Increase In Fluorescence Lifetime Research Articles

Longitudinal in vivo tracking of adverse effects following topical steroid treatment.

Topical steroids are known for their anti-inflammatory properties and are commonly prescribed to treat many adverse skin conditions such as eczema and psoriasis. While these treatments are known to be effective, adverse effects including skin atrophy are common. In this study, the progression of these effects is investigated in an in vivo mouse model using multimodal optical microscopy. Utilizing a system capable of performing two-photon excitation fluorescence microscopy (TPEF) of reduced nicotinamide adenine dinucleotide (NADH) to visualize the epidermal cell layers and second harmonic generation (SHG) microscopy to identify collagen in the dermis, these processes can be studied at the cellular level. Fluorescence lifetime imaging microscopy (FLIM) is also utilized to image intracellular NADH levels to obtain molecular information regarding metabolic activity following steroid treatment. In this study, fluticasone propionate (FP)-treated, mometasone furoate (MF)-treated and untreated animals were imaged longitudinally using a custom-built multimodal optical microscope. Prolonged steroid treatment over the course of 21 days is shown to result in a significant increase in mean fluorescence lifetime of NADH, suggesting a faster rate of maturation of epidermal keratinocytes. Alterations to collagen organization and the structural microenvironment are also observed. These results give insight into the structural and biochemical processes of skin atrophy associated with prolonged steroid treatment.

Genetically encoded far-red fluorescent sensors for caspase-3 activity.

Caspase-3 is a key effector caspase that is activated in both extrinsic and intrinsic pathways of apoptosis. Available fluorescent sensors for caspase-3 activity operate in relatively short wavelength regions and are nonoptimal for multiparameter microscopy and whole-body imaging. In the present work, we developed new genetically encoded sensors for caspase-3 activity possessing the most red-shifted spectra to date. These consist of Förster resonance energy transfer (FRET) pairs in which a far-red fluorescent protein (mKate2 or eqFP650) is connected to the infrared fluorescent protein iRFP through a linker containing the DEVD caspase-3 cleavage site. During staurosporine-induced apoptosis of mammalian cells (HeLa and CT26), both mKate2-DEVD-iRFP and eqFP650-DEVD-iRFP sensors showed a robust response (1.6-fold increase of the donor fluorescence intensity). However, eqFP650-DEVD-iRFP displayed aggregation in some cells. For stably transfected CT26 mKate2-DEVD-iRFP cells, fluorescence lifetime imaging (FLIM) enabled us to detect caspase-3 activation due to the increase of mKate2 donor fluorescence lifetime from 1.45 to 2.05 ns. We took advantage of the strongly red-shifted spectrum of mKate2-DEVD-iRFP to perform simultaneous imaging of EGFP-Bax translocation during apoptosis. We conclude that mKate2-DEVD-iRFP is well-suited for multiparameter imaging and also potentially beneficial for in vivo imaging in animal tissues.

Interactions of the beta-blocker drug, propranolol, with detergents, beta-cyclodextrin and living cells studied using fluorescence spectroscopy and imaging

Interactions of the β-blocker drug, propranolol, with amphipathic systems have been studied using fluorescence spectroscopy. The results show a strong binding of propranolol with micelles of sodium dodecyl sulfate revealed through changes in the fluorescence spectrum and an increase in fluorescence lifetime. Quenching of propranolol fluorescence by iodide is used to demonstrate interaction with β-cyclodextrin. At high concentrations, self-quenching of propranolol fluorescence was also observed with κq=2.5×109 dm3 mol–1 s–1. Two-photon excited (630 nm) fluorescence lifetime imaging of propranolol in cells showed propranolol to be widely distributed in the cell cytoplasm, with fluorescence lifetimes shorter than in solution. The results suggest that intracellular propranolol is mainly confined within the aqueous cytoplasm and rather than membrane associated.

Two-Dimensional, Acene-Containing Conjugated Polymers That Show Ratiometric Fluorescent Response to Singlet Oxygen

This paper describes two-dimensional conjugated poly(phenylene–ethynylene)s (PPEs) linked to singlet oxygen-reactive diethynyltetracene units through phenylene–ethynylene (PE) bridges that are conjugated to the polymer backbones. Successive Sonogashira coupling reactions enabled the preparation of the tetracene-containing PE pendants, the linking of the pendants to the monomer unit, and the polymerization reactions. Small molecule models of the polymers showed ratiometric responses of fluorescence upon exposure to photogenerated singlet oxygen due to cycloaddition reactions increasing the excited state of individual chromophores. The fluorescent responses of the tetracene-linked PPEs, however, showed markedly different behavior: (i) an initial increase in fluorescence intensity and fluorescence lifetime of the side-chain tetracenes upon exposure to 1O2 indicated an analyte-induced slowing of self-quenching due to high local acene concentration, and (ii) ratiometric blue-shifted response did not occur unti...

Photocatalytic performance of Pd decorated TiO2–CdO composite: Role of in situ formed CdS in the photocatalytic activity

We report an enhanced photocatalytic activity for TiO2–CdO composite for hydrogen generation from aqueous solution of Na2S + Na2SO3 compared to pure CdO and TiO2. An in situ conversion of CdO to CdS is observed during the photocatalytic reaction resulting in the formation of a CdO–CdS–TiO2 ternary composite, which play a role in the enhanced activity. Presence of Pd as a co-catalyst in the composite increases the hydrogen production nearly ten times. As prepared composite exists as anatase phase of TiO2 and cubic phase of CdO. Characterization of the catalyst by powder XRD, SEM and TEM suggest that a nanosized TiO2 exists as a dispersed phase on aggregated CdO. UV-visible absorption spectrum of the composite shows features of both CdO and TiO2. Composite sample exhibits increased photocurrent response and has increased fluorescence lifetime for the charge carriers compared to pure CdO and TiO2. A detailed characterization of the used catalysts clearly shows the formation of CdS phase besides TiO2 and CdO. This is the first report on the photocatalytic activity of TiO2–CdO system for hydrogen generation from water due to in situ bulk formation of CdS during the photocatalytic reaction. The in situ formed CdS in the composite enhances the photocatalytic activity in two ways: (i) CdS, whose conduction band is at higher negative potential than CdO and TiO2, can reduce H+ more efficiently and (ii) efficient separation of photogenerated charges can occur in this composite system, resulting in increased lifetime for the charge carriers.

Enhancement of early cervical cancer diagnosis with epithelial layer analysis of fluorescence lifetime images.

This work reports the use of layer analysis to aid the fluorescence lifetime diagnosis of cervical intraepithelial neoplasia (CIN) from H&E stained cervical tissue sections. The mean and standard deviation of lifetimes in single region of interest (ROI) of cervical epithelium were previously shown to correlate to the gold standard histopathological classification of early cervical cancer. These previously defined single ROIs were evenly divided into layers for analysis. A 10-layer model revealed a steady increase in fluorescence lifetime from the inner to the outer epithelial layers of healthy tissue sections, suggesting a close association with cellular maturity. The shorter lifetime and minimal lifetime increase towards the epithelial surface of CIN-affected regions are in good agreement with the absence of cellular maturation in CIN. Mean layer lifetimes in the top-half cervical epithelium were used as feature vectors for extreme learning machine (ELM) classifier discriminations. It was found that the proposed layer analysis technique greatly improves the sensitivity and specificity to 94.6% and 84.3%, respectively, which can better supplement the traditional gold standard cervical histopathological examinations.

Single cell FRET analysis for the identification of optimal FRET-pairs in Bacillus subtilis using a prototype MEM-FLIM system.

Protein-protein interactions can be studied in vitro, e.g. with bacterial or yeast two-hybrid systems or surface plasmon resonance. In contrast to in vitro techniques, in vivo studies of protein-protein interactions allow examination of spatial and temporal behavior of such interactions in their native environment. One approach to study protein-protein interactions in vivo is via Förster Resonance Energy Transfer (FRET). Here, FRET efficiency of selected FRET-pairs was studied at the single cell level using sensitized emission and Frequency Domain-Fluorescence Lifetime Imaging Microscopy (FD-FLIM). For FRET-FLIM, a prototype Modulated Electron-Multiplied FLIM system was used, which is, to the best of our knowledge, the first account of Frequency Domain FLIM to analyze FRET in single bacterial cells. To perform FRET-FLIM, we first determined and benchmarked the best fluorescent protein-pair for FRET in Bacillus subtilis using a novel BglBrick-compatible integration vector. We show that GFP-tagRFP is an excellent donor-acceptor pair for B. subtilis in vivo FRET studies. As a proof of concept, selected donor and acceptor fluorescent proteins were fused using a linker that contained a tobacco etch virus (TEV)-protease recognition sequence. Induction of TEV-protease results in loss of FRET efficiency and increase in fluorescence lifetime. The loss of FRET efficiency after TEV induction can be followed in time in single cells via time-lapse microscopy. This work will facilitate future studies of in vivo dynamics of protein complexes in single B. subtilis cells.

Interaction of quinine sulfate with anionic micelles of sodium dodecylsulfate: A time-resolved fluorescence spectroscopy at different pH

Photophysical behavior and rotational relaxation dynamics of quinine sulfate (QS) in anionic surfactant, sodium dodecylsulfate (SDS) at different pH have been studied using steady state and time resolved fluorescence spectroscopy. It has been observed that the cationic form of quinine sulfate (at pH 2) forms a fluorescent ion pair complex with the surfactant molecules at lower concentrations of surfactant. However, for higher concentrations of SDS, the probe molecules bind strongly with the micelles and reside at the water–micelle interface. At pH 7, QS is singly protonated in bulk aqueous solution. At lower concentrations of SDS aggregation between probe and surfactant molecules has been observed. However, for higher concentrations of SDS, an additional fluorescence peak corresponding to dicationic form of QS appears and this has been attributed to double protonation of the QS molecule in micellar solution. At pH 7, in the presence of SDS micelles, the photophysical properties of QS showed substantial changes compared to that in the bulk water solution. At pH 12, an increase in fluorescence intensity and lifetime has been observed and this has been attributed to the increase in radiative rate due to the incorporation of QS at the micelle–water interface. The local pH at micellar surface has been found different from the pH of bulk solution.

Dependence of spectroscopic and thermal properties on concentration and temperature for Yb:Y2O3 transparent ceramics

High transparency ytterbium doping yttria (Yb:Y2O3) ceramics were fabricated by vacuum sintering. The influence of temperature and doping concentration on optical and thermal properties of Yb:Y2O3 ceramics were evaluated. The increased Yb doping concentration causes the red-shift of absorption edge. The intensities of absorption peaks increase linearly with Yb3+ ion concentration, and the absorption cross-section at ∼978nm is calculated to be 1.15×10−20cm2. When Yb3+ doping content is 5.0at.%, the strongest peak centers at the wavelength of 1030nm with the full width at half maximum (FWHM) of 17nm, and stimulated emission cross-section is measured to be 1.58×10−20cm2. Both absorption coefficient and fluorescence lifetime increase with increasing Yb3+ concentration. The optimum doping concentration of Yb3+ ion in Y2O3 transparent ceramic is in the range of 5.0–7.0at.%. For 5.0at.% Yb:Y2O3 transparent ceramic, as temperature increases from 10K to room temperature (RT), the fluorescence intensity decreases and the peaks are broaden.

Features of temporal behavior of fluorescence recovery in Synechocystis sp. PCC6803.

Under high photon flux density of solar radiation, the photosynthetic apparatus can be damaged. To prevent this photodestruction, cyanobacteria developed special mechanisms of non-photochemical quenching (NPQ) of excitation energy in phycobilisomes. In Synechocystis, NPQ is triggered by the orange carotenoid protein (OCP), which is sensitive to blue-green illumination allowing it to bind to the phycobilisome reducing the flow of energy to the photosystems. Consequent decoupling of OCP and recovery of phycobilisome fluorescence in vivo is controlled by the so called fluorescence recovery protein (FRP). In this work, the role of the phycobilisome core components, apcD and apcF, in non-photochemical quenching and subsequent fluorescence recovery in the phycobilisomes of the cyanobacterium Synechocystis sp. PCC6803 has been investigated. Using a single photon counting technique, we have registered fluorescence decay spectra with picosecond time resolution during fluorescence recovery. In order to estimate the activation energy for the photocycle, spectroscopic studies in dependency on the temperature from 5 to 45°C have been performed. It was found that fluorescence quenching and recovery were strongly temperature dependent for all strains exhibiting characteristic non-linear time courses. The rise of the fluorescence intensity during fluorescence recovery after NPQ can be completely described by the increase of the phycobilisome core fluorescence lifetime. It was shown that fluorescence recovery of apcD- and apcF-deficient mutants is characterized by a significantly lower activation energy barrier compared to wild type. This phenomenon indicates that apcD and apcF gene products may be required for proper interaction of FRP and OCP coupled to the phycobilisome core. In addition, we found that the rate of fluorescence recovery decreases with an increase of the non-photochemical quenching amplitude, probably due to depletion of substrate for the enzymatic reaction catalyzed by FRP.

Interaction of the nonsteroidal anti-inflammatory drug indomethacin with micelles and its release.

In this study, we have reported the binding interaction and photophysics of a nonsteroidal anti-inflammatory drug (NSAID) indomethacin (IMC) in the presence of different micelles. We have used several spectroscopic techniques such as UV-vis absorption, steady state fluorescence and time-resolved fluorescence emission spectroscopy. The spectral properties of IMC were modulated in the presence of micelles compared to that in neat water. The weak emitting drug molecule (IMC) becomes highly fluorescent after binding with the micelles. The fluorescence quantum yield and fluorescence lifetime increase in the presence of micelles compared to those in neat water. The isothermal titration calorimetry (ITC) method was used to study the binding interaction of IMC with different micelles. The thermodynamic parameters and the nature of binding between IMC and different micelles have been estimated. Moreover, addition of KCl salt in the respective micelles releases IMC molecule from the micelles to the aqueous medium. This study will help elicidate the binding behavior of IMC in the presence of different micelles for possible use as potential drug delivery systems.

Interaction mechanism of Eu(III) with MX-80 bentonite studied by batch, TRLFS and kinetic desorption techniques

Speciation of surface adsorbed lanthanide/actinide ions at solid/water interface is very important for the evaluation of their physicochemical behavior in the natural environment. Herein, the sorption mechanism of Eu(III) on MX-80 bentonite is studied by batch sorption experiments, surface complexation modelling, time resolved laser fluorescence spectroscopy study (TRLFS) and kinetic dissociation measurements. The fluorescing adsorbed species are characterized with their emission spectra [the ratio of emission intensities of 5D0→7F1 (λ=594nm) and 5D0→7F2 (λ=619nm) transitions] and their fluorescence lifetime. The decrease of the intensity ratio points to the ongoing sorption/complexation with increasing pH. The increase of fluorescence lifetime with increasing pH indicates the changes from the formation of outer-sphere surface complexes to inner-sphere surface complexes. The species of adsorbed Eu(III) ions at bentonite surface are further demonstrated by surface complexation modeling, and the fitted results reveal that the sorption of Eu(III) on bentonite can be satisfactorily simulated by diffuse layer model with the strong and weak sites. The kinetic dissociation results of surface adsorbed Eu(III) from bentonite using chelating resin indicate that two different Eu–bentonite species (i.e., irreversible and reversible species) are required to explain the kinetic desorption results. The Eu species moves from the reversible to irreversible species with increasing pH values. The results are crucial to understand the physicochemical behavior of lanthanides in the natural environment.

Pyrene Schiff base: photophysics, aggregation induced emission, and antimicrobial properties.

Pyrene containing Schiff base molecule, namely 4-[(pyren-1-ylmethylene)amino]phenol (KB-1), was successfully synthesized and well characterized by using (1)H, (13)C NMR, FT-IR, and EI-MS spectrometry. UV-visible absorption, steady-state fluorescence, time-resolved fluorescence, and transient absorption spectroscopic techniques have been employed to elucidate the photophysical processes of KB-1. It has been demonstrated that the absorption characteristics of KB-1 have been bathochromatically tuned to the visible region by extending the π-conjugation. The extended π-conjugation is evidently confirmed by DFT calculations and reveals that π→π* transition is the major factor responsible for electronic absorption of KB-1. The photophysical property of KB-1 was carefully examined in different organic solvents at different concentrations and the results show that the fluorescence of this molecule is completely quenched due to photoinduced electron transfer. Intriguingly, the fluorescence intensity of KB-1 increases enormously by the gradual addition of water up to 90% with concomitant increase in fluorescence lifetime. This clearly signifies that this molecule has aggregation-induced emission (AIE) property. The mechanism of AIE of this molecule is suppression of photoinduced electron transfer (PET) due to hydrogen bonding interaction of imine donor with water. A direct evidence of PET process has been presented by using nanosecond transient absorption measurements. Further, KB-1 was successfully used for antimicrobial and bioimaging studies. The antimicrobial studies were carried out through disc diffusion method. KB-1 is used against both Gram-positive (Rhodococcus rhodochrous and Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacterial species and also fungal species (Candida albicans). The result shows KB-1 can act as an excellent antimicrobial agent and as a photolabeling agent. S. aureus, P. aeruginosa, and C. albicans were found to be the most susceptible microorganisms at 1 mM concentration among the bacteria used in the present investigation.

Stimuli-sensitive breathing of Cucurbit[7]uril cavity: monitoring through the environment responsive fluorescence of 1'-hydroxy-2'-acetonaphthone (HAN).

In this work, we have focused on the supramolecular interactions of a water-soluble host Cucurbit[7]uril (CB[7]) with an excited state intramolecular proton transfer (ESIPT) probe 1'-hydroxy-2'-acetonaphthone (HAN) through steady-state and time-resolved fluorescence measurements. In water HAN is almost nonfluorescent in nature with a very low fluorescence quantum yield (Φ = 0.009). With gradual addition of CB[7] absorption maximum of HAN is red-shifted (292 cm(-1)) and hence confirming the formation of an inclusion complex in the ground state between HAN and CB[7]. Due to this complexation CB[7] offers a hydrophobic microenvironment to the HAN which is completely different from that of homogeneous water. Upon encapsulation into the nanocavity of CB[7], HAN exhibits a 20-fold increase in fluorescence intensity along with a 36 nm (1618 cm(-1)) hypsochromic shift in emission maxima. This hypsochromic shift is an indication about the modulation of excited state photophysical behavior of HAN due to the formation of HAN-CB[7] inclusion complex. Moreover, huge partition coefficient of HAN from water to CB[7] along with a∼ 12-fold increase in fluorescence lifetime confirm the favorable interaction between HAN and CB[7]. We have also observed the stimuli-sensitive (temperature and cationic stimuli) breathing of CB[7] cavity i.e., in the presence of different additives the portals of CB[7] open up to release HAN in water and take up the additives. Time-resolved anisotropy measurements further indicate about the probable location of HAN inside the CB[7]. The observation of a 1.7 ns component in the presence of CB[7] signifies the highly restricted rotational motion of HAN inside the cavity of CB[7] corroborates our finding.

Fluorescence properties of Eu3+-doped alumino silicate glasses

Alumino silicate glasses of a very broad range of molar compositions doped with 1⋅1020 Eu3+ cm−3 (about 0.2mol% Eu2O3) were prepared. As network modifier oxides Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, PbO, Y2O3 and La2O3 have been used. All glasses show relatively broad fluorescence excitation and emission spectra. For most glasses only a weak effect of the glass composition on the excitation and emission spectra is observed. Although the glasses should be structurally similar, notable differences are found for the fluorescence lifetimes. These increase steadily with decreasing mean atomic weight, decreasing refractive index and decreasing optical basicity of the glasses, which may be explained by local field effects. An exception from this rule are the strontium, barium and potassium containing glasses, which show significantly increased fluorescence lifetimes despite of their high refractive index, optical basicity and molecular weight. The non mono-exponential fluorescence decay curves as well as the fluorescence spectra indicate a massive change in the local surroundings of the doped rare earth ions for these glasses.

Chromophore Bending Controls Fluorescence Lifetime in Single Conjugated Polymer Chains.

Single-molecule spectroscopy of conjugated polymers offers unique insight into the interplay between the spatial arrangement of monomer units-twisting and bending-and the characteristics of the primary excitonic photoexcitation, provided that a single conjugated segment can be isolated. β-phase polyfluorene constitutes an ideal model to study variations in intermonomeric coupling, determined by nanoscale molecular shape, on the fundamental optical transition. If structural relaxation in the excited state is weak, exciton self-trapping occurs stochastically along the conjugated segment. Bending of the π-system is then revealed by a reduction in single-photon polarization anisotropy, correlating directly with increased fluorescence lifetime. Strong relaxation raises emission anisotropy because of deterministic exciton localization, decelerating fluorescence decay due to a decrease in exciton coherence length.

Effect of Ca²⁺ on the steady-state and time-resolved emission properties of the genetically encoded fluorescent sensor CatchER.

We previously designed a calcium sensor CatchER (a GFP-based Calcium sensor for detecting high concentrations in the high calcium concentration environment such as ER) with a capability for monitoring calcium ion responses in various types of cells. Calcium binding to CatchER induces the ratiometric changes in the absorption spectra, as well as an increase in fluorescence emission at 510 nm upon excitation at both 395 and 488 nm. Here, we have applied the combination of the steady-state and time-resolved optical methods and Hydrogen/Deuterium isotope exchange to understand the origin of such calcium-induced optical property changes of CatchER. We first demonstrated that calcium binding results in a 44% mean fluorescence lifetime increase of the indirectly excited anionic chromophore. Thus, CatchER is the first protein-based calcium indicator with the single fluorescent moiety to show the direct correlation between the lifetime and calcium binding. Calcium exhibits a strong inhibition on the excited-state proton transfer nonadiabatic geminate recombination in protic (vs deuteric) medium. Analysis of CatchER crystal structures and the MD simulations reveal the proton transfer mechanism in which the disrupted proton migration path in CatchER is rescued by calcium binding. Our finding provides important insights for a strategy to design calcium sensors and suggests that CatchER could be a useful probe for FLIM imaging of calcium in situ.

Dependence of optical and thermal properties on concentration and temperature for Yb:YAG laser ceramics

This paper reports the influence of temperature and doping concentration on optical and thermal properties of Yb:YAG transparent ceramics. The rise of Yb doping concentration causes the gradual red-shift of absorption edge, and both Yb3+absorption coefficient and fluorescence lifetime increases. For 5% Yb:YAG ceramic, as temperature increases from 100K to room temperature, the fluorescence intensity decreases with broadening of each peak. By using a 940nm diode laser as the pumping source, we obtained a high slope efficiency of 49% for 5%Yb:YAG ceramics, compared with 41% for 10%Yb:YAG ceramic.

An Insight into the Speciation and Extraction Behavior of Eu(III) with Dinonyl Phenyl Phosphoric Acid and Di(2-ethylhexyl) Phosphoric Acid: Solvent Extraction and Fluorescence Studies

The speciation of Eu(III) with dinonyl phenyl phosphoric acid (DNPPA) and di(2-ethylhexyl) phosphoric acid (D2EHPA) extracted from nitric acid medium were investigated using time resolved fluorescence spectroscopy (TRFS) technique. The fluorescence life time measurements on both the systems indicated that the Eu(III)-DNPPA complex contains 2H2O molecules in the inner coordination sphere while Eu(III)-D2EHPA complex does not contain any H2O molecule. These studies indicated the formation of Eu(HA2)3 · 2H2O species in the organic phase using DNPPA and Eu(HA2)3 using D2EHPA as extractants (HA: DNPPA/D2EHPA). No change in fluorescence lifetimes and spectra with increased nitric acid and extractant concentration indicated the presence of identical species. However, the presence of neutral donors such as tri-n-butyl phosphate (TBP), Cyanex 923 (a mixture of four trialkyl phosphine oxides viz. R3PO, R2R′PO, RR′2PO and R′3PO where R: n-octyl and R′: n-hexyl chain) showed spectral changes for both the extractants. There was an increase in fluorescence life time from ∼400 µs to ∼1500 μs for Eu(III)-DNPPA system in the presence of neutral donors indicating complete dehydration of the extracted species. By contrast, no change in fluorescence life time was observed in the case of Eu(III)-D2EHPA system after the addition of neutral donors.

A new organic far-red mechanofluorochromic compound derived from cyano-substituted diarylethene

A new cyano-substituted diarylethene derivative (R-NH2) with reversible far-red mechanofluorochromic property was synthesized and confirmed by standard spectroscopic methods. To the best of our knowledge, the 684 nm red-shifted wavelength of the ground R-NH2 is the longest wavelength that has appeared in the literature. The mechanofluorochromic mechanism was investigated by small and wide-angle X-ray scattering and was ascribed to the destruction of crystalline structure. More in-depth study by infrared spectra and time-resolved emission-decay behaviors showed that the changes of C–H out-of-plane bending vibrations in aryl group of the compound and the obvious increase of fluorescence lifetime might be the fundamental reasons. The synthetic strategy reported here can be extended to prepare more and more long-wavelength emission mechanofluorochromic materials, which can broaden the scope of application of such materials and for thoroughly understanding the mechanofluorochromic mechanism.