Nano-Au-decorated Co-LDH nanocages as self-cleaning flexible SERS gas sensor for label-free multiplex volatile organic compounds detection with ultrahigh sensitivity

Flexible surface-enhanced Raman scattering (SERS) sensors have shown great advantages in the field of gas detection. However, the label-free sensitive detection of volatile organic compounds (VOCs) remain a significant challenge due to their inherently small Raman scattering cross-sections and low molecular density. Herein, we report a one-step redox strategy to construct gold-doped cobalt mesoporous structure of layered double hydroxides (LDHs) nanocage flexible gas sensor (CFC/Au@Co-LDH), demonstrating remarkable adsorption capacity and excellent SERS sensitivity. The three-dimensional frame structure of cotton fabrics and micropores of LDHs significantly improved the enrichment capacity of various VOCs near the plasmonic hotspots. Moreover, the finite-difference time-domain simulations and the density-functional theory calculations reveal that the interactions between the substrate and the molecules facilitate charge transfer, and the localized surface plasmon resonance of Au nanostructures to induce electromagnetic field enhancement. Combining these merits, the as-prepared CFC/Au@Co-LDH sensor exhibited excellent recycling ability (10 cycles, RSD=3.56%) and outstanding label-free sensitivity (nitrobenzene: 0.73 ppb). Finally, visual color barcodes can be used for visual reading of the composition of complex samples, enabling the detection and analysis of various VOCs mixtures. This versatile SERS gas sensor has significant potential for environmental detection and health monitoring and will inspire the design of next-generation wearable SERS sensors.