isolated Bi^(3+)emission.These findings clarify the controversy about the PL origin in ns^(2-)metal ion-doped lead-free luminescent metal halides,thereby paving the way for exploring their optoelectronic applications.
基金support from the National Natural Science Foundation of China(21073168,21290193)The National Basic Research Program of China(2011CB808501)is acknowledged
文摘We review our recent work on the methodology development of the excited-state properties for the molecules in vacuum and liquid solution.The general algorithms of analytical energy derivatives for the specific properties such as the first and second geometrical derivatives and IR/Raman intensities are demonstrated in the framework of the time-dependent density functional theory(TDDFT).The performance of the analytical approaches on the calculation of excited-state energy Hessian has also been shown.It is found that the analytical approaches are superior to the finite-difference method on the computational accuracy and efficiency.The computational cost for a TDDFT excited-state Hessian calculation is only 2–3 times as that for the DFT ground-state Hessian calculation.With the low computational complexity of the developed analytical approaches,it becomes feasible to realize the large-scale numerical calculations on the excited-state vibrational frequencies,vibrational spectroscopies and the electronic-structure parameters which enter the spectrum calculations of electronic absorption and emission,and resonance Raman spectroscopies for medium-to large-sized systems.
基金supported by the National Natural Science Foundation of China(61805118,21674048)the Natural Science Foundation of Jiangsu Province of China(BK20171020)Open Research Fund of Key Laboratory for Organic Electronics and Information Displays。
文摘Photo-induced excited-state dynamics within organic materials fundamentally determine their photophysical properties for various applications,and thus understanding the primary excited-state dynamics behavior is of fundamental and practical significance.Until recently,the excited-state dynamics of organic materials towards biophotonics have been rarely studied,although numerous endeavors have been devoted to the design of organic materials for biophotonics.Herein,various spectroscopy technologies including femtosecond transient absorption(fs-TA)spectroscopy clearly reveal a totally different excited state dynamics behavior within Bodipy monomer(2B-BDP dye)and aggregates(2B-BDP NPs),indicating strongly morphology dependent character.2B-BDP dye undergoes an ultrafast conversion from S1 to intramolecular charge transfer(ICT)state for subsequent photoluminescence(PL)and nonradiative(NR)decay,while 2B-BDP NPs show an accelerated excited-state deactivation mainly through S1→S0 NR decay.The potential bioapplications based on the corresponding excited state dynamics behavior are discussed together with experimental results.Interestingly,the accelerated NR decay in 2B-BDP NPs does not yield a stronger photoacoustic(PA)signal than that in 2B-BDP dye,which violates the conventional wisdom that faster NR decay would benefit the photothermal effects for better photoacoustic imaging(PAI).These insightful and fundamental observations of the excited-state dynamics may contribute an alternative approach at the molecular level towards the future design of functional Bodipy-based organic molecules with desirable performances.
基金We acknowledge the National Natural Science Foundation of China(No.21601178).
文摘Doping foreign atom(s)in metal nanoclusters is an effective strategy to engineer the properties and functionalities of metal nanoclusters.However,until now,to dope Pd atom into Ag nanoclusters remains a huge challenge.Here we develop a one-step rapid method to synthesize the Pd-doped Ag nanocluster with high yield.The prepared Pd1Ag28 nanocluster was characterized by mass spectroscopy,X-ray photoelectron spectroscopy,X-ray crystallography,fluorescence spectroscopy,ultraviolet-visible absorption spectroscopy and transient absorption spectroscopy.The nanocluster exhibits a perfect face-centered cubic(FCC)kernel structure with a tetrahedron-like shell.Of note,Pd1Ag28 nanocluster had an unexpectedly long excited-state lifetime of 3.3 microseconds,which is the longest excited-state lifetime for Ag-based nanoclusters S0 far.Meanwhile,the excellent near-infrared luminescence indicated the nanocluster has the potential in fluorescent bio-imaging.Besides,it was revealed that Pd1Ag28 nanocluster could be transformed into Au1Ag28 nanocluster via ion exchange reaction of AuPPhzCl with Pd1Ag28 nanocluster.This work provides an efficient synthetic protocol of alloy nanoclusters and wil contribute to study the effect of foreign atom on the properties of metal nanoclusters.
基金D.Jacquemm acknowledges the European Research Council(ERC)the Règion des Pays de la Loire for financial support in the framework of a Starting Grant(Marches-278845)a recrutement sur poste stratègique,respectively
文摘Recently, the spectroscopic signatures of a benzoselenadiazole derivative have been investigated in the framework of designing a new ratiometric fluoride sensor （Saravanan et al., Org Lett, 2014, 16： 354-357）. It was suggested that this sensor is un- dergoing excited-state intramolecular proton transfer. In this work, we provide a new look at these experimental data, using a state-of-the-art time-dependent density fimctiona/theory approach to mimic the spectroscopic signatures. New insights about the nature of the excited-state processes are obtained.
文摘In recent periods, some organic conjugated polymers with large nonlinear optical effectand fast responses are being studied widely. With them, people hope to produce ultrafastoptronic devices, such as optical switches or optical modulators. However, up to now, fewpolymeric samples have been discovered to have enough large nonlinear optical effect orfast time responses to satisfy the practical applications. In this note, we report
基金Project supported by the National Natural Science Foundation of China
文摘The research results of the excited-state properties of asymmetric pentaazadentate ex-panded-porphyrins are reported. The results show that the emission spectra appear in the 770-820 nm region in accord with the different substituents on the benzene ring. The quantum yield of fluorescence is less than 0.02, and the lifetime of the first singlet excited state (S1) is shorter than 1ns. There are excellent linear relationships between the energy of the S1 and the Hammett constants as well as the quantum yield of fluorescence and the electrophilic substituent constants σ+. The energies of the lowest excited triplet state (T1) of the complexes are in the range of 94 -130kJ/mol. The lifetime of T 1 is as long as tens of microseconds. The T1-Tn transient absorption spectra appear in 450-550 nm region. And the quantum yield of title compounds for generating singlet oxygen is as high as 0.9.
