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Letters to Analytical Chemistry Phosphorescent Oxygen Sensors Based on Nanostructured Polyolefin Substrates Ross N. Gillanders,† Olga V. Arzhakova,‡ Andreas Hempel,§ Alla Dolgova,‡ Joe P. Kerry,§ Larisa M. Yarysheva,‡ Nikolai F. Bakeev,‡ Alexander L. Volynskii,‡ and Dmitri B. Papkovsky*,† Biochemistry Department, Cavanagh Pharmacy Building, University College Cork, Cork, Ireland, Department of Polymer Science, Moscow State University, Leninskie Gory, Moscow, 119991, Russia, and Department of Food Science and Nutrition, University College Cork, College Road, Cork, Ireland New phosphorescent oxygen-sensitive materials based on nanostructured high density polyethylene and polypropylene films are described. The polymer substrates undergo treatment by a solvent crazing process to create a welldeveloped network of controlled, nanometer-size pores. Indicator dye molecules are then embedded by physical entrapment in such nanostructures which subsequently can be healed. Such sensors demonstrate improved working characteristics and allow simple, cost-efficient production and disposable use. They are well suited for large-scale applications such as nondestructive control of residual oxygen and “smart” packaging. Quenched-luminescence O2 sensors are used extensively in industrial process control, biomedical, food, and environmental applications.1-5 O2-sensitive materials are produced in the form of solid-state coatings, soluble supramolecular6-8 and particlebased9-11 probes, or more complex composites.12-14 Solid-state sensors are attractive as they do not contaminate the sample, provide high signals, reduced interferences, and allow disposable * To whom correspondence should be addressed. E-mail:
[email protected]. † Biochemistry Department, University College Cork. ‡ Moscow State University. § Department of Food Science and Nutrition, University College Cork. (1) Wolfbeis, O. S. Anal. Chem. 2008, 80, 4269. (2) Mills, A. Chem. Soc. Rev. 2005, 34, 1003. (3) John, G. T.; Klimant, I.; Wittmann, C.; Heinzle, E. Biotechnol. Bioeng. 2003, 81, 829. (4) Kellner, K.; Liebsch, G.; Klimant, I.; Wolfbeis, O. S.; Blunk, T.; Schulz, M. B.; Gopferich, A. Biotechnol. Bioeng. 2002, 80, 73. (5) O’Mahony, F. C.; O’Rriordan, T. C.; Papkovskaia, N.; Kerry, J. P.; Papkovsky, D. B. Food Control 2006, 17, 286. (6) Dunphy, I.; Vinogradov, S. A.; Wilson, D. F. Anal. Biochem. 2002, 310, 191. (7) Will, Y.; Hynes, J.; Ogurtsov, V. I.; Papkovsky, D. B. Nat. Protoc. 2006, 1, 2563. (8) Brinas, R. P.; Troxler, T.; Hochstrasser, R. M.; Vinogradov, S. A. J. Am. Chem. Soc. 2005, 127, 11851. (9) Ji, J.; Rosenzweig, N.; Jones, I.; Rosenzweig, Z. Anal. Chem. 2001, 73, 3521. (10) Cao, Y.; Lee Koo, Y. E.; Kopelman, R. Analyst 2004, 129, 745. (11) Borisov, S. M.; Mayr, T.; Klimant, I. Anal. Chem. 2008, 80, 573. (12) Chojnacki, P.; Mistlberger, G.; Klimant, I. Angew. Chem. 2007, 46, 8850. (13) Wu, C.; Bull, B.; Christensen, K.; McNeill, J. Angew. Chem. 2009, 48, 2741. (14) Baleizao, C.; Nagl, S.; Schaferling, M.; Berberan-Santos, M. N.; Wolfbeis, O. S. Anal. Chem. 2008, 80, 6449.
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use and reuse. In such materials, an oxygen-sensitive photoluminescent dye is embedded in a suitable polymeric matrix to achieve the desired sensitivity, selectivity and other operational requirements. Sample O2 diffuses into the sensor, interacts with excited dye molecules, and quenches emission intensity and lifetime, thus allowing the nonchemical, contactless, and reversible sensing and quantification of O2. Solid-state sensors are usually fabricated by dissolving their components in organic solvent, applying on a suitable support, and allowing it to dry, polymerize, or cure to form a thin film coating.15 The support used to improve mechanical properties requires stable attachment of the coating without delamination or formation of mixed polymer phases that may alter sensor behavior. These fabrication technologies are complex and produce sensors stressed by a solidification process which show heterogeneity,16 variability between batches, and compromised performance. This increases sensor production costs and limits largescale applications such as packaging. We describe an alternative technology which enables simple and scalable production of planar O2 sensors with improved working characteristics. It uses ordinary high density polyethylene (PE) or polypropylene (PP) films as quenching medium for the dye, and it does not require additional components or support material. These polymers have appropriate chemical and physical properties, diffusion characteristics, and processability17 but poor compatibility with traditional sensor dyes and fabrication technologies. We investigated impregnation of semicrystalline PE and PP films with the O2-sensitive dyes by solvent crazing (SC). This process involves drawing the polymer under controlled conditions while submerged in crazing solvent, thus producing a well-defined 3-D network of nanopores (size
