Pulsed lamps based on electric discharges in xenon are of interest for water treatment because they are free of mercury, have instant-on capability, and may provide enhanced effects due to the high irradiance of pulses or spectral differences. This study provides quantitative comparisons of standard mercury UV lamps with both a commercial flashlamp and a pulsed surface discharge lamp. Unlike mercury lamps, the UV performance of pulsed lamps is a function of operating parameters. In this study the measured UV efficiency of a flashlamp, with a specified practical lifetime, increased as the pulse length decreased, from 4.4% at 796 µs to 9.0% at 71 µs. The surface discharge lamp, which overcomes limitations of flashlamps, had a measured UV efficiency of 17% at 12 µs. In comparison, standard commercial low pressure and medium pressure mercury lamps evaluated in this study had UV efficiencies of 34.6% and 12.2%, respectively.Résumé : Les lampes à impulsions basées sur les décharges électriques dans le xénon sont intéressantes pour le traitement de l'eau puisqu'elles ne contiennent pas de mercure; elles possèdent la capacité d'être mises en marche instantanément et elles peuvent avoir des effets accrus en raison de la haute irradiance des impulsions ou des différences spectrales. La présente étude compare quantitativement les lampes standards UV à la vapeur de mercure avec des lampes-éclairs commerciales et une lampe à décharge superficielle à impulsions. Contrairement aux lampes à vapeur de mercure, le rendement UV des lampes à impulsions est fonction des paramètres de fonctionnement. Dans cette étude, l'efficacité mesurée d'une lampe-éclair UV, ayant une durée de vie utile spécifiée, augmentait à mesure que diminuait la longueur de l'impulsion, de 4,4 % à 796 µs à 9,0 % à 71 µs. La lampe à décharge superficielle, qui comble les limites des lampeséclairs, présentait une efficacité UV mesurée de 17 % à 12 µs. En comparaison, les lampes commerciales standards à faible et à moyenne pression de vapeur de mercure évaluées lors de cette étude présentaient respectivement des efficacités UV de 34,6 % et de 12,2 %.Mots-clés : UV à impulsions, traitement de l'eau, lampe-éclair, décharge superficielle, mercure.[Traduit par la Rédaction]

A fluorescence-based integrated optics microfluidic device is presented, capable of detecting single DNA molecules in a high throughput and reproducible manner. The device integrates microfluidics for DNA stretching with two optical elements for single molecule detection (SMD): a plano-aspheric refractive lens for fluorescence excitation (illuminator) and a solid parabolic reflective mirror for fluorescence collection (collector). Although miniaturized in size, both optical components were produced and assembled onto the microfluidic device by readily manufacturable fabrication techniques. The optical resolution of the device is determined by the small and relatively low numerical aperture (NA) illuminator lens (0.10 effective NA, 4.0 mm diameter) that delivers excitation light to a diffraction limited 2.0 microm diameter spot at full width half maximum within the microfluidic channel. The collector (0.82 annular NA, 15 mm diameter) reflects the fluorescence over a large collection angle, representing 71% of a hemisphere, toward a single photon counting module in an infinity-corrected scheme. As a proof-of-principle experiment for this simple integrated device, individual intercalated lambda-phage DNA molecules (48.5 kb) were stretched in a mixed elongational-shear microflow, detected, and sized with a fluorescence signal to noise ratio of 9.9 +/-1.0. We have demonstrated that SMD does not require traditional high numerical aperture objective lenses and sub-micron positioning systems conventionally used in many applications. Rather, standard manufacturing processes can be combined in a novel way that promises greater accessibility and affordability for microfluidic-based single molecule applications.

Laponite films provide versatile inorganic scaffolds with materials architectures that direct the self-assembly of CdSe quantum dots (QDs or EviTags) and catalytic surfaces that promote the in situ polymerization of polyaniline (PANI) to yield novel nanocomposites for light emitting diodes (LEDs) and solar cell applications. Water-soluble CdSe EviTags with varying, overlapping emission wavelengths in the visible spectrum were incorporated using soft chemistry routes within Na-Laponite host film platforms to achieve broadband emission in the visible spectrum. QD concentrations, composition and synthesis approach were varied to optimize photophysical properties of the films and to mediate self-assembly, optical cascading and energy transfer. In addition, aniline tetramers coupled to CdSe (QD-AT) surfaces using a dithioate linker were embedded within Cu-Laponite nanoscaffolds and electronically coupled to PANI via vapor phase exposure. Nanotethering and specific host-guest and guest-guest interactions that mediate nanocomposite photophysical behavior were probed using electronic absorption and fluorescence spectroscopies, optical microscopy, AFM, SEM, powder XRD, NMR and ATR-FTIR. Morphology studies indicated that Lap/QD-AT films synthesized using mixed solvent, layer by layer (LbL) methods exhibited anisotropic supramolecular structures with unique mesoscopic ordering that affords bifunctional networks to optimize charge transport.