Parallel-packaged multiple-gas microsensors based on hollowed nanostructures of doped tin oxides

Hollow nanofiber multiple-gas microsensors containing a ceramic package in parallel were developed via doping metal oxides in tin oxide (SnO₂) and electrospinning and calcination. Different metal oxides including nickel oxide (NiO), copper oxide (CuO), and indium oxide (In₂O₃) were doped into SnO₂ individually as sensing films for the detection of acetone (CH₃COCH), ammonia (NH₃), and hydrogen sulfide (H₂S) with high selectivity. After heating and calcination, the hollow electrospun nanofibers formed with high specific surface area and porosity resulting in increased sensing area and enhancing the rate of surface chemical reaction and responsivity. The experiments show that the optimal local operation temperature of the activated sensors was 330 °C. High responsivity of the packaged gas sensors was obtained with high accuracy and repeatability. Gas sensitivities were 0.071, 0.075, and 0.09 for sensors of acetone, ammonia, and hydrogen sulfide, respectively, at concentrations of 1 ppm. The response and recovery times of the acetone, ammonia, and hydrogen sulfide gas sensors were 4 and 8 s, 5 and 9 s, and 5 and 12 s, respectively.