Cd₃As₂ nanowires (NWs) have great potential in the near-infrared (NIR) photodetection field due to their excellent optoelectronic properties as a typical Dirac semimetal. However, the existence of surface oxidization limits their photoresponse performance for practical applications. Here, we modified the surface of Cd₃As₂ NWs with sulfur to prevent surface oxidizing and optimize the bandgap structure to improve the photoresponse performance. The S-modified Cd₃As₂ samples existed as core/shell Cd₃As₂/CdS NWs and the corresponding single NW device showed a responsivity of 0.95 A/W in the NIR band at a 0 V bias, which is three orders of magnitude higher than that of an unmodified NW. This study provides an efficient and universally applicable way to prevent semimetals nanostructures from oxidizing and promote their optoelectronic properties.

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.