Fiber-optic sensors for pH and carbon dioxide using a self-referencing dye

Abstract

pH and C02 fiber-optic sensors were prepared using self-referencing dyes from the seminaphthorhodamine family (SNARF). The ratio of the emission from the acid and base tautomers of these dyes is insensitive to photobleaching and variations in the excitation intensity. The photophysics of the dyes has been determined. At high concentrations formation of nonfluorescent aggregates of the dyes results in reduced emission yields. The fluorescent lifetimes of the dyes are unaffected by concentration. The p of the dyepolymer composite is sensitive to the structure of the polymer. This sensitivity is attributed to a difference in energy of the conjugate base of the dye as a function of the amount of cross-linking of the polymer. The pH sensors show mpH response in the physiological pH range (6.8-7.S) and fast hydration and response times. The C02 sensors show 1-2 Torr response with partial pressures of C02 in the range of 10-100 Torr and have response and hydration times on the order of several minutes.

A novel fiber-optic pH sensor incorporating carboxy SNAFL-2 and fluorescent wavelength-ratiometric detection

“…Similar red shift in the spectrum of fluorescent dye after conjugation to polymers has been reported previously. 10 These data show that SNAFL-2 was bound successfully onto the poly(acrylamide-co-vinylamine) and that the conjugation procedure does not destroy the unique optical property of the pH probe molecule. In addition, by using the absorption spectrum of the unconjugated SNAFL-2 of known concentration, we quantified the degree of substitution of SNAFL-2 on the poly(acrylamide-co-vinylamine).…”

“…However, current immobilization procedures, which use poly(hydroxyethyl methacrylate) (PHEMA) as a polymer matrix and a thermal crosslinker (dimethylacetamide) do not provide good adhesion stability between the probe-PHEMA membrane and the fiber surface needed for lengthy applications. 10,17 Fluorinated aryl azide has been reported to create aryl nitrines under photolysis, 19 all of which undergo the characteristic reactions of this group, including C-H bond insertion onto most polymers with high efficiency. Photoaffinity crosslinking has enabled us simultaneously to create a crosslinked pH sensing membrane and to covalently bind the membrane onto the surface of a poly(methyl methacrylate) (PMMA) optical fiber.…”

“…Besides, the dynamic range of the available pH indicators also is narrow. 10 The wavelength-ratiometric method was first employed in pH sensing using the pH-sensitive fluorophore, pyranine. 11 This approach is based on the analyte causing a wavelength shift in the excitation or emission spectrum, thus permitting the amount of analyte to be correlated with the ratio of fluorescence intensities at the two wavelengths.…”

Fluorescent Carbon Dioxide Indicators

“…gaseous or dissolved carbon dioxide, and (iii) the type of measurement required, i.e. luminescence intensity or lifetime [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] . A key to all the abbreviations used in this, and all other tables and in the text, is provided at the end of this article.…”

A pH optode based on thymol blue: application to determination of CO2 using flow injection analysis system

“…Since those reported by Zhujun and Seitz [9] and Optiz and Lübbers [10] in 1984, based on Severinghaus electrode [11]. In these optodes [12][13][14][15][16][17][18][19], the CO 2 molecules diffuse through a hydrophobic membrane, which separates the sodium bicarbonate buffer internal solution from the sample, the carbon dioxide is converted to HCO 3 -in the internal solution, changing its pH, which one is followed by using colorimetric or fluorescent pH indicators. However, the greater problems in these optodes are the internal solution use to detect the pH variations, and the type of membrane used to separate the internal and the analysed solutions.…”