Journal of Materials Chemistry C最新文献

The rapid advancement of electromagnetic wave (EMW) technology has significantly increased the military's demand for anti-reconnaissance measures and the need to mitigate electromagnetic interference in daily life. High-entropy alloys (HEAs) have garnered widespread attention as a new generation of absorbers due to their tunable EMW absorption properties and strong stability. Among them, FeCoNiAl-based HEAs are known for their strong magnetic loss capabilities and moderate oxidation resistance, which are critical for the regulation of microwave absorption performance and adaptation to high-temperature environments. However, limitations such as a narrow effective absorption bandwidth (EAB), a narrow slow-oxidation temperature range, and relatively high density have been reported in current studies. In this work, as a lightweight and corrosion-resistant element with a large atomic radius and low valence electron count, Ti was introduced to induce a phase transformation of the alloy structure toward a BCC phase with superior magnetic loss capabilities, while reducing density and improving oxidation resistance. FeCoNiAlTi_0.6 prepared via high-energy ball milling exhibits excellent EMW absorption performance and oxidation resistance, achieving the minimum reflection loss (RL_min) of −66.38 dB with a thickness of 1.68 mm, and the widest EAB of 6.11 GHz, covering a slow oxidation temperature range of 0 to 900 °C.

Low-dimensional magnets provide avenues to explore novel excitations and critical behaviour that are not typically found in their higher-dimension analogues. Herein, we investigate the critical behaviour of the canted antiferromagnet α-Cu₂V₂O₇ in the vicinity of magnetic phase transition by measuring isothermal magnetization curves. The α-Cu₂V₂O₇ sample is synthesized using the conventional solid-state route, and it stabilizes in an orthorhombic crystal structure with the Fdd2 space group, as determined from X-ray diffraction analysis. Critical exponents (β = 0.283(8), γ = 2.418(6) and δ = 9.16) obtained using the modified Arrott plot (MAP) suggest that α-Cu₂V₂O₇ does not belong to any of the existing magnetic universality classes. The reliability and self-consistency of the estimated exponents are further validated using Widom scaling relation and scaling analysis equations. To link the above obtained critical exponents to the underlying spatial-dimensionality (d) and spin-dimensionality (n) of the system, we used the renormalization group theory approach to estimate a set of critical exponents spanning various spin and spatial dimensions. Notably, the critical exponents obtained from renormalization group theory analysis by considering that (d(spatial-dimensionality) : n(spin-dimensionality)) = (1 : 3) closely matches with the value derived from MAP, revealing that α-Cu₂V₂O₇ can be considered a 1-D Heisenberg antiferromagnetic system. Finally, critical behaviour analysis testifies that α-Cu₂V₂O₇ exhibits long-range type exchange interaction J(r), which decays with r as J(r) ∼ r^−1.84.

Organic electrochemical transistors (OECTs) are emerging as promising neural electrodes due to their capabilities for on-site signal amplification, customizable mechanical flexibility, biocompatibility, and stability in biotic conditions. However, documented flexible OECT arrays face limitations in channel count and spatiotemporal resolution. Here, we report a high-density, ultraflexible OECT array designed explicitly for the high-resolution electrocorticogram (ECoG) signal recording. Featuring vertically stacked source and drain electrodes, the array incorporates 1024 channels in a compact form factor, only 4.2 μm thick, achieving a density of 10 000 transistors per square centimeter. A 16 × 16 segment of the 1024-channel array was utilized to map whisker-related signals in a mouse model, effectively locating neural activities in response to tactile stimulation. Besides, it demonstrates high mechanical compliance and long-term stability, remaining effective for three months post-implantation and beyond. With its excellent resolution and durability, the ultraflexible OECT array promises to enhance the monitoring and understanding of neural dynamics across a wide spatiotemporal scale.

We propose a tri-band metamaterial sensor operating in the terahertz range, structured with a semiconductor–dielectric–semiconductor configuration. Tri-band resonance is produced by this structure at 4.216 THz, 5.210 THz, and 5.770 THz. The physical mechanism underlying these absorption peaks is elucidated through impedance matching theory. The dependence of geometric parameters on the resonant frequency is analyzed based on an LC model. Furthermore, to obtain the best sensitivity, an analysis is conducted on the influence of the analyte thickness change on the sensor performance. Additionally, we analyze the sensing performance parameters within the analyte refractive index range of 1.33 to 1.4. Our findings highlight that, for the third resonant frequency, the sensor achieves maximum sensitivity, Q factor, and figure of merit of 3.3512 THz RIU⁻¹, 432.5, and 261.81 RIU⁻¹, respectively. Notably, given that most biosensing applications are in the refractive index range of 1.33 to 1.4, our sensor offers promising potential for biomedical diagnostics due to its high sensitivity.

Plasmonic nanostructures provide unique structural coloration features via resonant interactions with light, rendering them useful in various optical applications. Here, new types of novel plasmonic–photonic Janus (PPJ) films are developed by introducing aluminum nanoislands on the surface of colloidal photonic crystal (CPC) arrays. Notably, the obtained PPJ films show vivid and tunable plasmonic colors ranging from purple to golden that can be regulated by the sizes of nanoisland architectures. Exquisite multicolored patterns on PPJ films have also been successfully achieved via regioselective deposition, showcasing enormous potential in decorations. More intriguingly, by virtue of the sensitivity of Al nanoislands to the medium, the PPJ films display superior colorimetric detection ability in response to different solvents and biomolecule glucose. Leveraging these merits, advanced rewritable papers and reliable express waybills have been demonstrated based on PPJ films, offering abilities to deliver information reversibly and erase them on-demand. This work establishes a new platform for achieving versatile applications within a single plasmonic system, opening up vast possibilities for advancements in information delivery and personal information security.

Efficient nonlinear optical materials remain a subject of significant interest in the scientific community, with ongoing efforts focused on optimizing their properties for practical applications. This paper aims at exploring how the nonlinear optical properties of silver nanoprisms are affected by the interaction with graphene oxide sheets. For this purpose, we produce nanocomposites consisting of citrate-passivated silver nanoprisms anchored both electrostatically and covalently on graphene oxide nanosheets in a cost-effective and reproducible manner. The novelty of the technique hinges on the covalent functionalization of silver nanoprisms onto graphene oxide (GO) nanosheets according to the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride crosslinking method, using the existing carboxylic groups present both at the surfaces of the nanoprisms and the GO nanosheets. The formed hybrid nanocomposites were characterized by TEM measurements and exhibit nonlinear optical (NLO) properties, in particular a strong second harmonic scattering response as well as a multiphoton excited fluorescence spectrum characterized by a broad band in the visible range between 350 and 700 nm. In addition, the NLO response is sensitive to the nature of the interaction (electrostatic or covalent), which might be attributed to different charge transfer capabilities between covalently or electrostatically bound silver particles onto graphene oxide. Such nanocomposites are therefore promising for new applications in the areas of optoelectronics and photovoltaics.

Photoreactivity in crystals is one of the essential properties for creating photo-functional crystalline materials. This study explores the impact of the dihedral angle in aryl groups on the photocyclization reactivity of inverse-type diarylethenes, both in solution and crystalline phases. By synthesizing various diarylethene derivatives with different dihedral angles, the relationship between structural geometry and photoreactivity is systematically examined. We find that larger dihedral angles between the thiophene and phenyl rings enhance photocyclization reactivity in solution, indicating that destabilized π-conjugation lowers the activation barrier. In fact, ultrafast spectroscopy confirms that the cyclization time constant decreases with larger dihedral angles. In the crystalline phase, X-ray crystallographic analysis shows that all diarylethene derivatives adopt ideally photoreactive anti-parallel conformations, but only crystals with a dihedral angle exceeding approximately 81° exhibit photocyclization. These findings indicate that a certain threshold dihedral angle is essential for photocyclization to occur in crystals. The results of this work provide new insights into the role of molecular geometry in photoreactivity and offer a strategy for designing functional photochromic materials that operate efficiently in the solid state.

In recent years, flexible wearable pressure sensors have emerged as a pivotal technology in the realms of intelligent health monitoring and artificial intelligence, steadily gaining traction as a prominent research focus. However, the conventional production process for conductive fillers is often cumbersome and costly, which limits their widespread application and large-scale manufacturing. In this study, a flexible pressure sensor based on polypropylene fluted woven fabric MXene/PS was proposed. The flexible pressure sensor uses spin-coated PS surface encapsulation technology to make the fabric surface hydrophobic, in order to improve the stability of the sensor. The sensor exhibits a wide strain range (0–565 kPa), excellent repeatability and stability (over 15 000 s), and a fast response–recovery time (75/159 ms), which can be attributed to the superior mechanical properties of the polypropylene-potted woven fabric. The MXene/PS pressure sensor can detect subtle deformations of small and medium-sized joints, making it suitable for detecting human motion signals. Additionally, combined with the deep belief network (DBN) algorithm, it can efficiently and accurately recognize human yoga postures, which shows its great application potential in human motion posture monitoring and low-cost flexible electronic products.

A growing need for accurate monitoring of both outdoor and indoor pollution sources demands enhanced gas sensors with improved sensitivity, selectivity, stability, fast response and low detection limits. Metal–organic frameworks (MOFs), a class of porous materials, stand out as superior candidates for high performance gas detection due to their exceptional structure characteristics, including tunable porosity, limitless structural motifs, and customizable chemical components. Tailoring the structure and functionalization of MOFs through etching has opened up new opportunities to adjust the gas-sensing capabilities of MOFs. In this review article, we provide a concise overview of the most recent advancements in three distinct aspects of etching MOFs: pore engineering, chemical modification, and transformation of MOFs into targeted derivatives. Despite extensive progress, research on etching strategies to elucidate the intricate relationship between the innovative structure and the sensing properties remains in its infancy. Focusing on MOFs and their derivative-based gas sensors with distinct critical structural features, the schemes to enhance sensor performance are introduced. We also outline the current barriers and future prospects in the field of gas sensing. This review seeks to offer guidance on modulating MOF-based gas sensors by strategically applying efficient etching methods, navigating contemporary challenges and future prospects in the gas sensing field.

Detection of mechanical stresses requires microscopic molecular motion triggered by macroscopically applied force. Polydiacetylene (PDA), a stimuli-responsive color-changing material, generally has no responsiveness to compression stresses. We found that a layered PDA with weakened interlayer interactions exhibits direct visible color changes in response to compression stresses. An amphiphilic diacetylene (DA) monomer, 1-(10,12-pentacosadiynyl) pyridinium bromide (PCPy⁺Br⁻), formed a lamellar structure with weakened interlayer and intermolecular interactions originating from the bulky cations and anions in the interlayer space. The resultant PDA exhibited blue-to-red color changes in response to compression stresses (P) in the range of 2.5–125 MPa. In previous works, visible detection of P < 50 MPa without excitation light has not been achieved using only mechanoresponsive materials. Moreover, the compression-stress distribution was visualized using the PDA-coated paper substrate.