TNT, meet graphene: Explosive sensor

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  • Published: May 1, 2013
  • Author: David Bradley
  • Channels: Raman
thumbnail image: TNT, meet graphene: Explosive sensor

Graphene pie

Another chemical pie in which graphene has its lacy carbon fingers is in the form of a sensitive and selective detection system for the common explosive trinitrotoluene (TNT). Silver nanoparticles functionalised with p-aminothiophenol (PATP) and supported on graphene sheets allow the straightforward surface-enhanced Raman spectroscopic (SERS) detection of the explosive. Credit: Chen et al/Elsevier

Another chemical pie in which graphene has its lacy carbon fingers is in the form of a sensitive and selective detection system for the common explosive trinitrotoluene (TNT). Silver nanoparticles functionalised with p-aminothiophenol (PATP) and supported on graphene sheets allow the straightforward surface-enhanced Raman spectroscopic (SERS) detection of the explosive.

Minmin Liu and Wei Chen of the State Key Laboratory of Electroanalytical Chemistry at Changchun Institute of Applied Chemistry, part of the Chinese Academy of Sciences, in Changchun, China, point out that detected nitrated explosives, including the most familiar such compound, 2,4,6-trinitrotoluene (TNT), is of increasing interest in terms of homeland security, environmental concerns and humanitarian issues. TNT is commonly in mining and in underwater blasting where it represents a toxic threat to ecosystems but also more insidiously in landmines and in other military and terrorist activities.

Explosive detection

Techniques based on fluorescence with functional polymers and nanoparticles quenched by TNT, colorimetrics using changes in plasmon absorbance, redox-sensitive electrochemistry have been developed for TNT detection. X-ray analysis and Raman spectroscopy have been used previously. Raman spectroscopy offers great potential but always suffers from low signal intensity, which is overcome to some degree by the use of roughened metal surfaces to enhance the effect. Liu and Chen have now turned to graphene as alternative substrate for creating an enhancing surface using silver nanoparticles. The combination of an electrochemical and a chemical mechanism would, as with conventional SERS, lead to a substantial enhancement. Moreover, the presence of the graphene quenches the interfering excited state luminescence others have found.

The team prepared silver nanoparticles by reducing silver nitrate with sodium citrate, which they then functionalised with PATP exploiting the fact that imprinting would create "hot spots" through aggregation on the surface of the PATP-modified silver nanoparticles on the graphene nanosheets. They could then demonstrated that intense spectral resonance from the DMAB-TNT-DMAB bridges formed between the silver-graphene nanosheets allowed them to detect trace quantities of TNT at a concentration as low as 5x10-16 molar.

Enhancement

"The present study not only provides a facile method for ultrasensitive and selective detection of TNT but also could develop a graphene-based SERS platform," the team says. Nitrobenzene, 2-nitrotoluene, 4-nitrophenol and 2, 4- dinitrotoluene showed much lower SERS enhancement, the researchers add.

Related Links

Biosens Bioelectron 2013, 46, 68-73: "Graphene nanosheets-supported Ag nanoparticles for ultrasensitive detection of TNT by surface-enhanced Raman spectroscopy"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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