Highly Sensitive and Selective Trimethylamine Sensor Using Yolk-shell Structured Mo-doped Co₃O₄ Spheres

Pure and 0.5, 1, 2, 5, and 10 at% of Mo-doped Co3O4 yolk-shell spheres were synthesized by ultrasonic spray pyrolysis of droplets containing Co nitrate, ammonium molybdate, and sucrose and their gas sensing characteristics to 5 ppm trimethylamine (TMA), ethanol, p-xylene, toluene, ammonia, carbon monoxide, and benzene were measured at 225-325 oC. The sensor using pure Co3O4 yolk-shell spheres showed the highest response to p-xylene and very low response to TMA at 250 oC, while the doping of Mo into Co3O4 tended to increase the overall responses of gas sensors. In particular, the sensor using 5 at% Mo-doped Co3O4 yolk-shell spheres exhibited the high response to TMA with low cross-responses to other interfering gases. The high response and selectivity of Mo-doped Co3O4 yolkshell spheres to TMA are attributed to the electronic sensitization by higher valent Mo doping and acid-base interaction between TMA and Mo components.