Nitrogen dioxide (NO2) is a potent greenhouse
gas produced
through the combustion of fossil fuels, posing significant threats
to both the environment and human health. This study focuses on the
development of a low-cost and highly sensitive NO2 sensor
for improved public health and environmental protection. A chemiresistive
NO2 sensor based on a thiophene polymer with oligoethylene
glycol side chains (p(g42T-TT)) is presented. The sensor operates
on the principle of change in the electrical resistance of the sensing
material upon exposure to NO2 gas. P(g42T-TT) exhibits
a high sensitivity to NO2 due to its high highest occupied
molecular orbital (HOMO) level, making it susceptible to oxidation
by NO2. The doping process was validated through UV–vis–NIR
spectroscopy, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy.
The film morphology analysis using GIWAX and AFM techniques confirmed
the partially crystallized structures in the NO2-doped
p(g42T-TT) film. The doped film exhibited a conductivity of 12 S/cm
and a Seebeck coefficient of 1.6 μV/K, indicating the high doping
level of p(g42T-TT). The chemiresistive NO2 sensor was
tested under various concentrations and showed an ultrahigh sensitivity
with a response of 3.58 ± 2.38 × 100% at the 20 ppb level,
which is among the highest reported sensitivity in conducting polymer
(CP)-based chemiresistive NO2 sensors. The simplicity,
flexibility, and high sensitivity of the p(g42T-TT)-based chemiresistor
make it a promising candidate for one-time use in NO2 sensing
applications. These findings provide valuable insights for further
advancements in chemiresistive gas sensor technologies.