Highly sensitive hybrid nanofiber-based room-temperature CO sensors: Experiments and density functional theory simulations

Chemical sensors (CSs) are an emerging area in nanoscience research, which focuses on the highly sensitive detection of toxic and hazardous gases and disease-related volatile organics. While the field has advanced rapidly in recent years, it lacks the theoretical support required for the rational design of innovative materials with tunable measurement responses. Herein, we present a one-dimensional (1D) hybrid nanofiber decorated with ultrafine NiO nanoparticles (NiO NPs) as an efficient active component for CSs. Highly dispersed (110)-facet NiO NPs with a high percentage of Ni²⁺ active sites with unsaturated coordination were confined in a TiO₂ nanofiber (TiO₂ NF) matrix that is favorable for surface catalytic reactions. The CSs constructed using the 1D heterostructure NiO/TiO₂ nanofibers (NiO/TiO₂ HNFs) exhibited a highly selective response to trace CO gas molecules (1 ppm) with high sensitivity (ΔR/R₀ = 1.02), ultrafast response/recovery time (T_res/T_recov < 20 s), and remarkable reproducibility at room temperature. The density functional theory (DFT) simulations and experimental results confirmed that the selective response could be attributed to the high molecular adsorption energy of the NiO nanoparticles with (110) facets and abundant interfaces, which act synergistically to promote CO adsorption and facilitate charge transfer.