Preparation and gas-sensing properties of bis[phthalocyaninato] Sm[Pc*]2 LB films

Bis[phthalocyaninato] S-m[Pc*]2 [P-c*=P-c(OC8H17)(8)] has a sandwich-type structure with samarium at the center of two phthalocyanine ligands each other in a staggered form. Spreading solution of 0.42 mg/ml was prepared by dissolving Sm[P-c(*)](2) in chloroform before Sm[Pc*](2) Langmuir-Blodgett (LB) films were deposited on silicon substrate. In order to produce stable LB films, S-m[Pc*](2) was mixed with octadecanol (OA) at different molar ratios of 1:1, 1:3 1:6 and 1:9. It is found that a mixture of 1(S-m[P-c*](2)) : 3 (OA) generates an excellent material for the fabrication of gas-sensing LB films resulting from the optimization of film-forming characteristics. A new gas sensor has been fabricated by incorporating the multiplayer LB film into the gate electrode of charge-flow transistor (CFT), forming an array of charge-flow transistor. Given a gate voltage (V-GS) which is greater than threshold voltage (V-TH), a delay was observed in the response of the drain current. This is due to the time taken for the resistive gas-sensing film to charge UP to VGS. This characteristic delay was found to depend on the concentration of NO, gas. Results are presented showing that the device can detect reversibly the concentration of NO, gas down to 5ppm at room temperature.