Ormosil-coated conjugated polymers for the detection of explosives in aqueous environments

This project has received funding from the TIRAMISU project, funded by the European Commission’s Seventh Framework Programme (FP7/2007-2013) under grant agreement 284747, and the Engineering and Physical Sciences Research Council under grants EP/K503940/1, EP/K503162/1, EP/N509759/1. IDWS acknowledges a Royal Society Wolfson Research Merit Award. The research data supporting this publication can be accessed at http://dx.doi.org/10.17630/3875a099-bb75-4ae1-82e5-0b98b6b7ebc6.A fluorescence-based sensor for detecting explosives, based on a conjugated polymer coated with an ormosil layer, has been developed for use in aqueous environments. The conjugated polymer Super Yellow was spin-coated onto glass substrates prior to a further spin-coating of an MTEOS/TFP-TMOS-based ormosil film, giving an inexpensive, solution-based barrier material for ruggedization of the polymer to an aqueous environment. The sensors showed good sensitivity to 2,4-DNT in the aqueous phase at micromolar and millimolar concentrations, and also showed good recovery of fluorescence when the explosive was removed.PostprintPeer reviewe

Preconcentration techniques for trace explosive sensing

This project has received funding from NATO Science for Peace & Security under grant agreement MYP G5355, the European Union’s Seventh Framework Programme for research, technological development and demonstration under agreement no 284747, and the EPSRC under EP/K503940/1.Trace sensing of explosive vapours is a method in humanitarian demining and Improvised Explosives Device (IED) detection that has received increasing attention recently, since accurate, fast, and reliable chemical detection is highly important for threat identification. However, trace molecule sampling in the field can be extremely difficult due to factors including weather, locale, and very low vapour pressure of the explosive. Preconcentration of target molecules onto a substrate can provide a method to collect higher amounts of analyte for analysis. We used the commercial fluoropolymer Aflas as a preconcentrator material to sorb explosive molecules to the surface, allowing subsequent detection of the explosives via the luminescence quenching response from the organic polymer Super Yellow. The preconcentration effect of Aflas was confirmed and characterised with 2,4-DNT, prior to field sampling being conducted at a test minefield in Croatia by placing preconcentration strips in the entrance of the hives, where honeybees have collected explosive materials during free-flying. In this work we show for the first time a method for confirmation of landmines combining honeybee colonies containing a preconcentration material and subsequent monitoring of luminescence quenching.PostprintPeer reviewe

Flexible and ultra-lightweight polymer membrane lasers

The authors acknowledge financial support from the European Research Council (ERC StG ABLASE, 640012), the Scottish Funding Council (via SUPA) and EPSRC (EP/P030017/1). M.K. and J.M.E.G. acknowledge funding from the EPSRC DTG (EP/M506631/1 and EP/L505079/1). M.S. acknowledges funding from the European Commission for a Marie Sklodowska-Curie Individual Fellowship (659213). I.D.W.S. acknowledges funding from a Royal Society Wolfson research merit award.Organic semiconductors enable the fabrication of a range of lightweight and mechanically flexible optoelectronic devices. Most organic semiconductor lasers, however, have remained rigid until now, predominantly due to the need for a support substrate. Here, we use a simple fabrication process to make membrane-based, substrate-less and extremely thin (< 500 nm) organic distributed feedback lasers that offer ultralow-weight (m/A <0.5 gm−2) and excellent mechanical flexibility. We show operation of the lasers as free-standing membranes and transfer them onto other substrates, e.g. a banknote, where the unique lasing spectrum is readily read out and used as security feature. The pump thresholds and emission intensity of our membrane lasers are well within the permissible exposures for ocular safety and we demonstrate integration on contact lenses as wearable security tags.Publisher PDFPeer reviewe

An Organic Vortex Laser

Optical vortex beams are at the heart of a number of novel research directions, both as carriers of information and for the investigation of optical activity and chiral molecules. Optical vortex beams are beams of light with a helical wavefront and associated orbital angular momentum. They are typically generated using bulk optics methods or by a passive element such as a forked grating or a metasurface to imprint the required phase distribution onto an incident beam. Since many applications benefit from further miniaturization, a more integrated yet scalable method is highly desirable. Here, we demonstrate the generation of an azimuthally polarized vortex beam directly by an organic semiconductor laser that meets these requirements. The organic vortex laser uses a spiral grating as a feedback element that gives control over phase, handedness, and degree of helicity of the emitted beam. We demonstrate vortex beams up to an azimuthal index <i>l</i> = 3 that can be readily multiplexed into an array configuration