| Fluorescence quenching is a primary online-method for monitoring dissolved oxygen. Ithas wide applications in sewage treatment, biochemical reaction, aquaculture，clinicalmedicine, life sciences and so on. Fluorescent membrane sensitive to oxygen is the key to thisfluorescent analysis technique. Of polymer materials, silicone rubber has highest oxygenpermeability and dissolvability as well as processing ability; while platinum porphyrin andruthenium phenanthroline complexes have large stokes shift, long exciting lifetime, highfluorescence quantum yield. But the dissolvability of the polar platinum and rutheniumcomplexes are very poor in the non-polar silicone rubber. Improving the molecular dispersionof the complexes in silicone rubber is most important to develop silicone based fluorescentmembrane for dissolved oxygen sensor.In this thesis, to improve the dispersity of Ru(dpp)3Cl2molecules in silicone rubber,silica modified with silicone groups was used to adsorb the complexes and then filled insilicone rubber. The filled silicone rubbers are evaluated as the fluorescent membrane anddissolved oxygen sensor.MQ resins, modified silica, were synthesized from TEOS and HMDSO in different ratiosand the obtained MQ resins were imaged with SEM. The adsorbing ability of the MQ resin toRu(dpp)3Cl2was determined with spectrophotometer. The fluorescence spectra ofRu(dpp)3Cl2adsorbed on different MQ resins were analyzed. The MQ resins carriedRu(dpp)3Cl2were mixed with silicone rubber and fluorescent silicone membranes wereprepared. With a dissolved oxygen meter, the fluorescence outputs of the fluorescent siliconemembranes in water saturated with nitrogen and oxygen were measured, respectively, andoxygen quenching ratio were calculated. The effect of silica types and structures on thefluorescence output and oxygen quenching ratio were investigated and selected fluorescentsilicone membranes were evaluated for dissolved oxygen sensor.The fluorescence spectrum of Ru(dpp)3Cl2adsorbed on precipitated and fumed silicashifted about20nm towards long wavelength direction than that in extreme thin solution.Methyl silicone introduced to silica would depress the interaction between Ru(dpp)3Cl2andsilica and reduce the red shift about10nm; meanwhile, it enhanced the fluorescence output about10times as the precipitated and fumed silica were replaced with MQ resin. For filledfluorescent silicone membranes, MQ resin brought about highest fluorescence quantum yieldto Ru(dpp)3Cl2and precipitated silica gave the lowest one; while the oxygen quenching ratiowere about8. But at Ru(dpp)3Cl2dosages above0.1phr, the relation of Ru(dpp)3Cl2tofluorescence output deviated from linear response and the fluorescence quantum yielddecreased.In M/Q charging ratio from0.4to0.9, the size of the synthesized MQ rein increased firstwith M/Q ratio but decreased as M/Q ratio was higher than0.6. It got maximum about360nm at M/Q ratio0.6; at M/Q ratio0.4and0.9, the diameters of the MQ resins were100and180nm, respectively. The adsorbing ability of MQ resin to Ru(dpp)3Cl2was contrary to theeffect of charging ratio to particle size. For filled fluorescent silicone membranes, thevariation of the fluorescence output in water saturated with nitrogen was contrary to the effectof charging ratio to particle size, too. The fluorescence output in water saturated with oxygendid not change much. The time for fluorescence to stable was opposite to particle size.Alkaline hydrolysis of PMMA and surface treatment with KH570coupling agent couldensured the interface bonding between PMMA optical lens and the fluorescent siliconemembrane. The fluorescent membrane mounted on sensor could used for monitoringdissolved oxygen in water at temperature from10to30oC. The errors were less than5%andthe precision could meet the requirements. In field testing at an aquaculture site, thedeveloped dissolved oxygen sensor gave similar results as the dissolved oxygen sensor madeby Hach, US. |
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