electromagnetic compatibility of electronic devices and protection of biological tissue against harmful radiation. [1] High-performance EMI shields, involving high EMI shielding effectiveness (SE), low thickness and weight, good mechanical strength and flexibility, and considerable stability, are highly desirable. [2] Owing to the excellent electrical conductivity and the large aspect ratios, low-dimensional nanomaterials such as metal nanowires, [3] carbon nanotubes (CNTs), [4] graphene, [5] or transition metal carbides and nitrides (MXenes) [6] offer great potential for bottom-up construction of EMI shielding macrostructures. Among these materials, novel 2D MXene sheets, commonly known as Ti 3 C 2 T x MXenes, have attracted attention for constructing high-performance EMI shielding materials due to the metallic conductivity and the solution processability derived from their hydrophilic functional groups (F, O, and OH). [7] For instance, vacuum filtrated MXene films showed an excellent EMI SE of 68 dB at a thickness of 11 µm. [8] This resulted in an ultrahigh surface-specific SE (SSE), [1b,8] defined as the SE divided by the thickness and density of shields, of 25 863 dB cm 2 g −1 for the MXene films. Compared to solid copper or stainless steel with SSE values of around 30 dB cm 2 g −1 , [9] MXene-based films show great Transition metal carbides and nitrides (MXenes) have shown great potential for constructing thin, high-performance electromagnetic interference (EMI) shields. The challenges with these materials involve the weak interfacial interactions of MXenes, which results in inferior mechanical properties and structure of the MXene films and a conductivity/EMI shielding performance decay related to the poor MXene oxidation stability. Numerous efforts have been devoted to improving the mechanical properties or oxidation stability of the films, which always comes at the expense of EMI shielding performance. Here, ultrafine (≈1.4 nm) cellulose nanofibers are employed to achieve physical and chemical dual cross-linking of MXene (PC-MXene) nanosheets. The procedure involves drying of flexible and highly conductive PC-MXene films at ambient pressure and is energy-efficient and scalable. Compared to the MXene films, the PC-MXene films show significantly improved mechanical strength, hydrophobicity, oxidation stability, and are waterproof, without compromising the excellent EMI shielding effectiveness (SE). Moreover, the freestanding PC-MXene films reach a thickness of merely 0.9 µm and exhibit a high SE of 33.3 dB, which cannot be achieved by pure MXene films. This leads to ultrahigh thickness-specific SE and surface-specific SE values of 37 000 dB mm −1 and 148 000 dB cm 2 g −1 respectively, significantly surpassing those of previously reported MXene-based films.

In modern society, there is a constant need for developing reliable, sustainable and costeffective antibacterial materials. Here, we investigate the preparation of cellulose nanocrystallysozyme composite films via the well-established method of evaporation-induced self-assembly.We consider the effects of lysozyme concentration and aggregation state (native lysozyme , lysozyme amyloid fibers, and sonicated lysozyme amyloid fibers) on suspension aggregation and film-forming ability. Although at higher lysozyme loading levels (ca. 10 wt%), composite films lost their characteristic chiral nematic structuring, these films demonstrated improved mechanical properties and antibacterial activity with respect to CNC-only films, regardless of lysozyme aggregation state. We anticipate that the results presented herein could also contribute to the preparation of other CNC/protein-based materials, including films, hydrogels and aerogels, with improved mechanical performance and antibacterial activity.

Antimicrobial resistance in microorganisms will cause millions of deaths and pose a vast burden on health systems; therefore, alternatives to existing small-molecule antibiotics have to be developed. Lysozyme is an antimicrobial enzyme and has broad-spectrum antimicrobial activity in different aggregated forms. Here, we propose a reductive pathway to obtain colloidally stable amyloidlike worm-shaped lysozyme nanoparticles (worms) from hen egg white lysozyme (HEWL) and compare them to amyloid fibrils made in an acid hydrolysis pathway. The aggregation of HEWL into worms follows strongly pH-dependent kinetics and induces a structural transition from α-helices to β-sheets. Both HEWL worms and amyloid fibrils show broad-spectrum antimicrobial activity against the bacteria Staphylococcus aureus (Gram-positive), Escherichia coli (Gram-negative), and the fungus Candida albicans. The colloidal stability of the worms allows the determination of minimum inhibitory concentrations, which are lower than that for native HEWL in the case of S. aureus. Overall, amyloid fibrils have the strongest antimicrobial effect, likely due to the increased positive charge compared to native HEWL. The structural and functional characterizations of HEWL worms and amyloids investigated herein are critical for understanding the detailed mechanisms of antimicrobial activity and opens up new avenues for the design of broad-spectrum antimicrobial materials for use in various applications.