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Novel sol-gel derived films for luminescence-based oxygen and pH sensing

Wencel D., Higgins C., Klukowska A., Maccraith B. D., Mcdonagh C.

Materials Science Poland

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2007

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Vol. 25, No. 3

767--779

EN

A range of both sol-gel and polymer derived sensor films have been developed for optical oxygen and pH sensing. Oxygen sensing is based on the luminescence quenching of the ruthenium complex [Ru(II)-tris( 4,7-diphenyl-1,10-phenanthroline)]dichloride, ([Ru(dpp)3]2+), which is entrapped in the sol-gel matrix. The oxygen-dependent luminescence is detected using the principle of phase fluorometry, which facilitates indirect monitoring of the luminescence lifetime. The pH sensor uses excitation ratiometric detection of the fluorescence from the pH sensitive dye, 1-hydroxypyrene-3,6,8-trisulfonic acid, ion-paired with cetyl trimethyl ammonium bromide (HPTS_IP). The phase-based detection scheme, dual lifetime referencing (DLR), was also examined as an alternative sensing strategy. ORMOSIL oxygen sensor films were fabricated using a range of organosilicon precursors including methyltriethoxysilane (MTEOS), ethyltriethoxysilane (ETEOS), n-propyltriethoxysilane (PTEOS) and phenyltriethoxysilane (PhTEOS). In addition to optimising the sensor performance, issues such as the influence of humidity on oxygen sensing were addressed. By varying the processing parameters, the surface characteristics and microstructure were tailored to suit applications such as breath gas analysis and bioprocess monitoring. pH sensor films were prepared by hydrolyzing and co-condensing (3-aminopropyl) trimethoxysilane (APTMS) with an organosilicon monomer such as ETEOS or PTEOS or the polymer, ethyl cellulose (EC). Optimised pH sensors showed good reproducibility, reversibility and short response times. The dynamic range for these sensor films extends from pH 6.00 to 8.50 which is relevant for bioprocess monitoring applications. The spectral compatibility of the luminophores and the printability of the sol-gels present the possibility of simultaneous oxygen and pH sensing using low-cost LEDs as excitation sources along with common detection electronics.

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Photochromic sol-gel derived hybrid polymer coatings: the influence of matrix properties on kinetics and photodegradation

Klukowska A., Posset U., Schottner G., Jankowska-Frydel A., Malatesta V.

Materials Science Poland

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2004

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Vol. 22, No. 3

187--199

EN

Photochromic dyes undergo a reversible change in their absorption characteristics upon UV light irradiation. By incorporating such photochromophores into sol-gel derived inorganic-organic hybrid polymers, versatile coatings with a fast photochromic response and high photochromic activity can be obtained. In the present study, the isomerization kinetics of spirooxazine dyes entrapped in hybrid polymer coatings were investigated in situ. The chemical properties of the matrices used were characterised in terms of their inorganic network connectivity (NMR measurements) and paramagnetic properties (EPR spectroscopy). Their photodegradation behaviour was studied by means of artificial weathering.

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Photochromic hybrid sol-gel coatings: preparation, properties, and applications

Klukowska A., Posset U., Schottner G., Wis M. L., Salemi-Delvaux C., Malatesta V.

Materials Science

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2002

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Vol. 20, No. 1

95--104

EN

Inorganic-organic hybrid polymer (ORMOCER?) coatings with a fast photochromic response and high photochromic activity were prepared by incorporation of the photochromophore Variacrol ?Blue D into hydrolysates of organofunctional alkoxysilanes, with subsequent thermal curing. Besides the traditional way of doping the sol-gel materials by physically dissolving the dye, a graftable derivative was prepared and covalently attached to two matrices of different rigidity. The resulting thin films showed good photochromic activity, no blooming, mechanical properties at least comparable to the pure host material, and can be applied to different glass and plastic substrates. Photochemical degradation was studied by means of artificial weathering and factors infl uencing the fatigue behaviour of the coatings assessed. The graftable dye showed improved photochemical fatigue resistance. The more rigid matrix was preferable, too, in terms of photodegradation.