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.

Behaviors of Leucine and Isoleucine in Ion Mobility- Quadrupole Time of Flight Mass Spectrometry

In this study, ion mobility separation coupled with tandem mass spectrometry （IM-tandem MS） was utilized to investigate the ionization behaviors of two amino acids including leucine and isoleucine. Under the electrospray ionization （ESI） mode, two protonation sites in each molecular sturcture caused two forms of protomer. One arose from the amino being protonated （amino-protomer） and the other from the carboxyl being protonated （car- boxyl-protomer）. In the two-dimensional （drift time, m/z） spectrum, the protomers had the same mass, but the dis- tinguishable drift times and fragmentation patterns. For the characterization purpose, the theoretical collision cross section （CCS） values of the protomers were calculated and proven to be consistent with the experimental. Moreover, the quantified relationship between the amino acids and their protomers was evaluated. It showed that the abun- dance of the carboxyl-protomer was proportional to the concentration of the amino acid, whereas that of the amino- protomer did not have the same trend. Under the atmospheric pressure chemical ionization （APCI） mode, only the carboxyl-protomer was observed. In addition, the amino-protomer and the cluster ions observed under ESI were absent completely. The results demonstrate that the ionization mode impacts heavily on the ionization behaviors of leucine and isoleucine not only on the form of therir protomers but also On the quantified relationship.

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.

X-site doping in ABX_(3) triggers phase transition and higher T_(c) of the dielectric switch in perovskite

Material stability is always the key factor for applied materials especially the working environment that requires higher temperature sensitivity or temperature fluctuation range.In which,the stimulus-response perovskite materials are just sensitive to stability to ensure the accuracy and stability of the signals,in the applied devices of batteries and memory storage devices and so on.However,it is still a tremendous challenge to improve the stability of perovskite materials,and maintain reliability in the devices.Here,a novel ABX_(2)X'_(1)(X-site doping in an ABX_(3))compound[CEMP]-[CdBr_(2)(SCN)](1,CEMP=1-(2-chloro-ethyl)-1-methyl-piperidine)with remarkable high-temperature reversible dielectric switching behavior was proposed.The strategy of[SCN]^(−)doping in perovskite for improving the stability was successfully achieved.Meanwhile,the steric hindrance is increased while the energy barrier is also increased by replacing hydrogen with flexible groups,which leads to a high-temperature reversible phase transition.The new finding provides a new direction to enrich new applications and design ideas of perovskite materials.Especially the X-site strategy of doping or substitution in the ABX_(3),it will promote ingenious and perfect experimental results in material synthesis and performance improvement by chemistry disciplines.

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.

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.