Metalloporphyrin-functionalised diamond nano-particles as sensitive layer for nitroaromatic vapours detection at room-temperature

A new sensitive coating for surface acoustic wave (SAW) transducers based on diamond nano-particles functionalised with a zinc porphyrin complex is investigated for the detection of nitroaromatic vapours. The role of diamond nano-particles is to offer a stable sp3 carbon porous matrix onto which the metalloporphyrin receptor is immobilised. This functionalised matrix can then be deposited by a layer-by-layer deposition method homogeneously on the transducer surface while featuring a high surface area. Good repeatability was obtained from sensor to sensor. The resulting sensors show a very high sensitivity of typically 120 Hz ppb−1 with a limit of detection (LOD) at 1 ppb level towards 2,4-dinitrotoluene (DNT) vapours, a tracer for explosive trinitrotoluene (TNT). The response is enhanced by more than a factor 10 when using diamond nano-particles as opposed to a transducer with only the metalloporphyrin complex deposited on the surface. The response time t90% is approximately 4 min and the sensor response is fully reversible. The cross-sensitivity of the sensor is low when exposed to polar compounds such as ethanol or moisture. Those results are encouraging towards the development of low cost portable explosive vapour detectors. Furthermore, the carbon terminated surface of diamond nano-particles offers wide opportunities for grafting other types or receptors for chemical or biological gravimetric detection.