Detecting chemical hazards The ability to rapidly detect and identify chemical hazards would be enormously valuable for first responders dealing with the aftermath of accidents and industrial leaks. We spoke to Dr Damir Asoli about the work of the SERSing project in developing a low-weight, handheld device to identify chemical hazards at low concentrations. An industrial accident or terrorist
SERSing project
attack can lead to the leak of hazardous chemical substances into public places, which may represent a significant threat to the health of first responders and people in the surrounding area. The ability to rapidly identify the nature of a threat would help first responders deal with it effectively, an issue central to the EU-funded SERSing project. “First responders have to come to the scene of an industrial accident or terrorist attack and find out what the threat is,” says Dr Damir Asoli, a member of the project management group. The project brings together nine partners from across Europe to develop devices to detect and identify chemical hazards, focusing on five nerve agents in particular. “In the project we are mainly looking at A-234 (Novichok), Tabun, VX, hydrogen cyanide, hydrogen sulfide and sarin,” outlines Dr Asoli. “Some of these chemical hazards are in the liquid phase, while others are in the gas phase.”
The project team is working to develop portable, low-weight handheld SERS-based (Surface Enhanced Raman Spectroscopy) devices to detect and identify these chemical hazards, which would be much easier to use than the often cumbersome detectors used today. The device itself is a little bigger than a human hand, with a washer and a nanostructured silver or gold substrate in the middle, which is the active part. “The washer is there solely for handling purposes. A first responder at the scene of an accident would collect an extremely small amount of liquid in a bottle – typically we use 2 microlitres – then put it over the active area of the device, which is the substrate,” explains Dr Asoli. An optical phenomenon called localized surface plasmon resonance (LSPR) is used to amplify the Raman scattering signal from molecules, which in practice involves (1) depositing analyte on the substrate, (2) sending light from the device to the substrate, (3)
collecting and analysing the Raman scattered light “We typically use a 785 nanometre laser wavelength to detect and identify relevant compounds,” continues Dr Asoli. Under the right conditions, a strong SERS signal can be generated, which allows even trace detection of analytes, i.e. detection at an extremely low analyte concentration level. In addition, each compound displays a specific Raman ‘fingerprint’ spectrum, which means that sample identification can be performed within minutes. Typical SERS substrates are nanostructured silver or gold, which display favourable optical properties in the visible and near-infrared spectral regions. One key requirement is that analyte molecules need to be located very close to the nanostructured metal surface, or preferably adsorbed on the metal surface. Dr Asoli says that the SERS substrates can also be functionalised to get a better response in cases where molecules don’t stick to the metal surface. “You can
Field trials with end-users at SUJCHBO.
www.euresearcher.com
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