benxue liu

Ultrastrong and superstretchable ionogels tougher than that of metals are produced through the synergy of force-induced crystallization and halometallate ionic liquid created supramolecular ionic networks. The prepared ionogels with environmental applicability and sustainability are expected to replace lightweight high-strength materials, such as plastics and rubbers in the applications of aerospace, robotics, and other fields.

Abstract

Common natural and synthetic high-strength materials (such as rubber, plastics, ceramics, and metals) undergo the occurrence of poor deformability. Achieving high strength and large deformation simultaneously is a huge challenge. Herein, high-strength ionogels are developed through the synergy of force-induced crystallization and halometallate ionic liquid created supramolecular ionic networks. The prepared poly(vinyl alcohol)/halometallate ionic liquid ionogels show excellent mechanical properties, including ultimate fracture stress (63.1 ± 2.1 MPa), strain (5248 ± 113%), and unprecedented toughness (1947 ± 52 MJ m⁻³), which is much higher than that of most metals and alloys. Furthermore, the ionogels can achieve reversibility by water to realize green recovery and restoration of damaged mechanical properties.

An ultralight and hyperelastic nanofiber-woven hybrid carbon assembly (NWHCA) is fabricated by nanofiber weaving of isotropic porous and mechanical brittle quasi-aerogels. The 3D-ordered lamella–bridge-structured NWHCA exhibits outstanding electrochemical activity and mechanical elasticity ascribing to the combination of metallogel-derived quasi-aerogel hybridization and nitrogen/phosphorus co-doping. Integrated wearable sensing devices based on NWHCA are demonstrated for detecting sophisticated human motions.

Abstract

The development of a 3D carbon assembly with a combination of extraordinary electrochemical and mechanical properties is desirable yet challenging. Herein, an ultralight and hyperelastic nanofiber-woven hybrid carbon assembly (NWHCA) is fabricated by nanofiber weaving of isotropic porous and mechanical brittle quasi-aerogels. Upon subsequent pyrolysis, metallogel-derived quasi-aerogel hybridization and nitrogen/phosphorus co-doping are integrated into the NWHCA. Finite element simulation indicates that the 3D lamella–bridge architecture of NWHCA with the quasi-aerogel hybridization contributes to resisting plastic deformation and structural damage under high compression, experimentally demonstrated by complete deformation recovery at 80% compression and unprecedented fatigue resistance (>94% retention after 5000 cycles). Due to the superelasticity and quasi-aerogel integration, the zinc–air battery assembled based on NWHCA shows excellent electrochemical performance and flexibility. A proof-of-concept integrated device is presented, in which the flexible battery powers a piezoresistive sensor, using the NWHCA as the air cathode and the elastic conductor respectively, which can detect full-range and sophisticated motions while attached to human skin. The nanofiber weaving strategy allows the construction of lightweight, superelastic, and multifunctional hybrid carbon assemblies with great potential in wearable and integrated electronics.

Nacre-mimetic nanocomposite aerogels featuring a “porous brick and fiber” architecture are fabricated via in situ nanoscale hetero-assembly and ambient pressure drying, in which mesoporous minerals are generated in a lamellar cellulose nanofibrous network. The aerogels integrate challenging requirements of thermal superinsulation, excellent compressive stiffness, superelasticity, high bending flexibility, good impact resistance, and easy scalability for robust thermal management under extreme conditions.

Abstract

Thermal protection under extreme conditions requires materials with excellent thermal insulation properties and exceptional mechanical properties to withstand a variety of complex external stresses. Mesoporous silica aerogels are the most widely used insulation materials due to their ultralow thermal conductivity. However, they still suffer from mechanical fragility and structural instability in practical applications. Herein, a nacre-mimetic nanocomposite aerogel, synthesized via in situ growth of inorganic minerals in a lamellar cellulose nanofibrous network, is reported. The multiscale structural adaptation of the inorganic–organic components endows nanocomposite aerogels with rapid configuration recovery during ambient pressure drying. The resulting aerogels show ultralow thermal conductivities (17.4 mW m⁻¹ K⁻¹ at 1.0 atm). These aerogels also integrate challenging mechanical properties, including high compressive stiffness to resist deformation under the pressure of an adult, superelasticity to prevent static and dynamic stress cracking even under the crushing of a vehicle (1.6 t), and high bending flexibility to adapt to any surface. Moreover, they exhibit excellent structural stability under fatigue stress/strain cycles over a wide temperature range (−196 to 200 °C). The combination of high thermal insulation performance and excellent mechanical properties offers a potential material system for robust thermal superinsulation under extreme conditions, especially for aerospace applications.

In combination with in situ liquid time-of-flight secondary ion mass spectrometry, the assembly behavior of organic cations involved in perovskite frameworks is visualized by investigating the precursor species. The feasibility of modulating the quantum wells structure for the fabrication of low-dimensional perovskite photovoltaics is further verified.

Abstract

The multiple quantum wells (QWs) distribution in low-dimensional perovskite films hinders charge transport due to the fundamental difficulty of controlling crystal growth from precursor solutions, yielding poorly homogeneous low-dimensional perovskite solar cells (PSCs), especially in upscaling fabrication. Here, efficient low-dimensional PSCs are realized by modulating the colloidal assembly behavior in the precursor solution to induce intermediate structures. In combination with in situ liquid time-of-flight secondary ion mass spectrometry, the assembly behavior of organic cations involved lead iodide-dominated colloidal soft framework is visualized by investigating the precursor species differences under hydrogen bonding interactions. Subsequently, solid-state reactions emerge and the formamidine (FA)-based perovskite films exhibit significantly suppressed multiple QWs distribution. Encouragingly, the FA device (n=9, by meniscus-assisted coating) achieves a power conversion efficiency (PCE) of 20.28 % for a size of 0.04 cm² and a PCE of 15.35 % for a mini-module of 16.94 cm² with superior stability.

A long-focus thermal lens with equivalent negative thermal conductivity is designed and experimentally realized to achieve a remote heating/cooling effect. The thermal lens consists of active thermal metasurfaces, which are constructed by p/n-type semiconductor pairs driven by a DC power supply. The proposed method can also achieve other novel thermal effects, such as thermal superlens and thermal tunneling effects.

Abstract

Remote temperature control can be obtained by a long-focus thermal lens that can focus heat fluxes into a spot far from the back surface of the lens and create a virtual thermal source/sink in the background material, around which the temperature field distribution can be remotely controlled by varying the parameters of the thermal lens. However, because of the lack of negative thermal conductivity, existing thermal lenses have extremely short focal lengths and cannot be used to remotely control the temperature field around the virtual thermal source/sink. In this study, a general approach is proposed to equivalently realize materials with negative thermal conductivity using elaborately distributed active thermal metasurfaces (ATMSs). Subsequently, the proposed ATMS is used to implement a novel thermal lens with a long focal length designed using transformation thermodynamics, and finally realize the ATMS with realistic materials and experimentally verify the performance of the designed long-focus thermal lens (measured focal length of 19.8 mm) for remote heating/cooling. The proposed method expands the scope of the thermal conductivity and provides new pathways to realize unprecedented thermal effects with effective negative thermal conductivity, such as “thermal surface plasmon polaritons,” a thermal superlens, the thermal tunneling effect, and the thermal invisible gateway.

A new chemical mechanism for the generation of gaseous N₂O₅ in atmosphere via the photocatalytic oxidation of NO₂ on TiO₂ is shown, and this new source of N₂O₅ may have important implications to the near-ground air quality in urban areas and day time due to the presence of both abundant TiO₂-containing building materials and high NO_x concentrations.

Abstract

N₂O₅ is an important intermediate in the atmospheric nitrogen cycle. Using a flow tube reactor, N₂O₅ was found to be released from the TiO₂ surface during the photocatalytic oxidation of NO₂, revealing a previously unreported source of N₂O₅. The rate of N₂O₅ release from TiO₂ was dependent on the initial NO₂ concentration, relative humidity, O₂/N₂ ratio, and irradiation intensity. Experimental evidence and quantum chemical calculations showed that NO₂ can react with the surface hydroxyl groups and the generated electron holes on the TiO₂, followed by combining with another NO₂ molecule to form N₂O₅. The latter was physisorbed on TiO₂ and had a low adsorption energy of −0.13 eV. Box model simulations indicated that the new source of N₂O₅ released from TiO₂ can increase the daytime N₂O₅ concentration by up to 20 % in urban areas if abundant TiO₂-containing materials and high NOx concentrations were present. This joint experimental/theoretical study not only demonstrates a new chemical mechanism for N₂O₅ formation but also has important implications for air quality in urban areas.

Nature Materials, Published online: 13 April 2023; doi:10.1038/s41563-023-01508-1

Alternative solid electrolytes with enhanced thermal and chemical stability are key for advancing lithium batteries. A soft solid electrolyte with improved stability and ionic conductivity, overcoming several limitations of conventional materials, is now reported.

Low-dose integrated differential phase-contrast scanning transmission electron microscopy (iDPC-STEM) enables visualization of oxygen shifting during polarization switching and correlated polar–nonpolar phase transitions among multiple metastable phases in ZrO₂ nanocrystals. Bidirectional transitions between antiferroelectric and ferroelectric orders and interfacial polarization relaxation are clarified at unit-cell scale. Meanwhile, polarization switching is strongly correlated with polar–nonpolar phase transitions among O/M/T phases.

Abstract

Unconventional ferroelectricity in fluorite-structure oxides enables tremendous opportunities in nanoelectronics owing to their superior scalability and silicon compatibility. However, their polarization order and switching process remain elusive due to the challenges of visualizing oxygen ions in nanocrystalline films. In this work, the oxygen shifting during polarization switching and correlated polar–nonpolar phase transitions are directly captured among multiple metastable phases in freestanding ZrO₂ thin films by low-dose integrated differential phase-contrast scanning transmission electron microscopy (iDPC-STEM). Bidirectional transitions between antiferroelectric and ferroelectric orders and interfacial polarization relaxation are clarified at unit-cell scale. Meanwhile, polarization switching is strongly correlated with Zr–O displacement in reversible martensitic transformation between monoclinic and orthorhombic phases and two-step tetrahedral-to-orthorhombic phase transition. These findings provide atomic insights into the transition pathways between metastable polymorphs and unravel the evolution of polarization orders in (anti)ferroelectric fluorite oxides.

By ab-initio molecular dynamics simulations we show that the CeO₂(100) surface, despite its strongly hydrophilic nature, exhibits hydrophobic behaviour when immersed in water. This effect is induced by the first water layer that is in immediate contact with the hydroxylated CeO₂(100) surface, and it is manifested by a measurable water contact angle and a considerable diffusion enhancement of the confined liquid water as compared with bulk water.

Abstract

The nature of the hydrophobicity found in rare-earth oxides is intriguing. The CeO₂ (100) surface, despite its strongly hydrophilic nature, exhibits hydrophobic behaviour when immersed in water. In order to understand this puzzling and counter-intuitive effect we performed a detailed analysis of the confined water structure and dynamics. We report here an ab-initio molecular dynamics simulation (AIMD) study which demonstrates that the first adsorbed water layer, in immediate contact with the hydroxylated CeO₂ surface, generates a hydrophobic interface with respect to the rest of the liquid water. The hydrophobicity is manifested in several ways: a considerable diffusion enhancement of the confined liquid water as compared with bulk water at the same thermodynamic condition, a weak adhesion energy and few H-bonds above the hydrophobic water layer, which may also sustain a water droplet. These findings introduce a new concept in water/rare-earth oxide interfaces: hydrophobicity mediated by specific water patterns on a hydrophilic surface.

Hype in science is commonplace, compounded by the hypocrisy of those who engage in or tolerate it while disapproving of the consequences. These are first steps along a slippery slope of hype, hypocrisy, data falsification, and dissemination of fake science, encouraged by systemic drivers in the contemporary structure of the science establishment. Collective, concerted intervention is required to discourage entry to this dangerous pathway; chemists must play an active role.

Abstract

In chemistry and other sciences, hype has become commonplace, compounded by the hypocrisy of those who tolerate or encourage it while disapproving of the consequences. This reduces the credibility and trust upon which all science depends for support. Hype and hypocrisy are but first steps down a slippery slope towards falsification of results and dissemination of fake science. Systemic drivers in the contemporary structure of the science establishment encourage exaggeration and may lure the individual into further steps along the hype‐hypocrisy‐falsification‐fakery continuum. Collective, concerted intervention is required to effectively discourage entry to this dangerous pathway and to restore and protect the probity and reputation of the science system. Chemists must play and active role in this effort.