Structural materials with shorter gas diffusion pathways,
lower
electrical resistance, and crystal size play a vital role in resistive-type
gas sensors. In the present work, ZnO was doped with Ga to lower its
electrical resistance and inhibit crystal growth for acetylene sensing.
Ga-doped ZnO microbelts were synthesized by electrospinning a solution
containing metal precursors and quillaja saponin as a template for
the evolution of the belt structure, followed by calcination to achieve
microbelts with a BET surface area of 68.5 m2 g–1, an average pore size of 4.6 nm, and ZnO crystals as small as 16.5
nm. The Ga-doped ZnO microbelts exhibited a response (R
a/R
g) of up to 21.0, and a
fast response (7.6 s) to 20 ppm acetylene at 400 °C in dry conditions.
The materials also showed outstanding repeatability of response of
10.04 ± 0.04 against 10 cycles of 5-ppm acetylene, a response
of 2.0 to acetylene as low as 0.2 ppm, and excellent selectivity against
5 ppm of hydrogen, pentane, toluene, carbon monoxide, and methane.
The results suggested that Ga doping could effectively improve the
electrical conductivity and acetylene sensing performance of ZnO-based
sensors.