4-t-butyl-CuPc-PODT molecular composite material for an effective gas sensor

The sensing properties of molecular composites, tetratertbutyl copper phthalocyanine (TBCPC) and polyoctadecyl thiophene (PODT), were investigated by optical and conductance measurements. A standard substrate for gas sensing was made, consisting of a set of eight interdigitated gold electrodes, 230 mum wide and spaced, and 0.10 mum thick, photo-lithographically fixed on an SiO2 coated silicon wafer. LB films of different thickness and composite compositions were fabricated at different surface pressures. The gas sensing behavior of the films, on exposure to NO2 and NH3 gases, depends on the mutual ratio of components of the composite. The film thickness determines the response speed on exposure to gases and their reversal. It was also found that the films deposited at lower surface pressures show larger and faster response and better recovery kinetics. The electrical properties of gold contacts to these Langmuir-Blodgett (LB) layers were evaluated by current-voltage characteristics, which are linear over the whole measuring range. Very short response times, reasonably good reproducibility, and fair composition dependent sensitivity at room temperature make this molecular composite a very promising candidate for neuron network sensing elements.