Explosives Sensing by Using Electron-Rich Supramolecular Polymers: Role of Intermolecular Hydrogen Bonding in Significant Enhancement of Sensitivity

Gole, Bappaditya and Song, Wentao and Lackinger, Markus and Mukherjee, Partha Sarathi (2014) Explosives Sensing by Using Electron-Rich Supramolecular Polymers: Role of Intermolecular Hydrogen Bonding in Significant Enhancement of Sensitivity. In: CHEMISTRY-A EUROPEAN JOURNAL, 20 (42). pp. 13662-13680.

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Abstract

We demonstrate here that supramolecular interactions enhance the sensitivity towards detection of electron-deficient nitro-aromatic compounds (NACs) over discrete analogues. NACs are the most commonly used explosive ingredients and are common constituents of many unexploded landmines used during World WarII. In this study, we have synthesised a series of pyrene-based polycarboxylic acids along with their corresponding discrete esters. Due to the electron richness and the fluorescent behaviour of the pyrene moiety, all the compounds act as sensors for electron-deficient NACs through a fluorescence quenching mechanism. A Stern-Volmer quenching constant determination revealed that the carboxylic acids are more sensitive than the corresponding esters towards NACs in solution. The high sensitivity of the acids was attributed to supramolecular polymer formation through hydrogen bonding in the case of the acids, and the enhancement mechanism is based on an exciton energy migration upon excitation along the hydrogen-bond backbone. The presence of intermolecular hydrogen bonding in the acids in solution was established by solvent-dependent fluorescence studies and dynamic light scattering (DLS) experiments. In addition, the importance of intermolecular hydrogen bonds in solid-state sensing was further explored by scanning tunnelling microscopy (STM) experiments at the liquid-solid interface, in which structures of self-assembled monolayer of the acids and the corresponding esters were compared. The sensitivity tests revealed that these supramolecular sensors can even detect picric acid and trinitrotoluene in solution at levels as low as parts per trillion (ppt), which is much below the recommended permissible level of these constituents in drinking water.

Item Type:	Journal Article
Publication:	CHEMISTRY-A EUROPEAN JOURNAL
Publisher:	WILEY-V C H VERLAG GMBH
Additional Information:	Copy right for this article belongs to the WILEY-V C H VERLAG GMBH, BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY
Keywords:	explosive detection; nitroaromatics; self-assembly; scanning tunnelling microscopy; supramolecular polymers
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	14 Nov 2014 07:25
Last Modified:	14 Nov 2014 07:25
URI:	http://eprints.iisc.ac.in/id/eprint/50250

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