Photoacoustic sensor for trace detection of post-blast explosive and hazardous molecules

The development of a sensor based on laser photoacoustic spectroscopic technique for detection of nanogram quantity of hazardous molecules, drugs and post-blast explosive is discussed. Traces of explosive and hazardous molecules on nanogram scales collected by swiping small pieces of paper on the contaminated surfaces have been detected. The Photoacoustic cell used in the sensor is of T type. The cell is designed using COMSOL software and developed with a compatible sensitive microphone. The photoacoustic signal is detected via indirect method. Sample kept in the cell was not in direct contact of the microphone. Indirect photoacoustic experiments have been done in closed cell. Tunable quantum cascade laser having tunability in the wavelength range of 7-9 μm (wavenumber 1400-1100 cm−1) was used in the experiments. A phase sensitive data acquisition system has also been developed. The developed sensor is capable to identify traces of explosives up to the order of ppb level in post blast materials.