Ratio-Tuning of Silica Aerogel Co-Hydrolyzed Precursors Enables Broadband,Angle-Independent,Deformation-Tolerant,Achieving 99.7% Reflectivity

The super-white body might be defined as its reflectivity exceeding 98% at any angle in the visible light spectrum, which can be used in a variety of emerging fields including optics, energy, environment, aerospace, etc. However, elaborate synthesis of a light-weight, highly reflective super-white aerogel body remains a great challenge. In this work, fine-tuning of silica aerogel co-hydrolyzed precursor ratios, 99.7% reflectivity with angle-independence in the visible light spectrum has been successfully achieved when the areal density is only 0.129 g cm⁻², which breaks through the theoretical bandwidth limit of photonic crystals as well as the measured reflectivity limit of conventional porous materials. Furthermore, the reflectivity of super-white silica aerogel remains unchanged after various harsh deformations including compression and bending 1000 times, solar (≈800 W m⁻²), ultraviolet (≈0.68 W m⁻²), and humidity (100%) aging for 100 days, liquid nitrogen (−196 °C) and high-temperature (300 °C) thermal shock 100 times. As proofs of performance, the resulting super-white silica aerogels have been used as the novel standard white plate  for better spectrum calibration, as the flexible projector curtains for optical display, as well as the transmitted light reflective layer in the photovoltaic cell for improving the relative power conversion efficiency of 5.6%.     

Self-Intercalated Magnetic Heterostructures in 2D Chromium Telluride

Emerging 2D magnetic heterojunctions attract substantial interest due to their potential applications in spintronics. Achieving magnetic phase engineering with structural integrity in 2D heterojunctions is of paramount importance for their magnetism manipulation. Herein, starting with chromium ditelluride (CrTe₂) as the backbone framework, various lateral and vertical magnetic heterojunctions are obtained via self-intercalated 2D chromium telluride (Cr_xTe_y). A Cr₂Te₃-Cr₅Te₈ lateral heterojunction prototype is demonstrated for the manipulation of magnetic moments under different magnitudes of magnetic excitation, showing a sharply stepped hysteresis loop with a dual spin-flip transition at high Curie temperatures up to 150 and 210 K by magneto-optical Kerr measurement. High-resolution scanning transmission electron microscopy and first-principles calculations reveal a preferred random location of Cr intercalants at the phase boundary, allowing lowering energy associated with crystal field splitting. The overall structural rigidity of chromium-telluride heterostructure with magnetic phase decoupled behaviors is promising for 2D spintronic devices.     

Ionic strength directed self-assembled polyelectrolyte single-bilayer membrane for low-pressure nanofiltration

Layer-by-layer assembly is a versatile technique for fabricating nanofiltration membranes, where multiple layers of polyelectrolytes are usually required to achieve reasonable separation performance. In this work, an ionic strength directed self-assembly procedure is described for the preparation of nanofiltration membranes consisting of only a single bilayer of poly(diallyldimethylammoniumchloride) and poly(sodium-4-styrenesulfoate). The influence of background ionic strength as well as membrane substrate properties on the formation of single-bilayer membranes are systematically evaluated. Such a simplified polyelectrolyte deposition procedure results in membranes having outstanding separation performance with permeating flux of 14.2 ± 1.5 L∙m^–2∙h^–1∙bar^–1 and Na₂SO₄ rejection of 97.1% ± 0.8% under a low applied pressure of 1 bar. These results surpass the ones for conventional multilayered polyelectrolyte membranes. This work encompasses an investigation of ionic strength induced coiling of the polyelectrolyte chains and emphasizes the interplay between-polyelectrolyte chain configuration and substrate pore profile. It thus introduces a new concept on the control of membrane fabrication process toward high performance nanofiltration.     

Elimination of Drying-Dependent Component Deviation Using a Composite Solvent Strategy Enables High-Performance Inkjet-Printed Organic Solar Cells with Efficiency Approaching 16%

Inkjet printing (IJP) is a roll-to-roll (R2R) compatible fabrication method for large-area organic solar cells (OSCs). Unlike the coating process, the films are formed through droplet leveling and merging during IJP, and the pre-deposited droplets are partly dissolved by the subsequent droplets. Such a process yields undesired printing pattern lines, especially in large-area printed films. This study reveals that such a temperature-dependent “drying lines-related” phase separation morphology has caused component variation in the organic blend films, which leads to an obvious inhomogeneity of photocurrent in the printed OSCs. Such a phenomenon is attributed to the solubility difference between organic donor and acceptor molecules in the main printing solvent. A composite solvent strategy of ortho-dichlorobenzene (oDCB)/trimethylbenzene (TMB) and tetralin (THN) is developed to solve this problem. The introduction of THN suppresses the formation of printing drying lines during high-temperature printing due to the preferential miscibility of acceptor in THN, leading to the efficiency improvement to 13.96% and 15.78% for the binary and ternary devices. In addition, the 1 cm² device with a disruptive pattern gives an efficiency of 12.80% and a certificated efficiency of 12.18%.     

A Near-Surface Structure Reconfiguration Strategy to Regulate Mn3+/Mn4+ and O2−/(O2)n− Redox for Stabilizing Lithium-Rich Oxide Cathode

Lithium-rich layered oxides (LROs) are one class of the most competitive high-capacity cathode materials due to their anion/cation synergistic redox activity. However, excessive oxidation of the oxygen sublattices can induce serious oxygen loss and structural imbalance. Hence, a near-surface reconfiguration strategy by fluorinating graphene is proposed to precisely regulate Mn³⁺/Mn⁴⁺ and O²⁻/(O₂)ⁿ⁻ redox couples for remarkably stabilizing high-capacity LROs and realizing the simultaneous reduction of the lattice stress, regulation of the Mn metal at a lower charge state, and construction of 3D Li⁺ diffusion channels. Combining with a highly conductive graphene-coating layer, the surface oxygen loss, transition metal dissolution, and electrolyte catalytic decomposition are suppressed. Benefiting from this synergy, the modified LROs disclose higher initial Coulombic efficiency and discharge-specific capacity and improve cyclability compared with pristine LROs. Further, it is revealed that the F⁻ impact becomes easier for the O sites at the lattice interface of C2/m and R$\overline{3}$m to sufficiently buffer lattice stress. Moreover, lithium ions coupled to the doped F atoms at the lattice interface migrate to the Ni-rich R$\overline{3}$m lattice sites with lower migration energies. This consolidated understanding will open new avenues to regulate reversible oxygen redox of LROs for high-energy-density lithium-ion batteries.     

Achieving Synergetic Anion-Cation Redox Chemistry in Freestanding Amorphous Vanadium Oxysulfide Cathodes toward Ultrafast and Stable Aqueous Zinc-Ion Batteries

Flexible aqueous zinc-ion batteries (AZIBs) with high safety and low cost hold great promise for potential applications in wearable electronics, but the strong electrostatic interaction between Zn²⁺ and crystalline structures, and the traditional cathodes with single cationic redox center remain stumbling blocks to developing high-performance AZIBs. Herein, freestanding amorphous vanadium oxysulfide (AVSO) cathodes with abundant defects and auxiliary anionic redox centers are developed via in situ anodic oxidation strategy. The well-designed amorphous AVSO cathodes demonstrate numerous Zn²⁺ isotropic pathways and rapid reaction kinetics, performing a high reversible capacity of 538.7 mAhg^-1 and high-rate capability (237.8 mAhg^-1@40Ag^-1). Experimental results and theoretical simulations reveal that vanadium cations serve as the main redox centers while sulfur anions in AVSO cathode as the supporting redox centers to compensate local electron-transfer ability of active sites. Significantly, the amorphous structure with sulfur chemistry can tolerate volumetric change upon Zn²⁺/H⁺ insertion and weaken electrostatic interaction between Zn²⁺ and host materials. Consequently, the AVSO composites display alleviated structural degradation and exceptional long-term cyclability (89.8% retention after 20 000 cycles at 40 Ag^-1). This work can be generally extended to various freestanding amorphous cathode materials of multiple redox reactions, inspiring development of designing ultrafast and long-life wearable AZIBs.     

Time temperature indicators made with sublimating azulene derivatives as the functional dye for use of fast reaction rate

Time temperature indicators (TTIs) based on a dye sublimation process have been developed for full time monitoring of heat sensitive vaccines with shorter shelf-life during cold chain transportation and storage. The structure of TTI and the methods to make the TTI are introduced. TTI 1 and TTI 2 introduced in the article were made with methyl azulene-1-carboxylate and methyl 3-methylazulene-1-carboxylate as the functional dyes, respectively. The kinetic parameters of TTI 1 and TTI 2 were studied. To achieve a change of 30 in ∆E*ab, it takes 9.1 h at 37°C, 39.7 h at 25°C, 5.61 days at 15°C and 23.3 days at 5°C for TTI 1 and 37.2 h at 37°C, 128.8 h at 25°C, 37.5 days at 15°C and 102.5 days at 5°C for TTI 2. The activation energies (E_a) are calculated to be 91.87 kJ mol⁻¹ and 97.99 kJ mol⁻¹ for TTI 1 and TTI 2, respectively. A field simulation study was conducted on TTI 2 associated with bivalent oral polio vaccine (bOPV), yielding excellent correlation between the reaction rate of TTI 2 and the titre change of bOPV.     

Super-White Boron Nitride Aerogel-Enabled High-Energy Laser Irradiation Protection

Aerogels are ultralight solid materials with three-dimensional interconnected porous structures that offer considerable advantages for various protective applications. Lasers have led to various technological revolutions in aerospace, medical science, and industrial manufacturing. However, shielding against high-energy laser irradiation using aerogels has rarely been reported. A super-white (reflectivity >98%) boron nitride (BN) aerogel constructed using BN nanoribbons is developed in this study for high-energy laser protection. Large numbers of BN nanoribbons serve as randomized and disordered optical nanobarriers for intense backlight scattering, which contribute to high broadband reflectivity. Combined with the low thermal conductivity of the aerogel structure and the excellent high-temperature stability of BN, the resulting BN aerogel exhibits a high protective threshold of 2.1 × 10⁴ W cm⁻². Moreover, the BN aerogel possesses a soft porous network and a low thermal expansion coefficient, which is promising for tolerating the thermal stress and shock of local high-temperature fields caused by laser irradiation. The successful laser shielding by the super-white BN aerogel may be helpful for designing and fabricating advanced aerogel-based lightweight anti-laser materials.