Development of Optical Sensors ("Optodes") for Carbon Dioxide and their Application to Modified Atmosphere Packaging (MAP) Dissertation zur Erlangung des Doktorgrades der Naturwissenschaften (Dr. rer. nat.) an der Naturwissenschaftlichen Fakultät IV – Chemie und Pharmazie der Universität Regensburg vorgelegt von Christoph Alexander Johannes von Bültzingslöwen aus Regensburg 2003 Diese Arbeit wurde angeleitet von Prof. Dr. Otto Wolfbeis Promotionsgesuch eingereicht am: Tag des Kolloquiums: Prüfungsausschuss: Prof. Dr. O. Reiser (Vorsitzender) Prof. Dr. O. Wolfbeis Prof. Dr. B. McCraith N. N. Contents Contents Contents ..............................................................................................I Abbreviations and Symbols...............................................................IV 1. Introduction .............................................................................. 1 1.1. Modified Atmosphere Packaging ................................................. 1 1.2. Oxygen Optodes for MAP Analysis .............................................. 2 1.3. Carbon Dioxide Optodes ............................................................ 4 1.3.1. Wet Sensors........................................................................... 5 1.3.2. Solid Sensors ......................................................................... 6 1.3.3. MAP-Sensing Strategies .......................................................... 7 1.4. Sol-Gel Material ......................................................................... 8 1.4.1. Hydrolysis and Condensation................................................... 9 1.4.2. Gelation ............................................................................... 10 1.4.3. Aging................................................................................... 10 1.4.4. Drying ................................................................................. 12 1.5. Objectives............................................................................... 13 1.6. References.............................................................................. 14 2. Energy Transfer ....................................................................... 17 2.1. Introduction ............................................................................ 17 2.1.1. Phase-Domain Lifetime Measurement .................................... 17 2.1.2. Fluorescence Resonance Energy Transfer .............................. 20 2.2. Experimental........................................................................... 23 2.2.1. pH-Indicator......................................................................... 23 2.2.2. Donor .................................................................................. 27 2.2.3. Base .................................................................................... 27 2.2.4. Preparation .......................................................................... 30 2.2.5. Instrumentation ................................................................... 31 2.3. Theory.................................................................................... 32 2.4. Characterisation ...................................................................... 35 2.4.1. Sensitivity ............................................................................ 35 2.4.2. Temperature Dependence..................................................... 38 -I- Contents 2.4.3. Humidity Dependence........................................................... 40 2.4.4. Oxygen Cross-Sensitivity....................................................... 41 2.4.5. Results ................................................................................ 42 2.5. Improvement Strategies .......................................................... 43 2.6. Conclusion .............................................................................. 44 2.7. References.............................................................................. 45 3. Dual Luminophore Referencing............................................... 47 3.1. DLR-Introduction..................................................................... 47 3.2. Experimental........................................................................... 51 3.2.1. pH-Indicator......................................................................... 51 3.2.2. Reference luminophore......................................................... 53 3.2.3. Base .................................................................................... 54 3.2.4. Preparation .......................................................................... 56 3.2.5. Instrumentation ................................................................... 56 3.3. Theory.................................................................................... 57 3.3.1. Mathematical Description ...................................................... 57 3.3.2. Simulation............................................................................ 59 3.4. Characterisation ...................................................................... 63 3.4.1. Sensitivity ............................................................................ 63 3.4.2. Stability ............................................................................... 65 3.4.3. Temperature ........................................................................ 66 3.4.4. Humidity.............................................................................. 68 3.4.5. Oxygen................................................................................ 69 3.4.6. Results ................................................................................ 71 3.5. Conclusion .............................................................................. 72 3.6. References.............................................................................. 73 4. Materials and Characteriation................................................. 75 4.1. Introduction ............................................................................ 75 4.1.1. Polymers.............................................................................. 75 4.1.2. Organically modified silica glasses ......................................... 76 4.2. Experimental........................................................................... 77 4.2.1. Energy Transfer Sensor ........................................................ 77 4.2.2. Dual Luminophore Referencing Sensor................................... 78 4.2.3. Instrumentation ................................................................... 78 -II- Contents 4.3. Characterisation ...................................................................... 79 4.3.1. Energy Transfer Sensor ........................................................ 79 4.3.2. Dual Luminophore Referencing Sensor................................... 81 4.4. Conclusion .............................................................................. 82 4.5. References.............................................................................. 83 5. Sol-Gel Reference Particles..................................................... 84 5.1. Introduction ............................................................................ 84 5.1.1. PAN-Particles ....................................................................... 84 5.1.2. Sol-gel particles.................................................................... 85 5.2. Experimental........................................................................... 87 5.2.1. Preparation .......................................................................... 87 5.2.2. Instrumentation ................................................................... 87 5.3. Characterisation ...................................................................... 88 5.3.1. Sensitivity ............................................................................ 88 5.3.2. Repeatability ........................................................................ 90 5.3.3. Oxygen................................................................................ 92 5.3.4. Temperature ........................................................................ 94 5.3.5. Results ................................................................................ 95 5.4. Conclusion .............................................................................. 97 5.5. References.............................................................................. 98 Summary .......................................................................................... 99 Zusammenfassung ......................................................................... 102 Curriculum Vitae ............................................................................ 105 Publications and Presentations ..................................................... 106 -III- Abbreviations and Symbols Abbreviations and Symbols CTA-OH Cetyl-trimethylammonium hydroxide D- Deprotonated pH-indicator dye DH Protonated pH-indicator dye DLR Dual Luminophore Referencing dm Demodulation EA Activation energy EtCell Ethyl cellulose ETEOS Ethyltriethoxysilane f Modulation frequency FRET Fluorescence resonance energy transfer HPTS 1-Hydroxypyrene-3,6,8-trisulfonate I Luminescence intensity J Spectral overlap integral J0 Spectral overlap integral when dye is completely protonated K Equilibrium constant KSV Stern-Volmer constant LED Light emitting diode LOD Limit of detection MAP Modified atmosphere packaging