Materials Horizons最新文献

Given extremely high porosity, aerogels have demonstrated remarkable advantages in serving as thermal insulation and wave-transparent materials. Unfortunately, their practical applications are greatly confined by their inherent fragility. The recent emergence of polymer aerogels presents an ideal platform for the development of flexible aerogel films. However, additional cross-linking agents are necessitated for constructing a robust structure, complicating the production process. Herein, we report a flexible aerogel film based on meta-aramid composites, inspired by the porous structure of penguin feathers. The intermolecular hydrogen bonds function as natural cross-linking agents. Their disruption results in the dissolution of meta-aramid fibers, while their reconstruction facilitates localized rearrangement of meta-aramid chains during the sol-gel process, generating closed nanopores. Furthermore, fluorinated hollow glass microspheres are filled, compressing the nanopores situated near the interface to 75-150 nm. This meets the critical threshold required by the Knudsen effect, decreasing the thermal conductivity to levels below that of ambient air. At an optimized doping ratio of 3 wt%, the thermal conductivity is 21.6 mW m^-1 K^-1, while achieving a low dielectric constant of 1.43. Simultaneously, aerogel films exhibit enhanced mechanical properties, and also show benefits of hydrophobicity, colorability, ultralightness, and flame retardancy, making themselves multifunctional materials suitable for practical applications.

Stretchable electromagnetic interference (EMI) shields with strain-insensitive EMI shielding and Joule heating performances are highly desirable to be integrated with wearable electronics. To explore the possibility of applying geometric design in elastomeric liquid metal (LM) composites and fully investigate the influence of LM geometry on stretchable EMI shielding and Joule heating, multifunctional wrinkle-structured LM/Ecoflex sandwich films with excellent stretchability are developed. The denser LM wrinkle enables not only better electrical conduction, higher shielding effectiveness (SE) and steady-state temperature, but also enhanced strain-stable far-field/near-field shielding performance and Joule-heating capability. More strikingly, compared to most previously reported stretchable EMI shields or electric heaters, the densely wrinkled film could achieve multidirectional strain-insensitive shielding behavior with slightly strain-enhanced or strain-invariant EMI SE under stretching parallel or perpendicular to the electric field of EM waves, as well as show ideal strain-insensitive Joule-heating behavior over a larger strain range of 250%. The current findings suggest an effective strategy for developing stretchable LM-based composites with strain-insensitive properties.

Circularly polarized luminescence (CPL) materials have developed rapidly in recent years due to their wide application prospects in fields like 3D displays and anti-counterfeiting. Utilizing energy transfer processes to transfer chirality has been proven as an efficient way to obtain CPL materials. However, the physics behind energy-transfer induced CPL is still not clear. Herein, in a well-designed heteronuclear Ce^III-Mn^II complex system [(Ce((R/S)-L)Br(μ-Br))₂]MnBr₄ [(R/S)-L = (2R,3R)- or (2S,3S)-2,3-dimethyl-1,4,7,10,13,16-hexaoxacyclooctadecane] with intra energy transfer from Ce^III to Mn^II, the luminescence dissymmetry factor of Mn^II obtained by excitation of Ce^III is around 10 times higher than that obtained by direct excitation of Mn^II, while the Ce^III center itself shows an almost negligible CPL. To address this unusual phenomenon, we proposed a new mechanism named structural relaxation chirality transfer (SRCT) where structural relaxation of the excited chiral donor amplified chirality transfer to the acceptor by intramolecular interactions. As an assistant proof, a mixture of Ce^III-Zn^II and La^III-Mn^II complexes with inter energy transfer showed no CPL amplification. These results will inspire more breakthroughs in the physics nature and development of energy-transfer induced CPL.

Adhesion-switchable ultralow-hysteresis polymer ionogels are highly demanded in soft electronics to avoid debonding damage and signal distortion, yet the design and fabrication of such ionogels are challenging. Herein, we propose a novel method to design switchable adhesive ionogels by using binary ionic solvents with two opposite-affinity ionic components. The obtained ionogels exhibit moisture-induced phase separation, facilitating switchable adhesion with a high detaching efficiency (>99%). Moreover, before and after phase separation, the viscoelastic behavior of the ionogels is maintained in the rubbery plateau region within common frequency ranges with ultralow mechanical hysteresis (∼3%) under large strain, enabling accurate and stable strain and pressure sensing. Accordingly, the ionogel films can be used as functional elements in a smart clamp to realize flytrap-like selective activation, based on high sensitivity to the vibration intensity from the targeted prey. This work may inspire future research on the development of advanced soft electronics.

Flexible hydrogel sensors have found extensive applications. However, the insufficient sensing sensitivity and the propensity to freeze at low temperatures restrict their use, particularly in frigid conditions. Herein, a multifunctional eutectogel with high transparency, anti-freezing, anti-swelling, adhesive, and self-healing properties is prepared by a one-step photopolymerization of acrylic acid and lauryl methacrylate in a binary solvent comprising water and deep eutectic solvent (DES). The results from the molecular dynamics simulations and density functional theory indicate that the hydrogen bonds between DES and water mixtures possess better stability than those between water molecules. On the other hand, DES breaks down hydrogen bonds in water, providing eutectogels with excellent anti-freezing even at -60 °C. Cetyltrimethylammonium bromide is incorporated to establish stable hydrophobic interactions and electrostatic attractions with polymer chains in the eutectogel network, resulting in superior mechanical (elongation at break of 2890%) and anti-swelling (only 2% swelling in water over 7 days) properties. The eutectogel-based strain sensors exhibit remarkable sensitivity, achieving a gauge factor of up to 15.4. The multifunctional eutectogel sensors can monitor motion and transmit encrypted information at low temperatures, demonstrating considerable potential for applications in flexible electronics within low-temperature environments.

Silver-based fast ionic conductors show promising potential in thermoelectric applications. Among these, Ag₂S offers unique high plasticity but low electrical conductivity, whereas Ag₂Te exhibits high intrinsic electrical conductivity yet faces limitations due to high thermal conductivity and poor plasticity. Developing a composite thermoelectric material that combines the benefits of both is therefore essential. Here, this study reports the successful synthesis of Ag₂Te/Ag₂S composites via a facile and low-cost solvothermal method. By finely adjusting the composition of Ag₂S and Ag₂Te to obtain the optimized carrier concentration and the enhanced mobility, the figure of merit ZT of Ag₂Te/Ag₂S composites reached ∼0.42 at 373 K and ∼0.38 at 298 K, both surpassing those of pure Ag₂S and Ag₂Te. This increase in ZT also benefits from lattice defects created by the solvothermally synthesized biphasic composition, effectively scattering phonons of various wavelengths and reducing thermal conductivity compared to pure Ag₂Te. Additionally, the plasticity of the Ag₂Te/Ag₂S composites improved considerably over pure Ag₂Te, achieving a bending strain of ∼2.5% (versus ∼1.2% for intrinsic Ag₂Te). This study can fill a critical gap in the research on composite silver-based fast ionic conductors synthesized via wet chemical methods and provide valuable guidance for future exploration.

The semi-hydrogenation of alkynes into alkenes rather than alkanes is of great importance in the chemical industry, and palladium-based metallic catalysts are currently employed. Unfortunately, a fairly high cost and uncontrollable over-hydrogenation impeded the application of Pd-based catalysts on a large scale. Herein, a sandwich structure single atom Pd catalyst, Z@Pd@Z, was prepared via impregnation exchange and epitaxial growth methods (Z stands for ZIF-8), in which Pd single atoms were stabilized by pyrrolic N in a zeolitic imidazolate framework (ZIF-8). Semi-hydrogenation of acetylene was performed and Z@Pd@Z achieved 100% acetylene conversion at 120 °C with an ethylene selectivity of more than 98.3% at an extra low Pd concentration. Z@Pd@Z exhibited a specific activity of 1872.69 mL_C2H4 mg_Pd^-1 h^-1, surpassing most of the reported Pd-based catalysts. The existence of Pd single atoms coordinated by nitrogen (Pd-N₄) was verified by XAS (synchrotron X-ray absorption spectroscopy), which provided active sites for H₂ dissociation and the dissociated hydrogen quickly spilled over the surface of the outer ZIF layer to hydrogenate alkyne to ethene; besides, the catalytic activity could be controlled by adjusting the thickness of the outer ZIF layer. The confinement of the ZIF on Pd single-atom sites and the high energy barrier of ethylene hydrogenation were found to be responsible for the superior C₂H₂ semi-hydrogenation activity. This work opens up valuable insights into the design of ZIF-derived single-atom catalysts for efficient acetylene selective hydrogenation.

In such an era of information explosion, improving the level of information security is still a challenging task. Self-erasing luminescent hydrogels are becoming ideal candidates for improving the level of information security with simple encryption and decryption methods. Herein, a lanthanide-polyoxometalate-based self-erasing luminescent hydrogel with time-dependent and resilient properties was constructed through a covalent crosslinked network constructed with polyacrylamide and a non-covalent crosslinked network constructed with [2-(methacryloyloxy)ethyl]trimethyl ammonium chloride/Na₉DyW₁₀O₃₆, along with doping urease. This acquired hydrogel exhibited reversible luminescence switching properties in the presence of HCl-urea mixed solution. At the same time, obvious changes in the luminescence intensity can be seen on the timescale by modulating the concentrations of HCl and urea/urease. Based on this, the information loaded onto the hydrogel by using a HCl-urea mixed solution self-erased over time, leading to misinformation during this process. The real information can only be recognized at a specific time. Moreover, the information is self-erased permanently, which can avoid secondary leakage of information. In addition, the hydrogel has excellent resilience. The information can be loaded in the stretched state of the hydrogel, resulting in the information only being recognized in the re-stretched state of the hydrogel while the information cannot be recognized in the normal state of the hydrogel. The combination of time-dependent and resilient properties of the hydrogel can further improve the level of information security effectively. This self-erasing luminescent hydrogel with time-dependent and resilient properties has great potential in improving the security of information encryption.

Linearly-polarized organic electroluminescent devices have gained significant attention due to their potential applications across various fields. However, traditional thin-film organic light-emitting diodes (OLEDs) face significant challenges, primarily due to the necessity of incorporating complex optical elements. In this study, we present linearly-polarized OLEDs (LP-OLEDs) based on organic single crystals that we have designed and prepared. These devices exhibit a degree of polarization (DOP) of up to 0.96 for photoluminescence and 0.95 for electroluminescence, values that are close to the ideal linearly-polarized light (DOP = 1). The LP-OLEDs demonstrate outstanding performance, with a low turn-on voltage of just 2.5 volts, an exceptionally high brightness of 200 000 cd m^-2, and a current density surpassing 300 A cm^-2. This is the best overall performance reported for single crystal-based OLEDs to date. These results open the door to the development of next-generation, low-power consumption displays, marking a significant step forward in the field of organic single crystal-based LP-OLEDs.

The porous polymer is a common and fascinating category within the vast family of porous materials. It offers valuable features such as sufficient raw materials, easy processability, controllable pore structures, and adjustable surface functionality by combining the inherent properties of both porous structures and polymers. These characteristics make it an effective choice for designing functional and advanced materials. In this review, the structural features, processing techniques and application fields of the porous polymer are discussed comprehensively to present their current status and provide a valuable tutorial guide and help for researchers. Firstly, the basic classification and structural features of porous polymers are elaborated upon to provide a comprehensive analysis from a mesoscopic to macroscopic perspective. Secondly, several established techniques for fabricating porous polymers are introduced, including their respective basic principles, characteristics of the resulting pores, and applied scopes. Thirdly, we demonstrate application research of porous polymers in various emerging frontier fields from multiple perspectives, including pressure sensing, thermal control, electromagnetic shielding, acoustic reduction, air purification, water treatment, health management, and so on. Finally, the review explores future directions for porous polymers and evaluates their future challenges and opportunities.