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
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
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
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
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 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
Carbon monoxide(CO)is a crucial gaseous signaling molecule that regulates various physiological and pathological processes,and may exert an anti-inflammatory and protective role in drug-induced liver injury(DILI).Desp...Carbon monoxide(CO)is a crucial gaseous signaling molecule that regulates various physiological and pathological processes,and may exert an anti-inflammatory and protective role in drug-induced liver injury(DILI).Despite this,understanding the exact relationship between CO and the occurrence and development of DILI remains challenging.Hence,there is an urgent need to develop a reliable and robust tool for the rapid visual detection and assessment of CO in this context.Herein,we presented a novel near-infrared(NIR)fluorescent nanoprobe with aggregation-induced emission(AIE)properties and excited-state intramolecular proton transfer(ESIPT)characteristics for the detection and imaging of CO both in vitro and in vivo.Simultaneously,the nanoprobe enables self-assembly form nanoaggregates in aqueous media with high biocompatible,which can sense CO in situ through the conversion of yellowto-red fluorescence facilitated aggregation-induced dual-color fluorescence.What is more,this nanoprobe shows ratiometric respond to CO,which demonstrates excellent stability,high sensitivity(with a detection limit of 12.5 nmol/L),and superior selectivity.Crucially,this nanoprobe enables the visual detection of exogenous and endogenous CO in living cells and tissues affected by DILI,offering a user-friendly tool for real-time visualization of CO in living system.Hence,it holds great promise in advancing our understanding of CO’s role.展开更多
Correlation between tunable optical properties and push-pull structural characters has attracted extensive attention in material science and nonlinear optics.Here,several indacenodithiophene(IDT)derivatives denoted as...Correlation between tunable optical properties and push-pull structural characters has attracted extensive attention in material science and nonlinear optics.Here,several indacenodithiophene(IDT)derivatives denoted as IDT-2NA,NA-IDT-CN,and IDT-2CN with different terminal substituents are investigated comparatively to demonstrate their intrinsic structure-property relationships.Interestingly,the IDT core acts diverse roles as acceptor(A)and donor(D)in the obtained three derivatives.Symmetric IDT-2NA with a D-A-D architecture shows an absorption maximum around 459 nm in THF.Contrary to the symmetric analog IDT-2CN with a reverse A-D-A feature,NA-IDT-CN with a different D-D'-A motif characterizes an obvious solvent polarity effect.Theo-retical calculation and electrostatic potential results confirm the terminal substituents with different electronic conjugation play vital roles in affecting the resultant photophysical properties.Utilizing the femtosecond open-aperture Z-scan technique,significant two-photon absorption(2PA)capabilities are obtained ranging from 540 to 900 nm.The 2PA cross section(δ_(2pA) )maximum about 5390 GM of centrosymmetric IDT-2CN exhibits at 600 nm.Distinct excited-state dynamics with the help of femtosecond transition absorption supports the effective intramolecular charge transfer which accounts for enhancing theδ_(2pA) values.Their potential optical power limiting applications based on the 2PA mechanism were further evaluated.The limiting thresholds were found to be 2.793.35 mJ/cm^(2) for the three IDT derivatives with a sequence of IDT-2CN<IDT-2NA<NA-IDT-CN.The distinct structural motifs and effective 2PA capabilities in the current work may provide reliable insights into the push-pull IDT chromophores for advanced nonlinear optical applications.展开更多
To emulate the functionality of the human retina and achieve a neuromorphic visual system,the development of a photonic synapse capable of multispectral color discrimination is of paramount importance.However,attainin...To emulate the functionality of the human retina and achieve a neuromorphic visual system,the development of a photonic synapse capable of multispectral color discrimination is of paramount importance.However,attaining robust color discrimination across a wide intensity range,even irrespective of medium limitations in the channel layer,poses a significant challenge.Here,we propose an approach that can bestow the color-discriminating synaptic functionality upon a three-terminal transistor flash memory even with enhanced discriminating capabilities.By incorporating the strong induced dipole moment effect at the excitation,modulated by the wavelength of the incident light,into the floating gate,we achieve outstanding RGB color-discriminating synaptic functionality within a remarkable intensity range spanning from 0.05 to 40 mW cm^(-2).This approach is not restricted to a specific medium in the channel layer,thereby enhancing its applicability.The effectiveness of this color-discriminating synaptic functionality is demonstrated through visual pre-processing of a photonic synapse array,involving the differentiation of RGB channels and the enhancement of image contrast with noise reduction.Consequently,a convolutional neural network can achieve an impressive inference accuracy of over 94%for Canadian-Institute-For-Advanced-Research-10 colorful image recognition task after the pre-processing.Our proposed approach offers a promising solution for achieving robust and versatile RGB color discrimination in photonic synapses,enabling significant advancements in artificial visual systems.展开更多
Constructing multi-dimensional hydrogen bond(H-bond)regulated single-molecule systems with multiemission remains a challenge.Herein,we report the design of a new excited-state intramolecular proton transfer(ESIPT)feat...Constructing multi-dimensional hydrogen bond(H-bond)regulated single-molecule systems with multiemission remains a challenge.Herein,we report the design of a new excited-state intramolecular proton transfer(ESIPT)featured chromophore(HBT-DPI)that shows flexible emission tunability via the multidimensional regulation of intra-and intermolecular H-bonds.The feature of switchable intramolecular Hbonds is induced via incorporating several hydrogen bond acceptors and donors into one single HBT-DPI molecule,allowing the“turn on/off”of ESIPT process by forming isomers with distinct intramolecular Hbonds configurations.In response to different external H-bonding environments,the obtained four types of crystal/cocrystals vary in the contents of isomers and the molecular packing modes,which are mainly guided by the intermolecular H-bonds,exhibiting non-emissive features or emissions ranging from green to orange.Utilizing the feature of intermolecular H-bond guided molecular packing,we demonstrate the utility of this fluorescent material for visualizing hydrophobic/hydrophilic areas on large-scale heterogeneous surfaces of modified poly(1,1-difluoroethylene)(PVDF)membranes and quantitatively estimating the surface hydrophobicity,providing a new approach for hydrophobicity/hydrophilicity monitoring and measurement.Overall,this study represents a new design strategy for constructing multi-dimensional hydrogen bond regulated ESIPT-based fluorescent materials that enable multiple emissions and unique applications.展开更多
We present a comprehensive study on the role of various excited states in high-order harmonic generation of hydrogen atoms driven by a long-wavelength(1500 nm)laser field.By numerically solving the time-dependent Schr...We present a comprehensive study on the role of various excited states in high-order harmonic generation of hydrogen atoms driven by a long-wavelength(1500 nm)laser field.By numerically solving the time-dependent Schrodinger equation(TDSE)and performing a time-frequency analysis,we investigate the influence of individual excited states on the harmonic spectrum.Our results reveal that the 2s excited state primarily contributes to the enhancement of high-energy harmonic yields by facilitating long electron trajectories,while the 2p excited state predominantly suppresses harmonic yields in the lower-energy region(20th-50th orders)by altering the contributions of electron trajectories.Our results highlight the critical role of the excited states in the HHG process,even at longer laser wavelengths.展开更多
A squarylium dye is dissolved in 4-cyano-4＇-pentylbiphenyl （SCB） and oriented by sandwiching mixtures between two pieces of rubbed glass plates. The optical absorption spectra of the oriented squarylium dye-5CB lay...A squarylium dye is dissolved in 4-cyano-4＇-pentylbiphenyl （SCB） and oriented by sandwiching mixtures between two pieces of rubbed glass plates. The optical absorption spectra of the oriented squarylium dye-5CB layers exhibit high anisotropy. The third-order nonlinear optical responses and susceptibilities X^（3）e of squarylium dye in 5CB are measured with light polarizations parallel and perpendicular to the orientational direction by the resonant femtosecond degenerate four-wave mixing （DFWM） technique. Temporal profiles of the DFWM signal of the oriented squarylium dye-5CB layers with light polarizations parallel and perpendicular to the orientational direction are measured with a time resolution of 0.3ps （FWHM）, and are found to consist of two components, i.e., the coherent instantaneous nonlinear response and slow response due to the formation of excited molecules. A high anisotropic ratio of x^（3）e, 10.8 ：k 1.2, is observed for the oriented layers.展开更多
Effects of meta-substituent of 3,4＇/4,3＇/3,3＇-substituted benzylideneanilines （XBAYs） on the electrochemical reduction potentials （E（Red）） were investigated, in which 49 samples of target compounds were synth...Effects of meta-substituent of 3,4＇/4,3＇/3,3＇-substituted benzylideneanilines （XBAYs） on the electrochemical reduction potentials （E（Red）） were investigated, in which 49 samples of target compounds were synthesized, and their reduction potentials were measured by cyclic voltammetry. The substituent effects on the E（Red） of target compounds were analyzed and an optimality equation with four parameters （Hammett constant a of X, Hammett constant a of Y, excited-state substituent constant σexCC of X, and the substituent specific cross-interaction effect △σexCC2 between X and Y） was obtained. The results show that the factors affecting the E（Red） of 3,4＇/4,31/3,3P-substituted XBAYs are different from those of 4,4＇-substituted XBAYs. For 3,4＇/4,3＇/3,3＇-substituted XBAYs, σ（X） and σ（Y） must be employed, and the contribution of △σexCC2 is important and not negligible. Compared with 4,4＇-substituted XBAYs, X group contributes less to 3,4＇/4,3＇/3,3＇-substituted XBAYs, while Y group contributes more to them. Additionally, it was observed that either para-substituted XBAYs or meta-substituted XBAYs, the substituent effects of X are larger than those of Y on the E（Red） of substituted XBAYs.展开更多
Dielectric barrier discharge （DBD） cold plasma at atmospheric pressure was used for preparation of copper nanoparticles by reduction of copper oxide （CuO）. Power X-ray diffraction （XRD） was used to characterize ...Dielectric barrier discharge （DBD） cold plasma at atmospheric pressure was used for preparation of copper nanoparticles by reduction of copper oxide （CuO）. Power X-ray diffraction （XRD） was used to characterize the structure of the copper oxide samples treated by DBD plasma. Influences of H2 content and the treating time on the reduction of copper oxide by DBD plasma were investigated. The results show that the reduction ratio of copper oxide was increased initially and then decreased with increasing H2 content, and the highest reduction ratio was achieved at 20% H2 content. Moreover, the copper oxide samples were gradually reduced by DBD plasma into copper nanoparticles with the increase in treating time. However, the average reduction rate was decreased as a result of the diffusion of the active hydrogen species. Optical emission spectra （OES） were observed during the reduction of the copper oxide samples by DBD plasma, and the reduction mechanism was explored accordingly. Instead of high-energy electrons, atomic hydrogen （H） radicals, and the heating effect, excited-state hydrogen molecules are suspected to be one kind of important reducing agents. Atmospheric-pressure DBD cold plasma is proved to be an efficient method for preparing copper nanoparticles.展开更多
By extending the Levy wavefunction constrained search to Fock Space,one can define a wavefunction constrained search for electron densities in systems having noninteger number of electrons.For pure-state v-representab...By extending the Levy wavefunction constrained search to Fock Space,one can define a wavefunction constrained search for electron densities in systems having noninteger number of electrons.For pure-state v-representable densities,the results are equivalent to what one would obtain with the zero-temperature grand canonical ensemble.In other cases,the wavefunction constrained search in Fock space presents an upper bound to the grand canonical ensemble functional.One advantage of the Fock-space wavefunction constrained search functional over the zero-temperature grand-canonical ensemble constrained search functional is that certain specific excited states(i.e.,those that are not ground-statev-representable) are the stationary points of the Fock-space functional.However,a potential disadvantage of the Fock-space constrained search functional is that it is not convex.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.
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 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.
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 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 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the National Natural Science Foundation of China(Nos.82272067,81974386,22107123 and M-0696)the Natural Science Foundation of Hunan Province(Nos.2021JJ41008,2022JJ80052,2022JJ40656,2023JJ20077)+2 种基金the Key Project of Changsha Science and Technology Plan(No.kh2201059)the Scientific Research Project of Health Commission of Hunan Province(No.B202313057213)the Youth Science Foundation of Xiangya Hospital(No.2022Q16).
文摘Carbon monoxide(CO)is a crucial gaseous signaling molecule that regulates various physiological and pathological processes,and may exert an anti-inflammatory and protective role in drug-induced liver injury(DILI).Despite this,understanding the exact relationship between CO and the occurrence and development of DILI remains challenging.Hence,there is an urgent need to develop a reliable and robust tool for the rapid visual detection and assessment of CO in this context.Herein,we presented a novel near-infrared(NIR)fluorescent nanoprobe with aggregation-induced emission(AIE)properties and excited-state intramolecular proton transfer(ESIPT)characteristics for the detection and imaging of CO both in vitro and in vivo.Simultaneously,the nanoprobe enables self-assembly form nanoaggregates in aqueous media with high biocompatible,which can sense CO in situ through the conversion of yellowto-red fluorescence facilitated aggregation-induced dual-color fluorescence.What is more,this nanoprobe shows ratiometric respond to CO,which demonstrates excellent stability,high sensitivity(with a detection limit of 12.5 nmol/L),and superior selectivity.Crucially,this nanoprobe enables the visual detection of exogenous and endogenous CO in living cells and tissues affected by DILI,offering a user-friendly tool for real-time visualization of CO in living system.Hence,it holds great promise in advancing our understanding of CO’s role.
基金the National Natural Science Foundation of China(22172097)the Shaanxi Provincial Sci-ence Fund for Distinguished Young Scholars(2025JC-JCQN-044)+1 种基金the National Key Research and Development Program of China(2022YFA1205502)the 111 Project(B14041).
文摘Correlation between tunable optical properties and push-pull structural characters has attracted extensive attention in material science and nonlinear optics.Here,several indacenodithiophene(IDT)derivatives denoted as IDT-2NA,NA-IDT-CN,and IDT-2CN with different terminal substituents are investigated comparatively to demonstrate their intrinsic structure-property relationships.Interestingly,the IDT core acts diverse roles as acceptor(A)and donor(D)in the obtained three derivatives.Symmetric IDT-2NA with a D-A-D architecture shows an absorption maximum around 459 nm in THF.Contrary to the symmetric analog IDT-2CN with a reverse A-D-A feature,NA-IDT-CN with a different D-D'-A motif characterizes an obvious solvent polarity effect.Theo-retical calculation and electrostatic potential results confirm the terminal substituents with different electronic conjugation play vital roles in affecting the resultant photophysical properties.Utilizing the femtosecond open-aperture Z-scan technique,significant two-photon absorption(2PA)capabilities are obtained ranging from 540 to 900 nm.The 2PA cross section(δ_(2pA) )maximum about 5390 GM of centrosymmetric IDT-2CN exhibits at 600 nm.Distinct excited-state dynamics with the help of femtosecond transition absorption supports the effective intramolecular charge transfer which accounts for enhancing theδ_(2pA) values.Their potential optical power limiting applications based on the 2PA mechanism were further evaluated.The limiting thresholds were found to be 2.793.35 mJ/cm^(2) for the three IDT derivatives with a sequence of IDT-2CN<IDT-2NA<NA-IDT-CN.The distinct structural motifs and effective 2PA capabilities in the current work may provide reliable insights into the push-pull IDT chromophores for advanced nonlinear optical applications.
基金supported by National Research Foundation of Korea(NRF)[RS-2024-00350701 and RS-2023-00207828].
文摘To emulate the functionality of the human retina and achieve a neuromorphic visual system,the development of a photonic synapse capable of multispectral color discrimination is of paramount importance.However,attaining robust color discrimination across a wide intensity range,even irrespective of medium limitations in the channel layer,poses a significant challenge.Here,we propose an approach that can bestow the color-discriminating synaptic functionality upon a three-terminal transistor flash memory even with enhanced discriminating capabilities.By incorporating the strong induced dipole moment effect at the excitation,modulated by the wavelength of the incident light,into the floating gate,we achieve outstanding RGB color-discriminating synaptic functionality within a remarkable intensity range spanning from 0.05 to 40 mW cm^(-2).This approach is not restricted to a specific medium in the channel layer,thereby enhancing its applicability.The effectiveness of this color-discriminating synaptic functionality is demonstrated through visual pre-processing of a photonic synapse array,involving the differentiation of RGB channels and the enhancement of image contrast with noise reduction.Consequently,a convolutional neural network can achieve an impressive inference accuracy of over 94%for Canadian-Institute-For-Advanced-Research-10 colorful image recognition task after the pre-processing.Our proposed approach offers a promising solution for achieving robust and versatile RGB color discrimination in photonic synapses,enabling significant advancements in artificial visual systems.
基金supported by the National Key R&D Program of China(No.2021YFC2103600)the National Natural Science Foundation of China(Nos.21878156,21978131,22275085,and 22278224)+2 种基金the Natural Science Foundation of Jiangsu Province(Nos.BK20200089 and BK20200691)the Project of Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the State Key Laboratory of Materials-Oriented Chemical Engineering(No.KL21-08).
文摘Constructing multi-dimensional hydrogen bond(H-bond)regulated single-molecule systems with multiemission remains a challenge.Herein,we report the design of a new excited-state intramolecular proton transfer(ESIPT)featured chromophore(HBT-DPI)that shows flexible emission tunability via the multidimensional regulation of intra-and intermolecular H-bonds.The feature of switchable intramolecular Hbonds is induced via incorporating several hydrogen bond acceptors and donors into one single HBT-DPI molecule,allowing the“turn on/off”of ESIPT process by forming isomers with distinct intramolecular Hbonds configurations.In response to different external H-bonding environments,the obtained four types of crystal/cocrystals vary in the contents of isomers and the molecular packing modes,which are mainly guided by the intermolecular H-bonds,exhibiting non-emissive features or emissions ranging from green to orange.Utilizing the feature of intermolecular H-bond guided molecular packing,we demonstrate the utility of this fluorescent material for visualizing hydrophobic/hydrophilic areas on large-scale heterogeneous surfaces of modified poly(1,1-difluoroethylene)(PVDF)membranes and quantitatively estimating the surface hydrophobicity,providing a new approach for hydrophobicity/hydrophilicity monitoring and measurement.Overall,this study represents a new design strategy for constructing multi-dimensional hydrogen bond regulated ESIPT-based fluorescent materials that enable multiple emissions and unique applications.
基金supported by the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi。
文摘We present a comprehensive study on the role of various excited states in high-order harmonic generation of hydrogen atoms driven by a long-wavelength(1500 nm)laser field.By numerically solving the time-dependent Schrodinger equation(TDSE)and performing a time-frequency analysis,we investigate the influence of individual excited states on the harmonic spectrum.Our results reveal that the 2s excited state primarily contributes to the enhancement of high-energy harmonic yields by facilitating long electron trajectories,while the 2p excited state predominantly suppresses harmonic yields in the lower-energy region(20th-50th orders)by altering the contributions of electron trajectories.Our results highlight the critical role of the excited states in the HHG process,even at longer laser wavelengths.
文摘A squarylium dye is dissolved in 4-cyano-4＇-pentylbiphenyl （SCB） and oriented by sandwiching mixtures between two pieces of rubbed glass plates. The optical absorption spectra of the oriented squarylium dye-5CB layers exhibit high anisotropy. The third-order nonlinear optical responses and susceptibilities X^（3）e of squarylium dye in 5CB are measured with light polarizations parallel and perpendicular to the orientational direction by the resonant femtosecond degenerate four-wave mixing （DFWM） technique. Temporal profiles of the DFWM signal of the oriented squarylium dye-5CB layers with light polarizations parallel and perpendicular to the orientational direction are measured with a time resolution of 0.3ps （FWHM）, and are found to consist of two components, i.e., the coherent instantaneous nonlinear response and slow response due to the formation of excited molecules. A high anisotropic ratio of x^（3）e, 10.8 ：k 1.2, is observed for the oriented layers.
文摘Effects of meta-substituent of 3,4＇/4,3＇/3,3＇-substituted benzylideneanilines （XBAYs） on the electrochemical reduction potentials （E（Red）） were investigated, in which 49 samples of target compounds were synthesized, and their reduction potentials were measured by cyclic voltammetry. The substituent effects on the E（Red） of target compounds were analyzed and an optimality equation with four parameters （Hammett constant a of X, Hammett constant a of Y, excited-state substituent constant σexCC of X, and the substituent specific cross-interaction effect △σexCC2 between X and Y） was obtained. The results show that the factors affecting the E（Red） of 3,4＇/4,31/3,3P-substituted XBAYs are different from those of 4,4＇-substituted XBAYs. For 3,4＇/4,3＇/3,3＇-substituted XBAYs, σ（X） and σ（Y） must be employed, and the contribution of △σexCC2 is important and not negligible. Compared with 4,4＇-substituted XBAYs, X group contributes less to 3,4＇/4,3＇/3,3＇-substituted XBAYs, while Y group contributes more to them. Additionally, it was observed that either para-substituted XBAYs or meta-substituted XBAYs, the substituent effects of X are larger than those of Y on the E（Red） of substituted XBAYs.
基金supported by National Natural Science Foundation of China(No.21173028)the Science and Technology Research Project of Liaoning Provincial Education Department of China(No.L2013464)the Scientific Research Foundation for the Doctor of Liaoning Province of China(No.20131004)
文摘Dielectric barrier discharge （DBD） cold plasma at atmospheric pressure was used for preparation of copper nanoparticles by reduction of copper oxide （CuO）. Power X-ray diffraction （XRD） was used to characterize the structure of the copper oxide samples treated by DBD plasma. Influences of H2 content and the treating time on the reduction of copper oxide by DBD plasma were investigated. The results show that the reduction ratio of copper oxide was increased initially and then decreased with increasing H2 content, and the highest reduction ratio was achieved at 20% H2 content. Moreover, the copper oxide samples were gradually reduced by DBD plasma into copper nanoparticles with the increase in treating time. However, the average reduction rate was decreased as a result of the diffusion of the active hydrogen species. Optical emission spectra （OES） were observed during the reduction of the copper oxide samples by DBD plasma, and the reduction mechanism was explored accordingly. Instead of high-energy electrons, atomic hydrogen （H） radicals, and the heating effect, excited-state hydrogen molecules are suspected to be one kind of important reducing agents. Atmospheric-pressure DBD cold plasma is proved to be an efficient method for preparing copper nanoparticles.
文摘By extending the Levy wavefunction constrained search to Fock Space,one can define a wavefunction constrained search for electron densities in systems having noninteger number of electrons.For pure-state v-representable densities,the results are equivalent to what one would obtain with the zero-temperature grand canonical ensemble.In other cases,the wavefunction constrained search in Fock space presents an upper bound to the grand canonical ensemble functional.One advantage of the Fock-space wavefunction constrained search functional over the zero-temperature grand-canonical ensemble constrained search functional is that certain specific excited states(i.e.,those that are not ground-statev-representable) are the stationary points of the Fock-space functional.However,a potential disadvantage of the Fock-space constrained search functional is that it is not convex.
