Strain-Induced Tunable Enhancement of Piezoelectricity in a Novel Molecular Multiferroic Material.

Multiferroics are appealing because of application potentials in data storage devices, sensors, transducers, and energy harvesters. Molecular multiferroics emerge as a promising alternative to inorganic multiferroics due to flexibility, light weight, low toxicity, solution processing, structural diversity, and chemical tunability. While researches have predominantly focused on perovskite structures, studies on molecular ionic multiferroics remain relatively limited.

Organic-Inorganic Hybrid Perovskite for Ferroelectric Catalysis.

Organic-inorganic hybrid perovskite ferroelectric has gained significant attention for its structural flexibility and diversity. They can directly utilize metal nodes and organic groups as active sites in catalysis. Additionally, their ferroelectric polarization occurs around these active sites, significantly enhancing catalytic activity and demonstrating immense potential for applications.

A Melt-Processable Metal Halide Perovskite Ferroelectric.

Molecular ferroelectrics have increasingly garnered significant attention in both fundamental scientific research and technological applications due to their ease of processing, lightweight nature, and mechanical flexibility. Among these, metal halide perovskite ferroelectrics (MHP FEs), a subset of molecule-based ferroelectrics, exhibit diverse functionalities owing to their distinctive structures, thus emerging as a focal point of molecular ferroelectrics research. However, thin films, the predominant application form for MHP FEs, primarily rely on spin-coating, which presents considerable limitations.

SHG Assisted Mixed-Phases Anatomizing in a Molecular Ferroelectric.

Anatomizing mixed-phases, referring to analyzing the mixing profiles and quantifying the phases' proportions in a material, which is of great significance in the genuine applications. Here, by using second-harmonic generation (SHG) polarimetry and piezoresponse force microscopy (PFM) techniques, this work elucidates the contributions and distributions of two different symmetric phases mixed in an archetype monoaxial molecular ferroelectric, diisopropylammonium chloride (DIPACl). The two competing phases are preferred in thermodynamics or kinetic process respectively, and this work evidences the switching behavior between the two competing phases facilitated by an external electrical field as opposed to a heating process.

Enhancement of phase transition temperature through hydrogen bond modification in molecular ferroelectrics.

Molecular ferroelectrics are attracting great interest due to their light weight, mechanical flexibility, low cost, ease of processing and environmental friendliness. These advantages make molecular ferroelectrics viable alternatives or supplements to inorganic ceramics and polymer ferroelectrics. It is expected that molecular ferroelectrics with good performance can be fabricated, which in turns calls for effective chemical design strategies in crystal engineering.

Organic-Inorganic Hybrid Perovskite Ferroelectric Nanosheets Synthesized by a Room-Temperature Antisolvent Method.

Over the past years, the application potential of ferroelectric nanomaterials with unique physical properties for modern electronics is highlighted to a large extent. However, it is relatively challenging to fabricate inorganic ferroelectric nanomaterials, which is a process depending on a vacuum atmosphere at high temperatures. As significant complements to inorganic ferroelectric nanomaterials, the nanomaterials of molecular ferroelectrics are rarely reported.

The past 10 years of molecular ferroelectrics: structures, design, and properties.

Ferroelectricity, which has diverse important applications such as memory elements, capacitors, and sensors, was first discovered in a molecular compound, Rochelle salt, in 1920 by Valasek. Owing to their superiorities of lightweight, biocompatibility, structural tunability, mechanical flexibility, , the past decade has witnessed the renaissance of molecular ferroelectrics as promising complementary materials to commercial inorganic ferroelectrics. Thus, on the 100th anniversary of ferroelectricity, it is an opportune time to look into the future, specifically into how to push the boundaries of material design in molecular ferroelectric systems and finally overcome the hurdles to their commercialization.

Wireless Deep Brain Stimulation by Ultrasound-Responsive Molecular Piezoelectric Nanogenerators.

Implantable neural stimulation devices are becoming prevalent in bioelectronic medicine for the precise treatment of various clinical diseases. Nevertheless, the limited lifespan and buckling size of the implanted devices remain significant obstacles for chronic clinical application. In this study, we developed an ultrasound-driven battery-free neurostimulator based on a high-performance mini-sized nanogenerator and demonstrated its successful application for the deep-brain-stimulation (DBS) therapy of Parkinson's disease in a rat model.

First Observation of Negative Capacitance in Molecular Ferroelectric Thin Films.

On the path of persisting Moore's Law, one of the biggest obstacles is the "Boltzmann tyranny," which defines the lower limit of power consumption of individual transistors. Negative capacitance (NC) in ferroelectrics could provide a solution and has garnered significant attention in the fields of nanoelectronics, materials science, and solid-state physics. Molecular ferroelectrics, as an integral part of ferroelectrics, have developed rapidly in terms of both performance and functionality, with their inherent advantages such as easy fabrication, mechanical flexibility, low processing temperature, and structural tunability.

The First Demonstration of Strain-Controlled Periodic Ferroelectric Domains with Superior Piezoelectric Response in Molecular Materials.

Achieving a periodic domain structure in ferroelectric materials to tailor the macroscopic properties or realize new functions has always been a hot topic. However, methods to construct periodic domain structures, such as epitaxial growth, direct writing by scanning tips, and the patterned electrode method, are difficult or inefficient to implement in emerging molecular ferroelectrics, which have the advantages of lightweight, flexibility, biocompatibility, etc. An efficient method for constructing and controlling periodic domain structures is urgently needed to facilitate the development of molecular ferroelectrics in nanoelectronic devices.

Rational Design of Molecular Ferroelectrics with Negatively Charged Domain Walls.

Ferroelectric domains and domain walls are unique characteristics of ferroelectric materials. Among them, charged domain walls (CDWs) are a special kind of peculiar microstructure that highly improve conductivity, piezoelectricity, and photovoltaic efficiency. Thus, CDWs are believed to be the key to ferroelectrics' future application in fields of energy, sensing, information storage, and so forth.

An Effective Strategy of Introducing Chirality to Achieve Multifunctionality in Rare-Earth Double Perovskite Ferroelectrics.

The hybrid rare-earth double perovskite (HREDP) system provides great convenience for the construction of multifunctional materials. However, suffering from the high symmetry of their intrinsic structure, HREDPs face the challenges in the realization and optimization of ferroelectric and piezoelectric properties. For the first time, after a systematic investigation of the chirality transformation principle, it is found that the introduction of chirality is an efficient strategy for the targeted construction of multifunctionality, which simultaneously increases the possibility of obtaining multiaxial ferroelectricity and ferroelasticity, and effectively realizes a large piezoelectric response.

Fluorinated 2D Lead Iodide Perovskite Ferroelectrics.

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 NH PbI is still under debate, and obtaining ferroelectric lead iodide perovskites is still challenging.

A Nickel(II) Nitrite Based Molecular Perovskite Ferroelectric.

The X-site ion in organic-inorganic hybrid ABX perovskites (OHPs) varies from halide ion to bridging linkers like HCOO , N , NO , and CN . However, no nitrite-based OHP ferroelectrics have been reported so far. Now, based on non-ferroelectric [(CH ) N][Ni(NO ) ], through the combined methodologies of quasi-spherical shape, hydrogen bonding functionality, and H/F substitution, we have successfully synthesized an OHP ferroelectric, [FMeTP][Ni(NO ) ] (FMeTP=N-fluoromethyl tropine).