Enhancing the Fluorescence of an Aggregation-Induced Emission-Active Polymorphic System With Remarkable Mechanochromism for Visualizing Microcracks and Stress Distribution in Textiles

Abstract

Visualization of microcracks and stress distribution is crucial for material usability and safety assessment, yet effective monitoring technologies remain very limited. In this work, an organic luminogen TPEXD with aggregation-induced emission (AIE) properties has been developed by introducing a 3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione group onto tetraphenylethylene via a nonconjugated methylene linkage. TPEXD forms two polymorphs: a deep-blue fluorescent crystal SCb with a low photoluminescence quantum yield (Φ_PL) of 2.4% and a blue fluorescent crystal SCc with a high Φ_PL of 22.6%. Notably, SCb exhibits remarkable mechanochromism (MC) properties and force-induced emission enhancement (FIEE) characteristics opposite to classical mechano-responsive AIE materials, with the Φ_PL increasing to 30.1% under external force. SCb integrates three mechano-responsive properties, including MC, FIEE, and mechanoluminescence (ML). Under pressure increased from 0 to 17.33 GPa, the emission maximum of SCb gradually red-shifts by 106 nm. Inspired by the MC and FIEE properties, the SCb were leveraged for inkless writing, impact indication, visualized monitoring of microcracks, and stress distribution in textiles. This work provides helpful guidance for developing AIE materials with MC and FIEE characteristics and offers a practical approach for the visualized monitoring of microcracks and stress distribution in materials.

Keywords

aggregation-induced emission / mechanochromism / force-induced emission enhancement / mechanoluminescence / visualization of microcracks and stress distribution

References

[1] J. Zhang, A. Li, H. Zou, et al., “A “Simple” Donor-Acceptor AIEgen With Multi-stimuli Responsive Behavior,” Materials Horizons 7 (2020): 135-142.

[2] J.-A. Li, J. Zhou, Z. Mao, et al., “Transient and Persistent Room-Temperature Mechanoluminescence From a White-Light-Emitting AIEgen With Tricolor Emission Switching Triggered by Light,” Angewandte Chemie International Edition 57 (2018): 6449-6453.

[3] M. Zhang, J. Zhang, Z. Zhang, et al., “Multifunctional Hydrazone-Based AIEgens Enabled by Hydrogen-Halogen Interaction,” Advanced Optical Materials 12 (2024): 2302781.

[4] J. Chen, F. Lin, D. Guo, et al., “In Situ Reversible and Robust Mechano-Responsive Ultralong Phosphorescence of Polyurethane Elastomer,” Advanced Materials 36 (2024): 2409642.

[5] Y. Chen, C. Xu, B. Xu, et al., “Chirality-Activated Mechanoluminescence From Aggregation-Induced Emission Enantiomers With High Contrast Mechanochromism and Force-Induced Delayed Fluorescence,” Materials Chemistry Frontiers 3 (2019): 1800-1806.

[6] K. Chang, J. Gu, L. Yuan, et al., “Achieving Ultrasound-Excited Emission With Organic Mechanoluminescent Materials,” Advanced Materials 36 (2024): 2407875.

[7] H. Yan, Y. He, D. Wang, T. Han, and B. Z. Tang, “Aggregation-induced emission polymer systems With circularly polarized luminescence,” Aggregate 4 (2023): e331.

[8] C. Ma, J. He, Y. Wu, et al., “Multistimuli-Responsive Fluorescence Behaviours of Aggregation-Induced Emission Small-Molecule and Electrospun Nanofibre Films for Acid-Base Vapour Sensing,” Luminescence 38 (2023): 1720-1728.

[9] M. Huang, R. Yu, K. Xu, et al., “An Arch-Bridge-Type Fluorophore for Bridging the Gap between Aggregation-Caused Quenching (ACQ) and Aggregation-Induced Emission (AIE),” Chemical Science 7 (2016): 4485-4491.

[10] G. Qian, Z. Zhong, M. Luo, et al., “Simple and Efficient Near-Infrared Organic Chromophores for Light-Emitting Diodes With Single Electroluminescent Emission Above 1000 nm,” Advanced Materials 21 (2009): 111-116.

[11] J. Luo, Z. Xie, J. W. Y. Lam, et al., “Aggregation-Induced Emission of 1-Methyl-1,2,3,4,5-pentaphenylsilole,” Chemical Communications 18 (2001): 1740-1741.

[12] X. Yang, Z. Huang, K. Ding, et al., “Near-Infrared Organic Photosensitizers With Aggregation-Induced Emission and Switchable Fluorescence for Fungal Infection Therapy,” Science China Chemistry 68 (2025): 1426-1433.

[13] X. Yang, Q. Wang, P. Hu, et al., “Achieving Remarkable and Reversible Mechanochromism From a Bright Ionic AIEgen With High Specificity for Mitochondrial Imaging and Secondary Aggregation Emission Enhancement for Long-Term Tracking of Tumors,” Materials Chemistry Frontiers 4 (2020): 941-949.

[14] X. Zhao, J. Gong, Z. Li, et al., “Au···I Coinage Bonds: Boosting Photoluminescence Efficiency and Solid-State Molecular Motion,” Aggregate 6 (2025): e686.

[15] C. Ma, Z. Li, C. Zhang, et al., “Design and Synthesis of AIE-Based Small-Molecule and Nanofibrous Film for Fluorescent Sensing Application,” Frontiers in Chemistry 9 (2021): 727631.

[16] S.-S. Zhao, L. Chen, L. Wang, and Z. Xie, “Two Tetraphenylethene-Containing Coordination Polymers for Reversible Mechanochromism,” Chemical Communications 53 (2017): 7048-7051.

[17] X. Wang, C. Qi, Z. Fu, et al., “A Synergy Between the Push-Pull Electronic Effect and Twisted Conformation for High-Contrast Mechanochromic AIEgens,” Materials Horizons 8 (2021): 630-638.

[18] B. Fang, L. Lai, M. Chu, Y. Shi, and M. Yin, “A Multifunctional Triphenylamine-Benzothiazole Derivative With Blue-Shifted Mechanochromism, Acidochromism and Amplified Spontaneous Emission,” Chemistry, Photochemistry, and Photophysics 5 (2021): 270-274.

[19] X. Zhang, J.-Y. Wang, D. Qiao, and Z.-N. Chen, “Phosphorescent Mechanochromism Through the Contraction of Ag₁₂Cu₂ Clusters in Tetradecanuclear Copper-Silver Acetylide Complexes,” Journal of Materials Chemistry C 5 (2017): 8782-8787.

[20] S. Tan, Y. Yin, W. Chen, Z. Chen, W. Tian, and S. Pu, “Carbazole-Based Highly Solid-State Emissive Fluorene Derivatives With Various Mechanochromic Fluorescence Characteristics,” Dyes and Pigments 177 (2020): 108302.

[21] H. Li, Z. Chi, B. Xu, et al., “Aggregation-Induced Emission Enhancement Compounds Containing Triphenylamine-Anthrylenevinylene and Tetraphenylethene Moieties,” Journal of Materials Chemistry 21 (2011): 3760.

[22] Y. Zheng, L. Zhang, Z. Huang, et al., “Bright Organic Mechanoluminescence and Remarkable Mechanofluorochromism From Circularly Polarized TADF Enantiomers With Aggregation-Induced Emission Properties,” Chemistry-A European Journal 29 (2023): e202202594.

[23] Z. Chi, X. Zhang, B. Xu, et al., “Recent Advances in Organic Mechanofluorochromic Materials,” Chemical Society Reviews 41 (2012): 3878.

[24] T. Han, L. Liu, D. Wang, J. Yang, and B. Z. Tang, “Mechanochromic Fluorescent Polymers Enabled by AIE Processes,” Macromolecular Rapid Communications 42 (2021): 2000311.

[25] Q. Qi, J. Qian, X. Tan, et al., “Remarkable Turn-On and Color-Tuned Piezochromic Luminescence: Mechanically Switching Intramolecular Charge Transfer in Molecular Crystals,” Advanced Functional Materials 25 (2015): 4005-4010.

[26] J.-C. Yang, Z. Fu, H. Ma, et al., “Pressure/Thermo-Induced Hypsochromic-Shifted and Enhanced Luminescence Based on Carbazole Emitter,” ACS Materials Letters 5 (2023): 1441-1449.

[27] J. Peng, A. P. Tomsia, L. Jiang, B. Z. Tang, and Q. Cheng, “Stiff and Tough PDMS-MMT Layered Nanocomposites Visualized by AIE Luminogens,” Nature Communications 12 (2021): 4539..

[28] Z. Qiu, W. Zhao, M. Cao, et al., “Dynamic Visualization of Stress/Strain Distribution and Fatigue Crack Propagation by an Organic Mechanoresponsive AIE Luminogen,” Advanced Materials 30 (2018): 1803924.

[29] B. Lee, J.-Y. Oh, H. Cho, et al., “Ultraflexible and Transparent Electroluminescent Skin for Real-Time and Super-Resolution Imaging of Pressure Distribution,” Nature Communications 11 (2020): 663.

[30] Y. Zhang, Y. Fang, J. Li, et al., “Dual-Mode Electronic Skin With Integrated Tactile Sensing and Visualized Injury Warning,” ACS Applied Materials & Interfaces 9 (2017): 37493-37500.

[31] F. Yuan, H. Qi, B. Song, et al., “Tailorable Biosensors for Real-Time Monitoring of Stress Distribution in Soft Biomaterials and Living Tissues,” Nature Communications 16 (2025): 1081.

[32] Z. Zhang, X. Wei, L. Zhang, and B. Li, “Visualization and Depth Estimation of Inner Crack in High-Pressure Equipment Based on Organic Mechanochromic Luminescent Materials,” Advanced Materials Interfaces 10 (2023): 2300330.

[33] K.-Y. Jhang, “Nonlinear Ultrasonic Techniques for Nondestructive Assessment of Micro Damage in Material: A Review,” International Journal of Precision Engineering and Manufacturing 10 (2009): 123-135.

[34] F. Arenhart Soares and P. Besenius, “Mechanophoric Hydrogels: When Mechanical Stress Produces Useful Responses,” Organic Chemistry Frontiers 12 (2025): 3107-3128.

[35] M. Liu, Z. Liu, P. Jin, et al., “Analysis of Crack-Tip Stress Field in Unidirectional Fiber-Reinforced Composites Based on 3D Micromechanical Model,” Engineering Fracture Mechanics 301 (2024): 110029.

[36] W. Ding, J. Sun, G. Chen, et al., “Stretchable Multi-Luminescent Fibers With AIEgens,” Journal of Materials Chemistry C 7 (2019): 10769-10776.

[37] X. Feng, N. Zhou, H. Zhou, et al., “Achieving Tricolor Luminescence Switching From a Stimuli-Responsive Luminophore Based on a Bisarylic Methanone Derivative,” New Journal of Chemistry 46 (2022): 15657-15665.

[38] H. Liu, Y. Gu, Y. Dai, et al., “Pressure-Induced Blue-Shifted and Enhanced Emission: A Cooperative Effect Between Aggregation-Induced Emission and Energy-Transfer Suppression,” Journal of the American Chemical Society 142 (2020): 1153-1158.

[39] M. Wu, H. Liu, H. Liu, et al., “Pressure-Induced Restricting Intermolecular Vibration of a Herringbone Dimer for Significantly Enhanced Multicolor Emission in Rotor-Free Truxene Crystals,” The Journal of Physical Chemistry Letters 13 (2022): 2493-2499.

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2026 The Author(s). Aggregate published by SCUT, AIEI, and John Wiley & Sons Australia, Ltd.