Development of nanomaterial based sensors for the detection of explosives

Detection of low levels of illicit materials, such as explosives, is a key challenge for security and environmental monitoring. Recent advances in highly sensitive molecular-recognition techniques utilising nanomaterials may pro- vide a wealth of useful tools for this purpose. In this thesis two classes of nanomaterials are applied to explosives sensing. The first is a range of novel gold nanoparticles, produced via the facile reduction of chloroauric acid with mono- and di-ketones. The mechanism of this reaction and the resultant particles are characterised with spectroscopy and tunnelling electron microscopy. Several different sizes of gold colloid were created, but most interesting was the creation of gold nanostars, which have potential as a substrate for surface-enhanced Raman spectroscopy. The second nanomaterial-based sensor is a quantum dot array featuring supramolecular receptors for small-molecule explosive detection. By combining array elements into a single, multichannel platform; faster results can be obtained from smaller amounts of sample. The ability of quantum dots to act as luminescent probes in a multichannel array, due to their sharp, variable emissions from a single excitation wavelength, was exploited to detect five explosives - 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), tetryl (2,4,6-trinitrophenylmethylnitramine), cyclotrimethylenetrinitramine (RDX) and pentaerythritol tetranitrate (PETN). To create the array, each different colour quantum dot was functionalised with a different cavitand, aromatic or nucleophilic-heteroatom based receptor via a facile photoligation process. These receptors undergo supramolecular interactions with the explosives, inducing variable fluorescence quenching of the quantum dots. Pattern analysis of the fluorescence quenching data allowed for explosive detection and identification with limits-of-detection of < 1 part-per-million. Finally, the development of the quantum dot based sensors from solution phase to solid phase is examined, with the aim of creating point-of- test devices for use in the field. A key outcome was the development of supramolecular organogel/nanoparticle hybrid “smart” materials for sensing applications