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.