Effect of Nanosheet Size on NO₂ Sensing Performance at Room Temperature

This work presents a low-cost and scalable solution-processing based approach to investigate the size-dependent NO₂ sensing performance of WS₂ nanosheets (NSs). WS₂ NSs were prepared by liquid-phase shear exfoliation (LPSE) and then size-selected by centrifugation. Structural analyses confirmed that increasing the centrifugation speed decreased the average lateral size from ∼80 to ∼25 nm. Then, compacted and thickness-controlled WS₂ thin films were fabricated by interfacial self-assembly. Gas sensors based on the WS₂ NSs prepared at 3000 and 6000 r/min both exhibited p-type responses, with comparable sensitivity. However, the 3000-sensor showed slower response and incomplete recovery, whereas the 6000-sensor displayed faster response and recovery but an overrecovery behavior. This difference is primarily attributed to variations in the distribution and nature of active sites, along with their associated adsorption energies. The results highlight the importance of NSs size control in tuning the dynamic response of solution-processed WS₂ gas sensors.