Ti₃C₂T_x MXene: silk fibroin composite films—engineering DC conductivity and properties in the THz range

MXenes, a family of two-dimensional transition metal carbides and nitrides with high conductivity and stability, are promising materials for applications such as flexible and wearable electronics or electromagnetic interference (EMI) shielding. In this study, we explore MXene-silk composites using THz time-domain spectroscopy and time-resolved spectroscopy. We focus on Ti₃C₂T_x MXenes—silk fibroin films, aiming to develop materials with tunable electronic and thermal properties. While the composite films remain electrically conductive for films prepared from aqueous solutions with as much as 2 mg silk per mg of MXene, DC conductivity in such films decreases by over four orders of magnitude as compared to MXene-only films. At the same time, high THz range AC conductivity and EMI shielding efficiency in the THz range are largely preserved, as they are determined predominantly by the intra-flake electron transport and are less impacted by the increased inter-flake distances. Using time-resolved THz spectroscopy, we also find that while optical excitation of both pure MXene films and MXene-silk composite films results in transiently enhanced THz transmission due to thermal suppression of conductivity, silk encapsulation accelerates thermal relaxation. Thus, the DC conductivity and thermal properties of MXene-silk composites can be effectively tuned by adjusting the silk fibroin content, largely without impacting their EMI shielding performance in the THz range. This tunability opens a pathway to designing biocompatible electronic materials with customizable properties tailored to specific applications.