Superhydrophobic MXene Spherical Cavity Arrays as Surface-Enhanced Raman Scattering Sensors for Label-Free Gas...

High-performance surface-enhanced Raman scattering (SERS) gas sensing has significant potential in environmental monitoring and public health safeguard. However, label-free gas detection remains a substantial challenge due to the high mobility of gaseous molecules and low Raman scattering cross sections. Herein, we proposed Ti₃C₂ MXene spherical cavity array-modified silver nanoparticles (AgNPs) and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FOTS) as a versatile SERS substrate by the sacrificial template method. The vortex effect induced by spherical cavity arrays and abundant surface functional groups of the Ti₃C₂ material reduces the gas flow rate and enhances the interaction between the molecules and the substrate. The excellent superhydrophobic property derived from FOTS overcomes the characteristic of Ti₃C₂ that is prone to oxidation and enhances the stability of the substrate. Based on the electromagnetic enhancement of AgNPs and the chemical enhancement from Ti₃C₂, the composite substrate realizes volatile organic compound gas detection with superior sensitivity and a lower detection limit at the ppb level. In addition, the composite substrate can achieve molecular desorption and readsorption due to the efficient photothermal effect of Ti₃C₂ and AgNPs, thereby enhancing the recirculation of the SERS substrate. The proposed strategy provides unique insights into the field of gas sensing and promotes the practical application of the MXene material.