Sensor for pollutants and explosives made from 'black silicon'

Organic substances containing nitrogen are ingredients of many explosives and are present in industrial waste streams, where they pose a significant threat because of their toxicity. Detecting such substances is difficult, partly because they tend to have low vapour pressure and sensors which can detect them tend to be insensitive.

Now, a team of researchers led by a chemist from Far Eastern Federal University (FEFU) in Vladivostok now reports a sensor composed from black silicon, made by etching commercially available silicon substrates, which they claim is highly sensitive to nitroaromatic compounds but does not react to organic substances not containing nitrogen.

Alexander Mironenko, the inventor of the sensor, worked with colleagues across FEFU and with researchers in Melbourne, Australia to develop the technology, which they describe in ACS Sensors. Black silicon is so named because the etching process creates a nanostructured spiky surface.

The researchers coated this surface with a monolayer of carbazole, itself a nitroaromatic compound. It is this coating which gives the sensor the ability to detect its target molecules, as they bind to the carbazole. This changes the fluorescence properties of the coating, creating a physical effect which can be used to determine the concentration of the nitroaromatic substance.