Bulk acoustic sensor of 2-nitro-5,10,15,20-tetraphenyl-21H,23H-porphinecopper(III) thin film to detect organic vapours

A bulk acoustic sensor system was fabricated to detect organic vapours of toluene, benzene, hexane and cyclohexane. The system consists of Langmuir Blodgett thin film deposited on a quartz crystal. The sensing sensitivity was based on the changes of the fundamental frequency of the quartz crystal upon exposure toward vapours. It was found that the thin film was sensitive to the present of gases by reducing the crystal frequency as high as 13 Hz, 8 Hz, 4 Hz, and 3 Hz for toluene, benzene, hexane and cyclohexane respectively. The response time to reach the maximum changes on the frequency was within 200 seconds. The recovery time after the vapors removed from the system was within 200 seconds. The variation of response with the type of vapours may be used as selectivity criteria for the sensor.