Fiber-optic dissolved oxygen and dissolved carbon dioxide sensors using fluorophores encapsulated in sol gel matrices.

摘要

Fiber optic chemical sensors (FOCS) for oxygen, dissolved oxygen (DO), and dissolved CO₂ sensing using thin films of fluorophores encapsulated in sol-gel matrices were made and tested. The DO/O₂ sensor used ruthenium(II) tris(4,7-diphenyl-1,10-phenanthroline) perchlorate (Ru(Ph ₂Phen)Cl₂) as the oxygen sensitive fluorophore and methyltrimethoxysilane (MTMS) sol-gel as the encapsulating matrix material. For the DCO₂ sensor, 8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt (HPTS) co-doped with sodium bicarbonate was used as the DCO₂ sensitive fluorophore-chemical system and diisobutoxy-alumino triethoxysilane (ASE) sol-gel was used as the encapsulating matrix material.; It was found that oxygen quenches the excited state Ru(Ph₂Phen)Cl ₂ by diffusing through the MTMS matrix. Continuous excitation of Ru(Ph ₂Phen)Cl₂ during MTMS drying resulted in long, single exponential lifetimes of the metal complex and increased sensor sensitivity. When the sensor was field tested, it was found to have an excellent match compared to conventional titration method for determining dissolved oxygen concentrations and had fast response times. It was determined that this sensor measured the vapor pressure of oxygen rather than the absolute concentration of dissolved oxygen. For DCO₂ sensing, it was found that the dynamic response of the senor could be tuned by varying the HPTS to NaHCO₃ ratios. The sensor had fast response times compared to other fiber optic DCO ₂ sensors reported which typically have response times of minutes.