Preparation of an optical sensing membrane for triple detection of oxygen, pH, and temperature using response surface methodology

An optical sensing membrane was prepared to detect oxygen, temperature, and pH simultaneously. Optimum amounts of the fluorescence indicators (tris(4,7-diphenyl-1,10-phenanthroline) ruthenium complex (Rudpp)-doped silica nanoparticles (RudppSi) for oxygen, 8-hydroxypyrene-1,3,6-trisulfonate (HPTS)-doped silica particles (HPTSSi) for pH, and CdSeTe quantum dots (QDs) for temperature) in a sensing membrane were identified using response surface methodology (RSM). The difference in fluorescence intensity between 0% DO (dissolved oxygen) and 100% DO, the difference in fluorescence intensity between pH 5 and pH 8, and the difference in fluorescence intensity between 15 degrees C and 45 degrees C in the sensing membrane were employed as statistical model responses. Optimum concentrations of fluorescence indicators in the sensing membrane were 5.68 mg RudppSi/ml sol-gel solution, 18.0 mg HPTSSi/ml sol-gel solution, and 1.98 mg CdSeTe QDs/ml sol-gel solution. Several optical sensing membranes were prepared based on the RSM analysis results, and tested experimentally on the sensitivity and performance. The membrane enabled triple detection of DO, pH, and temperature very well and could be used to monitor a variety of microbiological and medical applications. (C) 2013 Elsevier B.V. All rights reserved.