Molecular recognition of 2,4,6-trinitrotoluene by 6-aminohexanethiol and surface-enhanced Raman scattering sensor

• Published in: Sensors and actuators. B, Chemical Chemical, 2015-12, Vol.221, p.273-280
• Main Authors: Jamil, Arniza K.M., Sivanesan, Arumugam, Izake, Emad L., Ayoko, Godwin A., Fredericks, Peter M.
• Format: Article
• Language: English
• Subjects: 2,4,6-Trinitrotoluene (TNT) sensor; 6-Aminohexanethiol (AHT) and mixed monolayer; Analysis of explosives in soil; Complex formation; Electrochemical desorption and X-ray photoelectron spectroscopy (XPS); Monolayers; Nanostructure; Raman scattering; Raman spectroscopy; Recognition; Sensors; Surface-enhanced Raman spectroscopy (SERS); TNT
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2015.06.046

•AHT monolayer on gold nanostructured SERS active surface was used as a new recognition molecule for TNT.•The availability of the free amine groups and vertical orientation of AHT monolayer was supported by electrochemical desorption and XPS studies.•AHT:Butanethiol (9:1) mixed monolayer system showed enhanced SERS signal for TNT with the lowest detection limit of 100 fM.•Selective detection of TNT in soil was demonstrated. 2,4,6-Trinitrotoluene (TNT) is one of the most commonly used nitro aromatic explosives in landmine, military and mining industry. This article demonstrates rapid and selective identification of TNT by surface-enhanced Raman spectroscopy (SERS) using 6-aminohexanethiol (AHT) as a new recognition molecule. First, Meisenheimer complex formation between AHT and TNT is confirmed by the development of pink color and appearance of new band around 500nm in UV–vis spectrum. Solution Raman spectroscopy study also supported the AHT:TNT complex formation by demonstrating changes in the vibrational stretching of AHT molecule between 2800 and 3000cm−1. For surface enhanced Raman spectroscopy analysis, a self-assembled monolayer (SAM) of AHT is formed over the gold nanostructure (AuNS) SERS substrate in order to selectively capture TNT onto the surface. Electrochemical desorption and X-ray photoelectron studies are performed over AHT SAM modified surface to examine the presence of free amine groups with appropriate orientation for complex formation. Further, AHT and butanethiol (BT) mixed monolayer system is explored to improve the AHT:TNT complex formation efficiency. Using a 9:1 AHT:BT mixed monolayer, a very low detection limit (LOD) of 100fM TNT was realized. The new method delivers high selectivity towards TNT over 2,4 DNT and picric acid. Finally, real sample analysis is demonstrated by the extraction and SERS detection of 302pM of TNT from spiked.