The properties of praseodymium bis[octakis(octyloxy)phthalocyaninato] complex Langmuir–Blodgett films for NO2 sensor

Langmuir–Blodgett (LB) films of general organic semiconductor materials may be used as gas sensors because the conductivity depends on the presence of some gas species. Praseodymium bis[phthalocyaninato] complex-based LB films are very sensitive to the change of nitrogen dioxide(NO2) gas concentration. In the paper, a new kind of sandwich-like praseodymium bis[2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] complex Pr[Pc∗]2 (Pc∗=Pc(OC8H17)8) was used as film-forming material. It is found that a mixture of Pr[Pc∗]2 and octadecanol (OA) with 1:6 molar ratio formed an excellent material for the fabrication of gas-sensing LB film. The sensitive property of Pr[Pc∗]2 LB films to NO2 gas was monitored by the change of resistance during gas exposure. The detecting range was from 0 to 100 ppm, and the response time of 11-layer Pr[Pc∗]2 LB film to 20 ppm NO2 was 27 s at room temperature. Factors affecting gas-sensing properties of Pr[Pc∗]2 LB films to NO2 gas such as temperature, number of film layers and processing conditions were also discussed in the paper.