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A novel type of ion-selective nano-optode is proposed, in which a conjugated polymer is used as optical transducer and nanoprobe material.When a binding event occurs, positive charges are formed in the nanosphere, leading to a decrease in the oxidation state of the polymer, in the absence of redox potential change, resulting in increased emission. For the model system studied, the linear dependence of emission intensity on the logarithm of analyte (K+) concentration is obtained for a broad range from 10u5 M to 0.1 M.

Application of neutral ionophore based ion-selective sensors requires presence of ion-exchanger in the receptor phase, silently assuming that it is not only soluble but also dissociates to ions in the applied plasticizer. Although for typically applied ion-selective membrane constituents (plasticizers - ion-exchanger pairs) dissociation of ion-exchangers to ions is proven by theoretical (or close to) performance of resulting sensors, search for alternative plasticizers or ion-exchangers requires a method allowing estimation of the match of properties of involved compounds. In this work we propose a simple optical approach allowing estimation of ion-exchanger interactions with plasticizer. The results were confirmed by conductivity studies of model plasticizers solutions. The estimated dissociation constants of model ion-exchangers in plasticizers used are in excellent agreement with the results of optical studies. It was shown that solubility coupled with poor dissociation to ions of ion-exchanger affects performance of the resulting ion-selective membrane. Rational choice of properties of ion-exchanger and plasticizer allows finding a perfect match of the two, that results in improvements in performance of sensors (e.g. detection limits). As model sensors potassium and sodium ion-selective electrodes with poly(vinyl chloride) (PVC) based membranes, plasticized with classical plasticizer bis(2-ethylhexyl sebacate) or biodegradable alternative acetyl tributyl citrate, were prepared and studied using selected ion-exchangers. [Display omitted] • The effect of ion pair formation with the ion-selective receptor is studied with emphasis on sensor performance. • An optical approach allowing easy visualization of the dissociation of ion-exchanger in the plasticizer is proposed. • Ion pair formation between cation-exchanger and analyte cations affects performance of sensor. • The proposed optical approach can be helpful to predict suitability of ion-exchanger for the plasticizer. [ABSTRACT FROM AUTHOR]

A novel type of ion-selective nano-optode is proposed, in which a conjugated polymer is used as optical transducer and nanoprobe material. Thus, contrary to most of the proposed optodes, the response does not require presence of pH-sensitive dye in the sensor. The conjugated polymer nanosensor material is in partially oxidized form--it is bearing positive charges and its emission is quenched. The receptor is an optically silent uncharged ionophore selective for the analyte cation. When a binding event occurs, positive charges are formed in the nanosphere, leading to a decrease in the oxidation state of the polymer, in the absence of redox potential change, resulting in increased emission. This general approach herein proposed results in a simple sensor, benefitting from a novel optical transduction mechanism and high lipophilicity of the polymer matrix that results in linear responses over a broad concentration range of analyte. For the model system studied, the linear dependence of emission intensity on the logarithm of analyte (K+) concentration was obtained for a broad range from 10-5 M to 0.1 M [ABSTRACT FROM AUTHOR]