•Recent research on dielectric transition and ferroelectricity is overviewed.•Basic concepts and fundamentals of the two properties are introduced.•Structural changes during the phase transitions are ...discussed.
Structural phase transition in solid-state materials is an underlying factor for emergence and evolution of a number of important physical/chemical properties. In this review, we summarize recent achievements on two types of structural phase transition-associated properties, i.e., dielectric transition and ferroelectricity, in coordination compounds. The basic concepts and fundamentals of structural phase transition and the two properties are briefly introduced. This review aims to reveal the role of the structural phase transitions on bulk properties and afford a perspective on the connections among multiple topics of coordination chemistry from the structural phase transition viewpoint. It would be appealing to researchers in multidisciplinary fields such as coordination chemistry, crystal engineering, supramolecular chemistry, condensed matter physics, responsive materials and molecular machines.
Direct detection of circularly polarized light (CPL) is a challenging task due to limited materials and ambiguous structure–property relationships that lead to low distinguishability of the light ...helicities. Perovskite ferroelectric semiconductors incorporating chirality provide new opportunities in dealing with this issue. Herein, a pair of 2D chiral perovskite ferroelectrics is reported, which have enhanced CPL detection performance due to interplays among lattice, photon, charge, spin, and orbit. The chirality‐transfer‐induced chiral&polar ferroelectric phase enhances the asymmetric nature of the photoactive sublattice and achieves a switchable self‐powered detection via the bulk photovoltaic effect. The single‐crystal‐based device exhibits a CPL‐sensitive detection performance under 430 nm with an asymmetric factor of 0.20 for left‐ and right‐CPL differentiation, about two times that of the pure chiral counterparts. The enhanced CPL detection performance is ascribed to the Rashba–Dresselhaus effect that originates from the bulk inversion asymmetry and strong spin–orbit coupling, shown with a large Rashba coefficient, which is demonstrated by density functional theory calculation and circularly polarized light excited photoluminescence measurement. These results provide new perspectives on chiral Rashba ferroelectric semiconductors for direct CPL detection and ferroelectrics‐based chiroptics and spintronics.
A pair of 2D chiral perovskite Rashba ferroelectric semiconductors is reported. The fabricated single‐crystal device responds to circularly polarized light (CPL) under 430 nm with an anisotropy factor of 0.20 for the left‐ and right‐CPL differentiation, about two times of reported pure chiral counterparts. The enhanced performance is ascribed to the Rashba–Dresselhaus effect with a large Rashba coefficient of 0.93 eV Å.
Ferroelectricity was initially discovered in 1921 in Rochelle salt (potassium sodium tartrate tetrahydrate), a chiral compound containing a chiral unit. However, the inherent relationship between ...coupled ferroelectricity and optical activity in chiral ferroelectrics derived from achiral units, as well as in polar ferroelectrics, remains insufficiently explored. In this regard, we propose a fresh concept of optically active ferroelectrics, specifically those crystallizing in seven optically active point groups (1, 2, 4, 3, 6, m, mm2). Subsequently, we elucidate the mechanism of coupled ferroelectricity and optical activity, emphasizing the cooperative interplay of chirality and polarity flipping under the influence of an electric field. Finally, we expound on the applications of this principle for the in situ generation of chiral enantiomers and polar isomers, thereby providing valuable insights into the chiral/polar research community and advancing our comprehension of ferroelectricity.
Nitrate is both an important nutrient and a critical signaling molecule that regulates plant metabolism, growth, and development. Although several components of the nitrate signaling pathway have ...been identified, the molecular mechanism of nitrate signaling remains unclear. Here, we showed that the growth-related transcription factors HOMOLOG OF BRASSINOSTEROID ENHANCED EXPRESSION2 INTERACTING WITH IBH1 (HBI1) and its three closest homologs (HBIs) positively regulate nitrate signaling in Arabidopsis thaliana. HBI1 is rapidly induced by nitrate through NLP6 and NLP7, which are master regulators of nitrate signaling. Mutations in HBIs result in the reduced effects of nitrate on plant growth and ∼22% nitrate-responsive genes no longer to be regulated by nitrate. HBIs increase the expression levels of a set of antioxidant genes to reduce the accumulation of reactive oxygen species (ROS) in plants. Nitrate treatment induces the nuclear localization of NLP7, whereas such promoting effects of nitrate are significantly impaired in the hbi-q and cat2 cat3 mutants, which accumulate high levels of H2O2. These results demonstrate that HBI-mediated ROS homeostasis regulates nitrate signal transduction through modulating the nucleocytoplasmic shuttling of NLP7. Overall, our findings reveal that nitrate treatment reduces the accumulation of H2O2, and H2O2 inhibits nitrate signaling, thereby forming a feedback regulatory loop to regulate plant growth and development.
Soil salinization has adverse effects on plant growth due to direct ion toxicity or secondary damage, such as mineral nutrition imbalance and the water stress caused by low osmotic potential. The ...rhizosphere processes of plants are likely to play an important role in the biological improvement of saline soil. However, the understanding of this remains limited. This review summarizes the progress made recently in exploring the effects of root‐associated microbes especially from halophytic species on the growth stimulation of plants under salinity. For example, halophytes attract and absorb beneficial rhizosphere growth‐promoting bacteria by producing rhizosphere exudates such as organic acids and enzymes, which is conducive to plant growth under salt stress. The plant growth‐promoting exogenous rhizobacteria (PGPR), attached to the roots of halophytes, can promote the growth of plants mainly through the improved absorption of nutrients by the host plants or through producing plant growth regulators. In addition, the colonization of endophytes can regulate plant ion balance and produce secondary metabolites such as growth‐promoting hormone and extracellular enzymes, activating antioxidant systems, and inducing plant system resistance against pathogenic microorganisms, thus promoting the growth of plants under salt stress. The inoculation of arbuscular mycorrhizal fungi (AMF) under salt stress can facilitate plants to change the ion balance or obtain water from the soil, and that the formation of other hyphae may promote the transfer of water and nutrients to plants. Therefore, understanding the effects of root‐associated microbes on the growth stimulation of plants under salinity is of great significance to improving their salt tolerance, so as to improve saline‐alkali land for the construction of a more effective biological improvement model.
A series of organic‐inorganic hybrid perovskites ABX3 (A=diprotonated 1,4‐diazabicyclo2.2.2octane or piperazine; B=Na+ or K+; X=ClO4− or BF4−) has been synthesized. They feature a cubic cage‐like ...host‐guest structures of which A is the cationic guest residing in the anionic cage B8X12, B is the vertex of the cage with variable coordination numbers between six and twelve, and X is the bridging ligand with mono‐ and/or bidentate coordination modes. The extended Goldschmidt tolerance factor t is used to describe the phase stability of the compounds. Differential scanning calorimetry, variable‐temperature structural analyses, and dielectric measurements reveal that order‐disorder transitions of the A guest and/or X bridging ligand are supposed to be responsible for structural phase transitions and dielectric switching in the compounds.
Transform: A series of organic‐inorganic hybrid perovskites ABX3 (A=diprotonated 1,4‐diazabicyclo2.2.2octane or piperazine; B=Na+ or K+; X=ClO4‐ or BF4‐) has been synthesized, showing structural phase transitions and dielectric switching that are caused by order–disorder transitions of the A guest and/or X bridging ligand.
Abstract
Martensitic transformation, usually accompanied by ferroelastic and thermoelastic behaviors, is an interesting and useful mechanical-related property upon external stimuli. For molecular ...crystals, however, martensitic systems to show reversible stimuli-actuation behaviors are still limited because of a lack of designability and frequent crystal collapse due to large stress releases during the transformations. Here, a one-dimensional hybrid perovskite semiconductor (NMEA)PbI
3
(NMEA =
N
-methylethylammonium) was prepared by following a dimensionality reduction design principle. The crystal undergoes reversible ferroelastic and thermoelastic martensitic transformations, which are attributed to weak intermolecular interactions among the chains that easily trigger the interchain shearing movement. The actuation behavior occurring during the phase transition is very close to room temperature and demonstrated to behave as a mechanical actuator for switching. This work provides an effective approach to designing molecular actuators with promising applications in next-generation intelligence devices.
The construction of mechanically responsive materials with reversible shape‐shifting, shape‐locking, and stretchability holds promise for a wide range of applications in fields such as soft robotics ...and flexible electronics. Here, we report novel thermoelastic one‐dimensional organic–inorganic hybrids (R/S‐Hmpy)PbI3 (Hmpy=2‐hydroxymethyl‐pyrrolidinium) to show mechanical responses. The single crystals undergo two phase transitions at 310 K and 380 K. When heated to 380 K, they show shape‐shifting and expansion along the b‐axis by about 13.4 %, corresponding to a larger deformation than that of thermally activated shape memory alloys (8.5 %), and exhibit a strong actuation force. During the cooling process, the stretched crystal shape maintains and a shape‐locking phenomenon occurs, which is lifted when the temperature decreases to 305 K. Meanwhile, due to the introduction of chiral ions, the thermal switching shows a 10‐fold second‐order nonlinear switching contrast (common values typically below 3‐fold). This study presents a thermoelastic actuator based on shape‐shifting and ‐locking of organic–inorganic hybrids for the first time. The dielectric and nonlinear optical switching properties of organic–inorganic hybrids broaden the range of applications of mechanically responsive crystals.
Thermoelastic organic–inorganic hybrids (R/S‐Hmpy)PbI3 (Hmpy=2‐hydroxymethyl‐pyrrolidinium) undergo two phase transitions at 310 K and 380 K. When heated to 380 K, the crystals show shape shifting and expand along the b‐axis by about 13.4 %, corresponding to a larger deformation than that of thermally activated shape memory alloys (8.5 %), and exhibits a strong actuation force. During cooling process, the stretched crystal shape maintains and a shape‐locking phenomenon occurs, which is lifted when the temperature decreases to 305 K.
Nitrate is the main source of nitrogen for plants but often distributed heterogeneously in soil. Plants have evolved sophisticated strategies to achieve adequate nitrate by modulating the root system ...architecture. The nitrate acquisition system is triggered by the short mobile peptides C‐TERMINALLY ENCODED PEPTIDES (CEPs) that are synthesized on the nitrate‐starved roots, but induce the expression of nitrate transporters on the other nitrate‐rich roots through an unclear signal transduction pathway. Here, we demonstrate that the transcription factors HBI1 and TCP20 play important roles in plant growth and development in response to fluctuating nitrate supply. HBI1 physically interacts with TCP20, and this interaction was enhanced by the nitrate starvation. HBI1 and TCP20 directly bind to the promoters of CEPs and cooperatively induce their expression. Mutation in HBIs and/or TCP20 resulted in impaired systemic nitrate acquisition response. Our solid genetic and molecular evidence strongly indicate that the HBI1‐TCP20 module positively regulates the CEPs‐mediated systemic nitrate acquisition.
Nitrate starvation on one side of the root enhances the interaction between the transcription factors HBI1 and TCP20 to induce the expression of genes encoding the short, mobile peptides C‐TERMINALLY ENCODED PEPTIDES (CEPs), which activate systemic nitrate signal transduction and lead to compensatory nitrate uptake on the other side.
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