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Many aspects of optical chemical sensor design would benefit from a better knowledge of the diffusion properties of the analyte in the polymer host. The response times of such sensors to a step change of analyte concentration are of vital interest for many applications of fast-responding sensors. Further, the diffusion properties govern their quenching behavior and their sensitivity. A method for determination of the diffusion constant of oxygen in polymers has been developed and used by several groups in the past. The underlying mathematical model for luminescence quenching by molecules of a gas in a single sensing layer on an impermeable support has not yet been completely derived in an analytical form and still uses tedious numerical methods. We present a partial analytical solution to the problem of modeling the time dependence of luminescence generated by in- or out-diffusion of a gaseous quencher in a polymer film in which a luminophor is immobilized and offer a suitable method to predict sensor response times.

The effects of photobleaching on absorption properties and decay times of ruthenium complexes adsorbed on silica gel or dissolved in polystyrene or PVC are reported. While complexes with bipyridyl ligands adsorbed on silica gel did not show any decay time decrease at all, complexes having phenanthroline ligands exhibit a significant photodegradation which is manifested not only by a decrease in luminescence intensity but also by decay time decrease and specific absorption spectral changes. The effects are shown to depend strongly on the oxygen and dye concentrations present at the bleaching process. The absorption bands of the photoproducts of ruthenium-phenanthroline complexes overlap with the emission spectra of the intact molecules. Forster resonance energy transfer from intact ruthenium complexes to their own photoproducts, generated by singlet oxygen attack of the phenanthroline bridges of the ligands, is suggested to be responsible for the observed decay time effects.

A calibration study between two laboratories tracked the flow of sewage and pollutants in Narragansett Bay by using linear alkylbenzenes as markers.

On the European market there are several fire retardant products available, which reach class B in the European classification system. The producers promise their fire retardants are effective in reducing different reaction to fire parameters of wood such as the time to ignition, the mass loss rate, the heat release rate, the total heat release, the charring rate and the flame spread. This paper discusses the performance of fire retardant products as pressure impregnated wood, non-intumescence surface coatings and intumescence coatings on Norway spruce (Picea abies). The investigations are performed by using a cone calo- rimeter test according to ISO 5660. The thermal exposures of the investigations are 50 kW/m2 and the standard IS0 834 test curve. As result information about the heat release rate, the mass loss rate and the total heat release for duration of 900 seconds will be presented in this paper.

The design of luminescent oxygen sensors is guided by optimizing sensitivity and/or the form of the calibration function. Both qualities are governed by the molecular processes of luminescence quenching. To evaluate the influence of matrix effects, we prepared membranes based on oxygen-sensitive phosphorescent complexes of porphyrin ketones dissolved in plasticizer-free poly(vinyl chloride) (PVC) and polystyrene (PS). In a PVC matrix, both platinum(II) and palladium(II) octaethylporphyrin ketones exhibited perfectly linear Stern-Volmer intensity plots and almost single-exponential excited state decays. In a PS matrix, the sensitivity of palladium(II) octaethylporphyrin ketone was among the highest reported to date. Yet, slightly nonlinear Stern-Volmer plots and nonexponential decays illustrate the significance of matrix effects of PS. Addition of plasticizers to PVC-based sensors allowed tuning of the oxygen sensitivity in a wide range, while the Stern-Volmer plots became pronouncedly nonlinear. For the plasticizer bis(2-ethylhexyl) adipate, the decay profile was single-exponential in the absence but nonexponential in the presence of oxygen, which is attributed to a distribution of quenching rate constants.

Chemically homogeneous polymer layers loaded with oxygen-quenchable luminescent dyes may lead to promising applications for optical oxygen sensing. In this work, luminescence quenching of tris(4,7 [prime]-diphenyl-1,10 [prime]-phenanthroline)Ru(II) perchlorate, dissolved in a polystyrene layer, has been investigated. Although the dye appears to be molecularly dispersed in this glassy polymer, the Stern-Volmer intensity plot is nonlinear and the luminescence decay is not single exponential. This can be attributed to a spatial disorder in the polymer structure, which is likely to determine the excited state properties. It is shown that an analysis of intensity quenching and luminescence lifetime data based on a multicomponent approach, which was previously developed for dyes in chemically heterogeneous silica matrices, can also be applied to this polymer. Quenching is shown to be dynamic in nature. Some features of polystyrene-based optical oxygen sensors having an enhanced dye concentration are pointed out.

Conventional lifetime imaging requires rather complex and expensive instrumentation, like lasers and intensified CCD-cameras. We demonstrate that an array of light-emitting diodes and a directly gamble CCD-camera can be alternatively used for special applications as, for example, imaging of oxygen concentrations on a surface covered by an optical sensor. The suitability of low-cost devices is in this case favored by the microsecond decay times and the spectral properties of highly luminescent ruthenium(II) complexes. For an illuminated sensor area of 5 [cm.sup.2] and an aimed spatial resolution of 1 mm, oxygen resolution was better than [Delta]P[O.sub.2] = 0.4 Tort in the absence of oxygen and [Delta]P[O.sub.2] = 2.5 Torr at P[O.sub.2] = 100 Torr.

We report on the structuring of the backside surface of sapphire substrates in high-power flip-chip light-emitting diodes (LEDs) by femtosecond laser direct writing. Varying the laser powers has been found to affect the sizes of the inscribed patterns on a submicron scale which facilitates the control of the structure sizes with high precision. Accordingly, since on the one hand the light extraction efficiency reveals a strong dependence on pattern sizes, and on the other hand, femtosecond laser structuring provides a simple opportunity to inscribe diverse structures along the LED surfaces, LEDs with laterally controlled light extraction efficiencies can be fabricated. [ABSTRACT FROM AUTHOR]