Self-powered stimuli responsive material for dual stimulation of heat and guest molecules

Stimuli-responsive smart materials exhibit reverse chemical/physical changes in response to external stimuli and research on stimuli-responsive smart materials with self-powered properties is still uncultivated ground.Here,we report perovskite crystalline self-powered multiple stimuli-responsive materials triggered by chemical and thermal stimuli.[HMEP]PbI_(3)·(H_(2)O)(1;HMEP is a hydroxytris(1-methylethyl)phosphorus cation)crystallizes in a chiral space group P 21 at 293 K and has the piezoelectric reaction(d_(33)=10 pC/N and output voltage=1 V)of self-powered modes,this value is larger than the value of 3 pC/N for the classical piezoelectric material ZnO.Piezoelectric materials can generate energy due to mechanical deformation,and using thermal heating to lose water,[HMEP]PbI_(3)(2)can be obtained.2 crystallizes in the non-centrosymmetric space group,undergoes two reversible phase transitions at 243/255 K and 315/348 K,and shows second harmonic generation switching.Interestingly,2 can return to the hydrated form 1 after absorbing water.This work will lay the foundation for self-powered stimuli-responsive compounds and contribute to the construction of novel organic-inorganic hybrid materials with second harmonic generation switching.

Construction, photoelectric response and phase transition for new hybrid double perovskites showing narrow band gaps

To explore the lead-free key scientific issue in perovskite, double perovskite based on Ag Bi and Cu Bi was naturally selected as a competitive candidate due to its fascinating functional features, such as self-powered circularly polarized light detection, X-ray detection, photoluminescence and so on. However, the most challenging point is to simulate the structure and function of traditional lead-based perovskite in new double perovskite. At the same time, there are few suitable double perovskite systems with optical and electrical potential. The above two points greatly limit the competitiveness of double perovskite. In order to solve this problem, firstly, by analyzing and comparing previous studies,we used 2,2-dimethylpropan-1-aminium(abbreviated as 2,2-DPA) as the organic template to assemble materials. Solid-to-solid phase transition materials(2,2-DPA)3Bi2I91 and(2,2-DPA)3Pb2I72 were constructed. Along the path of lead-free and two-dimensional maintenance, we successfully synthesized(2,2-DPA)4AgBiI8.H_(2)O 3 and(2,2-DPA)_(4)CuBiI8.H_(2)O 4. As two typical semiconductors, 3 and 4 with narrower optical band gaps of 1.98 and 1.76 e V show obvious photo-response when the xenon lamp with intensity of 20 m W/cm^(2)is on or off, implying that they may be applied to light-harvesting and light-detecting devices. By referring to the phase transition mechanism of 1 and 2, 3 may be caused by ordered-disordered transition of the organic part, which was proven to be the first solid-to-solid phase transition material with <100>-oriented layered double perovskites with n = 1 by systematic characterization methods after dehydration for all we know. We believed that this work can provide meaningful guidance for the development of lead-free double perovskites.

Tunable phase transition, band gap and SHG properties by halogen replacement of hybrid perovskites [(thiomorpholinium)PbX_(3), X = Cl,Br,I]

By the replacement of halogen anion,three new multifunctional organic-inorganic hybrid perovskites(thiomorpholinium)PbX_(3)(X=Cl,Br,I)were successfully synthesized and underwent reversible struc-tural transformation above room temperature,accompanied by the anomalous change of dielectric con-stant.With the adjustment of the halogen anion from Cl to I in the inorganic skeleton,the space group is transformed from centrosymmetric space group P2_(1)/c((thiomorpholinium)PbCl_(3))to chiral one P2_(1)2_(1)2_(1)((thiomorpholinium)PbBr3,(thiomorpholinium)PbI_(3))at room temperature.The ordered-disordered tran-sition of organic cations and the change of hydrogen bonds with the increase of temperature lead to above-room-temperature phase transitions.Ultraviolet absorption and second-harmonic generation(SHG)measurements confirmed that both the band gap and SHG activity of(thiomorpholinium)PbX_(3)(X=Cl,Br,I)crystals were tunable.The band gaps reveal a broadening trend with 3.532 e V,3.410 e V and 3.175 e V along the Cl→Br→I series.This work provides an effective molecular design for multifunctional organic-inorganic perovskites.

Deuteration triggered downward shift of dielectric phase transition temperature in a hydrogen-bonded molecular crystal

Deuteration of hydrogen-bonded phase transition crystals can increase the transition temperatures due to the isotope effect. But rare examples show the opposite trend that originates from the structural changes of the hydrogen bond, known as the geometric H/D isotope effect. Herein, we report an organic crystal, diethylammonium hydrogen 1,4-terephthalate, exhibits a reversible structural phase transition and dielectric switching. Structural study shows the cations reside in channels formed by one-dimensional hydrogen-bonded anionic chains and undergo an order-disorder transition at around 206 K. The deuterated counterpart shows an elongation of the O…O hydrogen bond by about 0.005 A. This geometric isotope effect releases the internal pressure of the anionic host on the cation guests and results in a downward shift of the phase transition temperature by 10 K.

Visualization of Ferroelectric Domains in Thin Films of Molecular Materials Using Confocal Micro-Raman Spectroscopy

Ferroelectrics are an important class of functional materials.Among all their unique properties,the study of their ferroelectric domains and domain walls is of great interest due to their importance in ferroelectric applications.There are many methods to characterize ferroelectric domains,namely,scanning probe microscopy,optical microscopy,electron microscopy,etc.Currently,newly emerged molecular ferroelectrics are attracting much attention from chemists,physicists and researchers in material sciences due to their structural flexibility,light mass,simple fabrication,etc.However,for the characterization of molecular ferroelectric domains,most conventional methods require either a complicated preparation process or direct contact between physical probes and material surfaces,limiting the development of molecular ferroelectric materials.In this report,we have demonstrated that confocal micro-Raman spectroscopy,as a nondestructive and noncontact in-situ method,is very suitable for studying the ferroelectric polarization and structures of domains in molecular ferroelectrics.Taking recently reported molecular ferroelectric trimethylchloromethyl ammonium trichlorocadmium(II)(TMCM-CdCl_(3))as an example,the non-180°domains have been characterized and visualized at different temperatures.Such a simple and extendable method requires minimum sample preparation,which would further benefit the research of molecular ferroelectric domain engineering and promote the miniaturization and integration of molecular ferroelectric films.

Lead-free bilayer heterometallic halide perovskite with reversible phase transition and photoluminescence properties

The layered heterometallic halide perovskites, as a newly explored material, have attracted great scientific attention. As one of the representatives of perovskite, lead-free or lead-substituted perovskite materials are widely applied in photovoltaic, sensors, catalysis, detectors and other fields. Therefore, it is urgent to carry out more systematic exploration and expand applicable preresearch, so as to make more interesting discoveries in this new hot spot. As an interesting candidate, heterometallic compounds will introduce more structural adjustability and novel physical properties, which is the main feature to be selected as the research hotspot. Here, we reported a lead-free bilayer heterometallic Ruddlesden-Popper(RP) type perovskite, [(MACH)_(2)CsAgBiBr_(7)](MACH = cyclohexanemethylamine), which possesses a reversible phase transition at 379.6 K/375.1 K during heating-cooling cycle. Besides, it exhibits reddish-brown light emission under 365 nm, meanwhile, CIE chromaticity coordinate is(0.32, 0.45) on the yellow side and correlated color temperature is about 6000 K. Moreover, both the experimental data and theoretical calculation results suggest that [(MACH)_(2)CsAgBiBr_(7)] shows indirect semiconducting characteristics. In summary, this work will inspire the design of lead-free heterometallic perovskite materials for the application of sensors and light-emitting diodes(LEDs) fields.

Hydrogen-Bonded Engineering Enhancing Phase Transition Temperature in Molecular Perovskite Ferroelastic

The broad operating temperature range is sought for molecular ferroic materials who are expected to be applied to flexible and electronic materials.Hydrogen bonds,an effective force between molecules,are important to regulate the molecule structure and their condition,helping a higher temperature range for ferroic materials.Here,we report a molecular perovskite ferroelastic(Me-Hdabco)Rb[BF_(4)]_(3)(Me-Hdabco=N-methyldabconium)which shows high temperature(T_(1)=322.5 K and T_(2)=381K)ferroelastic phase transitions.The ferroelastic phase transition temperature range of(Me-Hdabco)Rb[BF_(4)]_(3) is significantly increased by 71 K compared with[Meda-bco-F]Rb[BF_(4)]_(3)(Medabco-F=1-fluoro-4-methyl-1,4-diazoniabicyclo[2.2.2]octane).Structural analysis and thermal analysis demonstrate the ferroelastic phase transition is mainly attributed to dynamic cations order and disorder transformation.Therefore,new hydrogen bonds generated between cations and the Rb_(8)[BF_(4)]_(12) frame increase their intermolecular force,which is beneficial to improving the phase transition temperature.This finding has an important impact on the utilization of weak interactionforces to design and optimize functional materials.

High-temperature dielectric switch and second harmonic generation integrated in a stimulus responsive material

Stimulus re s ponsive materials can provide a variety of desirable properties in one equipment unit,such as optoelectronic devices,data communications,actuators,memories,sensors and capacitors.However,it remains a large challenge to design such stimulus responsive materials,especially functional materials having both dielectric switch and second harmonic generation(SHG).Here,a new stimuli-responsive switchable material [(CH_(3))_(3)N(CH_(2))_(2)Cl]_(2)]Mn(SCN)_(4)(H_(2)O)_(2)] was discovered as a potential secondharmonic generation(SHG) dielectric switch.It is worth noting that it has SHG characteristics before and after undergoing reversible high-temperature phase transitions.In this work,we successfully refined the tetramethylammonium cation to obtain a quasi-spherical cation,which is tetramethylchloroethylamine(TMCEM) cation.By substituting H with a halogen,the increased steric hindrance of the molecular makes energy barrier increased,resulting in the reversible high-temperature phase transition.At the same time,the interactions of quasi-spherical cations and [Mn(SCN)_(4)(H_(2)O)_(2)]^(2-) anions affect a noncentrosymmetric structure to induce the SHG effect.These findings provide a new approach to design novel functional switch materials.

杂化卤化铅光致变色铁弹体

多功能材料是当前交叉研究的热点,有机-无机杂化材料因其结构多样性为构筑多功能材料提供了极大的可能性.多功能铁弹材料在机械开关、形状记忆以及能量转换等领域具有广泛的应用前景,特别是具备光学电学协同特征的铁弹材料是新器件应用研究的亮点.尽管目前报道了大量具有光致发光、热致变色等优异性质的铁弹材料,但尚未破解将铁弹性和光致变色协同这一难题.本文通过功能阳离子与卤化铅骨架构筑了具有光致变色效应的铁弹体,(3-hydroxypyrrolidinium)_(4)Pb_(3)Br_(10),并通过分子间插入氢键的策略有效提高了材料的相变温度.该材料还可同时实现两步介电响应,具有可切换铁弹畴和光致变色的多通道物理特性,这对显示传感器件的探索研究非常有帮助.总之,本研究为多功能物理响应材料的合成提供了多学科交叉研究策略和思路.

Thermal-Induced Ferroelastics in Two Lead-Free Organic-Inorganic Hybrid Perovskites

Lead-based organic-inorganic hybrids occupy a niche in the field of optoelectronics due to exceptional semiconducting properties and potential ferroelasticity.Nevertheless,the possible toxicity of lead restricts their widespread application to a certain extent.Herein,two new lead-free ferroelastic semiconductors are reported:[DMMClEA]_(3)Bi_(2)Br_(9)(compound 1)and[DMMClEA]_(3)Sb_(2)Br_(9)(compound 2)(DMMClEA=N-(chloromethyl)-N,N-dimethylethylammonium),in which the inorganic framework neatly arranges with[Bi_(2)Br_(9)]^(3−)/[Sb_(2)Br_(9)]^(3−)polyhedrons shared by face,forming an A_(3)B_(2)X_(9)-type structure.Both compounds 1 and 2 possess two-step phase transitions,including a3mF2/m-type ferroelastic phase transition,based on the Aizu rule.In addition,dual dielectric switches endow the application toward sensor devices.This finding enriches A_(3)B_(2)X_(9)-type zero-dimensional hybrid ferroelastics and provides an approach to designing high-performance,lead-free perovskite semiconductors with dielectric functionality.

全温度覆盖的三重介电及荧光响应无铅杂化钙钛矿开关材料

光电响应材料在温度传感、执行器、存储和功能开关领域的应用引起了广泛关注.然而将各种功能整合形成多功能响应材料仍具有挑战性.分子基杂化材料通常是有机和无机成分的杂化混合体.因此,可以通过结构构建将多个功能复合在一个材料中.虽然器件应用需要全温度覆盖,迄今为止却很少能成功地合成全温度覆盖的多开关响应杂化材料.在本文中,动态[(CH3)3NOH]+阳离子和发光中心Mn(II)形成杂化材料[(CH3)3NOH][Mn Cl3],该材料在温度刺激下显示出多重响应行为.温度变化时,[(CH3)3NOH]-[Mn Cl3]在全温度范围(低温、室温和高温)下表现出多重介电态及发光强度或峰值变化的开关响应.这些响应行为是由[(CH3)3-NOH]+阳离子和无机骨架的运动或重新取向而触发的.总之,这种光电开关材料在多重加密存储和传感设备中具有潜在的应用.

一种罕见的三维杂化双金属卤化物铁电体:(3-Hydroxypyrrolidinium)2RbBiBr6

杂化双金属卤化物由于具有丰富的结构并且在光电和光伏器件领域中具有广阔的应用前景,因而引起广泛的关注.然而,RbIBiIII基杂化双金属卤化物的铁电性质尚未被探索.在本文中,我们报道了一例罕见的三维双金属卤化物铁电体:(3-hydroxypyrrolidinium)_(2)RbBiBr_(6)(1).其中,RbIBiII双金属多面体通过共面和共角顶联接成三维笼状无机框架,显现出4连接的lon拓扑结构,而有机阳离子位于其孔洞中.值得注意的是,该铁电体具有非常高的居里温度(432 K),较大的自发极化强度(5.73μC cm^(−2))和热释电系数(28.35μC m^(−2) K^(−1)).这项工作丰富了杂化金属卤化物体系,为探索稳定、绿色铁电材料提供了一种可行的策略.

机械化学促成可调谐光-电多功能响应二维杂化钙钛矿材料

二维有机-无机杂化钙钛矿因在光伏、光电子等领域的巨大应用潜力而备受关注.此外,该类材料具有突出的结构可调性和材料稳定性,为功能性质的设计调控及器件应用提供了丰富的材料设计平台.然而,将多种物理通道的性质整合实现材料的多功能性仍具有挑战性,而对其进行快速有效的调节更是难上加难.迄今为止,尚未成功实现可调谐的光电多通道响应材料.本文成功开发了一种简便有效的机械力化学合成方法,可实现二维杂化钙钛矿中的多功能光电集成和调控.温和的外部机械刺激可快速形成锰掺杂的二维杂化钙钛矿(Cyclopropylammonium)2Pb(1-x)MnxBr4,并迅速调节其光学性质并诱导高温介电开关,实现高效的蓝色、白色、粉红色和橙色荧光特性.这项工作将为多功能光电响应材料的快速有效设计提供新的视角,也将为低成本、高效率智能设备的进一步开发和应用提供新的机遇.

Hybrid Optical-Electrical Perovskite Can Be a Ferroelastic Semiconductor

Organic–inorganic hybrid perovskites(OIHPs)have been a hot research topic due to their advanced structural and functional features that cover almost all the research fields of intelligent materials including ferroelectric,photovoltaic,fluorescent,and dielectric.However,the development of the construction of an OIHP ferroelastic semiconductor with optical-electrical response has been a huge challenge and infrequently reported.In this work,a rare and interesting hybrid perovskite ferroelastic semiconductor,[BFDA]PbBr_(3)(BFDA=benzyl-(2-fluoro-ethyl)-dimethyl-ammonium),was synthesized,which benefits from the structural advantage of a long tail BFDA to be balanced by the suitable inorganic framework.[BFDA]PbBr_(3) shows a high-temperature ferroelastic phase transition at 365 K and a direct band gap of 3.33 eV.In addition,it can emit charming orange-pink light under a 365 nm UV lamp.To combine this with the ferroelastic,optical,and dielectric properties,[BFDA]PbBr_(3) can be identified as a very rarely reported ferroelastic semiconductor.The above-mentioned synthesis strategy is also helpful for the enrichment and development of the hybrid perovskite family.