Jump to main content
Jump to site search


Ultra-sensitive gas phase detection of 2,4,6-trinitrotoluene by non-covalently functionalized graphene field effect transistors

Author affiliations

Abstract

The high energy density (4.2 MJ kg−1) and low vapour pressure (7.2 × 10−9 atm) of chemical explosives such as TNT (2,4,6-trinitrotoluene) pose a grave security risk demanding immediate attention. Detection of such hazardous and highly challenging chemicals demands specific, ultra-sensitive and rapid detection platforms that can concomitantly transduce the signal as an electrical readout. Although chemo-sensitive strategies have been investigated, the majority of them are restricted to detecting TNT from solutions and are therefore not implementable in real-time, on-field situations. Addressing this demand, we report an ultra-sensitive (parts-per-billion) and rapid (∼40 s) detection platform for TNT based on non-covalently functionalized graphene field effect transistors (GFETs). This multi-parametric GFET detector exhibits a reliable and specific modulation in its Dirac point upon exposure to TNT in the vapour phase. The chemical specificity provided by 5-(4-hydroxyphenyl)-10,15,20-tri(p-tolyl) zinc porphyrin (ZnTTPOH) is synergistically combined with the high surface sensitivity of graphene through a non-covalent functionalization approach to realise p-doped GFETs (Zn-GFETs). Such a FET platform exhibits extremely sensitive shifts in Dirac point (ΔDP) that correlate with the number of nitro groups present in the analyte. Analytes with mono-, di-, and tri-nitro substituted aromatic molecules exhibit distinctly different ΔDP, leading to unprecedented specificity towards TNT. Additionally, the Dirac point of Zn-GFETs is invariant for common and potential interferons such as acetone and 2-propanol (perfume emulsifiers) thereby validating their practical applicability. Furthermore, the ΔDP is also manifested as changes in the contact potential of GFETs, indicating that sub-monolayer coverage of ZnTTPOH is sufficient to modulate the transfer characteristics of GFETs over an area 1000 times larger than the dopant dimensions. Specifically, ZnTTPOH-functionalized GFETs exhibit p-doped behaviour with positive ΔDP with respect to pristine GFETs. Such p-doped Zn-GFETs undergo selective charge-transfer mediated interactions with TNT resulting in enhanced electron withdrawal from Zn-GFETs. Thus the ΔDP shifts to a higher positive gate voltage leading to the dichotomous combination of the highest signal generation (1.2 × 1012 V mol−1) with ppb level molecular sensitivity. Significantly, the signal generated due to TNT is 105 times higher in magnitude compared to other potential interferons. The signal reliability is established in cross-sensitivity measurements carried out with a TNT–mDNB (1 : 10 molar ratio) mixture pointing to high specificity for immediate applications under atmospherically relevant conditions pertaining to homeland security and global safety.

Graphical abstract: Ultra-sensitive gas phase detection of 2,4,6-trinitrotoluene by non-covalently functionalized graphene field effect transistors

Back to tab navigation

Supplementary files

Publication details

The article was received on 02 Oct 2019, accepted on 12 Nov 2019 and first published on 12 Nov 2019


Article type: Paper
DOI: 10.1039/C9AN01962F
Analyst, 2020, Advance Article

  •   Request permissions

    Ultra-sensitive gas phase detection of 2,4,6-trinitrotoluene by non-covalently functionalized graphene field effect transistors

    A. S. Gajarushi, S. G. Surya, M. G. Walawalkar, M. Ravikanth, V. R. Rao and C. Subramaniam, Analyst, 2020, Advance Article , DOI: 10.1039/C9AN01962F

Search articles by author

Spotlight

Advertisements