Gas adsorption and gas-sensing properties of europium bisphthalocyanine derivative Langmuir-Blodgett thin films

In this paper, europium bisphthalocyanine derivative (EuPc'(2)) LB films transferred to an interdigital electrode have been prepared at room temperature. The dynamic response of the electrical conductance to Cl-2 gas is presented. At room temperature, the response time of 10-layer LB films of EuPc'(2) is 45 s and the recovery time is 1 min after exposure to a concentration of 50 ppm Cl-2. The reproducibility of the conductivity changes can be improved by using pulsed operation to reduce the exposure time to Cl-2. The change in film conductivity upon exposure of different concentrations of Cl-2 gas has been measured. The lowest detectable concentration of Cl-2 gas is 2 ppm. The maximum conductance change varies linearly with film thickness. The response time constants also increase with film thickness. The interaction between EuPc'(2) and Cl-2 in the LB films was monitored by UV-vis spectroscopy. LB films exposed to Cl-2 gave a red-shifted Q-band which can be predicted from the conductance data. (C) 1998 Elsevier Science B.V.