Colorimetric-based detection of TNT explosives using functionalized silica nanoparticles.

Hua Xu,Mike Pivnenko,Malik Qasim,Daping Chu,Zhongze Gu,Noorhayati Idros,Man Ho

doi:10.3390/s150612891

Abstract

This proof-of-concept study proposes a novel sensing mechanism for selective and label-free detection of 2,4,6-trinitrotoluene (TNT). It is realized by surface chemistry functionalization of silica nanoparticles (NPs) with 3-aminopropyl-triethoxysilane (APTES). The primary amine anchored to the surface of the silica nanoparticles (SiO2-NH2) acts as a capturing probe for TNT target binding to form Meisenheimer amine–TNT complexes. A colorimetric change of the self-assembled (SAM) NP samples from the initial green of a SiO2-NH2 nanoparticle film towards red was observed after successful attachment of TNT, which was confirmed as a result of the increased separation between the nanoparticles. The shift in the peak wavelength of the reflected light normal to the film surface (λpeak) and the associated change of the peak width were measured, and a merit function taking into account their combined effect was proposed for the detection of TNT concentrations from 10−12 to 10−4 molar. The selectivity of our sensing approach is confirmed by using TNT-bound nanoparticles incubated in AptamerX, with 2,4-dinitrotoluene (DNT) and toluene used as control and baseline, respectively. Our results show the repeatable systematic color change with the TNT concentration and the possibility to develop a robust, easy-to-use, and low-cost TNT detection method for performing a sensitive, reliable, and semi-quantitative detection in a wide detection range.

Highlights

Sensing of trace explosives such as 2,4,6-trinitrotoluene (TNT) is a complex and challenging task due to the lack of inexpensive sensors with high selectivity and sensitivity [1], the lack of detectable signals, and wide selection of explosive compositions [2,3]
The colorimetric response examined in this work was focused on dried nanoparticle films, from which the reflected light was studied
We expect that the reflected light from the functionalized nanoparticles in liquid will behave differently, which may reveal more information regarding the interactions between them

Summary

Introduction

Sensing of trace explosives such as 2,4,6-trinitrotoluene (TNT) is a complex and challenging task due to the lack of inexpensive sensors with high selectivity and sensitivity [1], the lack of detectable signals, and wide selection of explosive compositions [2,3]. Current sensing methods of nitro-based explosives are gas and liquid chromatography [14], mass spectrometry [15], ion-mobility spectroscopy [16], enzymatic assays [17], and electrochemical detection [18]. A simple and label-free alternative is to use optical detection in association with designed colorimetric arrays of charge-transfer acceptor/donor complexes made of colloidal mesoporous nanoparticles based on specific color responses via donor–acceptor interactions between TNT and primary amines [19,20], but how to detect TNT in a wide range of concentrations using such a method remains to be investigated

Methods

Results

Conclusion