MXene-Derived TiO₂ Nanoparticles Intercalating between RGO Nanosheets: An Assembly for Highly Sensitive Gas Detection

Tight stacking between two-dimensional (2D) sheet-like materials, such as graphene, in the solid state is a major challenge hindering their applications, especially in the gas sensing field. Here, we report on a TiO₂ nanoparticle-spaced reduced graphene oxide (RGO) assembly for the design of highly sensitive gas sensors. The TiO₂ nanospacers are derived from a 2D MXene that is intercalated between RGO sheets. The produced TiO₂-spaced RGO assembly exhibits a uniform nanoparticle distribution and highly wrinkled RGO sheets that interconnect in micrometer-scale pores. The space limitation between adjacent RGO sheets can restrict the particle growth and lead to the formation of TiO₂ nanoparticles with uniform diameters of ca. 6.2 nm. The sensitivity of the TiO₂-spaced RGO sensor to NO₂ improved by over 400% in comparison with pure RGO due to the more available surface area and active adsorption sites. Furthermore, fast response and recovery, excellent selectivity and flexibility, and reliable workability in a humid environment (with the relative humidity ranging from 5 to 95%) were also simultaneously achieved, demonstrating great potential for next-generation wearable sensors.