Properties of Self-recoverable Mechanoluminescence Phosphor Ca_(5)Ga_(6)O_(14)∶Eu^(3+) and Its Information Encryption Application

A novel self-recoverable mechanoluminescent phosphor Ca_(5)Ga_(6)O_(14)∶Eu^(3+) was developed by the high-tem-perature solid-state reaction method,and its luminescence properties were investigated.Ca_(5)Ga_(6)O_(14)∶Eu^(3+)can produce red mechanoluminescence,and importantly,it shows good repeatability.The mechanoluminescence of Ca_(5)Ga_(6)O_(14)∶Eu^(3+) results from the piezoelectric field generated inside the material under stress,rather than the charge carriers stored in the traps,which can be confirmed by the multiple cycles of mechanoluminescence tests and heat treatment tests.The mechanoluminescence color can be turned from red to green by co-doping varied concentrations of Tb^(3+),which may be meaningful for encrypted letter writing.The encryption scheme for secure communication was devised by harnessing mechanoluminescence patterns in diverse shapes and ASCII codes,which shows good encryption performance.The results suggest that the mechanoluminescence phosphor Ca_(5)Ga_(6)O_(14)∶Eu^(3+),Tb^(3+)may be applied to the optical information encryption.

Red Mechanoluminescence and Photoluminescence from Novel Europium Complexes

Two new binuclear (europium and lanthanum) beta-diketone complexes Eu0.9La0.1(TTA)(3)Phen and Eu0.5La0.5(TTA)(3)Phen in which Phen is 1,10-phenanthroline, TTA is an anion of thenoyltrifluoroacetone (HTTA) were synthesized for the first time. They showed intense photoluminescence (PL) and mechanoluminescence (ML), and had their maximum PL and ML spectra peaked at 613.5 nm with half bandwidth of 10 nm respectively. Their PL and ML intensity were obviously stronger than these from Eu(TTA)(3)Phen. It is considered that binuclear (europium and lanthanum) beta-diketones complexes are promising ML and PL materials.

Stress-induced CsPbBr3 nanocrystallization on glass surface:Unexpected mechanoluminescence and applications

In this work,we discovered an unexpected mechanoluminescence (ML) phenomena occurring when transforming amorphous into crystalline,due to the stress-induced precipitation of CsPbBr3 perovskite nanocrystals on glass surface.It is revealed that,unlike the conventional thermal-induced phase transformation mechanism,the breakage of bonding of glass network provides the energy for nucleation and growth,and the shear stress avoids the long-range migration of structural units for crystallization.Such unique ML phenomenon enables the visualization of dynamical force that is inaccessible by common strategy,and so,opens up some novel applications,such as the pressure-sensitive "glassy pencil" to learn people's writing habits,and the pb^2+-detection with good sensitivity and selectivity.These findings not only demonstrate an effective route for the preparation of perovskite materials in a green,time-saving,low cost,and scalable way,enrich the knowledge of glass crystallization mechanism,but also exploit a useful avenue to quantitatively visualize the dynamical force.

Mechanism of mechanical quenching and mechanoluminescence in phosphorescent CaZnOS:Cu

This article reports a new phosphorescent material,CaZnOS:Cu,that exhibits two types of mechano-optical conversion:mechanical quenching and mechanoluminescence.An intense mechanical quenching of phosphorescence corresponding to mechanical stimuli can be achieved in CaZnOS:Cu within a short decay time period.Over time,it gradually changes to mechanoluminescence when a mechanical load is applied.We propose that the mechanical quenching and mechanoluminescence arise from the different roles of shallow and deep traps in CaZnOS:Cu.CaZnOS:Cu has promising applications in monitoring mechanical stress in industrial plants,structures,and living bodies.

The initial attempt to reveal the emission processes of both mechanoluminescence and room temperature phosphorescence with the aid of circular dichroism in solid state

A phenothiazine derivative PtzChol containing non-conjugated chiral cholesterol group was designed and synthesized. By analyzing the single crystal structure of PtzChol carefully, coupled with the circular dichroism(CD) signals before and after grinding, it was found that the introduction of cholesterol produced a positive effect on the production of chiral space group, on mechanoluminescence(ML) and room temperature phosphorescence(RTP), and throughout the entire light-emitting process, the CD signal could well reflect the changes of molecular arrangement.

Lanthanide-doped metal-organic frameworks with multicolor mechanoluminescence

Metal-organic frameworks(MOFs)and mechanoluminescent(ML)materials have been considered as two types of promising materials that have their own application fields.It would be amazing to endow one material with the advantages of ML and MOFs,thus broadening their applications.However,there are quite few investigations on this topic,and the ML mechanism in ML-MOFs remains unclear.In this study,we proposed a strategy for developing ML-MOFs by doping lanthanide ions into the non-centrosymmetric SBD([Sr(μ-BDC)(DMF)]∞)MOF,and successfully synthesized a series of lanthanide-doped MOFs Ln-SBD(Ln=Tb,Dy,Sm,Eu)and Tb1-xEux-SBD(x=0.2,0.4,0.6,0.8)with multicolor ML.The lanthanide ions were uniformly distributed in the matrix of the SBD-MOF,and occupied the Sr site.The MLMOFs exhibited intense multicolor ML emissions varying from green to yellow to red by changing the co-doping ratios and species of lanthanide ions.The similar ML and photoluminescence(PL)spectra indicated that the ML emission was assigned to the radiative transition from the excited states to the ground states of lanthanide ions.The radiative transition was induced by the electron bombardment process that originated from the piezoelectric effect of the non-centrosymmetric SBD host.In addition,a pioneering temperature sensing research based on ML was carried out,which is promising for realizing dual-functional detection of stress and temperature without excitation light sources.This study gives a unique insight for developing more versatile and interesting smart materials by combining the versatility of MOF with the ML emission,imparting additional values to both MOF and ML materials.Moreover,this study provides a general rule for selecting MOFs with an acentric structure as the host for ML materials.

Trap modification and mechanoluminescence improvement by Si substitution for Sn in Sr_(2)SnO_(4):Sm^(3+) ceramics

A series of Sr_(1.96)Sn_(1-x)Si_(x)O_(4):0.04Sm^(3+)(x=0,0.1,0.15,_(0.2),0.3,0.4)were synthesized from solid-state reaction.The mechanoluminescence(ML)performance of Sr_(1.96)SnO_(4):0.04Sm^(3+)was greatly enhanced by partial Si^(4+)substitution for Sn^(4+),and the sample of Sr_(1.96)Sn_(0.8)Si_(0.2)O_(4):0.04Sm^(3+)showed weaker afterglow and twice stronger ML intensity than that in Sr_(1.96) SnO_(4):0.04Sm^(3+).The stress response of Sr_(1.96)Sn_(0.8)Si_(0.2)O_(4):0.04Sm^(3+)ranged from 250 to 1200 N,and its linearity was greatly restored.Particularly,it was very sensitive in the minimal stress response range.These properties of no load threshold for stress sensing and weak afterglow make Sr_(1.96)Sn_(0.8)Si_(0.2)O_(4):0.04Sm^(3+)superior to other excellent ML materials.The introduction of Si^(4+)caused lattice distortion and promoted defect formation in the system.The trap level energy greatly increased and the trap depth changed,which enhanced the trap ability and therefore improved effectively the ML properties.

Intense red emitting mechanoluminescence from CaZnOS:Mn,Li with c-axis preferred orientation

We report that the co-doping of Li^(+)ions significantly enhances the crystallinity and mechanoluminescence(ML)intensity of CaZnOS:Mn.The prepared CaZnOS:Mn,Li showed a preferred orientation of c-axis,and the particles possessed a plate-like morphology,which could be attributed to the layered structure of CaZnOS.At the same time,the ML induced by compressive load exhibited intense red emission and obvious intensity enhancement by the Li^(+)co-doping.

Novel elastico-mechanoluminescence materials CaZnOS:Mn^(2+)and CaZr(PO_(4))_(2):Eu^(2+)

This paper highlights our work on the recent progress in novel elastico-mechanoluminescence(EML)materials CaZnOS:Mn^(2+)and CaZr(PO_(4))_(2):Eu ^(2+),which can simultaneously"feel"(sense)and"see"(image)the applied mechanical stress as an intense and proportional luminescence.CaZnOS:Mn 2þcan sense various types of mechanical stress,including ultrasonic vibration,impact,friction and compression because of the large piezoelectric coefficient.CaZr(PO_(4))_(2):Eu ^(2+)with multiple trap levels shows a broad measurement range for dynamic load.Both of CaZnOS:Mn^(2+)and CaZr(PO_(4))_(2):Eu ^(2+)belong to the defect-controlled type pie-zoelectric phosphors,and their EML mechanisms could be explained using the piezoelectrically induced carrier de-trapping model.

Achieving Bright Mechanoluminescence in a Hydrogen-Bonded Organic Framework by Polar Molecular Rotor Incorporation

Luminescent hydrogen-bonded organic frameworks(HOFs)have attracted increasing attention due to their corresponding luminescence that enables readily visualization of structural dynamics.HOFs with the mechanoluminescence(ML)property can emit light without photon excitation and are greatly attractive for advanced applications,but research in this area has been limiting.Herein,we report the first example of an ML-active flexible HOF with permanent porosity,named 8PCOM,assembled from polar molecular rotors with an aggregation-induced emission property.When responding to different solvent vapors,reversible structural transformations between ML-active and-inactive 8PCOM frameworks occur,including a single-crystal-to-single-crystal(SCSC)transformation.Thus,guest-induced breathing behaviors are mainly attributed to phenyl rotations of polar molecular rotors induced by external stimuli.During reversible structural transformations of various 8PCOM frameworks with different pores,the significant ML property is achieved successfully through supramolecular dipole moment regulation.Upon mechanical force,bright emission of the ML-active 8PCOM framework is observed without UV irradiation,and the ML-active crystals can be easily prepared and regenerated.This work not only provides a valuable strategy for engineering future multifunctional HOFs but also enriches the types and applications of existing luminescent porous materials.

Mechanoluminescent-Triboelectric Bimodal Sensors for Self-Powered Sensing and Intelligent Control

Self-powered flexible devices with skin-like multiple sensing ability have attracted great attentions due to their broad applications in the Internet of Things(IoT).Various methods have been proposed to enhance mechano-optic or electric performance of the flexible devices;however,it remains challenging to realize the display and accurate recognition of motion trajectories for intelligent control.Here,we present a fully self-powered mechanoluminescent-triboelectric bimodal sensor based on micronanostructured mechanoluminescent elastomer,which can patterned-display the force trajectories.The deformable liquid metals used as stretchable electrode make the stress transfer stable through overall device to achieve outstanding mechanoluminescence(with a gray value of 107 under a stimulus force as low as 0.3 N and more than 2000 cycles reproducibility).Moreover,a microstructured surface is constructed which endows the resulted composite with significantly improved triboelectric performances(voltage increases from 8 to 24 V).Based on the excellent bimodal sensing performances and durability of the obtained composite,a highly reliable intelligent control system by machine learning has been developed for controlling trolley,providing an approach for advanced visual interaction devices and smart wearable electronics in the future IoT era.

Crystal structure and optical performance analysis of a new type of persistent luminescence material with multi-functional application prospects

Persistent luminescence (PersL) materials,as environmentally friendly and energy-saving materials,have broad application prospects in many fields such as lighting,chemistry and even biomedicine.However,studies on the types,performances and mechanism of PersL materials are still insufficient,which significantly restricts their development and application.Under this consideration,we successfully synthesized a yellow PersL material CaSrGa_(4)O_(8)(CSG).The crystal structure was studied in detail through Rotation Electron Diffraction (RED) and Powder X-ray Diffraction (PXRD).What’s more,by co-doping Mn^(2+) and Yb^(3+),the afterglow brightness of CSG could be increased by nearly 20 times,and the afterglow duration could reach more than 6 h.It is worth mentioning that the samples also have excellent performances in mechanical luminescence (ML),photostimulated luminescence (PSL) and cathodoluminescence (CL),which was also investigated systematically.Finally,an anti-counterfeiting label was designed by the samples to reveal the potential of their application in anti-counterfeiting.The results showed that our research not only provided a new candidate PersL material for multifunctional applications,but also gave good help for studying the physical and chemical properties of CSG.

Synthesis and Luminescence Properties of Pr^(3+) Doped Ca_xBa_(1-x)TiO_3 (0.3≤x<1) Fine Particles

CaxBa1-xTiO3 （CBT） fine particles doped with red luminescence center of Pr3＋ ions （Pr： CBT） were successfully synthesized by salt assisted spray pyrolysis （SASP） process. Scanning electronic microscope （SEM） and laser scattering analysis demonstrate that salt can be removed from the surface of particles by washing with Milli-Q water and the particles can be further separated by ball-milling to get well-dispersed Pr^3＋ ions doped CBT fine particles. The luminescence properties, such as photoluminescence （PL） and mechanoluminescence （ML）, of as-synthesized Pr： CBT particles were investigated. For Pr： CBT fine particles with different Ca molar ratios, all the samples show one emission at 612 nm, with increasing Ca molar ratio, PL intensity of Pr： CBT fine particles become stronger and stronger. When pressure was loaded on the Pr： CBT pellet, mechanoluminescence（ML） emission was measured. The results show that the ML intensity is proportional to the applied pressure.

Two New Zn(Ⅱ)/Cd(Ⅱ) One-dimensional Coordination Polymers Based on Naphthalimide Dicarboxylic Ligand

The assemble reactions of 5-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3 H)-yl)isophthalic acid(H2L)and Zn^2+/Cd^2+ions led to two compounds:[ZnL(DMSO)2]·3DMSO(1)and[Cd2 L2(DMSO)4]·DMF(2).1 and 2 feature 1 D coordination chains.Weakπ-πinteractions further connect the 1 D chains into 2D supramolecular networks.Upon grinding,1 and 2 show increase of quantum efficiencies(34.8 and 45.4 times of increase compared with original samples for the two compounds respectively)and red shift of the emission peaks(45 and 41 nm of shift compared with original samples for the two compounds,respectively).Both indicate the compounds are good mechanoluminescence responsive materials.

Bioinspired nanotransducers for neuromodulation

The field of neuromodulation has experienced significant advancements in the past decade,owing to breakthroughs in disciplines such as materials science,genetics,bioengineering,photonics,and beyond.The convergence of these fields has resulted in the development of nanotransducers,devices that harness the synergies of these diverse disciplines.These nanotransducers,essential for neuromodulation,often draw inspiration from energy conversion processes found in nature for their unique modalities.In this review,we will delve into the latest advancements in wireless neuromodulation facilitated by optical,magnetic,and mechanical nanotransducers.We will examine their working principles,properties,advantages,and limitations in comparison to current methods for deep brain neuromodulation,highlighting the impact of natural systems on their design and functionality.Additionally,we will underscore potential future directions,emphasizing how continued progress in materials science,neuroscience,and bioengineering might expand the horizons of what is achievable with nanotransducer-enabled neuromodulation.

Highly crystallization-induced emissive luminophores with mechanoluminescent features for two-photon harvesting fluorescence imaging and latent fingerprint identification

Fluorescence imaging can be employed in fields of medical treatment,astronomical exploration,and national defense security.Traditional fluorescence imaging often takes the single-photon techniques,which is vulnerable to background interference and photobleaching.Remedially,two-photon fluorescence imaging can achieve much higher-resolution fluorescence imaging for reducing scattering and deeper depth.Hence,by assembling the tetraphenylethylene backbones with nontoxic and non-noble K^(+)ions,compound 1([(Hdma)K(H_(2)ettc)]_(n),H_(4)ettc=4',4''',4''''',4'''''''-(ethene-1,1,2,2-tetrayl)tetrakis(([1,1'-biphenyl]-4-carboxylic acid)))with the crystallization-induced emissions exhibited charming fluorescence imaging under two-photon excitation microscopy(TPEM).Besides,luminescent powders based on compound 1 can achieve high-resolution fingerprint recognition,providing secure access control and identification for a novel authentication method.Compared with the commercial fluorescent dyes coumarin-6,the as-synthesized compound 1 showed great solvent stability,indicating its durability against harsh environment.Moreover,compound 1 shows mechanoluminescent properties for the perturbation of weak supramolecular interactions within ordered arrangements of the H_(2)ettc^(2−)ligands.This novel compound has provided an important insight to the development of twophoton fluorescence imaging and advanced external-stimuli responsive materials.

Artificial visual-tactile perception array for enhanced memory and neuromorphic computations

The emulation of human multisensory functions to construct artificial perception systems is an intriguing challenge for developing humanoid robotics and cross-modal human–machine interfaces.Inspired by human multisensory signal generation and neuroplasticity-based signal processing,here,an artificial perceptual neuro array with visual-tactile sensing,processing,learning,and memory is demonstrated.The neuromorphic bimodal perception array compactly combines an artificial photoelectric synapse network and an integrated mechanoluminescent layer,endowing individual and synergistic plastic modulation of optical and mechanical information,including short-term memory,long-term memory,paired pulse facilitation,and“learning-experience”behavior.Sequential or superimposed visual and tactile stimuli inputs can efficiently simulate the associative learning process of“Pavlov's dog”.The fusion of visual and tactile modulation enables enhanced memory of the stimulation image during the learning process.A machine-learning algorithm is coupled with an artificial neural network for pattern recognition,achieving a recognition accuracy of 70%for bimodal training,which is higher than that obtained by unimodal training.In addition,the artificial perceptual neuron has a low energy consumption of~20 pJ.With its mechanical compliance and simple architecture,the neuromorphic bimodal perception array has promising applications in largescale cross-modal interactions and high-throughput intelligent perceptions.

Continuous synthesis of ultra-fine fiber for wearable mechanoluminescent textile

Continuous mechanoluminescence(ML)fibers and fiber-woven textiles have the potential to serve as new wearable devices for sensors,healthcare,human-computer interfacing,and Internet of Things.Considering the demands on wearability and adaptability for the ML textiles,it is essential to realize the continuous synthesis of fiber,while maintaining a desired small diameter.Here,we develop a novel adhere-coating method to fabricate ML composite fiber,consisting of a thin polyurethane(PU)core and ZnS:Cu/polydimethylsiloxane(PDMS)shell,with the outer diameter of 120μm.By diluting PDMS to tune the thickness of liquid coating layer,droplets formation has been effectively prevented.The composite fiber exhibits a smooth surface structure and superior ML performances,including high brightness,excellent flexibility,and stability.In addition,a weft knitting textile fabricated by the continuous ML fiber can be easily delighted by manually stretching,and the ML fibers can emit visible signals upon human motion stimuli when woven into commercial cloth.Such continuous ultra-fine ML fibers are promising as wearable sensing devices for human motion detection and human-machine interactions.

Preparation of Eu^(2+),Dy^(3+),Zr^(4+)ions co-doped strontium aluminate/molybdate multi-optical functional hybrid pigments for anti-counterfeiting

Eu^(2+),Dy^(3+)and Zr_(4+)ions co-doped strontium aluminate(i.e.,SrAl_(2)O_(4):Eu^(2+),Dy^(3+),Zr_(4+))/molybdate(i.e.,Ho2MoO6or Nd2MoO6)with photo-/mechano-luminescence and allochroic effect as multi-optical functional hybrid pigments were prepared via solid state reactions and subsequent mixing.The phosphor and hybrid pigments were characterized by X-ray diffraction,scanning electron microscopy with energy dispersive X-ray spectroscopy,ultraviolet-visible spectroscopy,L*a*b*color scale analysis,spectrophotometry and mechanoluminescent measurement.The results show that the optimum luminescent emission intensity of SrAl_(2)O_(4):Eu^(2+),Dy^(3+),Zr_(4+)phosphor can be obtained when 5 mol%Zr_(4+)ions is doped into the lattice.Under the excitation of 365 nm wavelength,the hybrid pigments prepared with the phosphor and molybdate at a mass ratio of 1:1 present a green broad band emission located at 460-650 nm due to 4f65d1→4f7transitions of Eu^(2+)ions.The hybrid pigments have the superior mechanoluminescent property and emit light after being exerted by mechanical stresses.Besides,the hybrid pigments also exhibit an allochroic effect under different illuminants.In addition,the anti-counterfeiting of the hybrid pigments as a promising application was also presented.

基于动态硼酸酯键的室温自愈合应力发光材料

基于应力发光的应力传感技术因其独特的机械-光子转换性质在柔性电子、结构健康诊断、生物力学工程和自供电显示等领域显示出巨大的潜力.然而,应力发光传感技术面临的一大挑战是当施加的机械载荷超过其强度极限时,具有典型无机@有机结构的应力发光传感材料将被损坏,从而降低其传感系统的可靠性和耐久性.本文提出了一种自修复方法,即通过构建聚硼硅氧烷/聚二甲基硅氧烷(PBS/PDMS)双网络结构来解决传感材料的失效问题.PBS网络中的动态硼酸酯键提供自愈合能力,化学交联的PDMS网络使应力发光材料保持良好的弹性和结构稳定性.这种双网络结构材料的力学性能和应力发光性能即使在遭受致命的断裂后也能得到有效恢复,室温下修复10分钟后拉伸强度恢复率为75%,机械-光子转换效率恢复率近100%.这种自修复的应力发光材料可以极大地促进应力发光技术在复杂、高强度和柔性应力传感中的应用.