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Highlights A flexible freestanding TaS2 film (thickness = 3.1 μm) exhibits an ultralow void ratio of 6.01%, an ultra-high electrical conductivity of 2,666 S cm−1, an electromagnetic interference shielding effectiveness (EMI SE) of 41.8 dB, an absolute EMI SE (SSE/t) of 27,859 dB cm2 g−1, and excellent flexibility withstand 1,000 bends without rupture. The TaS2 composite films exhibit excellent EMI shielding properties and higher tensile strength with better mechanical flexibility, making them suitable for EMI shielding practical applications.

Highlights: A flexible freestanding TaS2 film (thickness = 3.1 μm) exhibits an ultralow void ratio of 6.01%, an ultra-high electrical conductivity of 2,666 S cm−1, an electromagnetic interference shielding effectiveness (EMI SE) of 41.8 dB, an absolute EMI SE (SSE/t) of 27,859 dB cm2 g−1, and excellent flexibility withstand 1,000 bends without rupture. The TaS2 composite films exhibit excellent EMI shielding properties and higher tensile strength with better mechanical flexibility, making them suitable for EMI shielding practical applications. Low-dimensional transition metal dichalcogenides (TMDs) have unique electronic structure, vibration modes, and physicochemical properties, making them suitable for fundamental studies and cutting-edge applications such as silicon electronics, optoelectronics, and bioelectronics. However, the brittleness, low toughness, and poor mechanical and electrical stabilities of TMD-based films limit their application. Herein, a TaS2 freestanding film with ultralow void ratio of 6.01% is restacked under the effect of bond-free van der Waals (vdW) interactions within the staggered 2H-TaS2 nanosheets. The restacked films demonstrated an exceptionally high electrical conductivity of 2,666 S cm−1, electromagnetic interference shielding effectiveness (EMI SE) of 41.8 dB, and absolute EMI SE (SSE/t) of 27,859 dB cm2 g−1, which is the highest value reported for TMD-based materials. The bond-free vdW interactions between the adjacent 2H-TaS2 nanosheets provide a natural interfacial strain relaxation, achieving excellent flexibility without rupture after 1,000 bends. In addition, the TaS2 nanosheets are further combined with the polymer fibers of bacterial cellulose and aramid nanofibers via electrostatic interactions to significantly enhance the tensile strength and flexibility of the films while maintaining their high electrical conductivity and EMI SE.This work provides promising alternatives for conventional materials used in EMI shielding and nanodevices. [ABSTRACT FROM AUTHOR]

Charge density waves spontaneously breaking lattice symmetry through periodic lattice distortion, and electron–electron and electron–phonon interactions, can lead to a new type of electronic band structure. Bulk 2H-TaS2 is an archetypal transition metal dichalcogenide supporting charge density waves with a phase transition at 75 K. Here, it is shown that charge density waves can exist in exfoliated monolayer 2H-TaS2 and the transition temperature can reach 140 K, which is much higher than that in the bulk. The degenerate breathing and wiggle modes of 2H-TaS2 originating from the periodic lattice distortion are probed by optical methods. The results open an avenue to investigating charge density wave phases in two-dimensional transition metal dichalcogenides and will be helpful for understanding and designing devices based on charge density waves.

Charge density waves spontaneously breaking lattice symmetry through periodic lattice distortion, and electron-electron and electron-phonon inter-actions, can lead to a new type of electronic band structure. Bulk 2H-TaS 2 is an archetypal transition metal dichalcogenide supporting charge density waves with a phase transition at 75 K. Here, it is shown that charge density waves can exist in exfoliated monolayer 2H-TaS 2 and the transition temperature can reach 140 K, which is much higher than that in the bulk. The degenerate breathing and wiggle modes of 2H-TaS 2 originating from the periodic lattice distortion are probed by optical methods. The results open an avenue to investigating charge density wave phases in two-dimensional transition metal dichalcogenides and will be helpful for understanding and designing devices based on charge density waves., (© Duan Zhang et al. 2020.)