Can clay emit light? Ru(bpy)32+-modified clay colloids and their application in the detection of glucose

In this paper, we describe the electrochemiluminescent (ECL) behavior of Ru(bpy)33+-incorporated clay colloids. Experimental results based on the electrochemical-quartz-crystal-microbalance (EQCM) techniques showed that Ru(bpy)33+ could be adsorbed by the clay colloids (montmorillonite K10, denoted K10). The resulting clay particles could emit light (λem 610 nm) when they were fabricated as thin films sandwiched by two conductive ITO electrodes with opposite biases. These Ru(bpy)33+-incorporated clay-modified electrodes could also emit light in aqueous oxalate solutions (pH 10) when potentials more positive than 0.9 V vs. SCE were applied. EDTA was an effective promoter for the Ru(bpy)3 (clay)3+-oxalate ECL reaction. The resulting ECL showed a remarkable sensitivity to oxygen. A glucose optrode was thus fabricated based on the Ru(bpy)33+-incorporated K10 colloids and glucose oxidase (GOx). The ECL signals behaved as a function of [glucose], covering a range from 0.1 to 10 mM at pH 10. The detection limits reached a level of 0.1 mM at this pH.