Curved Nanoflakes of Alkane-Grafted Ti3C2Tx MXene Thin Flims for Enhanced Terahertz Electromagnetic Interference Shielding

The sixth-generation wireless communication (6G) extends the electromagnetic pollution up to the terahertz band. The two-dimensional titanium carbide of intercalated structure Ti3C2Tx MXene attracts much attention because it exhibits high terahertz electromagnetic interference (EMI) shielding effectiveness (SE) due to the large intrinsic electrical conductivity as well as few-atom monosheet thickness. Scientists worldwide are making continuous efforts to optimize the MXene structures for EMI shielding application. Innovatively, we demonstrate a chemical method to bend the nanoflake by grafting two types of alkane, octane (C8H18) and dodecane (C12H26), onto the surface terminals. The chain length of alkane exceeds the bond length of surface functionalities Tx (=O, −OH, −F) to introduce intrananoflake and internanoflake strains into Ti3C2Tx MXene. The nanoflake's deformation leads to Raman peak redshift and broader line width. The element distribution shows that the alkane increases the oxygen–fluorine ratio of Ti3C2Tx MXene from 3:2 to 3:1 (Ti3C2Tx-C8H18) and even up to 4:1 (Ti3C2Tx-C12H26). Electronic microscopy (SEM/TEM) shows obvious edge-fold and tensile/compressive deformation of the nanoflake. The EMI SE of Ti3C2Tx-C12H26 achieves 35 dB, which is higher than those of Ti3C2Tx-C8H18 (26 dB) and Ti3C2Tx MXene (22 dB). The alkane grafting increases the absorption coefficient of the MXene thin film by more than 50% but has negligible contribution to the refractive index. Meanwhile, the conductivity of Ti3C2Tx-C8H18 MXene is over twice higher than that of Ti3C2Tx MXene, whereas the conductivity of Ti3C2Tx-C12H26 is three times higher than that of Ti3C2Tx MXene. The nanoflake curvature of alkane grafted Ti3C2Tx MXene enlarges the specific surface area and causes topological defects, which increase the absorption as well as the conductivity so that the terahertz EMI SE is enhanced correspondingly. The realization of Ti3C2Tx MXene of curved nanoflake for the enhancement of terahertz EMI SE is valuable for 6G electromagnetic protection.