Multiproperty Materials Research Articles

Rapid Discovery of Ferroelectric Photovoltaic Perovskites and Material Descriptors via Machine Learning

Rapid discovery of novel functional materials is urgent but a tremendous challenge using trial‐and‐error methods in vast chemical space. Here, a multistep screening scheme is developed by combining high‐throughput calculations and machine learning (ML) techniques. Successfully, 151 promising stable ferroelectric photovoltaic (FPV) perovskites with proper bandgap are screened out from 19 841 candidate compositions. Two new descriptors are proposed to describe mixed inorganic perovskites' formability through ML feature engineering. Additionally, phase‐transition energy difference is used as a criterion for directly judging whether the compound can expose spontaneous polarization. The ML prediction accuracy of both energy difference and bandgap regressions is over 90% and ML produces comparable results to density functional theory calculations. Moreover, bandgaps of eight selected FPV perovskites are all close to the optimal value of single‐junction solar cells. This scheme not only realizes the ML acceleration for targeted multiproperty materials' design and expansion of materials database, but also opens a way for descriptor development.

Bio-inspired multiproperty materials: strong, self-healing, and transparent artificial wood nanostructures.

Nanocomposite films possessing multiple interesting properties (mechanical strength, optical transparency, self-healing, and partial biodegradability) are discussed. We used Layer-by-Layer assembly to prepare micron thick wood-inspired films from anionic nanofibrillated cellulose and cationic poly(vinyl amine). The film growth was carried out at different pH values to obtain films of different chemical composition, whereby, and as expected, higher pH values led to a higher polycation content and also to 6 times higher film growth increments (from 9 to 55 nm per layer pair). In the pH range from 8 to 11, micron thick and optically transparent LbL films are obtained by automated dipping when dried regularly in a stream of air. Films with a size of 10 cm(2) or more can be peeled from flat surfaces; they show tensile strengths up to about 250 MPa and Young's moduli up to about 18 GPa as controlled by the polycation/polyanion ratio of the film. Experiments at different humidities revealed the plasticizing effect of water in the films and allowed reversible switching of their mechanical properties. Whereas dry films are strong and brittle (Young's modulus: 16 GPa, strain at break: 1.7%), wet films are soft and ductile (Young's modulus: 0.1 GPa, strain at break: 49%). Wet film surfaces even amalgamate upon contact to yield mechanically stable junctions. We attribute the switchability of the mechanical properties and the propensity for self-repair to changes in the polycation mobility that are brought about by the plastifying effect of water.

Synthetic Transition Metal Phyllosilicates and Organic‐Inorganic Related Phases

AbstractFor Abstract see ChemInform Abstract in Full Text.

Electric‐Field‐Induced Conductance Switching in FeCo Prussian Blue Analogues.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Electric-field-induced conductance switching in FeCo Prussian blue analogues.

FeCo Prussian blue analogues, which are known as typical molecule-based magnets, exhibited abrupt conductance switching by applying a high electric field as well as by varying the temperature. The current density versus electric field (J-E) curves of FeCo Prussian blue with Rb cations in interstitial sites shows so-called negative resistance effects at electric fields higher than the threshold voltage. This means that the FeCo Prussian blue analogues are multiproperty materials in the sense that their conducting, magnetic, and optical properties can be reversibly controlled by certain external stimuli.

Synthetic transition metal phyllosilicates and organic-inorganic related phases

We present a brief overview of the first-row transition metal phyllosilicates and their organically functionalised analogues obtained under autogenous pressure conditions. Some structural features of phyllosilicates are first recalled and the magnetic properties of Co2+ and Ni2+ phyllosilicates are described. In the second part, the state-of-the-art in organically functionalised phyllosilicates is reported, including our contributions on the structural and magnetic characterisation. The impetus is to enhance the potential of these new compounds as multi-property materials. Since our interest lies in low-dimensional magnetic properties, divalent transition metal cations are involved in the layered inorganic layers, whereas 3-aminopropyltriethoxysilane is used as the silicon source.

Third-Order Nonlinear Optical Properties of π-Conjugated Systems Involving Sulfur Atoms: A Proposal of Multi-Property Materials Combining Conductivity and Unique Third-Order Nonlinearity

We investigate the third-order nonlinear optical property for 1,6,6a-trithiapentalene (TTP) by using density functional method. A unique spatial contribution of π-electrons to the second hyperpolarizability (γ) is elucidated. Based on our classification rule of γ, the features of γ for other π-conjugated systems involving sulfur (S) atoms are also discussed from the viewpoint of the possibility of combining conductivity and third-order nonlinear optics.

Hybrid Materials Formed by Two Molecular Networks. Towards Multiproperty Materials

The possibilities offered by hybrid materials formed by two molecular networks in the context of the molecular magnets are illustrated. Molecule-based layered magnets are used as anionic hosts for electroactive molecules, with the aim of obtaining multiproperty materials exhibiting in addition to the cooperative magnetism other interesting properties according to the nature of the inserted molecules. In particular, hybrid molecular compounds containing molecular species giving rise to paramagnetic, conducting, or bi-stable properties are reported.

Multi-property materials combining conductivity and second-order optical nonlinearity

We present several new materials made of acceptor units (TCNQ and [Ni(dmit) 2]) and stilbazolium-based chromophores for second-order optical nonlinearity. The subtil adjustement in the redox potentials necessary for: ( i) maintaining the material in a semi-conducting state, to offer a good range of transparency in a broad nearinfrared domain; ( ii) allowing electronic interaction, to promote a pathway towards efficient interplays between the properties is analyzed The possibility of combining both properties on the same entity with the TTF skeleton is also discussed.

Hybrid molecular magnets incorporating organic donors and other electroactive molecules

Molecule-based bidimensional ferromagnets can be used as anionic hosts for electroactive molecules, with the aim of obtaining multiproperty materials exhibiting in addition to the cooperative magnetism other interesting properties according to the nature of the inserted molecules. In particular, hybrid molecular compounds containing conducting (TTF-type organic donors), bi-stable or non-linear optical species are reported.

Molecular magnets: Hybrid organic–inorganic layered compounds with very long-range ferromagnetism

The correlations between structures and magnetic properties of new hybrid layered compounds M 2(OH) 3X (M=Co or Cu), where X is an exchangeable organic anion, are investigated. When the anion is a simple spacer (aliphatic chain), ferromagnetic in-plane interactions dominate, and the situation depends to a large extent on the interlayer spacing d. For small spacings ( d<10 Å), 3D antiferromagnetic order is stabilized, while large spacings favor spontaneous magnetization, even for d≈40 Å, due to dipolar through-space interactions. When X is a radical anion, new metal-radical magnets, with d close to 20 Å, are achieved. Strong interactions between the 3d and π electrons are evidenced, and a net magnetic moment occurs at low temperature. Such compounds are promising for the design of new molecular multiproperty materials.

Multiproperty molecular materials combining conductivity and second‐order optical nonlinearities

The combination of electrical and nonlinear optical (NLO) properties in one material is described for the tetracyanoquinodimethane (TCNQ) radical ion paired with N‐methylstilbazolium‐based chromophores. One of the resulting hybrid materials has a conductivity of 2.3 × 10−3 Ω−1 cm−1 and a second‐harmonic generation efficiency 45 times that of urea. During the predicted transition from electronics to photonics, optoelectronics, which requires multiproperty materials such as those described here, will play an important role.