Characterisation of luminescent and electrochemical sensors.

Abstract

This thesis is concerned with electrochemical and optical sensors based on potentiometric and luminescent transduction. A series of oxa-diisobutylamide derivatives based on cis-cis-l,3,5-cyclo-hexanetriol was compared in standard polyvinyl chloride based ion-selective electrodes as ionophores for the detection of selected IA/IIA cations. The tripodal framework incorporated either mono-, di- or tri- substituted diisobutyl amide pendant groups to give possible coordination numbers of 4, 5 and 6 respectively, assuming a 1:1 cationionophore stoichiometry. A Nemstian response towards the detection of Ca(^2+) was observed with the ISE incorporating the di-substituted diamide analogue. The selectivity of the ISE was assessed using the Fixed Interference Method and a Nemstian response was observed in the extracellular Ca(^2+) concentration range (1.16-1.32 mmol dm(^-3)) in the presence of a simulated extracellular background of interfering cations. The effect of pH on the response of the ISE was also investigated as was the enhancement of the lower detection limit by including a Ca(^2+) buffer in the inner filling electrolyte. Luminescent lanthanide complexes were assessed as chemical transducers for the purpose of optical sensing of pH or dissolved oxygen, following immobilisation in sol- gel thin films prepared in acidic media. pH-dependent intensity or ratiometric methods were defined for europium and terbium complexes of cyclen based frameworks (12-N(_4)). These systems incorporated phenanthridine derivatives or para substituted aryl sulfonamide moieties as the sensitising chromophores, typically with apparent pH sensing ranges of 5.5 to 8.0.Dissolved oxygen-dependent modulation of the metal emission and excited state lifetime of a short series of terbium complexes was assessed. These systems were based on cyclen with either tetra-amide or mono-amide triphosphinate pendent groups.