  ZnS nanorods and Cr2O3 nanoparticle decorated ZnS nanorods were synthesized
using facile hydrothermal techniques and their ethanol sensing properties were
examined. X-ray diffraction and scanning electron microscopy revealed the good
crystallinity and size uniformity of the ZnS nanorods. The Cr2O3 nanoparticle
decorated ZnS nanorod sensor showed stronger response to ethanol than the
pristine ZnS nanorod sensor. The responses of the pristine and decorated
nanorod sensors to 200 ppm of ethanol at 300oC were 2.9 and 13.8, respectively.
Furthermore, under these conditions, the decorated nanorod sensor showed longer
response time (23 s) and shorter recovery time (20 s) than those of the
pristine one (19 and 35 s, respectively). Consequently, the total sensing time
of the decorated nanorod sensor (42 s) was shorter than that of the pristine
one (55 s). The decorated nanorod sensor showed excellent selectivity to
ethanol over other volatile organic compound gases including acetone, methanol,
benzene, toluene, whereas the pristine one failed to show selectivity to
ethanol over acetone. The improved sensing performance of the decorated nanorod
sensor is attributed to the modulation of the conduction channel width and the
potential barrier height at the ZnS Cr2O3 interface accompanying the adsorption
and desorption of ethanol gas as well as the greater surface to volume ratio of
the decorated nanorods than the pristine one due to the existence of the ZnS
Cr2O3 interface.
