Preparation and gas-sensing properties of bisphthalocyaninato SmP/sub c/*/sub 2/ LB films

摘要

Bis[phthalocyaninato] Sm[P/sub c/*]/sub 2/ [P/sub c/*=P/sub c/(OC/sub 8/H/sub 17/)/sub 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/sub c/*]/sub 2/ in chloroform before Sm[P/sub c/*]/sub 2/ Langmuir-Blodgett (LB) films were deposited on silicon substrate. In order to produce stable LB films, Sm[P/sub c/*]/sub 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(Sm[P/sub c/*]/sub 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 (VGs) which is greater than threshold voltage (VTH), 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/sub 2/ gas. Results are presented showing that the device can detect reversibly the concentration of NO/sub 2/ gas down to 5ppm at room temperature.