Methanol-water mixture evaporation-induced self-assembly of ZIF-8 particles.

We report a strategy for the self-assembly of zeolitic imidazolate framework-8 (ZIF-8) particles induced by the evaporation of a methanol-water mixture. This strategy effectively suppresses the coffee ring effect, facilitates the rapid assembly of ZIF-8 particles, and improves the orientation and optical properties of self-assembled superstructures.

Gold Nanoparticle-Bridge Array to Improve DNA Hybridization Efficiency of SERS Sensors.

The interfacial mass transfer rate of a target has a significant impact on the sensing performance. The surface reaction forms a concentration gradient perpendicular to the surface, wherein a slow mass transfer process decreases the interfacial reaction rate. In this work, we self-assembled gold nanoparticles (AuNPs) in the gap of a SiO2 opal array to form a AuNP-bridge array. The diffusion paths of vertical permeability and a microvortex effect provided by the AuNP-bridge array synergistically improved the target mass transfer efficiency. As a proof of concept, we used DNA hybridization efficiency as a research model, and the surface-enhanced Raman spectroscopy (SERS) signal acted as a readout index. The experimental verification and theoretical simulation show that the AuNP-bridge array exhibited rapid mass transfer and high sensitivity. The DNA hybridization efficiency of the AuNP-bridge array was 15-fold higher than that of the AuNP-planar array. We believe that AuNP-bridge arrays can be potentially applied for screening drug candidates, genetic variations, and disease biomarkers.

Influence of Elasticity of Hydrogel Nanoparticles on Their Tumor Delivery.

Polymeric nanocarriers have a broad range of clinical applications in recent years, but an inefficient delivery of polymeric nanocarriers to target tissues has always been a challenge. These results show that tuning the elasticity of hydrogel nanoparticles (HNPs) improves their delivery efficiency to tumors. Herein, a microfluidic system is constructed to evaluate cellular uptake of HNPs of different elasticity under flow conditions. It is found that soft HNPs are more efficiently taken up by cells than hard HNPs under flow conditions, owing to the greater adhesion between soft HNPs and cells. Furthermore, in vivo imaging reveals that soft HNPs have a more efficient tumor delivery than hard HNPs, and the greater targeting potential of soft HNPs is associated with both prolonged blood circulation and a high extent of cellular adhesion.

Considering uncertainties expands the lower tail of maize yield projections.

Crop yields are sensitive to extreme weather events. Improving the understanding of the mechanisms and the drivers of the projection uncertainties can help to improve decisions. Previous studies have provided important insights, but often sample only a small subset of potentially important uncertainties. Here we expand on a previous statistical modeling approach by refining the analyses of two uncertainty sources. Specifically, we assess the effects of uncertainties surrounding crop-yield model parameters and climate forcings on projected crop yield. We focus on maize yield projections in the eastern U.S.in this century. We quantify how considering more uncertainties expands the lower tail of yield projections. We characterized the relative importance of each uncertainty source and show that the uncertainty surrounding yield model parameters is the main driver of yield projection uncertainty.

Metal-Free Halide Perovskite Single Crystals with Very Long Charge Lifetimes for Efficient X-ray Imaging.

Metal-free halide perovskites, as a specific category of the perovskite family, have recently emerged as novel semiconductors for organic ferroelectrics and promise the wide chemical diversity of the ABX3 perovskite structure with mechanical flexibility, light weight, and eco-friendly processing. However, after the initial discovery 17 years ago, there has been no experimental information about their charge transport properties and only one brief mention of their optoelectronic properties. Here, growth of large single crystals of metal-free halide perovskite DABCO-NH4 Br3 (DABCO = N-N'-diazabicyclo[2.2.2]octonium) is reported together with characterization of their instrinsic optical and electronic properties and demonstration, of metal-free halide perovskite optoelectronics. The results reveal that the crystals have an unusually large semigap of ≈16 eV and a specific band nature with the valence band maximum and the conduction band minimum mainly dominated by the halide and DABCO2+ , respectively. The unusually large semigap rationalizes extremely long lifetimes approaching the millisecond regime, leading to very high charge diffusion lengths (tens of µm). The crystals also exhibit high X-ray attenuation as well as being lightweight. All these properties translate to high-performance X-ray imaging with sensitivity up to 173 µC Gyair -1 cm-2 . This makes metal-free perovskites novel candidates for the next generation of optoelectronics.

Mechanical and Tribological Performances Enhanced by Self-Assembled Structures.

Taking inspiration from natural materials, composite materials can be reinforced by creating matrix architectures that can better accommodate and control internal stresses. Despite the recent success in the synthesis of artificial assemblies for local reinforcement through the introduction of oriented fibers and plates into host multilayered composites, there is a lack of fundamental understanding of the factors that determine mechanical properties. Moreover, designing building blocks and interfaces that facilitate higher resistance and energy dissipation is highly challenging. When the intrinsic material is fixed, the mechanical and tribological properties can be further adjusted. In this study, europium oxide nanosheets are arranged in interlocked-junction superstructures that resist sliding at junction points, thereby enhancing the mechanical properties of the nanosheet assemblies compared to those of the conventional face-to-face superstructures formed by parallel nanosheets. Furthermore, the crystalline origin of building blocks is revealed by demonstrating that faulty crystal nanosheets adopting an amorphous structure are different from single-crystal nanosheets, with the former exhibiting superior mechanical reinforcement and improved abrasive resistance.

Publisher Correction: Nucleation-controlled growth of superior lead-free perovskite Cs3Bi2I9 single-crystals for high-performance X-ray detection.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Centimeter-Sized Single Crystal of Two-Dimensional Halide Perovskites Incorporating Straight-Chain Symmetric Diammonium Ion for X-Ray Detection.

Two-dimensional (2D) AA'n-1 Mn X3n+1 type halide perovskites incorporating straight-chain symmetric diammonium cations define a new type of structure, but their optoelectronic properties are largely unexplored. Reported here is the synthesis of a centimeter-sized AA'n-1 Mn X3n+1 type perovskite, BDAPbI4 (BDA=NH3 C4 H8 NH3 ), single crystal and its charge-transport properties under X-ray excitation. The crystal shows a staggered configuration of the [PbI6 ]4- layers, a band gap of 2.37 eV, and a low trap density of 3.1×109  cm-3 . The single-crystal X-ray detector exhibits an excellent sensitivity of 242 µC Gyair -1 cm-2 under the 10 V bias (0.31 V µm-1 ), a detection limit as low as 430 nGyair s-1 , ultrastable response current, a stable baseline with the lowest dark current drift of 6.06×10-9  nA cm-1 s-1 V-1 , and rapid response time of τrise =7.3 ms and τfall =22.5 ms. These crystals are promising candidates for the next generation of optoelectronic devices.

Nucleation-controlled growth of superior lead-free perovskite Cs3Bi2I9 single-crystals for high-performance X-ray detection.

The organic-inorganic hybrid lead halide perovskites have emerged as a series of star materials for solar cells, lasers and detectors. However, the issues raised by the toxic lead element and marginal stability due to the volatile organic components have severely limited their potential applications. In this work, we develop a nucleation-controlled solution method to grow large size high-quality Cs3Bi2I9 perovskite single crystals (PSCs). Using the technique, we harvest some centimeter-sized single crystals and achieved high device performance. We find that X-ray detectors based on PSCs exhibit high sensitivity of 1652.3 µC Gyair-1 cm-2 and very low detectable dose rate of 130 nGyair s-1, both desired in medical diagnostics. In addition, its outstanding thermal stability inspires us to develop a high temperature X-ray detector with stable response at up to 100 °C. Furthermore, PSCs exhibit high X-ray imaging capability thanks to its negligible signal drifting and extremely high stability.

Multi-inch single-crystalline perovskite membrane for high-detectivity flexible photosensors.

Single crystalline perovskites exhibit high optical absorption, long carrier lifetime, large carrier mobility, low trap-state-density and high defect tolerance. Unfortunately, all single crystalline perovskites attained so far are limited to bulk single crystals and small area wafers. As such, it is impossible to design highly demanded flexible single-crystalline electronics and wearable devices including displays, touch sensing devices, transistors, etc. Herein we report a method of induced peripheral crystallization to prepare large area flexible single-crystalline membrane (SCM) of phenylethylamine lead iodide (C6H5C2H4NH3)2PbI4 with area exceeding 2500 mm2 and thinness as little as 0.6 µm. The ultrathin flexible SCM exhibits ultralow defect density, superior uniformity and long-term stability. Using the superior ultrathin membrane, a series of flexible photosensors were designed and fabricated to exhibit very high external quantum efficiency of 26530%, responsivity of 98.17 A W-1 and detectivity as much as 1.62 × 1015 cm Hz1/2 W-1 (Jones).

A 1300 mm2 Ultrahigh-Performance Digital Imaging Assembly using High-Quality Perovskite Single Crystals.

By fine-tuning the crystal nucleation and growth process, a low-temperature-gradient crystallization method is developed to fabricate high-quality perovskite CH3 NH3 PbBr3 single crystals with high carrier mobility of 81 ± 5 cm2 V-1 s-1 (>3 times larger than their thin film counterpart), long carrier lifetime of 899 ± 127 ns (>5 times larger than their thin film counterpart), and ultralow trap state density of 6.2 ± 2.7 × 109 cm-3 (even four orders of magnitude lower than that of single-crystalline silicon wafers). In fact, they are better than perovskite single crystals reported in prior work: their application in photosensors gives superior detectivity as high as 6 × 1013 Jones, ≈10-100 times better than commercial sensors made of silicon and InGaAs. Meanwhile, the response speed is as fast as 40 µs, ≈3 orders of magnitude faster than their thin film devices. A large-area (≈1300 mm2 ) imaging assembly composed of a 729-pixel sensor array is further designed and constructed, showing excellent imaging capability thanks to its superior quality and uniformity. This opens a new possibility to use the high-quality perovskite single-crystal-based devices for more advanced imaging sensors.