Self-Assembled 3D Helical Hollow Superstructures with Enhanced Microwave Absorption Properties

Self-Sorted Chiral Nanofibrous Hydrogels for Enhanced Osteoarthritis Cartilage Regeneration

Self-sorting by supramolecular assembly involving homochiral building blocks is of vital importance in life systems, which allows the coexistence of multiple species in an orthogonal complex mixture to achieve respective biological functions simultaneously. However, self-sorting of chiral molecules, typically homochiral molecules, remains a challenge in artificial systems, limiting the biological function development of chiral materials. Herein, we report a self-sorted supramolecular hydrogel network formed by two l-phenylalanine derivatives, LPPF and LPFA, which independently self-assemble into nanofibers with distinct helical orientations and diameters. Compared to single-component systems, this self-sorted chiral fibrous hydrogel exhibits superior cell adhesion and proliferation capability due to promoted fibronectin adsorption. Furthermore, the hydrogel demonstrates strong potential for promoting chondrogenic differentiation, as evidenced by the up-regulated expression of cartilage-specific markers (SOX9, ACAN, and COL2) in vitro. In mouse models of osteoarthritis, the LPPF + LPFA hydrogel significantly improves cartilage repair, enhances the subchondral bone structure, and reduces osteophyte formation. These findings establish self-sorted chiral hydrogels as a promising approach for osteoarthritis treatment, which holds great potential for utilization in the field of regenerative medicine.

Polymer self-assembly guided heterogeneous structure engineering towards high-performance low-frequency electromagnetic wave absorption

Magnetic-dielectric synergy is currently regarded as among the most effective approaches to achieve low-frequency electromagnetic wave absorption (EMA). However, designing and fabricating EMA materials with tunable magnetic-dielectric balance towards high-performance low-frequency EMA remains challenging. Herein, a polymer self-assembly guided heterogeneous structure engineering strategy is proposed to fabricate hierarchical magnetic-dielectric nanocomposite. Polymer assemblies not only can be employed as intermediates to encapsulate metal-organic frameworks and load metal hydroxide, but also that they play a crucial role for the in-situ formation of polycrystalline FeCo/Co composite nanoparticles. As a result, the minimum reflection loss (RLmin) can reach -59.61 dB at 5.4 GHz (4.8 mm) with a 20 wt% filler loading, while the effective absorption bandwidth (EAB, RLmin ≤ -10 dB) is 2.16 GHz, exhibiting excellent low-frequency EMA performance. Systematic investigations demonstrate that hierarchical mesoporous carbon matrix that supports FeCo/Co composite nanoparticles is beneficial for optimizing impedance matching and increasing attenuation capacity. In general, this study opens up new prospects for developing magnetic-dielectric EMA materials using a polymer self-assembly guided heterogeneous structure engineering strategy, which may receive significant attention in future research.

Dual-Responsive Fe3O4@Polyaniline Chiral Superstructures for Information Encryption

Incorporating stimuli-responsive mechanisms into chiral assemblies of nanostructures offers numerous opportunities to create optical materials capable of dynamically modulating their chiroptical properties. In this study, we demonstrate the formation of chiral superstructures by assembling Fe3O4@polyaniline hybrid nanorods by using a gradient magnetic field. The resulting superstructures exhibit a dual response to changes in both the magnetic field and solution pH, enabling dynamic regulation of the position, intensity, and sign of its circular dichroism peaks. Such responsiveness allows for convenient control over the optical rotatory dispersion properties of the assemblies, which are further integrated into the design of a chiroptical switch that can display various colors and patterns when illuminated with light of different wavelengths and polarization states. Finally, an optical information encryption system is constructed through the controlled assembly of the hybrid nanorods to showcase the potential opportunities for practical applications brought by the resulting responsive chiral superstructures.

Electromagnetic Response of Multistage-Helical Nano-Micro Conducting Polymer Structures and their Enhanced Attenuation Mechanism of Multiscale-Chiral Synergistic Effect

Nowadays, the rapidly development of advanced antidetection technology raises stringent requirements for microwave absorption materials (MAMs) to focus more attention on wider bandwidth, thinner thickness, and lower density. Adding magnetic medium to realize broadband absorption may usually result in the decline of service performance and accelerating corrosion of MAMs. Chiral MAMs can produce extra magnetic loss without adding magnetic medium due to the unique electromagnetic cross polarization effect. However, more efforts should be taken to furtherly promote efficient bandwidth of chiral MAMs and reveal attenuation mode and modulation method of chiral structure. Herein, a novel superhelical nano-microstructure based on chiral polyaniline and helical polypyrrole is successfully achieved via in situ polymerization strategy. The enhanced multiscale-chiral synergistic effect contributes to broaden effective absorption bandwidth, covering 8.6 GHz at the thickness of 3.6 mm, and the minimum reflection loss can reach -51.3 dB simultaneously. Besides, to further explain response modes and loss mechanism of superhelical nano-microstructures, the electromagnetic simulation and test analysis are applied together to reveal their synergistic enhancement attenuation mechanism. Taken together, this strategy gives a new thought of how to design, prepare, and optimize the hierarchical structure materials to achieving broadband and high-performance microwave absorption.

Constructing and optimizing hollow ZnxFe3-xO4@polyaniline composites as high-performance microwave absorbers

In this study, a series of hollow Zn_xFe_3-xO₄@polyaniline composites (ZFO@PANI) were synthesized by a facile solvothermal process and followed by in-situ chemical oxidation polymerization method, and then evaluated as microwave absorption (MA) absorbers. The effect of ZFO content on the electrical conductivity, electromagnetic parameters and MA performance of the ZFO@PANI composites was also elaborately investigated. As anticipated, the optimized composites of S2 exhibits the minimum reflection loss (RL_min) of -59.44 dB at 11.04 GHz with a matching thickness of 2.31 mm, and the broadest effective absorption bandwidth (EAB, RL < -10 dB, >90% absorption) of up to 4.65 GHz (13.35-18.0 GHz) at 1.72 mm. Noticeably, by adjusting the thickness from 1.5 to 5.0 mm, it can be observed that its RL_min values are all much lower than -10 dB and the qualified EAB can cover the entire C, X and Ku bands. The enhanced MA performance of S2 is mainly due to the efficient synergistic effect between dielectric loss (PANI) and magnetic loss (ZFO nanosphere), and thus achieving the relative balance of impedance matching (appropriate ZFO content) and attenuation capability. Therefore, it has great prospect to be explored as attractive candidate in practical application.

Facile fabrication of sepiolite functionalized composites with tunable dielectric properties and their superior microwave absorption performance

Although various materials have been studied for the purpose of microwave absorption (MA), natural sepiolite (SEP) has never been reported as MA absorber. Herein, the series of sepiolite@polyaniline composites (SEP@PANI-x) with "skeleton/skin" structure were fabricated through a facile in-situ polymerization technique and firstly developed as MA materials. The electrical conductivity and dielectric properties can be well controlled via modulating the PANI content in the composites. With a lower mass ratio of 30 wt%, it is worth noting that the optimized SEP@PANI-50 could simultaneously display the optimal minimum reflection loss (RL_min) of -50.23 dB and effective absorption bandwidth (EAB, RL < -10 dB) of 5.01 GHz with thicknesses of 2.5 and 1.8 mm, respectively. Moreover, when changing absorber thickness (1.5-5.0 mm), the RL_min values lower than -20 dB (99% absorption) are all achieved and the EAB ranges the entire Ku, X, and C bands. Such excellent MA performance comes from rich conductive network and polarization relaxation, which ultimately balance the impedance matching and attenuation ability. In view of its facile synthesis route, low-cost, lightweight and excellent MA performance, SEP@PANI-50 would be a very promising MA candidate in many practical applications. More importantly, we also think that our findings will expand the application of SEP-based composites in the electromagnetic field.

Enhanced Polarization from Hollow Cube-like ZnSnO3 Wrapped by Multiwalled Carbon Nanotubes: As a Lightweight and High-Performance Microwave Absorber

Polarization and conduction loss play fundamentally important roles in the nonmagnetic microwave absorption process. In this paper, a uniform and monodisperse hollow ZnSnO₃ cube wrapped by multiwalled carbon nanotubes (ZSO@CNTs) was successfully synthesized via facile hydrothermal treatment. A reasonable mechanism related to Ostwald ripening was proposed to design the varied ZSO@CNTs for the special hollow conductive network. Scanning electron microscopy images clearly indicate that reaction temperature is the key factor for the composite structure, which has a significant effect on its electromagnetic properties. Electron holography proves the inhomogeneous distribution of charge density in the ZSO@CNT system, leading to the occurrence of interface polarization. Complex permittivity properties of ZSO@CNT composites under different reaction temperatures were investigated to optimize the morphology that can distinctly enhance microwave absorption performance. The maximum reflection loss that the ZSO@CNT-130 °C composite can reach is -52.1 dB at 13.5 GHz, and the absorption bandwidths range from 11.9 to 15.8 GHz with a thickness as thin as 1.6 mm. Adjusting the simulation thicknesses from 1 to 5 mm, the efficient absorption bandwidth (RL < -10 dB) that the ZSO@CNT composite could reach was 14.16 GHz (88.8% of 2-18 GHz). The excellent microwave absorption performance may be attributed to the synergistic effects of polarization, conduction loss, and special hollow cage structure. It is proposed that the specially controlled structure could provide an effective path for achieving a high-performance microwave absorber.