Organic-Inorganic Hybrid Ferroelectric and Antiferroelectric with Afterglow Emission.

Luminescent ferroelectrics are holding exciting prospect for integrated photoelectronic devices due to potential light-polarization interactions at electron scale. Integrating ferroelectricity and long-lived afterglow emission in a single material would offer new possibilities for fundamental research and applications, however, related reports have been a blank to date. For the first time, we here achieved the combination of notable ferroelectricity and afterglow emission in an organic-inorganic hybrid material. Remarkably, the presented (4-methylpiperidium)CdCl3 also shows noticeable antiferroelectric behavior. The implementation of cationic customization and halogen engineering not only enables a dramatic enhancement of Curie temperature of 114.4 K but also brings a record longest emission lifetime up to 117.11 ms under ambient conditions, realizing a leapfrog improvement of at least two orders of magnitude compared to reported hybrid ferroelectrics so far. This finding would herald the emergence of novel application potential, such as multi-level density data storage or multifunctional sensors, towards the future integrated optoelectronic devices with multitasking capabilities.

Unusual Thermal Quenching of Photoluminescence from an Organic-Inorganic Hybrid [MnBr4 ]2- -based Halide Mediated by Crystalline-Crystalline Phase Transition.

The ability to generate and manipulate photoluminescence (PL) behavior has been of primary importance for applications in information security. Excavating novel optical effects to create more possibilities for information encoding has become a continuous challenge. Herein, we present an unprecedented PL temporary quenching that highly couples with thermodynamic phase transition in a hybrid crystal (DMML)2 MnBr4 (DMML=N,N-dimethylmorpholinium). Such unusual PL behavior originates from the anomalous variation of [MnBr4 ]2- tetrahedrons that leads to non-radiation recombination near the phase transition temperature of 340 K. Remarkably, the suitable detectable temperature, narrow response window, high sensitivity, and good cyclability of this PL temporary quenching will endow encryption applications with high concealment, operational flexibility, durability, and commercial popularization. Profited from these attributes, a fire-new optical encryption model is devised to demonstrate high confidential information security. This unprecedented optical effect would provide new insights and paradigms for the development of luminescent materials to enlighten future information encryption.

The halogen substitution strategy of inorganic skeletons triggers dielectric and band gap regulation of hybrid perovskites.

Organic-inorganic hybrid perovskites (OIHPs) with dielectric switching functions have aroused comprehensive scientific interest, benefitting from their promising applications in sensors and information storage. However, to date, most of these materials discovered thus far possess a single function and are limited in their applicability, failing to meet the requirements of diverse applications. Moreover, the discovery of these materials has been largely serendipitous. Building multifunctional OIHPs with dielectric switching and semiconductors remains a daunting task. In this context, by introducing [C7H16N]+ as cations and in combination with lead halide with semiconducting properties, two OIHPs [C7H16N]PbI3 (1) and [C7H16N]PbBr3 (2) ([C7H16N]+ = (cyclopropylmethyl) trimethylammonium) have been successfully designed. They have dielectric switching properties close to 253 and 279 K and semiconducting behavior with band gaps of 2.67 and 3.22 eV. The phase transition temperature increased by 26 K through halogen substitution. In summary, our findings in this study provide insights into the application of the halogen substitution regulation strategy and open up new possibilities for designing perovskite semiconductors with dielectric switching functionality.

Targeted regulation and optimization of multifunctional phase transition materials by novel void occupancy engineering.

As an innovative form of stimulus-response materials, organic-inorganic hybrid phase transition materials have become a wonderful contender in the field of functional electronic equipment due to their versatile structure, intensive functions and straightforward preparation. However, the targeted regulation and optimization of the electrical/optical response, along with the establishment of regular structure-performance relationships, pose significant challenges in meeting the diverse demands of practical applications over an extended period. Herein, we conducted a systematic investigation into the role of lattice void occupancy in regulating phase transition temperature (Tp) and related optical/electrical bistability. By taking hybrid material [TMEA][Cd(SCN)3] featuring a flexible ammonium cation [TMEA]+ (TMEA = ethyltrimethylammonium) as the prototype, we successfully synthesized three phase transition materials, namely [DEDMA][Cd(SCN)3], [TEMA][Cd(SCN)3] and [TEA][Cd(SCN)3] (DEDMA = diethyldimethylammonium, TEMA = triethylmethylammonium, and TEA = tetraethylammonium), and the excellent regulation of the physical properties of these compounds was achieved through subtle engineering of void occupancy. More strikingly, [TEA][Cd(SCN)3] exhibits remarkable bistable properties in terms of dielectric and nonlinear optical responses (with second-harmonic generation intensity reaching 2.5 times that of KDP). This work provides a feasible avenue to reasonably customise organic-inorganic hybrid phase transition materials and finely adjust their intriguing functionalities.

Introducing Ferroelasticity into 1D Hybrid Lead Halide Semiconductor by Halogen Substitution Strategy.

Organic-inorganic hybrid lead halide perovskites (OLHPs), represented by (CH3 NH3 )PbI3 , are one of the research focus due to their exceptional performance in optoelectronic applications, and ferroelastic domain walls are benign to their charge carrier transport that is confirmed recently. Among them, the 1D OLHPs feature better stability against desorption and moisture, but related 1D ones possessing ferroelasticity are rarely investigated and reported so far. In this work, the 1D ferroelastic semiconductor (N-iodomethyl-N-methyl-morpholinium)PbI3 ((IDMML)PbI3 ) is prepared successfully by introducing successively halogenate atoms from Cl, Br to I into the organic cation of the prototype (N,N-dimethylmorpholinium)PbI3 ((DMML)PbI3 ). Notably, (IDMML)PbI3 shows the narrow bandgap energy (≈2.34 eV) according to the ultraviolet-visible absorption spectrum and the theoretical calculation, and possesses the evident photoconductive characteristic with the on/off ratio of current of ≈50 under the 405 nm light irradiation. This work provides a new case for the ferroelastic OLHPs and will inspire intriguing research in the field of optoelectronic.

Homochiral Chemistry Strategy to Trigger Second-Harmonic Generation and Dual Dielectric Switches.

Switchable materials have attracted enormous interest due to their promising applications in important fields such as sensing, electronic components, and information storage. Nevertheless, obtaining multifunctional switching materials is still a problem worth investigating. Herein, by incorporating (Rac-, L-, D-2-amino-1-propanol) as the templating cation, we have obtained (Rac-, L-, D-HTMPA)CdCl3 (HTMPA = 1-hydroxy-N, N, N-trimethyl-2-propanaminium). We have adopted a chiral chemistry strategy that causes (Rac-HTMPA)CdCl3 in the central symmetric space to crystallize in the chiral space group. Based on the modulation of the homochiral strategy, (L-, D-HTMPA)CdCl3 shows a dual phasic transition at 269 and 326 K and a switchable second-harmonic generation response. In addition, (L-, D-HTMPA)CdCl3 is chiral switchable material to exhibit stable dual dielectric and second-harmonic generation (SHG) switches. This work provides an approach to exploring multifunctional chiral switchable materials.

Methyl regulation triggers high-temperature ferroelastic phase transition.

The multifunctional tuning of solid-state dielectric switches constructed from organic-inorganic hybrid materials (OIHMs) has received great attention. In particular, molecular ferroelastics with dielectric phase transitions have considerable potential in the optical and electrical fields owing to their adjustable structures and physical features. However, it remains a challenge to effectively design ferroelastics with high phase transition temperature (Tc). We used [TTMA]2CdI4 (TTMA = tetramethylammonium, 1) as a template to continuously increase the molecular weight and change the structure of the hybrid material by modifying and extending the alkane chain in the cation. Therefore, a series of OIHMs were eventually developed: [TMEA]2CdI4 (TMEA = trimethylethylammonium, 2), [TMPA]2CdI4 (TMPA = trimethylpropylammonium, 3), and [TMIPA]2CdI4 (TMIPA = trimethyliso-propylammonium, 4). Among them, the Tc of ferroelastic 3 increased up to 387 K. DSC and temperature-related dielectric constant tests prove the occurrence of the phase transition for 1, 2, and 3. The structures further indicate that the phase transition is caused by the order-disorder cation motion. The extension of the alkyl chain greatly increases Tc and endows 3 with ferroelasticity at room temperature.

Research on the Efficacy of Ganpu Vine Tea in Inhibiting Uric Acid Production.

Ganpu vine tea is a new type of health care citrus fruit tea made from citrus shell, Pu-er tea, and vine tea baked as raw materials. In this study, the in vitro uric acid synthase inhibition system and hyperuric acid cell model were constructed to appraise the uric acid lowering efficacy of Ganpu vine tea, traditional Ganpu tea, and vine tea. Results showed that in the uric acid synthase inhibition system, the aqueous extract can inhibite the puric metabolically related enzymes, such as adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP), and xanthine oxidase (XOD). The ability of the aqueous extract to inhibit the above enzyme was as follows: vine tea > Ganpu vine tea > Ganpu tea; all teas had a strong effect on XOD inhibition. The hyperuric acid cell model test showed that the aqueous extract inhibited uric acid production through accumulating inosine and hypoxanthine and hindering xanthine synthesis. The uric acid reductive ability was as follows: Vine tea > Ganpu vine tea > Ganpu tea. The inhibition of enzymes related to uric acid synthesis and the inhibition of uric acid production were significantly enhanced through adding vine tea to Ganpu tea. It also shows that flavonoids are the main factor driving this ability because they are the main active ingredients in these botanical drinks.

Superior ferroelectricity and nonlinear optical response in a hybrid germanium iodide hexagonal perovskite.

Abundant chemical diversity and structural tunability make organic-inorganic hybrid perovskites (OIHPs) a rich ore for ferroelectrics. However, compared with their inorganic counterparts such as BaTiO3, their ferroelectric key properties, including large spontaneous polarization (Ps), low coercive field (Ec), and strong second harmonic generation (SHG) response, have long been great challenges, which hinder their commercial applications. Here, a quasi-one-dimensional OIHP DMAGeI3 (DMA = Dimethylamine) is reported, with notable ferroelectric attributes at room temperature: a large Ps of 24.14 µC/cm2 (on a par with BaTiO3), a low Ec below 2.2 kV/cm, and the strongest SHG intensity in OIHP family (about 12 times of KH2PO4 (KDP)). Revealed by the first-principles calculations, its large Ps originates from the synergistic effects of the stereochemically active 4s2 lone pair of Ge2+ and the ordering of organic cations, and its low kinetic energy barrier of small DMA cations results in a low Ec. Our work brings the comprehensive ferroelectric performances of OIHPs to a comparable level with commercial inorganic ferroelectric perovskites.

High-T c Single-Component Organosilicon Ferroelectric Crystal Obtained by H/F Substitution.

Organic single-component ferroelectrics are highly desirable for their low molecular mass, light weight, low processing temperature, and excellent film-forming properties. Organosilicon materials with a strong film-forming ability, weather resistance, nontoxicity, odorlessness, and physiological inertia are very suitable for device applications related to the human body. However, the discovery of high-T c organic single-component ferroelectrics has been very scarce, and the organosilicon ones even less so. Here, we used a chemical design strategy of H/F substitution to successfully synthesize a single-component organosilicon ferroelectric tetrakis(4-fluorophenylethynyl)silane (TFPES). Systematic characterizations and theory calculations revealed that, compared with the parent nonferroelectric tetrakis(phenylethynyl)silane, fluorination caused slight modifications of the lattice environment and intermolecular interactions, inducing a 4/mmmFmm2-type ferroelectric phase transition at a high T c of 475 K in TFPES. To our knowledge, this T c should be the highest among the reported organic single-component ferroelectrics, providing a wide operating temperature range for ferroelectrics. Moreover, fluorination also brought about a significant improvement in the piezoelectric performance. Combined with excellent film properties, the discovery of TFPES provides an efficient path for designing ferroelectrics suitable for biomedical and flexible electronic devices.

Nicotinic acid bromide: a simple organic salt optical-electrical ferroelastic with high Tc.

A new ferroelastic organic salt nicotinic acid bromide (N-Br) was connected by hydrogen bonding with nicotinic acid cations via a halogen substitution strategy. It exhibits a ferroelastic phase transition from P21/m to P1̄ with 2/mF1̄ Aizu notation with a high Curie temperature (Tc) of 402 K. Moreover, optical regulation from blue light to white light was achieved by halogen substitution.

A nickel(ii)-based one-dimensional organic-inorganic halide perovskite ferroelectric with the highest Curie temperature.

Organic-inorganic halide perovskites (OIHPs) are very eye-catching due to their chemical tunability and rich physical properties such as ferroelectricity, magnetism, photovoltaic properties and photoluminescence. However, no nickel-based OIHP ferroelectrics have been reported so far. Here, we designed an ABX3 OIHP ferroelectric (3-pyrrolinium)NiCl3, where the 3-pyrrolinium cations are located on the voids surrounded by one-dimensional chains composed of NiCl6-face-sharing octahedra via hydrogen bonding interactions. Such a unique structure enables the (3-pyrrolinium)NiCl3 with a high spontaneous polarization (P s) of 5.8 µC cm-2 and a high Curie temperature (T c) of 428 K, realizing dramatic enhancement of 112 and 52 K compared to its isostructural (3-pyrrolinium)MCl3 (M = Cd, Mn). To our knowledge, remarkably, (3-pyrrolinium)NiCl3 should be the first case of nickel(ii)-based OIHP ferroelectric to date, and its T c of 428 K (35 K above that of BaTiO3) is the highest among all reported one-dimensional OIHP ferroelectrics. This work offers a new structural building block for enriching the family of OIHP structures and will inspire the further exploration of new nickel(ii)-based OIHP ferroelectrics.

Axial-Chiral BINOL Multiferroic Crystals with Coexistence of Ferroelectricity and Ferroelasticity.

Chirality exists everywhere from natural amino acids to particle physics. The introduction of point chirality has recently been shown to be an efficient strategy for the construction of molecular ferroelectrics. In contrast to point chirality, however, axial chirality is rarely used to design ferroelectrics so far. Here, based on optically active 1,1'-bi-2-naphthol (BINOL), which has been applied extensively as a versatile chiral reagent in asymmetric catalysis, chiral recognition, and optics, we successfully design a pair of axial-chiral BINOL multiferroics, (R)-BINOL-DIPASi and (S)-BINOL-DIPASi. They experience a 2F1-type full ferroelectric/ferroelastic phase transition at a high temperature of 362 and 363 K, respectively. Piezoelectric force microscopy and polarization-voltage hysteresis loops demonstrate their ferroelectric domains and domain switching, and polarized light microscopy visualizes the evolution of stripe-shaped ferroelastic domains. The axial-chiral BINOL building block promotes the generation of the polar structure and ferroelectricity, and the organosilicon component increases the rotational energy barrier and thus the phase transition temperature. This work presents the first axial-chiral high-temperature multiferroic crystals, offering an efficient path for designing molecular multiferroics through the introduction of axial chirality.

The First Chiro-Inositol Organosilicon Ferroelectric Crystal.

Organosilicons have been used extensively in aerospace, electronics, food, medicine and other fields, due to their low viscosity, hydrophobicity, corrosion resistance, non-toxic, and physiologically inert features. Despite extensive interest, however, organosilicon ferroelectric crystals have never been found. Here, by using the chemical design strategy, we successfully obtained a molecular ferroelectric D-chiro-inositol-SiMe3 with polar P43 symmetry, whose spontaneous polarization can be electrically switchable on thin film. The introduction of organosilicon groups endows the thin films with excellent softness, ductility and flexibility (extremely low hardness of 72.8 MPa and small elastic modulus of 5.04 GPa) that are desirable for biomedical and human-compatible applications. As the first case of organosilicon ferroelectric crystal to date, this work offers a new structural paradigm for molecular ferroelectrics, and highlights their potential for flexible bio-electronic applications.

The construction of a two-dimensional organic-inorganic hybrid double perovskite ferroelastic with a high T c and narrow band gap.

Two-dimensional (2D) hybrid double perovskites have attracted extensive research interest for their fascinating physical properties, such as ferroelectricity, X-ray detection, light response and so on. In addition, ferroelastics, as an important branch of ferroic materials, exhibits wide prospects in mechanical switches, shape memory and templating electronic nanostructures. Here, we designed a 2D phase-transition double perovskite ferroelastic through a structurally progressive strategy. This evolution is core to our construction process from 0D to 1D and AgBi-based 2D. In this way, we successfully synthesized 2D lead-free ferroelastic (DPA)4AgBiBr8 (DPA = 2,2-dimethylpropan-1-aminium) with a high Curie temperature (T c), which shows a narrower band gap than 0D (DPA)4Bi2Br10 and 1D (DPA)5Pb2Br9. Moreover, the mechanism of structural phase transition and molecular motion are fully characterized by temperature dependent solid-state NMR and single crystal XRD. (DPA)4AgBiBr8 injects power into the discovery of new ferroelastics or the construction and dimensional adjustment in new hybrid double perovskites.

Homochiral Multiferroic Cyanido-Bridged Dimetallic Complexes Assembled by C-F⋠⋠⋠K Interactions.

Cyanido-bridged dimetallic complexes are attracting attention due to their varied structures and properties. However, homochiral cyanido-bridged dimetallic complexes are rare, and making them ferroelectric is a great challenge. Introducing C-F⋅⋅⋅K interactions between the guest chiral cations and the host [KFe(CN)6 ]2- framework, gives three-dimensional cyanido-bridged dimetallic multiferroics, [R- and S-3-fluoropyrrolidinium]2 [KFe(CN)6 ] (R- and S-3-FPC). The mirror-symmetric vibrational circular dichroism (VCD) signal shows their enantiomeric nature. R- and S-3-FPC crystallize in the same chiral-polar space group P21 at 298 K. Piezoresponse force microscopy (PFM), polarizing optical microscopy, and temperature-dependent second-harmonic generation (SHG) measurements show their multiferroic properties (the coexistence of ferroelectricity and ferroelasticity), in line with the Aizu notation of 222F2. R-3-FPC shows excellent ferroelectricity with saturated polarization up to 9.4 µC cm-2 .

Dehydration-activated structural phase transition in a two-dimensional hybrid double perovskite.

As a feasible lead-free scheme, organic-inorganic hybrid double perovskites show many excellent properties, including ferroelectricity, ferroelasticity, self-powered circularly polarized light detection and so on. In this work, the solid-to-solid structural phase transition of a two-dimensional hybrid double perovskite (CHA)4CuBiI8 was successfully activated via the dehydration of (CHA)4CuBiI8·H2O, which was proven by differential scanning calorimetry (DSC) and temperature-dependent dielectric measurements. Using variable-temperature single-crystal X-ray diffractometry, the cause behind the phase transition of (CHA)4CuBiI8 was determined to be the overall coordination of distortion and movement of the inorganic skeleton and thermal deformation of the cationic structure. In addition, the substance after dehydration shows good stability in multiple reversible switching during dielectric tests. The interesting dehydration-activated results of the material contribute towards a further expansion of the properties and potential application of hybrid double perovskites.

H/F Substitution induced switchable coordination bonds in a cyano-bridged hybrid double perovskite ferroelastic.

A three-dimensional cyano-bridged double perovskite ferroelastic [(CH3)3NCH2F]2[KFe(CN)6] was constructed by introducing unprecedented switchable C-F-K coordination bonds. H/F substitution not only preserves the basic structure of the parent [(CH3)4N]2[KFe(CN)6] but also affords an m3̄mF2/m-type ferroelastic phase transition.

In Situ Observation of Ferroelastic Domain and Phase Transition in a Three-Dimensional Molecular Crystal.

Massive efforts have been devoted to designing molecular ferroic materials by molecular modification. For molecular ferroelastic, previous work is focused on the temperature-dependent ferroelastic domains, however, few are related to controlling the ferroelastic domain by the stress. Inspired by the "quasi-spherical theory" and fluorination effect, we designed a more flexible (MedabcoF)2+ (MedabcoF=1-fluoro-4-methyl-1,4-diazoniabicyclo[2.2.2]octane) cation by introducing a methyl group and a fluorine atom at the two symmetrical ends of the Dabco (1,4-diazoniabicyclo[2.2.2]octane) and synthesized a hybrid 3D perovskite (MedabcoF)Rb(BF4 )3 (1) which displays three reversible phase transitions accompanying dual ferroelastic behavior. Besides, it not only exhibits ferroelastic domains switching by the thermal stimulation, and the sensitive reaction of in situ domains under the stress of it is also realized. This work not only achieves a force-controlled ferroelastic domain but develops a more profound comprehension of the relationship between the thermal motion behavior of guest cations and the intriguing properties of materials.

A multiaxial lead-free two-dimensional organic-inorganic perovskite ferroelectric.

Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) have recently gained tremendous interest because of their unique features in contrast to three-dimensional counterparts and traditional 2D materials. However, although some 2D HOIP ferroelectrics have been achieved, the issue of toxic Pb and uniaxial nature impede their further application. Herein, for the first time, we report a lead-free 2D HOIP multiaxial ferroelectric, [3,3-difluorocyclobutylammonium]2CuCl4 (1), which shows four ferroelectric axes and eight equivalent polarization directions, more than those of the other 2D HOIP ferroelectrics and even the inorganic perovskite ferroelectric BaTiO3 (three ferroelectric axes and six equivalent polarization directions). 1 also features a high Curie temperature of 380 K and exhibits remarkable thermochromism of color change from green-yellow to dark brown. To our knowledge, 1 is the first multiaxial lead-free 2D HOIP ferroelectric. This work sheds light on the exploration of better lead-free 2D HOIP ferroelectrics.