an0c02011_si_001.pdf (2.55 MB)
MoSe2 Crystalline Nanosheets for Room-Temperature Ammonia Sensing
journal contribution
posted on 2020-09-04, 22:04 authored by Sukhwinder Singh, Jyotirmoy Deb, Utpal Sarkar, Sandeep SharmaWe
report a highly sensitive and selective ammonia (NH3) gas
sensor made from liquid exfoliated MoSe2 nanosheets.
The powder obtained after exfoliation was used to make a two-terminal
sensor on a quartz substrate with predeposited silver contacts. The
device so obtained, exhibited excellent sensitivity (5.5%) at an ammonia
concentration down to 1 ppm, a fast response and recovery time of
15 and 135 s, respectively, better reproducibility, and impressive
selectivity against various gases at room temperature. Moreover, density
functional theory (DFT) simulations were used to understand the adsorption
kinetic and electronic structure and therefore to shed light on the
fundamentals of the sensing mechanism. Bader analysis was performed
to understand the charge transfer process between the adsorbed ammonia
gas molecule and underlying MoSe2 surface. The resulting
analysis confirmed that the electrons transfer from NH3 molecules to MoSe2. The slight shift of the valence band
toward the Fermi level which is clear from band structure analysis,
along with the experimental fact that after exposure to ammonia the
sensor displays an increase in resistance, indicates p-type behavior
of the processed MoSe2 crystalline nanosheets. These results
imply the potential use of scaled nanosheets of MoSe2 as
a promising sensing material for enhanced and selective NH3 gas monitoring at room-temperature.