Controlled exfoliation of molybdenum disulfide for developing thin film humidity sensor

• We firstly report the ultrasonic power dependent liquid exfoliation of MoS2.
• The size control of MoS2 nanosheets was achieved by tuning the ultrasonic power.
• We fabricated MoS2 nanosheets based thin film humidity sensor using a facile method.
• Small-size MoS2 nanosheets exhibit better sensing performance.

We report a facile, size-controllable exfoliation process using an ultrasound-assisted liquid method to fabricate few-layer molybdenum disulfide (MoS2) nanosheets. The morphology, structure and size distribution of the nanosheets processed with different ultrasonic powers were examined by atomic force microscopy, Raman spectroscopy and dynamic light scattering. It was revealed that the size of nanosheets reduces and final yield increases with elevating ultrasonic power. Bulk and exfoliated MoS2 based thin film sensors are fabricated by a simple drop casting method on alumina substrates. Our sensors exhibit excellent sensitivity with very quick response and recovery speed to humidity gas. Comparative studies are carried out to draw up the size or ultrasonic power dependent sensing behavior.