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  • 1
    Electronic Resource
    Electronic Resource
    Development of an optical membrane for humidity (1998)
    Springer
    Microchimica acta 130 (1998), S. 29-34 
    Details
    ISSN: 1436-5073
    Keywords: humidity-sensitive membrane ; chromoReactand ; ETHT4001
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 4-(N,N-dioctylamino)-4′-trifluoroacetyl-azobenzene (ETHT 4001), together with the catalyst tridodecylmethylammonium chloride, is dissolved in the hydrophilic polymer polyurethane Tecoflex. The resulting membrane layers show high sensitivity toward water vapour and allow the application of the membranes for humidity measurements. Upon exposure to humid air, the membrane exhibits a decrease in absorbance at a wavelength around 490 nm and an increase at around 430 nm. This signal change is caused by the conversion of the trifluoroacetyl group of the reactand into a diol, thus changing the electron delocalisation of the reactand. The sensor layer exhibits a dynamic range from 1% to 100% RH with highest sensitivity in the 5%–40% RH range. The limit of detection is 0.5% RH. The amount of added catalyst enables the sensitive range to be tailored. The selectivity over ethanol and carbonate is sufficient for the membrane to be used for long-term measurements of air. The change in colour of the humidity-sensitive membrane from red to yellow also means it can be used as an optical test strip.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01254587
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  • 2
    Electronic Resource
    Electronic Resource
    Optode membrane for continuous measurement of silver ions (1995)
    Springer
    Microchimica acta 121 (1995), S. 249-258 
    Details
    ISSN: 1436-5073
    Keywords: silver sensor ; optical sensors ; chromo-ionophore ; spectrophotometry ; PVC membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An optical sensor (optode) membrane for continuous monitoring of silver ion is presented. It is composed of plasticized poly(vinyl chloride) (PVC), a silver-sensitive chromo-ionophore, and a lipophilic borate salt acting as an anionic site. The membrane selectively responds to silver ion in the concentration range from 50 μM to 10 mM, giving a reversible colour change from blue to pink, with response times of the order of 2 min. The acridinium dye acts as both the recognition element and the chromo—ionophore. Its long-wave absorption band is at around 680 nm, which makes it compatible with existing LED light sources and diode lasers. A lipophilic octadecyl side chain renders it highly lipophilic and this prevents its leakage out of the PVC membrane. Hence, the operational lifetime exceeds 1 week, without any changes in the work function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01248254
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  • 3
    Electronic Resource
    Electronic Resource
    Investigation of potential-sensitive fluorescent dyes for application in nitrate sensitive polymer membranes (1997)
    Springer
    Fresenius' journal of analytical chemistry 357 (1997), S. 284-291 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The applicability of various potential-sensitive dyes (PSD) for optical sensing of anions is reported. Specifically, nitrate-responsive polymer membranes have been developed which are composed of a plasticized polymer, an anion exchange catalyst, and a fluorescent dye. On exposure to nitrate, the fluorescence intensity of such membranes increases, while the wavelengths of the excitation and emission maxima remain virtually unchanged. The membranes typically are 2–4 μm thick and exhibit highest sensitivity to nitrate in the 2 to 200 mgl–1 range. Signal changes on exposure to 100 mmol/l nitrate can be as high as +300%. The detection limit is 0.2 mgl–1. The cationic PSD octadecyl acridine organe was tested in combination with a tin-organic and an indium-organic anion carrier rather than with tridodecylmethylammonium chloride, but both carriers were found to display no improved selectivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050154
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of the Sol-Gel Matrix on the Performance of Ammonia Fluorosensors Based on Energy Transfer (1998)
    Springer
    Journal of fluorescence 8 (1998), S. 199-205 
    Details
    ISSN: 1573-4994
    Keywords: Ammonia optode ; sol-gel ; fluorescence energy transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report on the effect of organomodified sol-gel materials on fluorosensors for ammonia. The fluorosensors are based on ion pairs composed of an inert fluorophore and a pH-sensitive absorber dye and are embedded in sol-gel glass. Upon exposure to ammonia, deprotonation of the pH-sensitive dye bromophenolblue occurrs, and consequently, energy is transferred from the fluorophore rhodamine B or tetramethylrhodamine ethyl ester to the absorber. The response of the fluorosensors using different ratios of precursors, such as tetramethoxysilane and phenyltrimethoxysilane, is investigated. Detection limits for sol-gel layers composed of 50% tetramethoxysilane and 50% phenyltrimethoxysilane are as low as 0.1 mg/L of aqueous ammonia. Response times are of the order of 3 to 6 min for forward response. The reversibility of the sensor is related to the composition of the organically modified sol-gel glasses and is fastest for sensor layers composed of pure phenyltrimethoxysilane. Conditioning, regeneration, and storage of the layers are shown to be of vital importance for the performance of the sensor layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022549531746
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  • 5
    Electronic Resource
    Electronic Resource
    Application of a novel lipophilized fluorescent dye in an optical nitrate sensor (1995)
    Springer
    Journal of fluorescence 5 (1995), S. 135-138 
    Details
    ISSN: 1573-4994
    Keywords: Lipophilic fluorescent dye ; optical nitrate determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new lipophilic pH probe (1-hydroxypyrene-3,6,8-tris-octadecylsulfonamide) has been synthesized, and its spectral properties and applications in a solid state nitrate sensor are shown. The sensor is investigated with respect to sensitivity, limits of detection, and selectivity over other anions found in drinking water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00727530
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  • 6
    Electronic Resource
    Electronic Resource
    Novel optical sensor materials based on solubilization of polar dyes in apolar polymersWe thank the Austrian Science Foundation for providing G.J.M. with a Schrödinger Fellowship. Ute Kosch is acknowledged for having synthesized compound 5, and Achim Stangelmayer for making and investigating sensor membrane M5. (1997)
    Weinheim : Wiley-Blackwell
    Advanced Materials 9 (1997), S. 1108-1113 
    Details
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19970091410
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