MoSe2/multiwalled carbon nanotube composite for ammonia sensing in natural humid environment

Herein, we report ammonia sensing in a natural highly humid environment using MoSe2/multi-walled carbon nanotube (MWCNT) composite as sensing platform. The composite synthesis involved two steps, in the first step, MWCNTs were treated in an acidic medium to obtain -COOH group functionalized MWCNTs. In the second step, functionalized MWCNTs were probe sonicated with MoSe2 to obtain MoSe2/MWCNT composite. Proposed device exhibited superior sensing properties at a temperature down to 16∘ C and relative humidity of 80%. Under these extreme natural environmental conditions, the device exhibited a relative response of 21% for 0.5 ppm of ammonia and superior noise free signal further suggests their use even below this concentration. Composite based device has also displayed better adsorption selectivity towards NH3 as compared with other reducing and oxidizing gas molecules. Density functional theory simulations were further employed to understand the underlying adsorption process and selectivity behavior of the composite. Simulations predicted lowest negative adsorption energy for ammonia, implying physisorption (-0.387 eV) type exothermic adsorption process. Present results indicate that a composite with the rightly engineered MoSe2 and MWCNTs weight ratio may serve as a potential candidate for ammonia sensing in a highly humid environment.