Two-dimensional platinum diselenide (PtSe₂) has been explored for applications in visible and infrared photodetectors, owing to its tunable electrical and optoelectronic properties governed by layer-dependent bandgaps. Studies have explored both positive photoconductivity (PPC) and negative photoconductivity (NPC) behaviors in few-layer PtSe₂ thin films, proposing mechanisms related to gas molecule adsorption. However, these proposed mechanisms, typically based on models with ideal limit structures, often lacked consistency with the structure and scale of polycrystalline thin films employed in actual experiments. Here, photodetectors utilizing monolayer PtSe₂ ribbons were designed, demonstrating a significant NPC effect upon exposure to visible light in atmospheric conditions, with device resistance increasing to over threefold the initial state. Under vacuum conditions, the device demonstrated PPC characteristics. Density functional theory calculations indicated that oxygen molecules physically adsorbed at the edges of PtSe₂ ribbons were integral. Laser irradiation prompted the detachment of oxygen molecules from the ribbon’s edges, leading to a decreased carrier concentration in channel conductivity. The abundant edge sites of the ribbons endowed the photodetectors with a pronounced NPC response. This study diverted from traditional multilayer PtSe₂ films to explore monolayer PtSe₂ ribbons. These ribbons, as limit structures, offered a more fundamental insight into the intrinsic photoconductivity properties of PtSe₂. Photodetectors employing PtSe₂ ribbons presented novel application prospects in low-power photodetection, gas detection, and additional fields.

In the endeavor to develop three-dimensional (3D)-architected sophisticated hierarchical structures, the synergy between in-plane and out-of-plane interactions at interfaces offers new functionalities. This interplay, governed by van der Waals (vdW) interfacial nanoarchitectonics, facilitates the design of efficient thermally conductive pathways. This work delves into the kinetics underlying a dual-templating strategy, seamlessly integrating two-dimensional (2D)-graphene sheets with one-dimensional (1D)-cellulose chains at heterointerfaces, thereby transforming into 3D-shaped and 3D-continuously anisotropic structures, termed as (3D²GC) architecture. Hereby, we designed and fabricated an anisotropic graphene cellulose scaffold (GCS) employing a nickel template. The as-grown GCS replicates the 3D-shaped and configuration of the template. The 3D-continuously interconnected fibrous-porous network of the GCS, combined with its anisotropic thermal properties (λ_axial/λ_radial), not only is promising for advanced thermal technologies but also offers advantages in cost-effectiveness and eco-effectiveness.

Single-atom alloys (SAAs) have gained significant attention due to their remarkable atomic utilization efficiency, interactions between single atoms (SAs) and metal supports, and free-atom-like electronic structure of dopant elements. In this work, we observed the formation of SAs in pre-deposited metal particles by a two-step thermal evaporation technique, thereby establishing the first instance of discovering SAAs by thermal evaporation. The discovery of SAAs by thermal evaporation extends the range of SAAs preparation methods to include this traditional synthetic technique, which offers convenience, cost-efficiency, and universality. The formation mechanism of SAAs prepared using this technique was elucidated by density functional theory calculations. It was demonstrated that thermal evaporation can be utilized to prepare SAAs with multiple SAs, further highlighting its universal applicability.

Chemical vapor deposition (CVD) is the most promising method for the preparation of high-quality and large-area graphene films, especially the epitaxial growth of graphene on large-area single-crystal Cu foils. While single-crystal Cu foils are normally achieved by thermally annealing the commercial polycrystalline Cu foils, their size and therefore the size of graphene films grown on them are limited to the size of the reaction chamber. We report a simple and feasible method to prepare large-area Cu foils with decimeter grains by thermally annealing the rolled-up Cu foils, where the Cu layers are separated by thin porous carbon fiber cloths. The carbon fiber cloths prevent Cu layers from sticking to each other at high temperatures while do not block the gas transportation. In such a way, the utilization efficiency of the reaction chamber is significantly improved, e.g., 0.2 m × (1–2) m Cu foils can be processed even in a 5 cm diameter quartz tube chamber. High-quality graphene films grown on such Cu foils are then demonstrated. This method may be suitable for the annealing of other metal foils to enlarge grain size and the synthesis of other two-dimensional materials on them such as h-BN.

A facile way to grow few-layer graphene on high-entropy alloy sheets is presented in this work. We systematically investigate the growth mechanism of graphene using the unique properties of FeCoNiCu_0.25 high-entropy alloys. The intrinsic-trap-regulating growth mechanism derives from the synergistic effect of the multi-metal atoms and sluggish diffusion of high-entropy alloy. As a result, as-obtained few-layer of graphene has the characteristics of wide coverage, large size, good continuity, and high crystallinity with less amorphous carbon and extra wrinkles. Factors such as the Cu content, annealing time, growth temperature, growth time, carbon source flow rate, hydrogen flow rate and heat treatment method play a key role in the growth of high-quality graphene, and the best growth parameters have been explored. Besides, increasing alloy entropy is found to be responsible for the formation of high-quality graphene.

The development of efficient and stable electrocatalysts with earth-abundant elements for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in the same electrolyte is incontrovertibly vital in water electrolysis. However, their large-scale fabrication remains a great challenge. Here, we report a self-supported electrocatalyst in the form of Fe-doped Ni₃S₂ nanoparticles in-situ grown on three-dimensional (3D) conductive Fe-Ni alloy foam (Fe-Ni₃S₂/AF) by surface-assisted chemical vapor transport (SACVT) method. Homogeneous growth environment and scalability of SACVT method allow Fe-Ni₃S₂ nanoparticles uniformly growing on AF in large-scale. Fe-Ni₃S₂/AF exhibits high activity and durability when act as HER catalyst and OER precatalyst in alkaline media. The HER and OER overpotential at 10 mA/cm² is considerably small, only 75 and 267 mV, respectively. Moreover, the electrolyzer assembled by Fe-Ni₃S₂/AF for overall water splitting exhibits a low cell voltage and high durability in long-term test. Based on experiments and theoretical calculation, the significantly enhanced activity could be originated from the incorporation of Fe, which contributed to increase the electrochemical active surface area, enhance electrical conductivity, optimize the hydrogen and H₂O adsorption energy of Ni₃S₂ (101) surface in HER, and form active bimetallic Ni-Fe(oxy)hydroxide in OER. The excellent durability of self-supported Fe-Ni₃S₂/AF could be benefited from the in-situ growth of Fe-Ni₃S₂ nanoparticles on 3D AF, which could ensure closely mechanical adhesion between active materials and substrate, promote charge transport and increase surface area. This work provides a facile method for large-scale synthesis of electrocatalysts with high activity and long-term durability for efficient water electrolysis in alkaline media.

To substantially prevent electromagnetic threatens, microwave absorbing materials (MAMs) are required to eliminate surplus electromagnetic waves. As a typical MAM, Fe₃O₄ particles with complex permittivity and permeability have been widely applied due to the coexistence of magnetic loss and dielectric loss. However, the necessary high mass fraction significantly limited its applications, thus Fe₃O₄ nanostructures have been extensively investigated to overcome this problem. In this work, uniform Fe₃O₄ nanobelts were prepared by electrospinning and two-step thermal treatment. By controlling the composition and viscosity of the electrospinning precursor solution, Fe₃O₄ nanobelts with tunable lateral sizes (200 nm–1 μm) were obtained. The samples with low content (only 16.7 wt%) Fe₃O₄ exhibited wide maximum effective absorbing bandwidths (EAB) over 3 GHz, and Fe₃O₄ nanobelts with smaller lateral sizes showed a maximum EAB of 4.93 GHz. Meanwhile, Fe₃O₄ nanobelts with smaller lateral sizes presented superior reflection loss properties, the lowest reflection loss reached −53.93 dB at 10.10 GHz, while the maximum EAB was up to 2.98 GHz. The excellent microwave reflection loss of Fe₃O₄ nanobelts was contributed to the enhanced synergistic effect of magnetic loss, dielectric loss, and impedance matching, originated from the hierarchically cross-linked networks and shape anisotropies. This study could broaden the practical applications of magnetic absorbers, and provided an approach for the development of shape anisotropic magnetic materials.

Traditional ionic liquids are sensitive to humidity but with long response time and nonlinear response. Pure liquid-state ionic liquids are usually hard for dehydration which have ultralong response time for humidity sensing. The immobilization of ionic liquids provide a possible way for high performance humidity sensing. Hydrophobic materials and structures also promised faster response in humidity sensing, because of easier desorption of water. In this work, we prepared flexible humidity sensitive composites based on hydrophobic ionic liquid and polymer. The combination of hydrophobic ionic liquid with hydrophobic polymer realized linear response, high sensitivity with low hysteresis to humidity. By adjusting the ratio of ionic liquid, not only the impedance but also the hydrophobicity of composite could be modulated, which had a significant influence on the humidity sensing performance. The morphology and microstructure of the material also affected its interaction with water molecules. Due to the diverse processing methods of polymer, highly transparent film fabricated by spinning-coating and nanofibrous membrane fabricated by electrospinning could be prepared and exhibited different response time, which could be used for different application scenarios. Especially, the fibrous membrane made with electrospinning method showed an ultrafast response and could distinguish up to 120 Hz humidity change, due to its fibrous structure with high specific surface area. The humidity sensors with ultrafast, linear response and high sensitivity showed potential applications in human respiratory monitoring and flexible non-contact switch. To better show the multifunction of ionic liquid-polymer composite, as a proof of concept, we fabricated an integrated humidity sensitive color change device by utilizing lower ionic liquid content composite for sensing in the humidity sensing module and higher ionic liquid content composite as the electrolyte in the electrochromic module.

Although Fe₃O₄ particles have exhibited excellent microwave absorbing capacity and widely used in practical application due to the synergistic effect of magnetic loss and dielectric loss, their applications are still limited for the required high mass fraction in absorbers. To overcome this problem, the development of Fe₃O₄ materials with low dimensional structures is necessary. In this study, the shape anisotropic Fe₃O₄ nanotubes (NTs) with low mass ratios were applied to realize efficient microwave absorption. The NTs with different aspect ratios were prepared through facile electrospinning followed by two-step thermal treatments and mechanical shearing. The cross-linked nanotubular structure enabled the absorbers to have much higher electrical conductivity, multiple scattering, polarization relaxation and better anti-reflection surface, while the shape anisotropic NTs maintained significant multiple resonances with stronger coercivity. These all were beneficial to microwave absorption with enhanced dielectric loss, magnetic loss and sterling impedance matching. Results showed that the absorber with 33.3 wt.% of short Fe₃O₄ NTs had minimum reflection loss of -58.36 dB at 17.32 GHz with a thickness of 1.27 mm, and had the maximum effective absorbing bandwidth (EAB) of 5.27 GHz when the thickness was 1.53 mm. The absorber with 14.3 wt.% of long Fe₃O₄ NTs presented the widest EAB in certain radar band with attenuated 80.75% X band and 85% Ku band energy bellow -10 dB at the thickness of 2.65 and 1.53 mm, respectively. This study provided an approach for the development of shape anisotropic magnetic absorbing materials, and broadened their practical applications as magnetic absorbers.

Developing filtration media for particulate matter (PM) removal has been proven to be extremely challenging. Here, we report a facile and scalable strategy to fabricate a multi-level structured polyacrylonitrile/graphene oxide (PAN/GO) air filtration membrane to remove ultrafine particles in air by combining multi-jet electrospinning and physical bonding. Our approach allows the thin PAN nanofibers and two-dimensional GO nanosheets to form interpenetrating bonding structures on non-woven fabric and to assemble into stable filtration media. The resultant composite membranes can filtrate 300 nm particles with a high removal efficiency of 98.8%, a low pressure drop of 55 Pa, and a desirable quality factor of 0.34 Pa^-1. This multi-level PAN/GO filter is expected to have wider applications not only for the ultrafine particle filtration and separation but also for the design of three-dimensional functional structures in the future.