While halide perovskites (HPs) have achieved enormous success in the field of optoelectronic applications, much attention has been recently drawn to the unique polarization sensitivity of HPs, either intrinsic or extrinsic, which makes HPs a potential candidate for innovative applications in directly polarized luminescence and detection. Herein, the research status in the field of polarization-sensitive HPs, including linear polarization and circular polarization, is comprehensively summarized. To evaluate the effectiveness of HPs in generating and detecting linearly or circularly polarized light, the principles and characterization methods of polarized luminescence and detection are introduced. Sequentially, the state-of-the-art development of the strategies that induce the linear or circular polarization characteristics of HPs is systematically reviewed, based on which the application of polarization-sensitive HPs in the field of polarization luminescence and detection are summarized. Moreover, the current challenges and opportunities are discussed, and prospects of the future development in this promising field are outlined.

Polarization-Sensitive Halide Perovskites for Polarized Luminescence and Detection: Recent Advances and Perspectives.

Mechanochemistry with solvent‐free and environmentally friendly characteristics is one of the most promising alternatives to traditional liquid‐phase‐based reactions, demonstrating epoch‐making significance in the realization of different types of chemistry. Mechanochemistry utilizes mechanical energy to promote physical and chemical transformations to design complex molecules and nanostructured materials, encourage dispersion and recombination of multiphase components, and accelerate reaction rates and efficiencies via highly reactive surfaces. In particular, mechanochemistry deserves special attention because it is capable of endowing energy materials with unique characteristics and properties. Herein, the latest advances and progress in mechanochemistry for the preparation and modification of energy materials are reviewed. An outline of the basic knowledge, methods, and characteristics of different mechanochemical strategies is presented, distinguishing this review from most mechanochemistry reviews that only focus on ball‐milling. Next, this outline is followed by a detailed and insightful discussion of mechanochemistry‐involved energy conversion and storage applications. The discussion comprehensively covers aspects of energy transformations from mechanical/optical/chemical energy to electrical energy. Finally, next‐generation advanced energy materials are proposed. This review is intended to bring mechanochemistry to the frontline and guide this burgeoning field of interdisciplinary research for developing advanced energy materials with greener mechanical force.

A Review on Mechanochemistry: Approaching Advanced Energy Materials with Greener Force

Thioether-linked liquid crystal dimers and trimers: The twist-bend nematic phase

Two homologous series of sulfur-containing thioether-linked 4-cyanoazobenzene-based liquid crystal (LC) dimers were developed: a symmetric series based on 4-cyanoazobenzene arms [(CN)AzoSnSAzo(CN)]...

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Thioether-linked azobenzene-based liquid crystal dimers exhibiting the twist-bend nematic phase over a wide temperature range

Effect of graphene flakes, titanium dioxide and zinc oxide nanoparticles on the birefringence, I–V characteristics and photoluminescence properties of liquid crystal

We report the influence of photoisomerization on a guest-host composite comprising a soft-bent dimer exhibiting the presently sought-after twist-bend nematic (NTB) phase, doped with small amounts of a calamitic photoactive azobenzene-based dimer that assumes a bent shape when photo-driven. Trans-cis photoisomerization of the latter compound leads to a substantial decrease in the nematic-isotropic and nematic-NTB transition temperatures. The results bring out the puzzling feature that the thermal stability of the NTB phase, having a helical structure, despite the molecules being achiral, is influenced more than the regular nematic. Differential influence is also seen in the Frank elastic constants of the regular nematic: while the splay elastic constant is significantly diminished its bend counterpart is hardly affected. Molecular conformational aspects of the entities are proposed to explain these features. Through a judicious combination of this photo-driven effect and an AC electric field, an attractive type of optical memory device is demonstrated.We report the influence of photoisomerization on a guest-host composite comprising a soft-bent dimer exhibiting the presently sought-after twist-bend nematic (NTB) phase, doped with small amounts of a calamitic photoactive azobenzene-based dimer that assumes a bent shape when photo-driven. Trans-cis photoisomerization of the latter compound leads to a substantial decrease in the nematic-isotropic and nematic-NTB transition temperatures. The results bring out the puzzling feature that the thermal stability of the NTB phase, having a helical structure, despite the molecules being achiral, is influenced more than the regular nematic. Differential influence is also seen in the Frank elastic constants of the regular nematic: while the splay elastic constant is significantly diminished its bend counterpart is hardly affected. Molecular conformational aspects of the entities are proposed to explain the...

A soft-bent dimer composite exhibiting twist-bend nematic phase: Photo-driven effects and an optical memory device

Anisotropic Fast Electrically Switchable Emission from Composites of CsPbBr3 Perovskite Quantum Cuboids in a Nematic Liquid Crystal

An extensive study of the effect of terminal halogens on the structure–property relationship in three series of polar short-core hockey-stick-shaped or L-shaped mesogens has been elucidated. The behaviour of the halogens at the tip of the short arm and the role of the end alkyl chain at the long arm in the phase structure of the mesogens have been characterised explicitly. The compounds are shown to exhibit a long-range nematic phase composed of cybotactic clusters (Ncyb) along with an underlying orthogonal smectic phase that has a tendency to align in defect-free fashion in the planar cell. Investigations of X-ray diffraction and dielectric spectroscopy confirm the presence of cybotacticity. The measured elastic constants (K11 and K33) exhibited the usual behaviour (like bent-core mesogens) in the Iso–N phase; however, a trend reversal was observed towards smectic transition. Temperature-dependent Raman study confirms the formation of intermolecular H-bonding (via –CO) in the crystalline phase that systematically weakens and is finally disrupted as the system transforms through the smectic to nematic and isotropic phases. Density functional theory (DFT) study reveals the important molecular parameters that correlate with the experimental findings of the self-assembled structures.

Influence of terminal halogen moieties on the phase structure of short-core achiral hockey-stick-shaped mesogens: design, synthesis and structure–property relationship

A polymer stabilized liquid crystal (PSLC) system formed by a nematic contained in a biopolymer network of cellulose nanocrystals, exhibiting many attractive features, is demonstrated. The threshold or the minimum voltage needed to operate the electro-optic device does not depend on the concentration of the polymer, a feature that is in contrast to the standard PSLC systems. A second point, more important from the driving circuit point of view, is that the voltage-off response time drastically reduces and even becomes practically invariant over the thermal range of the nematic phase. A smart window fabricated using this biopolymer network system exhibits good contrast between the scattering and transparent states driven by voltage and shows an exceptionally high haze factor. A highlight of the device fabrication is that the employed protocol is facile, making it appealing for a potentially viable smart window application.

Switchable smart windows using a biopolymer network of cellulose nanocrystals imposed on a nematic liquid crystal

Better NIR (near infrared)-driven photomechanical actuation than reported for films containing carbon nanostructures such as carbon nanotubes and graphene has been achieved by incorporating porous carbon nanoparticles (PCNs) into single-layer films of polydimethylsiloxane (PDMS). The PCNs being obtained from a bio-waste source adds an exciting dimension to this work. The specific surface area (Asurf) of the pores, controlled using the pyrolization temperature and varying over a factor of 600 is seen to have a strong influence on the magnitude of the actuation as well as the time response of light-driven and relaxation processes. The quantity of the curing agent polymerizing the PDMS also has a notable role. The already significant actuation realized for single-layer films can be further enhanced (factor of two) by backing the PDMS film with an ultrathin gold layer. This addition, however, provides a novel way to control the direction of actuation, being opposite for the single and bilayer films. The mechanical properties obtained from stress versus strain measurements and the morphology of the films as imaged by electron microscopy, besides the coefficient of thermal expansion, have been employed to analyze the various observed behaviors. An important finding from the images is that the crystallinity of the PCNs plays a vital role in the magnitude of actuation: more the amorphous nature, larger is the actuation. Based on the results, which have much for bioengineering applications, a simple photo-stimulated LED switch is also presented.

Pragnya Satapathy

Papers

A soft-bent dimer composite exhibiting twist-bend nematic phase: Photo-driven effects and an optical memory device

Anisotropic Fast Electrically Switchable Emission from Composites of CsPbBr3 Perovskite Quantum Cuboids in a Nematic Liquid Crystal

Influence of terminal halogen moieties on the phase structure of short-core achiral hockey-stick-shaped mesogens: design, synthesis and structure–property relationship

Switchable smart windows using a biopolymer network of cellulose nanocrystals imposed on a nematic liquid crystal

Porous nanocarbon particles drive large magnitude and fast photomechanical actuators