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Broadband and efficient terahertz absorbing films are crucial to high-performance terahertz detectors, which are in demand for next-generation wireless communications, astronomy, security screening, medical imaging and so on. Recent studies reported a series of two-dimensional materials for enhanced light absorption in terahertz waves, such as graphene, transition metal dichalcogenides and topological insulators, among others. However, it is still challenging to achieve the intrinsic thin-film absorption limit (50%) across the whole ultrabroad terahertz band. Here we demonstrate that ultrathin 10.2-nm-thick (~λ/30,000) Ti3C2Tx MXene assemblies can reach the intrinsic thin-film absorption limit across the entire 0.5–10 THz band. Such intriguing phenomena are attributed to the highly concentrated free electrons (~1021 cm−3), short relaxation time (~10 fs) and unique intra- and interflake (hopping) electron transport properties in Ti3C2Tx MXenes. Our results are validated by alternating current impedance theory using the Drude–Smith model, rather than classic direct current impedance matching. We believe that our findings will stimulate more studies of broadband terahertz technologies with MXenes and beyond, providing a route to developing compact, supercontinuum terahertz optoelectronic or photothermoelectric devices. Ultrathin 10.2-nm-thick (~λ/30,000) Ti3C2Tx MXene assemblies that offer an absorption of 49.2%, which is close to the theoretical limit of 50%, in the range of 0.5–10 THz are reported, benefiting terahertz optoelectronic and photothermoelectric devices. [ABSTRACT FROM AUTHOR]

Although Ti3C2Tx MXene is a promising material for many applications such as catalysis, energy storage, electromagnetic interference shielding due to its metallic conductivity and high processability, it's poor resistance to oxidation at high temperatures makes its application under harsh environments challenging. Here, we report an air-stable Ti3C2Tx based composite with extracted bentonite (EB) nanosheets. In this case, oxygen molecules are shown to be preferentially adsorbed on EB. The saturated adsorption of oxygen on EB further inhibits more oxygen molecules to be adsorbed on the surface of Ti3C2Tx due to the weakened p-d orbital hybridization between adsorbed O2 and Ti3C2Tx, which is induced by the Ti3C2Tx/EB interface coupling. As a result, the composite is capable of tolerating high annealing temperatures (above 400 °C for several hours) both in air or humid environment, indicating highly improved antioxidation properties in harsh condition. The above finding is shown to be independent on the termination ratio of Ti3C2Tx obtained through different synthesis routes. Utilized as terahertz shielding materials, the composite retains its shielding ability after high-temperature treatment even up to 600 °C, while pristine Ti3C2Tx is completely oxidized with no terahertz shielding ability. Joule heating and thermal cycling performance are also demonstrated. A major challenge for the effective use of Ti-based MXenes in applications with harsh environmental conditions is their poor resistance to oxidation. Here, authors report an air-stable Ti3C2Tx composite with extracted bentonite able to endure high-temperature annealing in air by an oxygen adsorption competition mechanism. [ABSTRACT FROM AUTHOR]