Quasi-2D perovskite made with organic spacers co-crystallized with inorganic cesium lead bromide inorganics is demonstrated for near unity photoluminescence quantum yield at room temperature. However, light emitting diodes made with quasi-2D perovskites rapidly degrade which remains a major bottleneck in this field. In this work, It is shown that the bright emission originates from finely tuned multi-component 2D nano-crystalline phases that are thermodynamically unstable. The bright emission is extremely sensitive to external stimuli and the emission quickly dims away upon heating. After a detailed analysis of their optical and morphological properties, the degradation is attributed to 2D phase redistribution associated with the dissociation of the organic spacers departing from the inorganic lattice. To circumvent the instability problem, a diamine is investigated spacer that has both sides attached to the inorganic lattice. The diamine spacer incorporated perovskite film shows significantly improved thermal tolerance over maintaining a high photoluminescence quantum yield of over 50%, which will be a more robust material for lighting applications. This study guides designing quasi-2D perovskites to stabilize the emission properties.

The near-infrared (NIR) emission of silicon-germanium alloy nanocrystals (SiGe NCs) was sensitized by heterostructuring with a quasi two-dimensional (Q-2D) perovskite (CsPbBr3 blended with butylammonium bromide (BABr)). Colloidal SiGe NCs were synthesized by using a nonthermal plasma method with chloride precursors. As-synthesized SiGe NCs showed no detectable photoluminescence (PL). Embedding the SiGe NCs within the perovskite matrix via spin coating led to a heterostructure exhibiting dual emissions: green emission at 520 nm from the perovskite and NIR emission at 1035 nm from the SiGe NCs. Time-integrated and resolved PL measurements and transient absorption spectroscopy revealed energy transfer from the perovskite to the SiGe NCs, which sensitized the NIR emission from the SiGe NCs and quenched the green PL for the perovskite. These results demonstrate that Ge alloying can effectively tune the bandgap of Si NCs and highlight the feasibility of heterostructuring perovskites and photoluminescent NCs to enhance or activate their PL. This approach broadens their potential applications in the NIR region.

Hierarchically porous polymers offer large surface areas for enhanced catalytic activity, but incorporating photocatalytic sites into these pore channels remains challenging. Inspired by nature's disulfide bonds, which stabilize proteins and enable redox activity, this study introduces a hierarchically porous poly(aryl thioether) photocatalyst via dual disulfide and thioether linkages formed by polycondensation. Thiolate intermediates undergo partial oxidation in air, yielding a micro/mesoporous polymer with a 757 m 2 g⁻¹ surface area, comparable to its microporous counterpart synthesized in N₂. This structure exhibits enhanced adsorption capacity, as demonstrated by tests with volatile organic compounds and mercury ions. The disulfide‐functionalized pore walls enable thiyl radical formation under visible light, achieving outstanding diphenylacetylene oxidation performance. This heterogeneous photocatalyst surpasses homogeneous systems, showing >99% conversion efficiency with 3.5% apparent quantum yield at 440 nm. This study pioneers a linker engineering strategy to integrate hierarchical porous structure and photoactive radical generation in a single porous polymer photocatalyst.

Developing novel lead-free ferroelectric materials is crucial for next-generation microelectronic technologies that are energy efficient and environment friendly. However, materials discovery and property optimization are typically time-consuming due to the limited throughput of traditional synthesis methods. In this work, we use a high-throughput combinatorial synthesis approach to fabricate lead-free ferroelectric superlattices and solid solutions of (Ba 0.7 Ca 0.3 )TiO 3 (BCT) and Ba(Zr 0.2 Ti 0.8 )O 3 (BZT) phases with continuous variation of composition and layer thickness. High-resolution x-ray diffraction (XRD) and analytical scanning transmission electron microscopy (STEM) demonstrate high film quality and well-controlled compositional gradients. Ferroelectric and dielectric property measurements identify the “optimal property point” achieved at the composition of 48BZT–52BCT. Displacement vector maps reveal that ferroelectric domain sizes are tunable by varying {BCT–BZT} N superlattice geometry. This high-throughput synthesis approach can be applied to many other material systems to expedite new materials discovery and properties optimization, allowing for the exploration of a large area of phase space within a single growth.

Device-level implementation of soft materials for energy conversion and thermal management demands a comprehensive understanding of their thermal conductivity and elastic modulus to mitigate thermo-mechanical challenges and ensure long-term stability. Thermal conductivity and elastic modulus are usually positively correlated in soft materials, such as amorphous macromolecules, which poses a challenge to discover materials that are either soft and thermally conductive or hard and thermally insulative. Here, we show anomalous correlations of thermal conductivity and elastic modulus in two-dimensional (2D) hybrid organic-inorganic perovskites (HOIP) by engineering the molecular interactions between organic cations. By replacing conventional alkyl-alkyl and aryl-aryl type organic interactions with mixed alkyl-aryl interactions, we observe an enhancement in elastic modulus with a reduction in thermal conductivity. This anomalous dependence provides a route to engineer thermal conductivity and elastic modulus independently and a guideline to search for better thermal management materials. Further, introducing chirality into the organic cation induces a molecular packing that leads to the same thermal conductivity and elastic modulus regardless of the composition across all half-chiral 2D HOIPs. This finding provides substantial leeway for further investigations in chiral 2D HOIPs to tune optoelectronic properties without compromising thermal and mechanical stability.

High-quality quasi-2D perovskites in a GaN nano-wire matrix are grown to build a 3D hetero-structure for high-performance X-ray sensing. In the 3D hetero-structure, GaN nano-wire matrix serves as an n-type charge collector that can rapidly extract carriers through the bulk film of the perovskite layer. Together with a p-type top electrode, a p-i-n diode with the 3D hetero-structure is built, that exhibits a rectified current-voltage characteristic. After analyzing the interface energy alignment, it is found that the fermi levels of the perovskite and GaN are aligned in the dark, and a quasi-fermi level splits upon illumination, introducing a built-in electrical field at the interface. As a result, strong photo-induced current is observed from the diode without an external field. Finally, the 3D diode for X-ray detection demonstration is used, revealing a sensitivity of 308.9 mu C Gyair-1 cm-2 at an exceptionally low applied field of 0.125 V mu m-1. The X-ray-induced signal from the 3D diode is stable after 155 cycles of X-ray irradiation under a constant electric field. This demonstration informs a new 3D architecture for high-performance X-ray sensing, and it shows that GaN is a robust n-type interface for perovskite optoelectronic devices. A 3D hetero-junction photodiode with quasi-2D perovskite grown in GaN nanowire matrix is built for high-performance X-ray sensing. GaN nanowire serves as a robust n-type charge collection layer with proper band alignments that rapidly extracts electrons ionized through the bulk volume of perovskite. This work suggests a robust n-type interface for perovskite devices. image

A scrambled but selective polycondensation reaction introduced the simplest route to generate porous poly(aryl thioether)s. Through a multi-para nucleophilic substitution of perfluoroaromatic compounds with sodium sulfide, temperature-dependent formation of thioether linkages leads to stepwise transition of the polymers into network structures with controllable porosity and bandgap, as reported by Jeehye Byun, Sheng Li, Cafer T. Yavuz et al. in their Research Article (e202304378).

Porous poly(aryl thioether)s offer stability and electronic tunability by robust sulfur-aryl conjugated architecture, but synthetic access is hindered due to limited control over the nucleophilic nature of sulfides and the air sensitivity of aromatic thiols. Here, we report a simple, one-pot, inexpensive, regioselective synthesis of highly porous poly(aryl thioether)s through polycondensation of perfluoroaromatic compounds with sodium sulfide. The unprecedented temperature-dependent para-directing formation of thioether linkages leads to a stepwise transition of the polymer extension into a network, thereby allowing fine control of the porosity and optical band gaps. The obtained porous organic polymers with ultra-microporosity (<1 nm) and sulfur as the surface functional groups show size-dependent separation of organic micropollutants and selective removal of mercury ions from water. Our findings offer easy access to poly(aryl thioether)s with accessible sulfur functionalities and higher complexity, which will help in realizing advanced synthetic designs in applications such as adsorption, (photo)catalysis, and (opto)electronics.

2D hybrid organic-inorganic perovskites (HOIPs) are commonly found under subcritical cyclic stresses and suffer from fatigue issues during device operation. However, their fatigue properties remain unknown. Here, the fatigue behavior of (C4 H9 -NH3 )2 (CH3 NH3 )2 Pb3 I10 , the archetype 2D HOIP, is systematically investigated by atomic force microscopy (AFM). It is found that 2D HOIPs are much more fatigue resilient than polymers and can survive over 1 billion cycles. 2D HOIPs tend to exhibit brittle failure at high mean stress levels, but behave as ductile materials at low mean stress levels. These results suggest the presence of a plastic deformation mechanism in these ionic 2D HOIPs at low mean stress levels, which may contribute to the long fatigue lifetime, but is inhibited at higher mean stresses. The stiffness and strength of 2D HOIPs are gradually weakened under subcritical loading, potentially as a result of stress-induced defect nucleation and accumulation. The cyclic loading component can further accelerate this process. The fatigue lifetime of 2D HOIPs can be extended by reducing the mean stress, stress amplitude, or increasing the thickness. These results can provide indispensable insights into designing and engineering 2D HOIPs and other hybrid organic-inorganic materials for long-term mechanical durability.

The implementation of two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) in semiconductor device applications will have to accommodate the co-existence of strain and temperature stressors and requires a thorough understanding of the thermomechanical behavior of 2D HOIPs. This will mitigate thermomechanical stability issues and improve the durability of the devices, especially when one considers the high susceptibility of 2D HOIPs to temperature due to their soft nature. Here, we employ atomic force microscopy (AFM) stretching of suspended membranes to measure the temperature dependence of the in-plane Young's modulus (E∥) of model Ruddlesden-Popper 2D HOIPs with a general formula of (CH3(CH2)3NH3)2(CH3NH3)n-1PbnI3n+1 (here, n = 1, 3, or 5). We find that E∥ values of these 2D HOIPs exhibit a prominent non-monotonic dependence on temperature, particularly an abnormal thermal stiffening behavior (nearly 40% change in E∥) starting around the order-disorder transition temperature of the butylammonium spacer molecules, which is significantly different from the thermomechanical behavior expected from their 3D counterpart (CH3NH3PbI3) or other low-dimensional material systems. Further raising the temperature eventually reverses the trend to thermal softening. The magnitude of the thermally induced change in E∥ is also much higher in 2D HOIPs than in their 3D analogs. Our results can shed light on the structural origin of the thermomechanical behavior and provide needed guidance to design 2D HOIPs with desired thermomechanical properties to meet the application needs.

In this work, we investigated the effect of hole transporting poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) interfacing with Mn-doped CdS/ZnS quantum dots (QDs) deposited on an indium tin oxide (ITO) substrate on the photoemission of upconverted hot electrons under weak continuous wave photoexcitation in a vacuum. Among the various factors that can influence the photoemission of the upconverted hot electrons, we studied the role of PEDOT:PSS in facilitating the hole transfer from QDs and altering the energy of photoemitted hot electrons. Compared to hot electrons emitted from QDs deposited directly on the ITO substrate, the addition of the PEDOT:PSS layer between the QD and ITO layers increased the energy of the photoemitted hot electrons. The increased energy of the photoemitted hot electrons is attributed in part to the reduced steady-state positive charge on the QDs under continuous photoexcitation, which reduces the energy required to eject the electron from the conduction band.

Metal phosphorus trichalcogenides (MPTCs) are emerging 2D semiconductor materials with unique functional properties that set them apart from other 2D systems. Despite the importance of their mechanical properties for improving the semiconductor device's durability and performance, as well as for utilizing strain effects to customize material properties and create new functionality, our current understanding of MPTCs' mechanical behavior is lacking and lags behind our knowledge of their other properties. Here, we use LiInP2Se6 as a model example of MPTCs and report the first experimental measurements of the elastic and plastic (fracture) properties along both in plane and out-of-plane directions by atomic force microscopy and nanoindentation. Being a 2D material that is entirely inorganic, LiInP2Se6 surprisingly exhibits mechanical properties that resemble those of hybrid organic-inorganic materials rather than pure inorganic 2D materials. It has a soft crystal structure with low elastic moduli, a low difference in in-plane vs out-of-plane mechanical properties, and a combination of elastic and plastic characteristics of hybrid organic-inorganic materials. Our work provides the mechanical information critically needed to mitigate and/or harness the strain effects in LiInP2Se6-based semiconductor devices and sheds light on the mechanical behaviors of MPTCs with indispensable insights.

Chiral hybrid metal-halide semiconductors (MHS) pose as ideal candidates for spintronic applications owing to their strong spin-orbit coupling (SOC), and long spin relaxation times. Shedding light on the underlying structure-property relationships is of paramount importance for the targeted synthesis of materials with an optimum performance. Herein, we report the synthesis and optical properties of 1D chiral (R-/S-THBTD)SbBr5 (THBTD = 4,5,6,7-tetrahydro-benzothiazole-2,6-diamine) semiconductors using a multifunctional ligand as a countercation and a structure directing agent. (R-/S-THBTD)SbBr5 feature direct and indirect band gap characteristics, exhibiting photoluminescence (PL) light emission at RT that is accompanied by a lifetime of a few ns. Circular dichroism (CD), second harmonic generation (SHG), and piezoresponse force microscopy (PFM) studies validate the chiral nature of the synthesized materials. Density functional theory (DFT) calculations revealed a Rashba/Dresselhaus (R/D) spin splitting, supported by an energy splitting (ER) of 23 and 25 meV, and a Rashba parameter (αR) of 0.23 and 0.32 eV·Å for the R and S analogs, respectively. These values are comparable to those of the 3D and 2D perovskite materials. Notably, (S-THBTD)SbBr5 has been air-stable for a year, a record performance among chiral lead-free MHS. This work demonstrates that low-dimensional, lead-free, chiral semiconductors with exceptional air stability can be acquired, without compromising spin splitting and manipulation performance.

ABSTRACT Objectives: Excessive accumulation of extravascular lung water impairs respiratory gas exchange and results in respiratory distress. Real-time radiofrequency signals of ultrasound can continuously and quantitatively monitor excessive lung water. This study aims to evaluate the availability of continuous real-time quantitative pulmonary edema monitoring using ultrasound radiofrequency signals and compare it with Pa o 2 (partial pressure of arterial oxygen)/F io 2 (fraction of inspired oxygen) (PF) ratio, conventional lung ultrasound, and the Hounsfield unit of chest computed tomography. Methods: Male Yorkshire pigs (40.5 ± 0.5 kg) were anesthetized and mechanically ventilated. A balanced crystalloid was administered to induce hydrostatic pulmonary edema. Three different infusion rates of 2, 4, and 6 mL/kg per minute were tested to determine the infusion rate for the appropriate swine model. The chest computed tomography and ultrasonography with radiofrequency signals were taken every 5 min during the full inspiration. The ultrasonography scans with radiofrequency signals were measured at the intercostal space where the line crossing the two armpits and the right anterior axillary line intersected. Results: The infusion rate of fluid for the pulmonary edema model was determined to be 6 mL/kg per minute, and a total of four pigs were tested at an injection rate of 6 mL/kg. The adjusted R 2 values of regression analysis between the radiofrequency signal and computer tomography Hounsfield score were 0.990, 0.993, 0.988, and 0.993 (all P values <0.05). All radiofrequency signal changes preceded changes in PF ratio or lung ultrasound changes. The area under the receiver operating characteristic curve of the radiofrequency signal for predicting PF ratio <300 was 0.88 (95% confidence interval, 0.82–0.93). Conclusion: We evaluated ultrasound radiofrequency signals to assess pulmonary edema in a swine model that can worsen gradually and showed that quantitative ultrasound radiofrequency signal analysis could assess pulmonary edema and its progression before PF ratio or lung ultrasound changes.

The atomistic design of positive electrode materials requires understanding of (1) how guest cations diffuse through an intercalation host to fill empty interstices and (2) the distortions of the host lattice induced as a result of ion intercalation. Here, we report the use of topochemistry to access single-crystals of a metastable 2D van der Waals solid, γʹ-V2O5, and examine its single-crystal-to-single-crystal transformations upon lithiation up to γ-LiV2O5. High-resolution single-crystal diffraction provides an atomistic view of preferred interstitial sites occupied by Li ions and distortions of the 2D lattice in an extended solid-solution lithiation regime, which stands in stark contrast to the thermodynamic α-V2O5 phase. These results illustrate the potential of metastable compounds with reconfigured atomic connectivity to unlock lithiation pathways and mechanisms that are profoundly different from their thermodynamic counterparts. The study furthermore demonstrates the viability of combining topochemical modification with single-crystal diffraction to image intercalation phenomena with atomic resolution.

Mercury (Hg) contamination in aquatic systems still poses serious health risks through accumulation despite the strict regulations on drinking water and industrial discharge. One effective strategy is adsorptive removal, where a suitably functionalized porous material is added to water treatment protocols. Thiol (SH) group grafted structures perform commendably without due attention to the cost, scalability, and reusability and how the arrangement of sulfur atoms could affect the Hg (II) binding strength. We use an inexpensive and scalable porous covalent organic polymer (COP-130) to systematically introduce thiol functional groups with precise chain lengths and sulfur content. The thiol-functionalized COP-130 demonstrates enhanced wettability and excellent Hg (II) uptake up to 936 mg g-1, with fast kinetics and exceptionally high selectivity. These Hg adsorbents are easily regenerated with HCl and used at least six times even after strong acid treatments without loss of capacity, a rare performance in the Hg removal research domain.

Metal- halide perovskites (MHPs) possess enormous potential in optoelectronic and semiconductor devices. In these applications, MHPs are often subjected to mechanical stress, resulting in distorted lattice, severe degradation, and catastrophic failure in MHPs and their interfaces. Understanding these mechanics-coupled stability issues is crucial to the durability and, thus, commercial viability of MHP-based devices. Here, we review the impact of mechanical stress on the integrity and robustness of MHP devices to provide insights into mitigating the mechanics-coupled stability issues. We start with an overview of the structure-elastic-property relationship of MHPs, after which we discuss the current understanding of the cohesive and adhesive failures within MHPs and at MHP interfaces forced by mechanical stress, respectively. We further review the chemical stability issues of MHPs and interfaces induced by themechanical strain. Finally, we summarize the existing strategies to mitigate the mechanics-coupled stability issues and conclude with an outlook of future research directions.

In-plane strains are commonly found in two-dimensional (2D) metal halide organic-inorganic perovskites (HOIPs). The in-plane mechanical properties of 2D HOIPs are vital for mitigating the strain-induced stability issues of 2D HOIPs, yet their structure and mechanical property relationship largely remains unknown. Here, we employed atomic force microscope indentation to systematically investigate the in-plane Young's moduli E∥ of 2D lead halide Ruddlesden-Popper HOIPs with a general formula of (R-NH3)2PbX4, where the spacer molecules R-NH3+ are linear alkylammonium cations (CmH2m+1-NH3+, m = 4, 6, 8, or 12) and X = I, Br, or Cl. Fixing the spacer molecule to butylammonium, we discovered that the E∥ of 2D HOIPs generally follows the trend of Pb-X bond strength, different from the tendency found in the out-of-plane moduli E⊥, showing more prominent effects of the metal halide inorganic framework on E∥ than E⊥. E∥ exhibits nonmonotonic dependence on the chain length of the linear alkyl spacer molecules, which would first decrease and plateau but then increase again. This is likely due to the competition of the bond strength and structural distortion in the inorganic layer, the relative fraction of the soft organic spacers, and the interfacial mechanical coupling associated with the interdigitation of the alkyl chains. The mechanical anisotropy of 2D HOIPs, marked by E∥/E⊥, shows wide tunability based on structural composition, particularly for iodide-based 2D HOIPs. Our results provide valuable insights into the structure-property relationships regarding the mechanical anisotropy and in-plane mechanical behaviors of 2D HOIPs, which can guide the materials design and device optimization to achieve required mechanical performance in 2D HOIP-based applications.

In this study, we propose a long short-term memory (LSTM)-based user identification method using accelerometer data from smart shoes. In general, for the user identification with human walking data, we require a pre-processing stage in order to divide human walking data into individual steps. Next, user identification can be made with divided step data. In these approaches, when there exist partial data that cannot complete a single step, it is difficult to apply those data to the classification. Considering these facts, in this study, we present a stack LSTM-based user identification method for smart-shoes data. Rather than using a complicated analysis method, we designed an LSTM network for user identification with accelerometer data of smart shoes. In order to learn partial data, the LSTM network was trained using walking data with random sizes and random locations. Then, the identification can be made without any additional analysis such as step division. In the experiments, user walking data with 10 m were used. The experimental results show that the average recognition rate was about 93.41%, 97.19%, and 98.26% by using walking data of 2.6, 3.9, and 5.2 s, respectively. With the experimental results, we show that the proposed method can classify users effectively.

CO2 emissions are too large to tackle with a single process, but a combination of avoidance with chemical utilization may be able to slow global warming. In this Focus Review, we identify two large-scale CO2 conversion processes based on their viability and opposite energy requirements. In the high-energy, stationary path, CO2 reforming of methane could provide gigatons of CO2 utilization through synthesis gas. The main problem is the lack of a durable, effective, low-cost dry reforming catalyst. The exothermic cyclic carbonate formation from CO2 and organic epoxides offers a low-energy, mobile, nonredox route. The catalysts, however, must be metal-free and robust, have a high surface area, and be low-cost while being easily scalable. These two processes could potentially address at least a quarter of all current CO2 emissions.