Optical Properties in Freestanding Thin Films—MXene Nanosheets Assembly in 1D Cellulose

In this study, we delve into investigating freestanding thin films combining 2D material, Ti₃C₂T<i>_x</i> MXene, within 1D natural polymer network. Cellulose nanofibers (CNFs) derived from renewable resources, offering a sustainable alternative to synthetic polymers, create a unique environment for interactions at the interface with 2D MXene nanosheets. Our focus is centered on a distinct blend of two media where CNFs predominate, forming flexible, self-supporting thin films through hydrogen bonding and layered structure is obtained via vacuum-assisted filtration. Our approach utilizes minimal MXene content &lt; 1% volume fraction within cellulose media to highlight the influence of MXene organization on the optical characteristics and photonic behavior. The obtained flexible films of 3-4 μm thickness exhibit up to 85% transparency, which are also flexible and mechanically strong with a modulus of 8.5 ± 1 GPa and tensile strength of 220 ± 28 MPa. Furthermore, the unique advancement of this work is the color variations of MXene within polymeric medium due to multiple reflections and scattering events, that we investigated with hyperspectral high-resolution imaging. Prompted by the disordered arrangement of the nanosheets within the cellulose matrix and their interactions, this work not only broadens our understanding of MXene in natural polymer composites, but also underscores their potential in emerging freestanding films and advanced photonic applications for innovative device architectures.