Bactericidal Hollow S-NiCo₂O₄ Nanoneedles for Air Purification

One-dimensional (1D) nanoarray structures exhibit an electroporation effect at low voltages and are capable of transiently inactivating the passing bacteria, which is promising for air purification. However, the sterilization effect of electrode materials in current air filtration devices remains and needs further improvement owing to their low electron transfer efficiency and limited yield of reactive oxygen species (ROS). In this paper, we report the design of S-NiCo 2 O 4 nanoneedles with hollow structures that exhibit superior antibacterial effects against both Gram-negative and Gram-positive bacteria at lower AC voltage and could be applied to air purification as an instantaneous sterilization device. Due to the hollow structure and the sulfur doping, the local electric field strength and ROS yield of S-NiCo 2 O 4 were significantly increased. The results show that the inactivation rate of E. coli and S. aureus reached 99.9%, and 99.8% at a low AC voltage of 12 V and an air flow rate of 0.5 m/s. More importantly, through finite element simulation, the effects of hollow structure and curvature radius on the local electric field strength are analyzed, which in turn improve the electroporation effect. The experimental results also demonstrated that the increased active sites from S-doping led to remarkable growth in the ROS yield of the S-NiCo 2 O 4 nanoneedles and further improved the sterilization efficiency.