Mechanoluminescence Properties Research Articles

Mechanoluminescence from Organic-Inorganic Metal Halide Perovskite Derivative.

Metal halide perovskites and their derivatives are gaining significant attention as photoluminescent materials due to their exceptional light-emitting properties. However, most research has concentrated on electroluminescence and photoluminescence, there remains a substantial gap in the exploration of mechanoluminescence (ML) properties in perovskites, making this field largely uncharted. ML is an ancient and intriguing luminescent phenomenon that occurs when a material is subjected to mechanical forces. Here, the discovery of the first organic-inorganic hybrid terbium (Tb3+)-based metal halide, a type of perovskite derivative, which exhibits notable ML properties is reported. Through material orthogonal design, the critical roles played by molecular geometry and metal-site ions in achieving remarkable ML in organic-inorganic hybrid metal halides are identified.

Photoactivated Circularly Polarized Room‐Temperature Phosphorescence from Phenoselenazine Derivative and Its Application in Information Security†

Comprehensive SummaryRoom‐temperature phosphorescence (RTP) materials have experienced rapid development due to their potential in organic light‐ emitting diode, information security, bioimaging, etc. However, the design of chiral organic phosphors with circularly polarized RTP (CPP) property remains a formidable challenge. Here, we introduce a chiral perturbation approach using a combination of chiral binaphthol and phenoselenazine derivative to achieve CPP. The photoactivated CPP in polystyrene (PS) film demonstrates a luminescence dissymmetry factor (glum), emission efficiency, and RTP lifetime up to 9.32 × 10–3, 27.0%, and 40.0 ms, respectively. The remarkable sensitivity of PS film to oxygen and temperature enables the adjustable emission colors, ranging from green to offwhite and blue under varying conditions. The doping systems, utilizing hosts of triphenylphosphine and 9‐phenylcarbazole, demonstrate an extended CPP lifetime of 85.9 ms and exhibit a persistent mechanoluminescence property with low pressure response threshold as low as 0.15 N. The information security provided by this CPP material was attained via the using of diverse emission colors and afterglow generated by distinct UV irradiation times and host materials. Alternately, it can also be achieved by observing different emission patterns using R‐ and L‐polarizer. The research has presented a reliable approach for producing CPP materials with high emission efficiency and glum.

Pr3+-Doped Lithium Niobate and Sodium Niobate with Persistent Luminescence and Mechano-Luminescence Properties

In this research, a comprehensive series of Pr3+-doped lithium niobate and sodium niobate materials were obtained at different temperatures via solid-state sintering, and their structures and properties were compared. NaNbO3: 0.75% Pr3+ phosphors were synthesized by sintering at 1150 °C for 2 h and emitted red persistent luminescence for more than 1200 s, peaking at 612 nm under UV excitation, which was a typical long persistent luminescence phenomenon. Furthermore, the sample glowed when pressurized, and a red bright luminescence which lasted for several seconds was visible to the naked eye. This was a typical mechanical luminescence phenomenon of samples under mechanical stress, directly converting mechanical energy into light energy. It was determined that NaNbO3:Pr3+ and LiNbO3:Pr3+ both possess multimode luminescence. Owing to their red long persistent luminescence (LPL) and mechano-luminescence (ML) properties, Pr3+ phosphors can be employed in fields, such as display technologies, stress sensing, structural damage detection, and other complex applications.

The determining role of stacking fault in the mechanoluminescence properties of ZnS: Mn thin films

As a classical mechanoluminescence (ML) material, the ML behaviors of the doped-ZnS have been studied extensively, but the exact mechanism is still under debate. To address this problem, ZnS: Mn thin films with and without zinc blende ZnS (zb-ZnS) stacking faults on the surface were obtained though tuning growth times. XRD results show that small amount of zb-ZnS is introduced to the wurtzite ZnS (wz-ZnS) by means of annealing process. The 75-min grown film has a bright ML emission centered at 585 nm while the 45-min film is free of ML, but the XRD and XPS analyses show no significant difference in the phase composition of two samples. TEM results show that the 75-min film has a high density of zb-ZnS stacking faults on the surface while the 45-min film is free of stacking faults. Considering the friction-force is applied on the surface, it is reasonable to conclude that the stacking fault is the key for ML emission. Moreover, a model is proposed and well explains the phenomenon that the threshold of ZnS: Mn ML has a wide range rather than a single value. This study helps the understanding of ML mechanism and provides a new strategy to improve the ML efficiency.

Modulating Smart Mechanoluminescent Phosphors for Multistimuli Responsive Optical Wood.

Mechanoluminescence is a smart light-emitting phenomenon in which applied mechanical energy is directly converted into photon emissions. In particular, mechanoluminescent materials have shown considerable potential for applications in the fields of energy and sensing. This study thoroughly investigates the mechanoluminescence and long afterglow properties of singly doped and codoped Sr2 MgSi2 O7 (SMSO) with varying concentrations of Eu2+ and Dy3+ ions. Subsequently, a comprehensive analysis of its multimode luminescence properties, including photoluminescence, mechanoluminescence, long afterglow, and X-ray-induced luminescence, is conducted. In addition, the density of states mapping is acquired through first-principles calculations, confirming that the enhanced mechanoluminescence properties of SMSO primarily stem from the deep trap introduced by Dy3+ . In contrast to traditional mixing with Polydimethylsiloxane, in this study, the powders are incorporated into optically transparent wood to produce a multiresponse with mechanoluminescence, long afterglow, and X-ray-excited luminescence. This structure is achieved by pretreating natural wood, eliminating lignin, and subsequently modifying the wood to overall modification using various smart phosphors and epoxy resin composites. After natural drying, a multifunctional composite wood structure with diverse luminescence properties is obtained. Owing to its environmental friendliness, sustainability, self-power, and cost-effectiveness, this smart mechanoluminescence wood is anticipated to find extensive applications in construction materials and energy-efficient displays.

Luminescence and mechanoluminescence of Ba4Si6O16:Eu2+, RE phosphors.

The luminescence properties of green Ba4Si6O16:Eu2+, rare-earths (RE) (RE = Sc, Y, La and Lu except Pm) phosphors are reported. Their long-lasting phosphorescence is discussed in view of trap depths and concentrations determined from thermally stimulated luminescence experiments. A second emission band centered at 439nm was evidenced at low temperatures, which stems from the substitution of Eu2+ in the two non-equivalent Ba2+ sites of Ba4Si6O16. The mechanoluminescence properties of Ba4Si6O16:Eu2+, RE phosphors are described, and a new mechanoluminescence mechanism is proposed, in the case where RE = Ho3+, involving a trap distribution from 0.694 to 0.924eV. Mechanical loading (post UV irradiation) induces a decrease in depth of the trap distribution, leading to an increase of the luminescence intensity, whereas a drop of the luminescence intensity is observed upon unloading, following the faster release of the charge carriers.

A functional coating with mechanoluminescent properties for sensing cavitation erosion and early warning of protection failure

Protective materials coated on the surface of fluid machinery are often used to slow down the damage caused by cavitation. Once the protective material fails, there is no real-time monitoring to predict, which will directly threaten the safe operation of the equipment. In this work, we designed a functional SrAl2O4: Eu2+, Dy3+ coating by atmospheric plasma spraying (APS), which can sense the impact of bubble implosion and realize the early warning of the failure of anti-cavitation erosion polyurethane (PU) coating. It is found that the luminescent properties of the functional coatings are easily affected by lattice defects, amorphous phase and valence state of europium ions. The functional coating is more sensitive to the perception of micro-jets and shock waves after vacuum thermal reduction treatment, and can distinguish the difference in stress by the brightness of the light. More importantly, when the surface polyurethane coating is removed by cavitation erosion (CE) down to 0.1 mm, this functional coating emits light to warn the polyurethane coating of impending failure. Therefore, this work provided a solution for sensing CE and predicting when the protection would fail.

High-Pressure Near-Infrared Luminescence Studies of Fe3+-Activated LiGaO2.

A 0.25% iron (Fe3+)-doped LiGaO2 phosphor was synthesized by a high-temperature solid-state reaction method. The phosphor was characterized utilizing X-ray diffraction (XRD), scanning electron microscopy (SEM), high-pressure photoluminescence, and photoluminescence decay measurement techniques using diamond anvil cells (DACs). The powder X-ray analysis shows that the phosphor is a β polymorph of LiGaO2 with an orthorhombic crystallographic structure at room temperature. The SEM result also confirms the presence of well-dispersed micro-rod-like structures throughout the sample. The photoluminescence studies in the near-infrared (NIR) range were performed at ambient, low-temperature, and high-pressure conditions. The synthesized phosphor exhibits a photoluminescence band around 746 nm related to the 4T1 → 6A1 transition with a 28% quantum efficiency at ambient conditions, which shifts toward longer wavelengths with the increase of pressure. The excitation spectra of Fe3+ are very well fitted with the Tanabe-Sugano crystal-field theory. The phosphor luminescence decays with a millisecond lifetime. The high-pressure application transforms the β polymorph of LiGaO2 into a trigonal α structure at the pressure of about 3 GPa. Further increase of pressure quenches the Fe3+ luminescence due to the amorphization process of the material. The prepared phosphor exhibits also mechanoluminescence properties in the NIR spectral region.

Mechanoluminescent property of bis(phenylethynyl)platinum(II) complexes bearing substituted bipyridine and their application for developing rewritable data recording device

Two platinum(II) complexes, Pt(DiClBpy)(CCC6H5)2 (1) and Pt(DiBrBpy)(CCC6H5)2 (2) based on 4,4′-dichloro-2,2′-bipyridine (DiClbpy), 4,4′-dibromo-2,2′-bipyridine (DiBrbpy) and phenylacetylene ligands were synthesized and characterized. Both complexes display reversible and reproducible mechanochromic and mechanoluminescent properties with the luminescence red-shift exceeding 150 nm. Systematic studies on crystal structure, luminescence spectra, and PXRD demonstrate that the mechanochromic and mechanoluminescent properties of 1 and 2 are attributed to the formation/elimination of intermolecular Pt-Pt interactions during mechanical grinding/vapor absorption process, which lead to the transformation of the lowest energy excited states between MLCT and MMLCT transitions. In addition, based on such property, 1 and 2 were used as starting functional material to successfully develop the rewritable data recording device.

Optimizing the Mechanoluminescent Properties of CaZnOS:Tb via Microwave-Assisted Synthesis: A Comparative Study with Conventional Thermal Methods.

Recent developments in lighting and display technologies have led to an increased focus on materials and phosphors with high efficiency, chemical stability, and eco-friendliness. Mechanoluminescence (ML) is a promising technology for new lighting devices, specifically in pressure sensors and displays. CaZnOS has been identified as an efficient ML material, with potential applications as a stress sensor. This study focuses on optimizing the mechanoluminescent properties of CaZnOS:Tb through microwave-assisted synthesis. We successfully synthesized CaZnOS doped with Tb3+ using this method and compared it with samples obtained through conventional solid-state methods. We analyzed the material's characteristics using various techniques to investigate their structural, morphological, and optical properties. We then studied the material's mechanoluminescent properties through single impacts with varying energies. Our results show that materials synthesized through microwave methods exhibit similar optical and, primarily, mechanoluminescent properties, making them suitable for use in photonics applications. The comparison of the microwave and conventional solid-state synthesis methods highlights the potential of microwave-assisted methods to optimize the properties of mechanoluminescent materials for practical applications.

Occlusal splint with mechanoluminescence properties based on BaSi2O2N2:Eu2+ cyan phosphor prepared by deposition-precipitation method

A series of Eu2+ activated BaSi2O2N2 oxynitride cyan phosphors with high crystallinity have been successfully synthesized by a facile deposition-precipitation (DP) method. Under excitation of 375 nm, the photoluminescence emission intensity at 495 nm was enhanced by 157% for BaSi2O2N2:Eu2+ prepared by DP method compared to the sample prepared by traditional solid-state reaction (SSR) method due to the uniform distribution of Eu2+ ions. Accordingly, BaSi2O2N2:0.02Eu2+ phosphor prepared by DP method exhibits a longer fluorescence lifetime (553.6 ns) than that (472.8 ns) prepared by SSR method. Interestingly, Eu2+ ions can incorporate in BaSi2O2N2 lattices through DP process even at a lower temperature (1000 °C) compared to the conventional temperature (1450 °C) during SSR process. Finally, the flexible occlusal splints based on BSON:Eu2+/PDMS composite elastomers has been fabricated by the excellent mechanoluminescent (ML) property of BaSi2O2N2:Eu2+ phosphors. The ML signal of BSON:Eu2+/PDMS occlusal splints under mechanical stimulation allows visualization of force magnitude during occlusal examination for the treatment of clinical oral disorders such as temporomandibular disorders.

A multifunctional composite material with piezoresistivity and mechanoluminescence properties for a wearable sensor

Intelligent composite materials and devices are attracting a great interest owing to their potential impact on various future life applications. To meet the growing demand for multifunctional materials, the development and validation of visible sensing behavior is highly desirable, but the development of a single multifunctional wearable sensing material still remains a challenge to be achieved. To reach this goal, here we present a wearable intelligent fabric with piezoresistivity and mechanoluminescence ability based on a layer-structured graphene-based conductive cotton fabric and SrAl2O4:Eu2+, Dy3+/polyurethane foamed coating. The presence of the foamed coating structure endows the flexible composite fabric with a controllable positive/negative piezoresistivity (gauge factor from −2.5 to 17) and a bright mechanoluminescence ability that can be used in the darkness without additional batteries. Three-dimensional chromaticity diagrams have also been developed as advanced tools to quantitatively assess the luminescence, whose lightness, during the bending cycles, is highly repeatable with value in the range from ∼25 to ∼55. The multifunctional layered composite sensor provides multiple output signals which can be accurately recognized and assigned to independent triggering events, opening up new opportunities in advanced wearable devices based on commercial fabrics.

Controlled mechano-luminescence properties of SrGa2O4:Tb3+ co-doping with Dy3+ and Eu3+ ions.

Trap-controlled mechano-luminescence (ML) featuring photon emission under mechanical stimuli provides promising applications such as dynamic imaging of force, integrated optical sensing, information storage, and anti-counterfeiting encryption. However, the corresponding emission with a single color still limits the application of ML materials. Here, a trap-controlled ML phosphor of SrGa2O4:Tb3+ (SGO:Tb3+) with a green-emission is investigated with an adjustable ML color. The relationship between ML and thermoluminescence (TL) is verified by co-doping with Dy3+ and Eu3+ ions for the manipulation of the constructed traps. Accordingly, the as-explored ML phosphor with multicolor output is employed to create encrypted anticounterfeiting patterns, which produces bright and spatially resolvable optical codes under the single-point dynamic pressure of a ballpoint pen. Hence, it provides a new approach to achieve ML with multicolor and gives us an insight into understanding the mechanism of the ML procedure.

A novel class of highly flexible transparent boranil/polydimethylsiloxane composites for white light emission

Three triphenylamine-based poly substituted salicylaldimine (anils) and corresponding N, O-moiety chelated difluoroboron complexes B1, B2, and B3 (boranils) have been synthesized and characterized via different spectroscopic techniques. Due to the high luminescence intensity, mechanoluminescent properties, ICT (Intermolecular charge transfer), and significant Stokes shift, boranils have been implemented for light-emitting devices once incorporated inside PDMS (Polydimethylsiloxane), a silicon-based polymer matrix. The Bm (a 1:1:1 mixture, w/w, of B1, B2, and B3) covered the more extended emission region in solid and PDMS film and exhibited the white light-emitting tendency. All the individual boranil/PDMS composites showed significant stability when irradiated with UV light and played a crucial role in LED performance. Notably, boranils exhibit white light-emitting efficiency when illuminated on a 325 nm laser with high color rendering index (CRI) value (96–98%). They can be enacted in several household lighting applications, including electronic and signaling devices.

Designing of experimental setup for impact induced mechanoluminescence measurements

An alternative approach has been adopted to construct novel low-cost laboratory equipment for measuring the mechanical impact-induced mechanoluminescence (I-ML) properties of materials with high accuracy and sensitivity. In this setup, the correlation between the loss of kinetic energy of the projectiles during impact and the intensity of the impact-induced mechanoluminescence is studied by changing the angle of incidence of the shooting. The range of initial kinetic energy is controlled by selecting projectile masses. The designed apparatus is also useful for analyzing the mechanism of ML, by comparison of the time dependencies of ML and persistent luminescence at multishot with adjustable frequencies. The results of multiple measurements of the luminescence materials Sr0.95Ca0.05(SO4):Mn and SrAl2O4:Eu,Dy, justified the outstanding performance of the setup in different categories of mechanoluminescence studies. The designing and handling of the proposed setup are simple and highly beneficial for broad-range experimental analysis of the I-ML characteristics.

Multi-stimuli-responsive aryl-sulfone derivatives with room-temperature phosphorescence and mechanoluminescence properties

Two aryl-sulfone derivatives labeled CzSP and TBCzSP were developed. CzSP shows ultralong room-temperature phosphorescence (RTP) with the lifetimes of more than 720 ms and a quantum efficiency of 2.41% while TBCzSP displays RTP with the lifetimes of more than 4.8 μs and a quantum efficiency of 4.91%. Besides, a deep blue mechanoluminescence (ML) is observed when CzSP and TBCzSP are ground or rubbed. According to single crystal and TD-DFT calculations, molecular packing modes and S1→Tn transition play important roles in RTP and ML properties. In addition, intermolecular charge transfer and dipole moment cause the ML property. The ultralong RTP property indicates that CzSP can be effectively used to visualize printed images (especially for latent fingerprints detection).

Luminescent Coordination Polymer with Its Multistimuli-Responsive Sensitivity Enabled and Boosted by Its Dual Emission

Multistimuli-responsive luminescent materials have wide and promising applications but their designs and syntheses are very challenging. Here, we report a new dual-emitting Eu-based multiemissive coordination polymer (CP, 1) that can respond to different stimuli, i.e., grinding, pH, and aspartic acid (Asp). 1 exhibits a mechanoluminescence (MCL) property with a visible color change (pink ⇌ blue) upon grinding and can be restored upon exposure to dimethylformamide (DMF) vapor. Moreover, it undergoes a reversible color switching (pink ⇌ blue) with the pH interval in the range of 3–4 and can serve as a selective, reusable, and fast ratiometric probe for Asp in aqueous media, with a limit of detection (LOD) down to 2.48 μM. Moreover, a rapid, highly sensitive, and visualizable response to Asp is demonstrated using a CP-based luminescent film and logic device. Detailed mechanism studies including characterization of single-crystal-to-single-crystal transformation reveal that the multistimuli-responsive property is due to the different responses of the two emissions to the mechanical and pH stimuli and the accompanying changes in the energy transfer efficiency from the ligand to the Eu3+ ion (antenna effect). Multiemissive coordination polymers can be a very promising candidate for multistimuli-responsive luminescent materials with significantly improved functionalities to meet diverse applications.

Photo- and Mechanoluminescent Properties of SrAl2O4:(Eu2+, Dy3+) Phosphor and Its Use for Visualization of Deformation Dynamics of Materials

Photo- and Mechanoluminescent Properties of SrAl2O4:(Eu2+, Dy3+) Phosphor and Its Use for Visualization of Deformation Dynamics of Materials

Mechanoluminescence properties of Pr3+-doped B2O3-Al2O3-SrO system glass-ceramics

Among the many luminescent materials, mechanoluminescence materials which emit light due to stress, friction, and impact external forces have attracted more and more attention, however, red emission is still a technical challenge. As one of the red activators, Pr3+ has excellent optical properties. In this paper, the basic glass with different Pr3+ doping concentration was prepared by melt-quench technique. A group of B2O3-Al2O3-SrO glass ceramics containing SrAl2B2O7 crystal structure were prepared by different heat treatment systems, and the photoluminescence and mechanical luminescence spectra were measured. Glass ceramics showed strong orange red photoluminescence. The glass ceramics prepared by glass crystallization method has mechanoluminescence properties and has potential application prospects in high-resolution display imaging stress sensor, optical information storage and artificial skin applications.

Photo- and mechano-luminescent properties of color-tunable (Eu2+, Dy3+)-co-doped strontium/calcium aluminate phosphor

(Eu2+, Dy3+)-co-doped strontium/calcium aluminate phosphor as one of color-tunable emission materials was synthesized via solid-state reactions at 1300 °C for 3 h. Effect of strontium/calcium ratio on the crystal structure, particle size/morphology as well as photo- and mechano-luminescent properties of the phosphors was investigated by X-ray diffraction, Rietveld method, scanning electron microscopy with energy dispersive X-ray spectroscopy, and spectrophotometry. The mechano-luminescent properties were measured by two mechanical stress instruments (i.e., impact and compression), respectively. The results reveal that a mixed phase with SrAl2O4 and CaAl2O4 has a monoclinic structure with a space group P21 for SrxCa1-xAl2O4: 0.001Eu2+, 0.001Dy3+ phosphor (x = 0.2–0.8), resulting in the change of crystallographic parameters due to different calcium/strontium ratios. According to the results of photo- and mechano-luminescent characterizations, SrAl2O4: 0.001Eu2+, 0.001Dy3+ phosphor (x = 1.0) has a superior mechano-luminescent property rather than CaAl2O4: 0.001Eu2+, 0.001Dy3+ phosphor (x = 0), although they both have photo-luminescent properties. Furthermore, the CEI diagram indicates that the emission color of the phosphor can be tuned from blue to bluish white and eventually to green, and the mechano-luminescent peak appears and becomes intense as Sr2+ ions substitute for Ca2+ ions in the phosphor gradually. In addition, the photo- and mechano-luminescent mechanisms of phosphor were also discussed.