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
) 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.
An Organic Vortex Laser Stellinga, Daan; Pietrzyk, Monika E; Glackin, James M. E ...
ACS nano,
03/2018, Volume:
12, Issue:
3
Journal Article
Peer reviewed
Open access
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 l = 3 that can be readily multiplexed into an array configuration.
Swabs taken from the surface of a suspicious object are a standard method of identifying a concealed explosive device in security-conscious locations like airports. In this paper we demonstrate a ...sensitive method to collect and detect trace explosive residues from improvised explosive devices using swabs and an optical sensor element. Swabs coated with a commercial fluoropolymer are used to collect material and are subsequently heated to thermally desorb the explosives, causing the quenching of light emission from a thin film luminescent sensor. We report the sorption and desorption characteristics of swabs loaded with 2,4-DNT tested with Super Yellow fluorescent sensors in a laboratory setting, with detection that is up to three orders of magnitude more sensitive than standard colorimetric tests. The method was then applied in field tests with raw military-grade explosives TNT, PETN and RDX, on various objects containing the explosives, and post-blast craters. We show for the first time results using organic semiconductors to detect sub-milligram amounts of explosive sorbed onto a substrate from real explosives in the field, giving a promising new approach for IED detection.
Swabs taken from the surface of a suspicious object are a standard method of identifying a concealed explosive device in security-conscious locations like airports. Light-emitting polymer sensors can detect trace amounts
via
fluorescence quenching.
Trace sensing of explosive vapours is a method in humanitarian demining and Improvised Explosive 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 beehives, 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.
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•Trace detection of explosive vapours is challenging in real-world environments.•By “preconcentrating” trace vapours onto solid substrates, higher amounts can be collected for detection.•Our approach combines polymer preconcentrators, honeybees for sampling, and luminescent thin films as the sensing mechanism.•The inexpensive, commercially-available fluoropolymer Aflas has shown good preconcentration abilities for 2,4-DNT.•Lab and field results indicate this method is a promising tool for detecting trace explosive vapours in contaminated land.
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.
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•An ormosil coating is used to ruggedize a fluorescent polymersensor for aqueous use.•The ormosil layer allows efficient access of theanalyte to the polymer layer below.•The sensors show fast, sensitive response to2,4-DNT in aqueous and vapour phases.•The reversible response has potential for long-termmonitoring of explosives in water.
Humanitarian demining is a worldwide effort and the range of climates and environments prevent any one detection method being suitable for all sites, so more tools are required for safe and efficient ...explosives sensing. Landmines emit a chemical flux over time, and honeybees can collect the trace residues of explosives (as particles or as vapour) on their body hairs. This capability was exploited using a passive method allowing the honeybees to freely forage in a mined area, where trace explosives present in the environment stuck to the honeybee body, which were subsequently transferred onto an adsorbent material for analysis by a fluorescent polymer sensor. Potential false positive sources were investigated, namely common bee pheromones, the anti-varroa pesticide Amitraz, and the environment around a clean apiary, and no significant response was found to any from the sensor. The mined site gave a substantial response in the optical sensor films, with quenching efficiencies of up to 38%. A model was adapted to estimate the mass of explosives returned to the colony, which may be useful for estimating the number of mines in a given area.
•Collection and detection of trace explosives is challenging in real-world environments.•Honeybees are used to passively collect explosives on body hair via free-flying.•Returning to the colony, the bees deposit explosives onto a sorbing preconcentrator for analysis by optical sensor.•Several potential distractant chemicals are tested and found not to give false positives.•A model has been developed to estimate the amount of explosive returned to the colony by the foraging bees.
Flexible and Ultra-Lightweight Polymer Membrane Lasers Karl, Markus; Glackin, James M. E.; Schubert, Marcel ...
2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC),
2019-June
Conference Proceeding
Open access
We report on a laser in the form of a flexible and lightweight membrane that can be affixed to objects such as banknotes, contact lenses, and finger nails. Bendable and stretchable solar cells and ...LEDs based on carbon-based polymers and small molecules are described in the literature. However, the first organic lasers were rigid and relatively bulky, in part because they use a thick and stiff support substrate.
Trace detection of explosives is an important challenge in both humanitarian landmine clearance and in homeland security scenarios. The ability to detect the presence of explosives across an area of ...interest would be of particular use in technical surveys of suspected minefields. In this paper we present the development and application of fluorescence-based trace-explosives sensors based on organic semiconductor thin films. We show that these can be used to detect nano-gram level quantities of nitroaromatic (TNT-like) molecules, and combine them for the first time with a novel preconcentration approach to detect buried explosives. Initial field trials on a test minefield will also be presented, in which the sensors are used to detect trace explosives collected by colonies of foraging honeybees.
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