查看更多>>摘要：The aggregation-induced emission(AIE)effect and corresponding restriction of intramolecular motions strategy are important mechanisms for regulating the performance of novel organic light-emitting diode materials and constituent molecules,such as emission intensity and peak position.Nevertheless,molecules in the aggregate state usually yield a red-shifted fluorescence due to the π-π interaction enhancement.Here,we report a blue-shifted fluorescence mechanism induced by the restriction of intramolecular torsion in the aggregate state for an interesting excited-state intramolecular proton transfer fluorophore.A combined experimental and theoretical method is performed to investigate the excited state dynamics of the molecules in solvent and the aggregate state respectively.Multiple regression analysis reveals that the changes of reorganization energy caused by AIE effect induce the blue-shifted fluorescence.These findings contribute in several ways to our understanding of the AIE effect,and provide a new strategy to regulate the emission performance of AIE materials.
查看更多>>摘要：A new series of ferrocene(D)and methoxyphenyl(D')conjugated D-D'-π-A push-pull chromophores [Fc-(RPh)C=CH-CH=CN-R'{R,R'= H,CN U),OCH3,CN(2),H,C6H4NO2(3),OCH3,C6H4NO2(4)}] were synthesized and spectroscopically characterized.The structure of the chromophore 3 was confirmed by single crystal X-ray diffraction studies,and it was crystallized in triclinic crystal system with P-l centrosymmetric space group.In the crystal packing,several non-covalent interactions(H-bonding and C-H.....π)were observed.The thermal behaviour of the chromophores 3 and 4 has been investigated using thermogravimetric analysis and was found to be stable up to 230 ℃.The solvatochromic studies of the chromophores 1-4 showed a positive solvatochromism with red-shift from non-polar to polar solvents due to the high dipolar excited state in the presence of strong electron-donor and acceptor moieties.The electrochemical performance of the chromophores revealed the one-electron transfer from the ferrocene to ferrocenium ion(Fe~(2+)←→Fe~(3+)).The chromophores 1-4 exhibited low fluorescence intensity and quantum yield as a consequence of the quenching nature of ferrocene,it was further enhanced through the aggregation-induced emission(AIE)process in THF/H2O mixtures by the restriction of intramolecular rotation(RIR),and the chromophores 1-4 showed 2 times higher quantum yield in the aggregated state.The second-order nonlinear optical response was attained by Kurtz-Perry powder technique.The second harmonic generation(SHG)efficiencies of the chromophore 4 was close to the standard KDP,owing to the presence of multi-donor [Ferrocene(D)and methoxyphenyl(D')] and acceptor groups with extended π-conju-gation.In addition,the mesomeric effect(+M)of the methoxy group makes an effective charge transfer process.The optical and nonlinear optical properties of the chromophores were further analyzed by density functional theory(DFT)with different functionals(B3LYP,CAM-B3LYP and LC-BLYP).The hyperpolarizability values were underestimates in the B3LYP-hybrid functional because of the corrected long-range charge transfer between donor and acceptor in the D-π-A systems.The frontier molecular orbital(FMO)level helps for better understanding the charge transfer,nonlinear optical(NLO)properties,and the calculated HOMO-LUMO energy levels were in good agreement with the experimental results.
查看更多>>摘要：G-quadruplexes(G4s),DNA or RNA structures formed by guanine-rich sequences,play indispensable regulatory roles in numerous biological processes.Here we develop a Near Infrared(NIR)fluorescence G4 indicator(TAQ)which enables activatable imaging of G4s in live cells.The indicator TAQ is merely emissive in aqueous solution and its fluorescence at 677 nm is remarkably enhanced in the presence of a typical hybrid G4 structure.TAQ broadly interacts with different G4 structures,exhibiting high selectivity toward G4s over single-or double-stranded nucleic acids.It is demonstrated that TAQ affords dynamic fluorescence response to G4 concentrations in the range of 5.0-600 nM with an estimated limit of detection of 0.51 nM.Live cell studies demonstrate that TAQ delivers intense fluorescence signals upon specific interaction with G4 structures.We further employ TAQ to track the dynamics of RNA/DNA G4s in live cells.This NIR fluorescence indicator could provide a valuable tool for interrogating the dynamics of G4 structures in live cells.
查看更多>>摘要：Naphthalimides and their derivatives have been extensively studied in various research fields such as supra-molecular chemistry,sensor materials,and pharmaceutical chemistry,due to their ease of synthesis,the potential to tune their optical properties and biological activity.In this review,we highlight recent advances in the development of versatile naphthalimides as chemical sensors for metal ions,anions,reactive oxygen species,and cancer-associated enzymes,therapeutic agents,and photosensitizers,and described their optical response and sensing mechanisms,bioactivity and associated molecular docking studies,photosensitivity for photodynamic therapy and related density functional theory(DFT)calculations.Rational design concepts related to the chemical structure of naphthalimides in various applications ranging from sensing to therapeutic purposes are described.Additionally,this review demonstrates the behavior of these naphthalimides with a variety of analytical methods such as absorption and fluorescence spectroscopy,nuclear magnetic resonance and mass analyses,fluorescence confocal microscopic studies,molecular dynamics simulation,DTF calculation,molecular docking studies,and antiproliferative experiments in vitro and in vivo.We hope that this review will help in the future advances of versatile naphthalimides and in the design of optical and biological validation studies.Prospects for future research directions are provided by highlighting the optical and biological benefits of naphthalimides.
查看更多>>摘要：In this article,an effective host-guest system with intense afterglow and stimuli-responsive properties is described.Br-BID-Py(host)crystals emit weak phosphorescence and NMe2-BID-Py(guest)crystals are not phosphorescent.However,when NMe2-BID-Py is doped into the Br-BID-Py crystals,the afterglow of the host is enhanced.The afterglow exhibits a unique thermally activated property,which is due to the effective intersystem crossing from the guest to the host via energy transfer.Br-BID-Py(host)and NMe2-BID-Py(guest)show small structural differences,which facilitate energy transfer with each other in the crystal state.The energy transfer process is evidenced by excitation photoluminescence spectra and UV-vis absorption spectra.To date,the host-guest afterglow organic system where the guest enhances the intrinsic afterglow of the host is rarely reported.Moreover,both Br-BID-Py and NMe2-BID-Py display stimuli-responsive properties because of protonation of pyridine,which is inherited by the hybrid host-guest crystals.The host-guest crystals demonstrate rare proton-induced afterglow shift observed by direct visualization by eye.Finally,the application of the host-guest afterglow material and its stimulus-responsive property in information encryption is displayed.To our best knowledge,this example is a rare stimulus-responsive organic afterglow material fabricated via the strategy of a host-guest doping system.
查看更多>>摘要：The skin microbiota is an inseparable component of the skin barrier structure,which participates in the stabilization or impairment of the barrier function as well as the development of many skin diseases.In order to maintain the stability of skin bacteria community structure,people pay more and more attention to protecting probiotics,such as bacilli,and killing pathogens,such as Gram-positive cocci.We herein report a negatively charged photosensitizer TPA-3NBA with aggregation-induced emission(AIE)characteristics,which was synthesized by one-step reaction,can selectively and rapidly stain(within 0.5 min)and effectively kill Gram-positive cocci(killing 6.0 log_(10)of Staphylococcus aureus at a concentration of 1 μM)without affecting bacilli under white light irradiation.This selective bacterial imaging makes it possible to quickly identify locally bacterial infection.Furthermore,the normal concentration of divalent ion(Ca~(2+))in human body can significantly promote the absorption of TPA-3NBA by Gram-positive cocci,thus improving its antibacterial activity.To the best of our knowledge,this is the first photosensitizer to be reported with good performance in selective bacterial imaging and removal of Gram-positive pathogenic cocci,indicating its potential application prospect in targeted antimicrobial therapy.
查看更多>>摘要：The redox chemistry and status of different cell types and tissues has still not been well understood and thus represents a major focus for the development of novel responsive fluorophores.In this context,there is an ongoing search for reduction-sensitive probes that can globally or specifically image reducing environments or species in biological settings.Here,the synthesis and characterization of responsive cyanine dyes operating in the near-infrared(NIR)is reported based on the use of the hydroquinone/quinone and catechol/quinone couple.The introduction of a hydroquinone group into the meso-position of an indodicarbocyanine dye via a Suzuki cross-coupling reaction created a water-soluble fluorescent"on-off-on"probe whose fluorescence can be modulated through oxidation and reduction.By adding biologically relevant reducing species,such as glutathione,cysteine or ascorbate,the"off-probe could be rapidly turned on around 660 nm within 30 s.Reversible switching between the"on"and"off form was demonstrated.Furthermore,the sensor was applied in confocal microscopy studies as a reduction-sensitive probe for bioimaging in living cells.
查看更多>>摘要：Perhalogenated zinc-phthalocyanines(xZnPcs),with brilliant hue and durable chemical nature,are widely used organic pigments for green color filters.Due to sparing solubility in organic solvents,the film formation of xZnPc generally involves a time-consuming milling procedure in the presence of a polymeric dispersant.But,the severe aggregation issue still arises during the film formation,primarily originating from the inherent nature of phthalocyanine moiety.Here,we intend to effectively modify the solution processability and resulting optical property of xZnPcs by introducing the anion-π bonding.Perhalo-substitution on zinc-phthalocyanines facilitates the π-acidity in the four aromatic Pc skeletons.The electron-rich sulfide ions are attracted towards the highly electron-deficient xZnPc,making the pigment particles soluble in the form of the anion-π complex.A new band around 400-450 nm is observed for the complexes,accompanied by the change of the bluish-green suspension into olive green solution.~(19)F NMR studies provide information about the anion-π bonding between xZnPc2 and sulfide ions.The spray-coating method produces a uniform colored film,in which the sulfide content is confirmed by SEM-EDS analysis.In the UV-Vis spectra,the prepared films show a gradual decrease in the band absorption at 670 nm corresponding to the aggregation of phthalocyanines.Besides,the cyclic voltammetry measurement reveals the superior electrochemical behaviors of the anion-π complex.The current result presents a practical non-covalent approach suitable for preparing a pigment dispersion,which finds useful for color filter and image sensor applications.
查看更多>>摘要：Fluoride detection is important in environmental monitoring and disease screening.In many of detection methods,small molecule fluorescent probes have been developed rapidly in recent years for their high efficiency,selectivity and low cost.To develop quickly fluorescent probe for detection fluoride ions,a novel phenothiazine-based fluorescent probe PHT was designed and synthesized.The response time of PHT was only 1 min and the detection line of PHT reached to 1.3 ppb.Moreover,the stoke shift of PHT was close to 140 nm,which was much better than the previous reports.At last,the probe PHT was successfully used for HepG2 imaging and detection of biological samples with endemic disease.
查看更多>>摘要：Fluorescence bioimaging the dynamic of reactive oxygen species(ROS)in particular organelles has attracted extensive attention owing to their critical roles in many cellular processes.By tuning the electronic structures of rhodamine through the heteroatom-substitution,the highly oxidative peroxynitrite(ONOO~-)in lysosomes was sensitively tracked by the designed phosphorus-substituted rhodamine(PR)without incorporating any external trigger.The specific and efficient reaction between the designed PR probes(PR1-ONOO and PR2-ONOO)and ONOO~-have ensured the sensitivity and selectivity in the bioimaging of lysosomal ONOO~-in vivo.Cancer and normal cells,tumor and normal tissues were distinguished by the fluorescence bioimaging of the lysosomal ONOCT.Moreover,the unique structures and properties of PR ensured sensitively monitoring the dynamic of lysosomal ONOO~-monitored in the ferroptosis process.
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