Enhanced electrochemiluminescence sensor from tris(2,2′-bipyridyl)ruthenium(ii) incorporated into MCM-41 and an ionic liquid-based carbon paste electrode

Abstract

The electrochemiluminescence (ECL) of tris(2,2′-bipyridyl)ruthenium(II) [Ru(bpy)₃²⁺] ion-exchanged in the sulfonic-functionalized MCM-41 silicas was developed with tripropylamine (TPrA) as a co-reactant in a carbon paste electrode (CPE) using a room temperature ionic liquid (IL) as a binder. The sulfonic-functionalized silicas MCM-41 were used for preparing an ECL sensor by the electrostatic interactions between Ru(bpy)₃²⁺ cations and sulfonic acid groups. We used the IL as a binder to construct the CPE (IL-CPE) to replace the traditional binder of the CPE (T-CPE) – silicone oil. The results indicated that the MCM-41-modified IL-CPE had more open structures to allow faster diffusion of Ru(bpy)₃²⁺ and that the ionic liquid also acted as a conducting bridge to connect TPrA with Ru(bpy)₃²⁺ sites immobilized in the electrode, resulting in a higher ECL intensity compared with the MCM-41-modified T-CPE. Herein, the detection limit for TPrA of the MCM-41-modified IL-CPE was 7.2 nM, which was two orders of magnitude lower than that observed at the T-CPE. When this new sensor was used in flow injection analysis (FIA), the MCM-41-modified IL-CPE ECL sensor also showed good reproducibility. Furthermore, the sensor could also be renewed easily by mechanical polishing whenever needed.