Piezoelectric sensors that can work under various conditions with superior performance are highly desirable with the arrival of the Internet of Things. For practical applications, a large piezoelectric voltage coefficient g and a high Curie temperature T c are critical to the performance of piezoelectric sensors. Here, we report a two-dimensional perovskite ferroelectric (4-aminotetrahydropyran)2PbBr4 [(ATHP)2PbBr4] with a saturated polarization of 5.6 μC cm–2, high T c of 503 K [above that of BaTiO3 (BTO, 393 K)], and extremely large g 33 of 660.3 × 10–3 V m N–1 [much beyond that of Pb­(Zr,Ti)­O3 (PZT) ceramics (20 to 40 × 10–3 V m N–1), more than 2 times higher than that of poly­(vinylidene fluoride) (PVDF, about 286.7 × 10–3 V m N–1)]. Combined with the advantages of molecular ferroelectrics, such as light weight, easy and environmentally friendly processing, and mechanical flexibility, (ATHP)2PbBr4 would be a competitive candidate for next-generation smart piezoelectric sensors in flexible devices, soft robotics, and biomedical devices.

Topological defects, such as vortices and skyrmions, provide a wealth of splendid possibilities for new nanoscale devices because of their marvelous electronic, magnetic, and mechanical behaviors. Recently, great advances have been made in the study of the ferroelectric vortex in conventional perovskite oxides, such as BaTiO3 and BiFeO3. Despite extensive interest, however, no intriguing ferroelectric vortex structures have yet been found in organic–inorganic hybrid perovskites (OIHPs), which are desirable for their mechanical flexibility, ease of fabrication, and low acoustical impedance. We observed the robust vortex–antivortex topological configurations in a two-dimensional (2D) layered OIHP ferroelectric (4,4-DFPD)2PbI4 (4,4-DFPD is 4,4-di­fluoro­piper­idinium). This provides future directions for the study of perovskites and makes it a promising alternative for nanoscale ferroelectric devices in medical, micromechanical, and biomechanical applications.

Two-dimensional (2D) organic–inorganic perovskites (OIPs), with improved material stability over their 3D counterparts, are highly desirable for device applications. It is their considerable structural diversity that offers an unprecedented opportunity to engineer materials with fine-tuning functionalities. The isosteric substitution of hydrogen by an electronegative fluorine atom has been proposed as a useful route to improve the photovoltaic performance of 2D OIPs, whereas its valuable role in developing ferroelectricity is still waiting for further exploration. Herein, for the first time we applied fluorinated aromatic cations in extending the family of 2D OIP ferroelectrics, and successfully obtained [2-fluorobenzylammonium]2PbCl4 as a high-performance ferroelectric semiconductor. The failures in the nonferroelectric [4-fluorobenzylammonium]2PbCl4 and [3-fluorobenzylammonium]2PbCl4 demonstrate that the selective introduction of fluorine in correct structural positions is particularly essential. This work represents an unprecedented proof-of-concept in the use of fluorinated aromatic cations for the targeted design of excellent 2D OIP ferroelectrics, and is believed to inspire the future development of low-cost, high-efficiency, and stable device applications.

electrical transport performance, and long carrier lifetime. Besides these factors, the ferroelectric photovoltaic effect (FEPV) was also believed to contribute to the good performance in PSC. [6] Conventional photovoltaic devices utilize heterojunctions to create asymmetric electric potential to separate the photoinduced charge carriers. While, for FEPV, the photogenerated electron-hole pair is separated by the spontaneous polarization or domain walls in homogeneous ferroelectric materials. [7] Since FEPV is independent to the bending of energy band, it can generate extremely large open-circuit voltage comparable to the bandgap and is expected to enhanced efficiency in PSC. Although FEPV draws a very exciting picture, the ferroelectricity of MAPbI 3 is still controversial. [8] To study the detailed contribution of FEPV in PSC, obtaining a lead-iodide-based polar perovskite materials with settled ferroelectricity is very necessary as a useful complement to the current PSC materials and model system to investigate the role of ferroelectric polarization in photovoltaics.Besides the intensive competition on PCE, PSC are facing a more severe problem of stability. During operation, the applied electric field or optoelectrical field may induce migration of organic molecules and halogen ions. Even without light and electric field, in ambient condition, the moisture and oxygen may also decompose the perovskite. [9] Those factors limit the lifetime of PSC for only ≈1000 h, which is far away from that of conventional silicon-based solar cell panel (20-25 years). One possible solution to this problem is reducing the dimensionality from 3D to quasi-2D, which has large formation energy, high moisture stability, and long lifetime, however, such low-dimensional perovskite will affect transport properties and reduce PCE. [5,10] Until very recently, fluorination on 2D lead iodide perovskite was reported to enhance charge transport and PCE. [11] Thus, in order to achieve a good balance between PCE and stability, a fluorinated 2D lead iodide perovskite ferroelectric material is highly demanded, which is also a good platform to study the fundamental mechanism behind high PCE.Although we have reported several lead-based perovskite ferroelectrics with 2D layered structure, the ferroelectricity can only coexist with chlorine or bromine, even slight doping of iodine would alter the crystal structure and vanish the precious ferroelectric property. [12] Until now, rational design and synthesis of HOIP ferroelectrics is still very challenging and Hybrid perovskite materials are famous for their great application potential in photovoltaics and optoelectronics. Among them, lead-iodide-based perovskites receive great attention because of their good optical absorption ability and excellent electrical transport properties. Although many believe the ferroelectric photovoltaic effect (FEPV) plays a crucial role for the high conversion efficiency, the ferroelectricity in CH 3 NH 3 PbI 3 is still under debate, and obtaining ferroelectric lead i...

Thymol is a natural monoterpene phenol primarily found in thyme, oregano, and tangerine peel. It has been shown to possess anti-inflammatory property both in vivo and in vitro. In the present paper, we studied the anti-inflammatory effect of thymol in lipopolysaccharide (LPS)-stimulated mouse mammary epithelial cells (mMECs). The mMECs were stimulated with LPS in the presence or absence of thymol (10, 20, 40 μg/mL). The concentrations of tumor necrosis factor α (TNF-α), interleukin (IL)-6, and IL-1β in the supernatants of culture were determined using enzyme-linked immunosorbent assay. Cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), nuclear factor-κB (NF-κB), and inhibitor protein of NF-κB (IκBα) were measured using western blot. The results showed that thymol markedly inhibited the production of TNF-α and IL-6 in LPS-stimulated mMECs. The expression of iNOS and COX-2 was also suppressed by thymol in a dose-dependent manner. Furthermore, thymol blocked the phosphorylation of IκBα, NF-κB p65, ERK, JNK, and p38 mitogen-activated protein kinases (MAPKs) in LPS-stimulated mMECs. These results indicate that thymol exerted anti-inflammatory property in LPS-stimulated mMECs by interfering the activation of NF-κB and MAPK signaling pathways. Thereby, thymol may be a potential therapeutic agent against mastitis.