Ammonia Sensory Properties Based on Single-Crystalline Micro/Nanostructures of Perylenediimide Derivatives: Core-Substituted Effect

Ammonia sensory properties based on conductometric gas sensors composed of single-crystalline micro/nanostructures of PTCDI-C-12, PTCDI-Br2C12, and PTCDI-CN2C12 were investigated, and it was found that the core-cyanated PTCDI-CN2C12 sensor was response to NH3 gas. The initial sensitivity of the PTCDI-CN2C12 sensor had a value of 40%, then slightly decreased to 37% in 24 h, and could still keep a stable value of 37% after its exposure to air for 14 days. Detailed studies indicated that the addition of the strong electron-withdrawing group, CN, caused a significant decreasing of the reduction potential of PTCDI-CN2C12, which led to a notable increasing of the current of PTCDI-CN2C12 nanobelts with their exposure to NH3 gas due to the efficient charge exchange occurring between the PTCDI-CN2C12 and NH3 molecules so as to show that it is highly sensitive to NH3 molecules. The low LUMO energy level and highly ordered arrangement in nanobelts determined that the sensitivity of the PTCDI-CN2C12 sensor could keep a stable value even though it was exposed to air for 14 days. It is expected that this study can provide some valuable information for fabricating organic sensing devices with good sensitivity and stability.