Materials Horizons最新文献

Graphite (Gr) is the predominant anode material for current lithium-ion technologies. The Gr anode could offer a practical pathway for the development of lithium-sulfur (Li-S) batteries due to its superior stability and safety compared to Li-metal. However, Gr anodes are not compatible with the conventional dilute ether-based electrolytes typically used in Li-S systems. Here, an optimized ether electrolyte is presented, utilizing 1 M lithium bis(trifluoromethanesulfonyl)-imide (LiTFSI) in 1,3-dioxolane (DOL)/1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropylether (TTE). Without altering the salt concentration, this electrolyte regulates the solvation structure and promotes the formation of a robust solid-electrolyte interphase (SEI) layer, leading to a significant improvement in the cyclability of Gr anodes. Meanwhile, the DOL/TTE electrolyte maintains adequate kinetics for the sulfur cathode, enabling its pairing with Gr anodes without any cathode modification. The cell with a Gr anode delivers a reversible discharge capacity of 515 mA h g^-1 after 400 cycles at C/10 rate, in contrast to only 143 mA h g^-1 for the Li-metal anode cell. Moreover, a Gr || Li₂S full cell with a negative-to-positive capacity (N/P) ratio of 1.05 and a Li₂S loading of 3 mg cm^-2 shows a stable 58% capacity retention after 400 cycles.

The stabilization of metal-oxide-bound molecular catalysts is essential for enhancing their lifetime and commercial viability in heterogeneous catalysis. This is particularly relevant in dye-sensitized photoelectrochemical cells (DSPECs), where the surface-bound chromophores and catalysts exhibit instability in aqueous environments, particularly at elevated pH levels. In this work, we have successfully employed molecular layer deposition (MLD) to stabilize ruthenium-based catalysts (RuCP(OH₂)²⁺, denoted as RuCat). The application of polyimide (PI) via MLD onto the porous nanoITO surface significantly improved the stabilization of RuCat molecules for water oxidation. Additionally, time-resolved photoluminescence (TRPL) spectroscopy and femtosecond transient absorption spectroscopy (fs-TAS) results indicated that the MLD-deposited PI effectively preserved the robust redox capacity of the photogenerated electron-hole pairs associated with the catalyst molecules, thereby facilitating more efficient charge transfer. This research presents a novel approach for stabilizing surface-bound small molecules, which may contribute to advancements in heterogeneous catalysis and enhance its commercial viability.

While the accessible pores render an enormous variety of functionalities to the bulk of metal-organic frameworks (MOFs), the outer surfaces exposed by these crystalline materials also offer unique characteristics not available when using conventional substrates. By grafting hydrocarbon chains to well-defined MOF thin films (SURMOFs) prepared using layer-by-layer methods, we were able to fabricate superhydrophobic substrates with static water contact angles over 160°. A detailed theoretical modelling of the hydrocarbon chains grafted on the outer SURMOF surface with well-defined spacing between anchoring points reveals that the grafted hydrocarbon chains behave similarly to polymer brushes during wetting, where conformational entropy is traded with mixing entropy. The chains are coiled and can access many different conformations, as evidenced directly by infrared spectroscopy. The entropic contributions from the coiled state lead to a pronounced reduction of the surface free energy, rendering superhydrophobic properties to the functionalized SURMOFs. On the other side, the water adhesion strength could be decreased by increasing the surface roughness on the nanometer scale.

Using mechanical force to induce chemical reactions with two-dimensional (2D) materials provides an approach for both understanding mechanochemical processes on the molecular level, and a potential method for using mechanical strain as a means of directing the functionalization of 2D materials. To investigate this, we have designed a modular experimental platform which allows for in situ monitoring of reactions on strained graphene via Raman spectroscopy as a function of time. Both the strain present in graphene and the corresponding chemical changes it undergoes in the presence of a reagent can be followed concomitantly. As a case study, we have experimentally monitored and theoretically modeled the reactivity of a suspended single-layer graphene membrane under strain with water, where the graphene is strained via an applied backing pressure. While exposure of the unstrained membrane to water does not drive a chemical reaction, distortion of the membrane causes a rise in the I_D/I_G peak ratio, indicating an initial lattice conversion from crystalline to nanocrystalline due to reaction with water. With continued reaction, a decrease in the I_D/I_G peak ratio is then seen, indicative of a nanocrystalline to amorphous lattice transition. Using density functional theory (DFT) calculations, the reaction of water on graphene has been determined to be nucleated by epoxide defects, with the reaction barrier decreasing by nearly 5× for the strained vs. unstrained graphene. While demonstrated here for graphene, this approach also provides the opportunity to examine a host of force-driven chemical reactions with 2D materials.

The design of fast, endurant, and biocompatible porous frameworks with solvatochromism, aimed to addressing the multiple visual sensing of chemicals, still remains a challenge. Here, we report on a solvatochromic metal-organic framework (MOF) based on cobalt and trimesic acid. We examined its solvatochromism through the solvent exchange and revealed high selectivity to water/dimethylformamide combination. The color change over 50 cycles during the solvent exchange occurs for 0.1 s, being 2 orders of magnitude faster than for existing MOFs. Despite the cobalt content, toxicity assays in vivo and in vitro revealed high biocompatibility of the MOF. The latter allowed implementing the fastest, highly-endurant and biocompatible MOF-based visual sensor of humidity in a desiccator for storage of water-sensitive goods and chemicals. Finally, for such a sensor, we demonstrated its multiple uses through remote light-driven recovery that contributes to the sustainability of this functional MOF.

Sulfide solid-state electrolytes (SSSEs) have garnered overwhelming attention as promising candidates for high-energy-density all-solid-state sodium batteries (ASSSBs) due to their high room-temperature ionic conductivity and excellent mechanical properties. However, the poor chemical/electrochemical stability, narrow electrochemical windows, and limited adaptability to cathodes/anodes of SSSEs hinder the performance and application of SSSEs in ASSSBs. Consequently, a comprehensive understanding of the preparation methods, fundamental properties, modification techniques, and compatibility strategies between SSSEs and electrodes is crucial for the advancement of SSSE-based ASSSBs. This review summarizes the SSSEs based on their compositional makeup and crystal structure, aiming to elucidate the Na⁺ conduction mechanisms. It also provides an overview of modification strategies designed to enhance ionic conductivity, chemical/electrochemical stability, and interfacial compatibility with electrodes. Furthermore, we outline the challenges and strategies related to the interfaces of SSSEs with cathodes/anodes. Finally, we discuss the existing challenges facing SSSEs and propose the future research directions for SSSE-based ASSSBs.

Electrothermal-driven polymer fiber-based artificial muscles with helical or twisted structures are promising due to their low cost and high energy density output. However, the current cooling methods for these muscles, such as natural cooling or cold-liquid baths, limit their actuation frequency, especially for large-diameter artificial muscles, posing a technical barrier to their broader application. In this study, we developed an advanced tubular fluidic pump by introducing carbon nanotube electrodes, achieving pumping capabilities over 2 times that of conventional electrodes. We integrated this pump with tubular fiber artificial muscles, creating fluid pump-cooled electrothermal artificial muscle systems with parallel and series configurations. This integration reduced cooling time to about one-ninth of the original and increased mechanical energy output power density by 3 times, expanding the effective actuation frequency range by 3.5 times. Additionally, to effective control artificial muscle actuation, we incorporated a resistive sensing layer directly onto the surface of the artificial muscles, enabling position monitoring. On the application front, we demonstrated the potential of these artificial muscles in thermally responsive functional composite materials, deformable mechanical components, and bionic origami wrist joints.

Next-generation fabrics with excellent protection and intelligent sensing abilities will be beneficial to protect the elderly from accidents, as the ageing population will be a global challenge in the next decade. However, for widely used techniques such as fabric coating and multi-layer compositing, maintaining a balance between comfortability, stable anti-impact protection, and multi-function such as intelligent monitoring remains elusive. Herein, a full-fiber composite yarn with triboelectric ability was developed, which was then woven into an origami-structured knitted fabric (OSKF). Due to the coaxial torsional structure, the composite yarn exhibited outstanding fracture strength (219.18 MPa). The full-fiber multi-scale structure design endowed the OSKF with significantly improved energy absorption capacity (absorbing > 85% of the applied force) and the desired self-powered sensing performance without affecting the comfortability. The OSKF also had a unique ability to respond to various hazardous situations, such as external mechanical force stimuli, cutting by a sharp object, and accidental falls. This work sheds light on a new path toward the design of next-generation smart protection wearables based on knitted fabric structure design-based full-fiber materials.

The precise, rapid and direct visualization of 3D topographical dose in the target tissue that is crucial for effective radiation therapy remains a challenge. Herein, by combining hydrogel photonic crystals with film stacking or 3D printing, a 3D radiochromic dosimeter with a dose sensitivity of up to 10 nm Gy^-1, a spatial resolution <50 μm, and the ability to detect complex 3D topographical dose distribution was proposed for clinical radiation dose verification. The sensitivity and response range of the dosimeter by radiation-induced polymer cross-linking and consequent Bragg wavelength shift can be tuned via the solid content and extent of acrylate modification. The combination of rapid readout, low dose response, high spatial resolution, and great pre-irradiation and post-irradiation stability highlights the translational potential of this technology for topographical dose mapping in clinical radiotherapy applications.

Electronic skin (E-skin) has attracted considerable attention for simulating the human sensory system for use in prosthetics, human-machine interactions, and healthcare monitoring. However, it is still challenging to fully mimic the skin function that can de-couple stimuli such as normal/tangential forces, contact/non-contact behaviors, and react to high-frequency inputs. Herein, we propose fully bionic E-skin (FBE-skin), which consists of a magnetized micro-cilia array (MMCA), a micro-dome array (MDA), and flexible electrodes to completely duplicate the hairy layer, epidermis/dermis interface, and subcutaneous mechanoreceptors of human skin. The optimized MDA and interdigital electrode enable the FBE-skin to perceive static forces with a linear sensitivity of 96.6 kPa^-1 up to 100 kPa, while the branch of electromagnetic induction allows the FBE-skin to sensitively capture dynamic stimuli with vibrating signals up to 100 Hz. The top-down integration of MDA and MMCA not only replicates the three-dimensional structure of human skin, but also synergistically provides the FBE-skin with bionic rapidly adapting (RA) and slowly adapting (SA) receptors. Consequently, the FBE-skin is capable of perceiving dynamic/static, normal/tangential, and contact/non-contact stimuli with a broad range of working pressures and frequencies. We expect that the design of FBE-skin will be promising for widespread applications from intelligent sensing to human-machine interactions.