Crystalline metal halide perovskites (MHPs) have provided unprecedented advances in interdisciplinary fields of materials, electronics, and photonics. While crystallinity offers numerous advantages, the ability to access a glassy state with distinct properties provides unique opportunities to extend the associated structure–property relationship, as well as broaden the application space for MHPs. Amorphous analogs for MHPs have so far been restricted to high pressures, limiting detailed studies and applications. Here, a 2D MHP is structurally tailored using bulky chiral organic cations to exhibit an unusual confluence of exceptionally low melting temperature (175 °C) and inhibited crystallization. The chiral MHP can thus be melt‐quenched into a stable glassy state, otherwise inhibited in the analogous racemic MHP. Facile and reversible switching between glassy and crystalline states is demonstrated for the chiral MHP, each with distinct optoelectronic character, opening new opportunities for applications including, for example nonvolatile memory, optical communication, and neuromorphic computing.

SummaryProteins in basement membrane (BM) are long‐lived and accumulate chemical modifications during aging; advanced glycation endproduct (AGE) formation is one such modification. The human lens capsule is a BM secreted by lens epithelial cells. In this study, we have investigated the effect of aging and cataracts on the AGE levels in the human lens capsule and determined their role in the epithelial‐to‐mesenchymal transition (EMT) of lens epithelial cells. EMT occurs during posterior capsule opacification (PCO), also known as secondary cataract formation. We found age‐dependent increases in several AGEs and significantly higher levels in cataractous lens capsules than in normal lens capsules measured by LC‐MS/MS. The TGFβ2‐mediated upregulation of the mRNA levels (by qPCR) of EMT‐associated proteins was significantly enhanced in cells cultured on AGE‐modified BM and human lens capsule compared with those on unmodified proteins. Such responses were also observed for TGFβ1. In the human capsular bag model of PCO, the AGE content of the capsule proteins was correlated with the synthesis of TGFβ2‐mediated α‐smooth muscle actin (αSMA). Taken together, our data imply that AGEs in the lens capsule promote the TGFβ2‐mediated fibrosis of lens epithelial cells during PCO and suggest that AGEs in BMs could have a broader role in aging and diabetes‐associated fibrosis.

The recent discovery of glass-forming hybrid metal halide perovskite (MHP) semiconductors has opened the opportunity to explore their utility beyond the already celebrated fields of photovoltaics and light emitters, as enabled by their crystalline counterparts. Reversible switching phenomena between glassy and crystalline states further extends the potential application space, prospectively, to memory, computing, photonics, metamaterials, and phase change energy storage. To better identify the characteristic switching properties, the underlying kinetics of glass crystallization is studied for an e x e m p l a r y g l a s s -f o r m i n g ( S ) -( − ) -1 -( 1 -n a p h t h y l )ethylammonium lead bromide (SNPB) perovskite, using a combination of calorimetry, microscopy, and kinetic modeling techniques. The study shows an activation energy of ∼350 kJ/mol for the glass-crystalline transition and an Avrami parameter of n = 2.02 ± 0.11, and points to heterogeneous surface-mediated nucleation of crystallites with two-dimensional laminar growth in space. These results serve as an initial guide toward modeling the glass-crystallization kinetic effects in MHPs and to facilitate assessment of the suitability of the glass-forming MHPs for a broad range of prospective applications.

Due to their weak interlayer bonding, van der Waals (vdW) solids are very sensitive to external stimuli such as strain. Experimental studies of strain tuning of thermal properties in vdW solids have not yet been reported. Under ~9% cross-plane compressive strain created by hydrostatic pressure in a diamond anvil cell, we observed an increase of cross-plane thermal conductivity in bulk MoS 2 from 3.5 Wm-1 K-1 to about 25 Wm-1 K-1 , measured with a picosecond transient thermoreflectance technique. First-principles calculations and coherent phonon spectroscopy experiments reveal that this drastic change arises from the strain-enhanced interlayer interaction, heavily modified phonon dispersions, and decrease in phonon lifetimes due to unbundling effect along cross-plane direction. The contribution from the change of electronic thermal conductivity is negligible. Our results suggest possible parallel tuning of structural, thermal and electrical properties of vdW solids with strain in multi-physics devices. Main Text Strain is an effective tool to tune physical properties in a wide range of materials [1-4]. In transition metal dichalcogenides (TMDs), a family of two-dimensional (2D) van der Waals (vdW) solids, strain can alter the interlayer distance, as well as bond strength, length and angle between the transition metal and chalcogen atoms, modifying the interatomic orbital coupling, interlayer wavefunction overlap and valence band splitting [5-7]. Changes in these physical parameters can modulate electronic and phononic properties to a great extent. For example, the electronic band gap and phonon Raman peaks in TMDs have been shown experimentally very sensitive to strain, with an A 1g phonon Raman shift as large as ~5-6 cm-1 /% [8-13]. In traditional mechanical bending/stretching experiments, the 2D materials sit on a flexible substrate and strain is determined

Pore surface functionalization of a metal–organic framework (MOF) with an amine moiety has turned an innocent MOF into a chemiresistive sensor for acidic gases.