Mechanofluorochromic Behavior Research Articles

Biphenyl or naphthalene-modified fluorene fluorogenic molecules with different solid-state emission and mechanofluorochromic behaviors

The preparation of three-color mechanofluorochromic molecules is of crucial importance in the development of mechanically responsive smart materials with multicolor switching feature. Unfortunately, the related mechano-responsive luminogenic compounds are rare. In this work, four fluorene derivatives, which contain various sites of biphenyl or naphthalene, were synthesized. Interestingly, compounds 1–4 exhibited diverse high-brightness solid-state fluorescence and observable fluorescent changes in response to mechanical force stimulus. For fluorophor 1 in the solid state, upon light grinding, an orange-yellow to yellow-green mechanofluorochromic transition with the notable blue shift of 85 nm was noticed, and the yellow-green to yellow bathochromic mechanofluorochromic response was observed after vigorous grinding. Therefore, fluorogen 1 showcased an unfrequent bidirectional tricolored mechanofluorochromism with a blue shift followed by a red shift. As for luminogens 2–4 exhibited diverse two-color reversible red-shifted mechanofluorochromic responses. Furthermore, their mechanochromic emissive mechanisms of 1–4 were investigated by X-ray powder diffraction tests.

Three multifunctional difluoroboron fluorescent dyes with five member N-heterocyclic ring for mechanofluorochromic behaviors, the ink-free writing and latent fingerprints imaging

To further advance the development of multifunctional fluorescent dyes, three difluoroboron compounds (F-1, F-2, and F-3) containing five-membered N-heterocyclic ring moieties that act as the electron-withdrawing units were synthesized. It was observed that compound F-1, which incorporated a 1,2,4-triazole segment, and compound F-3 with 1,2,3-triazole portion exhibited aggregation-induced emission activities suitable for latent fingerprints imaging. In contrast, compound F-2 featuring a pyrazole unit demonstrated an aggregation-caused quenching phenomenon. Additionally, all three compounds displayed mechanofluorochromic behaviors. Specifically, the emission spectra of compound F-1 in the solid state experienced only a slight shift of approximately 5 nm upon grinding, however, compound F-2 underwent a red shift from 475 to 501 nm while compound F-3 shifted from 482 to 507 nm. Furthermore, both compounds F-2 and F-3 could be utilized in ink-free writing applications. Notably, the safety paper prepared using compound F-2 was designed for single-use due to its irreversible mechanofluorochromic behavior, conversely, the safety paper derived from compound F-3 was rewritable owing to its reversible mechanofluorochromic behavior. It provided a foundation for exploration the application of multifunctional difluoroboron compounds with 1,2,3-triazole moiety.

High contrast stimuli-responsive fluorescence emitters based on carbazole-cyanostilbene derivatives with aggregation induced emission properties

Due to the aggregation induced emission (AIE) materials exhibiting obvious fluorescent emission changes under the external stimuli of heat, solvent, force and so on, significant efforts have been directed toward developing AIE-active materials with high contrast stimuli-responsive fluorescence behaviors. Herein, three electron-donor(D)-electron-acceptor(A) and D-A-D type organic fluorescence emitters of Cz-DC-tBu, Cz-DC-CN and Cz-DC-OMe were facilely synthesized using carbazole group as D unit and cyano group as A unit. They showed typical AIE features and exhibited remarkable color changes under mechanical force and in different polarity solvents, respectively. The stimuli-responsive mechanism of the compounds were investigated by powder X-ray Diffraction (PXRD) and density functional theory calculations (DFT), which revealed that the mechanofluorochromic behaviors were associated with the molecular packing modes, and the solvatochromic effects were caused by the intramolecular charge-transfer transition (ICT) effect. Significantly, it was found that Cz-DC-tBu showed high contrast stimuli-responsive behaviors through adjusting the substituent groups on the cyanostilbene unit with CN, OMe, and tBu groups, respectively. This study provided a new strategy for the design of AIE-active stimuli-responsive fluorescence emitters, and made them possible using in stress sensors, chemical detection, memory storage, anti-counterfeiting applications.

Design and synthesis of dicyanoethylene derivatives functionalized with carbazole possessing the properties of obvious aggregation-induced emission and reversible high-contrast mechanofluorochromism

This study devotes to the design, preparation, and examination of two novel D-A structured molecules, designated as CCEDBF and BCCEDBF, which are derived from carbazole unit, dicyanoethylene segment, and dibenzofuran unit. The distinctive D-A molecular architectures and highly twisted spatial configurations of these compounds facilitate pronounced intramolecular charge transfer (ICT) while also imparting robust solid-state luminescence, exhibiting emission efficiencies of 0.518 and 0.739, respectively, and notable aggregation-induced emission (AIE) with AIE factors of 43 and 30. Significantly, both CCEDBF and BCCEDBF demonstrate reversible mechanofluorochromic (MFC) behavior characterized by high fluorescence contrast. Mechanical grinding of the initial powders results in a shift in their emission colors, transitioning from green and yellow-green to yellow and orange-red, respectively, alongside a corresponding shift in emission peaks from 525 nm to 536 nm–558 nm and 597 nm. Powder X-ray diffraction (PXRD) examination of the initially synthesized, mechanically processed, and vaporized samples reveals that the observed fluorescence color change is due to a structural transformation between ordered crystalline and disordered amorphous configurations induced by the application of the external force. The red shift in photoluminescence (PL) spectra post-grinding is attributed to a reduced band gap, driven by factors such as extended π-conjugation length, enhanced planar intramolecular charge transfer (PICT) effect, strengthened π-π interactions and exciton coupling, as well as the increase in the orbitals overlap between neighboring molecular. Moreover, the presence or absence of tert-butyl substituents attaching to the 3- and 6-positions of the carbazole units significantly impacts the photophysical properties of these materials.

Tetraphenylethene-based mononuclear aggregation-induced emission (AIE)-active mechanofluorochromism gold(I) complexes with different auxiliary ligands

In this study, a series of tetraphenylethene-containing gold(I) complexes with different auxiliary ligands have been synthesized. These complexes were characterized using a variety of techniques including nuclear magnetic resonance spectroscopy, mass spectrometry, and single crystal X-ray diffraction. Their aggregation-induced emission (AIE) behaviors were investigated through ultraviolet/visible and photoluminescence spectrum analyses, and dynamic light scattering measurements. Meanwhile, their mechanofluorochromic properties were also studied via solid-state photoluminescence spectroscopy. Intriguingly, all these mononuclear gold(I) molecules functionalized by tetraphenylethene group demonstrated AIE phenomena. Furthermore, five gold(I) complexes possessing diverse auxiliary ligands exhibited distinct fluorescence changes in response to mechanical grinding. For luminogens 2–5, their solids showed reversible mechanofluorochromic behaviors triggered by the mutual transformation of crystalline and amorphous states, while for luminogen 1, blue-green-cyan three-color solid fluorescence conversion was realized by sequential mechanical grinding and solvent fumigation. Based on this stimuli-responsive tricolored fluorescence feature of 1, an information encryption system was successfully constructed.

Study on four pyridine-based difluoroboron compounds for mechanofluorochromic behaviors, the ink-free writing and detection of latent fingerprints

With the increasing demand for multifunctional aggregation-induced emission materials, four pyridine-based difluoroboron compounds (1, 2, 3, and 4) with the anthryl unit as an electron donor and difluoroboron moiety as the electron acceptor were designed and successfully synthesized. It found that four compounds displayed significantly intramolecular charge transfer characteristics and solvatochromism phenomena. The other compounds possessed mechanofluorochromic behaviors under external mechanical stimulation except compound 1, owing to its lesser change value of the dipole moment between the ground and excited states. More importantly, they exhibited potential application in the field of ink-free writing due to reversible mechanochromism during the grinding and fumigation process. Additionally, four compounds were used for detection of latent fingerprints on the glass surface due to their excellent aggregation effects in the THF/water mixtures. This research provides a reference for exploring multifunctional aggregation-induced emission difluoroboron compounds with brightness luminescence.

Mechanofluorochromic behaviors and latent fingerprint detection of triphenylamine-based compounds with mono-/bis-BF2 fluorophores

To better understand the relationship between molecular structure of the mono-/bis-BF2-core compounds and mechanofluoroboron behaviors, two pyridine-based difluoroboron compounds with triphenylamine group (TPA-ts-BF2 and TPA-ts-2BF2) were designed and successfully synthesized, which TPA-ts-BF2 including a BF2 fluorophore and TPA-ts-2BF2 containing the bisBF2 fluorophores. Based on the photophysical properties measurements results, it was found that TPA-ts-2BF2 had more excellent intramolecular charge transfer characteristics than that of TPA-ts-BF2, and exhibited significant aggregation-induced emission activity, however, TPA-ts-BF2 displayed typical aggregation-caused quenching phenomenon. Meanwhile, the emission spectrum of the solid powders of TPA-ts-2BF2 was red-shifted 52 nm after grinding, that of TPA-ts-BF2 was red-shifted 46 nm, which was resulted from crystalline state switching to amorphous state. According to the theoretical calculations, we conjectured that TPA-ts-BF2 with uncoordinated amide linkage moiety had a tendency to forming a more twisted conformance and higher molecular polarity, which made that mechanofluorochromic behavior was worse than that of TPA-ts-2BF2. Additionally, TPA-ts-2BF2 was applied to latent fingerprint detection due to its prime aggregation-induced emission property.

Mechanofluorochromic behaviors and data security protection properties of salicylaldimine-based difluoroboron complexes with different aryl substituents.

To further explore the relationship between aryl substituents and mechanofluorochromic (MFC) behaviors, four salicylaldimine-based difluoroboron complexes (ts-Ph BF2, ts-Ph-NA BF2, ts-2NA BF2, and ts-triphenylamine [TPA] BF2), including aromatic substituents with different steric hindrance effects, were designed and successfully synthesized. Four complexes with twisted molecular conformation displayed intramolecular charge transfer and aggregation-induced emission properties. Under external mechanical stimuli, the as-synthesized powders of ts-Ph BF2, ts-Ph-NA BF2, and ts-TPA BF2 exhibited redshift fluorescence emission behaviors, and ts-Ph BF2 and ts-TPA BF2 could be recovered to original shifts by fuming, but ts-Ph-NA BF2 displayed irreversible switching. ts-2NA BF2 had no change during the grinding and fuming processes. The results indicated that the MFC behaviors could be attributed to the phase transformation between the well-defined crystalline and disordered amorphous states by X-ray diffraction measurement. Further research illustrated that ts-TPA BF2 with the most significant MFC phenomenon could be applied in data security protection in ink-free rewritable paper.

Reversible Red‐/Blue‐Shifted Mechanofluorochromic Properties of Indole‐Based Difluoroboron Compounds with Aggregation‐Induced Emission

AbstractTo further explore the relationship between structure and property of the mechanofluorochromic materials, two indole‐based aggregation‐induced emission compounds (I−Ph−BF2 and I−PhNp−BF2) with BF2‐core were designed and synthesized. They displayed intramolecular charge transfer characteristics and dissimilar reversible mechanofluorochromic behaviors (red‐shift for I−Ph−BF2 and blue‐shift for I−PhNp−BF2). Based the powder X‐ray diffraction patterns and quantum chemical calculation results, it was responsible for the blue‐shift mechanofluorochromic behavior of I−PhNp−BF2 that the reduced molecular polarity of the excited state and the undermined partially ordered structure. In contrast, the phase change between an ordered arrangement state and a disordered amorphous state of I−Ph−BF2 solid powder, as well as the appropriate molecular polarity, brought out red‐shift mechanofluorochromic effect. It provided a foundation for further exploration of the mechanofluorochromic property.

Study of two benzophenone-based difluoroboron compounds containing triphenylamine units: mechanofluorochromic behavior and latent fingerprint imaging

Compounds TPA-BP-BF2-1 and TPA-BP-BF2-2 with AIE properties could be used in LFP imaging. Compound TPA-BP-BF2-2 was explored as a sample LED paint-coating owing to its reversible MFC behavior.

A difluoroboron compound with latent fingerprint detection and inkless writing based on aggregation-induced emission enhancement and mechanofluorochromic behavior

A pyridine-based difluoroboron compound with the TPA group displayed excellent AIEE activity and MFC behavior, which was applied for latent fingerprint detection and inkless writing.

Triphenylamine-based 1,3,4-thiadiazole derivative: Solvatochromism, aggregation-induced emission and reversible turn-on mechanofluorochromism

In this work, a new versatile AIE-active triphenylamine-based donor-acceptor fluorophore DPTA (N,N-diphenyl-4-(5-phenyl-1,3,4-thiadiazol-2-yl)aniline) has been synthesized, whose photophysical properties in different solvents, aggregates emission behaviors and solid states were investigated systematically. It was found that DPTA exhibited well-defined ICT (intramolecular charge transfer) characteristics with remarkable positive solvatochromism. More importantly, DPTA exhibited reversible high-contrast turn-on mechanofluorochromism response to mechanical force with obviously increase of QY (the solid fluorescence quantum yield) from 6.4 % (pristine) to 31.8 % (being grinded), and the emitting wavelengths of DPTA were red-shifted from 469 nm to 496 nm upon grinding. The interesting mechanofluorochromic behaviors were rationalized to be caused by the reversible phase transition between ordered crystalline and amorphous states, which was proved by the measurement results of PXRD, DSC and FESEM. Single crystal X-ray diffraction analysis indicated the presence of twisted conformations and weak intermolecular hydrogen bonds, which are also responsible for the mechanofluorochromic behavior.

Regulation of aggregation-induced emission and reversible remarkable mechanofluorochromism by substitution position of the carbazole unit in D-A type carbazole-functionalized dicyanoethylene π-systems

In this study, two twisted D-A type dibenzothiophene- and carbazole-functionalized dicyanoethylene derivatives were formulated and synthesized. They were labeled as 2-substituted carbazole (BT-CE-C2) and 3-substituted carbazole (BT-CE-C3), respectively. Furthermore, an investigation into the correlation between the molecular structure of these derivates and their photophysical properties was conducted. The characteristic D-A structures and the highly distorted spatial conformations of the two fluorophores led to the emergence of a unique intramolecular charge transfer (ICT) effect and remarkable aggregation-induced emission (AIE) behavior. Notably, the position of substitution of the carbazole unit regulated the reversible high-contrast mechanofluorochromic (MFC) properties demonstrated by BT-CE-C2 and BT-CE-C3. The as-prepared solid powders of BT-CE-C2 and BT-CE-C3 produce blue-green and orange-yellow emissions at 508 and 567 nm, respectively. However, their ground powders emitted orange (at 589 nm) and orange-red (at 619 nm) lights. Notably, BT-CE-C2 exhibited enhanced fluorescence upon external stimulation, increasing its solid-state luminescence efficiency from 0.035 to 0.189. In contrast, the BT-CE-C3 exhibited a decrease in fluorescence, causing its solid-state luminescence efficiency to change from 0.426 to 0.348. The fluorescence lifetimes, powder X-ray diffraction (PXRD), and spectral analysis collectively identified the phase transition between the crystalline and amorphous states as the underlying cause of the MFC behavior observed in BT-CE-C2 and BT-CE-C3. Additionally, the red shift in photoluminescence (PL) spectra under external stimulus can be attributed to planarized-induced charge transfer (PICT), exciton coupling, increased π-π interactions, and enhanced orbital overlap between adjacent molecules. This combination of factors led to the observed MFC properties of these compounds.

Effects of substitution position with different charge characteristics groups on mechanofluorochromic behaviors of the pyridine-based difluoroboron compounds

Two donor-acceptor type pyridine-based difluoroboron compounds (3F-Py-TPA BF2 and TPA-Py-3F BF2) were designed and successfully synthesized, which including triphenylamine unit acted as the electron donor and difluoroboron moiety and 3,4,5-trifluorophenyl group served as the electron acceptors. Combined with the results of the photophysical properties, it was found that compound 3F-Py-TPA BF2 with 4-position of pyridine skeleton substituted by 3,4,5-trifluorophenyl unit and triphenylamine unit location at the end of the bridged phenyl displayed more excellent intramolecular charge transfer character and solvatochromic effect. Moreover, the solid emission spectrum of 3F-Py-TPA BF2 was red-shifted from 550 to 594 nm, that of TPA-Py-3F BF2 was red-shifted from 526 to 546 nm under external mechanical stimulation, which caused by phase transformation between the ordered crystalline and disordered amorphous states according to the powder X-ray diffraction measurements. Based on the results of theoretical calculations and X-ray single-crystal diffraction analysis, we speculated that TPA-Py-3F BF2 with 4-position of pyridine skeleton substituted by triphenylamine unit and 3,4,5-trifluorophenyl unit location at the end of the bridged phenyl had higher molecular polarity and too loose molecular packing mode, resulting in the mechanofluorochromic behavior was worser than that of 3F-Py-TPA BF2. This work presented a strategy for regulating mechanofluorochromic behaviors of the pyridine-based difluoroboron molecular materials.

D-A type π-systems containing tetraphenylethene exhibiting aggregation-induced emission and reversible mechanical force-induced luminescent enhancement and chromism

Two novel D-A type tetraphenylethene-based fluorophores, named XA-BZ-TPE and XA-DCE-TPE, were designed and synthesized. Both fluorophores exhibit typical intramolecular charge-transfer features, good solid-state luminescence, and remarkable aggregation-induced emission (AIE) behavior. The AIE factors for XA-BZ-TPE and XA-DCE-TPE were >243 and 12, respectively. Notably, both XA-BZ-TPE and XA-DCE-TPE display high-contrast mechanofluorochromic (MFC) properties. During the grinding of initially prepared solid powders, the emission colors transformed from blue and blue-green to blue-green and yellow, and their maximum emission wavelengths shifted from 449 to 485 nm to 481 and 557 nm, respectively. Importantly, the two fluorophores attained enhancement in luminescence efficiency and chromism when the mechanical force was applied. After grinding, the solid-state luminescence efficiencies were elevated from 0.243 to 0.132 to 0.484 and 0.278, respectively, for XA-BZ-TPE and XA-DCE-TPE. In XA-BZ-TPE and XA-DCE-TPE, according to the analysis using PXRD, fluorescence lifetimes, and spectral data, the MFC behavior can be attributed to the phase transition between the crystalline and amorphous states. The present study contributes to expanding the repertoire of D-A type MFC materials and provides valuable insights for the development of novel MFC materials incorporating tetraphenylethene units, which exhibit excellent responsiveness under solid-state emission stimuli.

Phenothiazine-cyanostilbene conjugates with dual-state emission for mechanofluorochromism and live-cell imaging

Dual-state luminophores (DSEgens) that exhibit intense emission in both molecularly dispersed state and the solid state have garnered significant interest due to their versatile applications in various fields. In this study, we report the synthesis of three conformationally twisting phenothiazine-cyanostilbene conjugates, PTZ 5–7, as bright DSEgens with intracellular charge transfer (ICT) character. Their photophysical properties in solution and the solid state are thoroughly investigated using spectroscopic measurements and quantum chemical calculations. Notably, it has been discovered that a simple modification involving anisole groups on the conjugate's flanks is highly effective in redshifting the emission by enhancing electronic conjugation and narrowing the energy gap between the ground and excited states. As a result, the introduction of two anisole groups on both flanks of the phenothiazine-cyanostilbene conjugate leads to the development of PTZ-7, a red-emissive DSEgen with high brightness (ΦTHF = 48.6 % and Φsolid = 42.3 %). Leveraging the DSE properties of these compounds, we demonstrate their effectiveness for imaging live cells across a wide concentration range in the dispersed state, as well as their mechanofluorochromic behavior in the aggregated state, exhibiting a spectral shift of over 40 nm.

Revealing the Friction Stress of Microalgae in Microfluidic Devices through Mechanofluorochromism

AbstractPolydiacetylenes are deeply investigated for their mechanofluorochromic behavior: the blue, non‐emitting solid phase, obtained by photopolymerization of the diacetylene precursor, is converted to the red, emitting one by a mechanical stimulus. Inspired by the great potentiality of these compounds to act as microscale force probes, the mechanofluorochromism is implemented in microalgae biotechnology. Indeed, mechanical solicitations in a microfluidic chip can weaken the cellular envelope and facilitate the extraction of high‐added value compounds produced by the microalgae. Herewith, a polydiacetylene‐based mechanofluorochromic sensor is reported to be able to detect the stress applied to microalgae in microchannels. A triethoxysilane diacetylene precursor is designed that photopolymerizes in a purple, low‐emissive phase, and is converted to the red, high‐emissive phase upon mechanical stress. Hereafter, a protocol is set up to chemically graft in the microfluidic channels a polydiacetylene layer, and eventually proves that upon compression of Chlamydomonas reinhardtii microalgae in restricted areas, the friction stress is revealed by the mechanofluorochromic response of the polydiacetylene, leading to a marked fluorescence enhancement up to 83%. This prototype of microscale force probes lays the ground for microscale stress detection in microfluidics environments, which can be applied not only to microalgae but also to any mechano‐responsive cellular sample.

Unique mechanofluorochromism and reversible multicolor switching of triphenylamine-functionalized sulfonyl hydrazone derivatives

Two new simple triphenylamine-based sulfonyl hydrazone derivatives DBBS ((E)-N'-(4-(diphenylamino)benzylidene)benzenesulfonohydrazide) and DBMS ((E)-N'-(4-(diphenylamino)benzylidene)-4-methylbenzenesulfonohydrazide) were designed and synthesized via one-step aldimine condensation reaction to investigate the influence of terminal methyl group on their photophysical, crystal stacking and mechanofluorochromic (MFC) properties. Interestingly, reversible multi-color fluorescence tuning and switching mechanofluorochromism was found for DBBS due to the nature of polymorphs, and DBMS exhibited reversible bicolor switching mechanofluorochromism. Additionally, the reversible MFC behavior was ascribed to the phase transition between the crystalline and amorphous states, which have been confirmed by powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM) and differential scanning calorimetry (DSC) results. The obtained results showed that terminal methyl group did not only regulate molecular conformations and/or intermolecular interactions in crystals, but also affect the force-stimuli responsiveness. The present study provided insight into the development of multicolor switching materials by rational modification of classic luminogens.

Dual Chromophoric Meso‐Aryl BODIPYs with Aggregation Induced Red‐Emission Characteristics: Optical Properties and their Application in Fe3+ Detection

AbstractHerein, we report the design of meso‐aryl BODIPYs as a structural motif for aggregation‐caused quenching (ACQ) to aggregation‐induced emission (AIE) transformation. A series of meso‐aryl BODIPY derivatives were synthesized, by systematically increasing the size of the chromophore at the meso‐position from phenyl to pyrene. The effect of various factors, such as the aryl ring size, solvents, viscosity, and metal cations, on the photophysical properties was analyzed. The emission properties are well correlated with the flexibility of the aromatic ring for free rotation around the Caryl−CBODIPY bond. Accordingly, meso‐phenanthrene BODIPY (PhB) has the highest emission characteristics. The emission property of less bulky aryl‐substituted BODIPYs increases by increasing the solvent viscosity. The interaction of Fe3+ ions with aryl‐BODIPYs provides a prominent photophysical response based on Lewis‐acid supported decomplexation of BF2 in aryl‐BODIPYs. The bichromophoric meso‐aryl BODIPYs exhibit notable intramolecular excitation energy transfer from the aromatic ring to the BODIPY core, which is higher in meso‐anthracene BODIPY(AB). Hence, decorating BODIPYs with polycyclic aromatic systems generates a twisted structure, which inhibits the π‐π stacking between the planar aromatic molecules. This can be proposed as an effective approach at the molecular level to convert planar aryl luminophores having ACQ to AIEgens. Besides, the meso‐pyrene BODIPY derivative shows excellent mechanofluorochromic behaviour.

Facile Synthesis of Tetraphenylethene (TPE)-Based Fluorophores Derived by π-Extended Systems: Opposite Mechanofluorochromism, Anti-Counterfeiting and Bioimaging.

Although remarkable progresses are achieved in the design and development of the mono-shift in photoluminescence for mechanofluorochromic materials, it is still a severe challenge to explore the opposite mechanofluorochromic materials with both blue- and red-shifted photoluminescence. Herein, two unprecedented 4,5-bis(TPE)-1H-imidazole fused pyridine or quinoline-based fluorophores X-1 and X-2 were designed and synthesized, and X-1 and X-2, exhibit completely opposite mechanofluorochromic behavior. Under UV lamp, the color of pristine X-1 changed from blue to green with reversible redshifted 27 nm in fluorescence emission spectra after ground, while the color of pristine X-2 changed from red to yellow with reversible blue-shifted 74 nm after ground. The detailed characterizations (including PXRD, SEM and DSC) confirmed that this opposite mechanofluorochromism was attributed to the transformation of order-crystalline and amorphous states. The crystal structure analysis and theoretical calculation further explain that opposite mechanofluorochromic behavior take into account different π-π stacking mode by induced π-extended systems. In addition, these TPE-based fluorophores (X-1 and X-2) exhibited excellent bio-compatibility and fluorescence properties for bio-imaging, writable data storage and anti-counterfeiting materials.