Highly sensitive ammonia sensor using newly synthesized carbazole based hypercrosslinked polymer and tin dioxide

Tin Dioxide (SnO₂), carbazole based hypercrosslinked polymer (C-HCP), and C-HCP/SnO₂ nanocomposites by different C-HCP weight percent concentration (0.05–0.15 %wt.) were synthesized by precipitation method and used as sensing materials for ammonia sensor. These materials were applied for ammonia detection in various temperature (100–350 °C) and ammonia concentration (100, 200, and 300 ppm). The electrical conductivity of materials was measured at different temperature and decreasing of electrical conductivity observed by temperature increasing. The resistance of sensor in air to that in presence of ammonia was considered as sensor response. According to the results, SnO₂ had much greater conductivity than different concentration of C-HCP/SnO₂ composite under same conditions. The results showed that in maximum sensor response with adding the C-HCP in SnO₂, the optimum temperature decrease. The optimum temperature for SnO₂ and 0.05, 0.1, and 0.15 %wt. of C-HCP in SnO₂ composites was obtained 300 °C, 250 °C, 200 °C, and 150 °C, respectively. According to the results, the maximum sensor response observed 0.10 %wt. for ammonia detection at 200 °C. The 0.10 %wt. C-HCP in SnO₂ based sensor showed a response three times higher than that by pure SnO₂ in ammonia detection. Finally, the repeatability of sensors to the ammonia was obtained suitable in 3 continuous cycle and the response and reduction times of sensors was measured.