Study of Nitrite Sensors Based on Co(III)/Rh(III)-Ligand Complexes as Selective Ionophores.

[摘要] In this dissertation, fundamental and applied studies of new ionophore-based ion-selective electrodes and optodes for selective nitrite detection are reported.The new ionophore systems are shown to be useful in the fabrication of sensitive and selective nitrite sensors via both electrochemical (potentiometric) and optical measurements.First, two metal ion ligand complexes, cobalt(III) 5,10,15-tris(4-tert-butylphenyl) corrole (Co-tBC) and rhodium(III) 5,10,15-tris(4-tert-butylphenyl) (Rh-tBC) are synthesized and characterized.The two complexes are then used, for the first time, within plasticized poly(vinyl chloride) membranes and studied as neutral carrier ionophores for developing potentiometric nitrite selective sensors.Both of the ionophores exhibit good binding affinity to nitrite, but Co-tBC has a stronger binding constant (log β = 5.57 toward nitrite than Rh-tBC (log β = 4.04).Co-tBC-based potentiometric sensors exhibit Nernstian response and greatly enhanced selectivity to nitrite over all other common anions.The selectivity to nitrite over thiocyanate is greater than that obtained from sensors prepared with a commercially available nitrite ionophore, a Co(III) aquocyanocobyrinate species.Sensing membranes doped with Rh-tBC also show Nernstian response and good selectivity to nitrite over most common anions.However, they suffer substantial interference from thiocyanate. The newly studied Co-tBC ionophore can also be incorporated along with an appropriate proton chromoionophore into plasticized poly(vinyl chloride) films to fabricate nitrite-selective bulk optodes via absorbance measurements.The resulting films yield sensitive, fast, and fully reversible optical nitrite response with significantly enhanced nitrite selectivity.Compared to previously studied ionophore-based optical sensors for nitrtie, the Co-tBC-based optical sensors have enhanced selectivity to nitrite over thiocyanate.The optical nitrite sensors are shown to be useful for detecting nitric oxide (NO) emission rates from NO releasing polymers containing S-nitroso-N-acetyl-penicillamine (SNAP).Finally, the use of an electropolymerized film of rhodium(III) porphyrin on afluorine-doped tin oxide (FTO) electrode for developing an amperometric sensor for nitrite is examined.Results suggest that at an applied potential of +0.6 V vs. Ag/AgCl, the modified electrode has rapid amperometric response to nitrite, with a linear range of 0.01 mM to 0.1 mM, a lower detection limit of 4.7 µM.

[发布机构] University of Michigan

[效力级别] Chemistry

[关键词] Nitrite-Selective Polymeric Membrane Electrodes/Optodes;Chemistry;Science;Chemistry