Highly Active Electrochemiluminescence of Ruthenium Complex Co-assembled Chalcogenide Nanoclusters and the Application for Label-Free Detection of Alkaline Phosphatase.

Rational design of electrochemiluminescence (ECL) reagents is essential for the development of ECL biosensors with superior performances. In this work, the assembly of tris(1,10-phenanthroline)ruthenium(II) [Ru(phen)32+] and tetrahedral chalcogenide nanoclusters of [Cd32S14(SC6H5)38]2- in the formation of complex nanoclusters (CdS-Ru) was developed, in which Ru(phen)32+ was uniformly encapsulated and dispersed at a molecular level in the chalcogenide nanocluster via multiple noncovalent interactions. It was observed that the promoted ECL emission was realized by the charge transfer between the tetrahedral CdS nanocluster and Ru(phen)32+ by the formation of the assembly complex, which was elucidated by cyclic voltammetry curves, ECL-potential curves, and in situ dynamic ECL spectra. Taking advantages of the facile charge transfer in the open framework CdS-Ru, a high ECL efficiency has been achieved with remarkable stability. Moreover, a solid-state ECL sensor based on the CdS-Ru modified electrode was fabricated for label-free detection of alkaline phosphatase (ALP) activity with a detection limit as low as 0.35 U/L and superior reproducibility. This solid-state ECL sensor also displayed favorable selectivity among various interferences and was applied for ALP activity analysis in human serum samples. These results implicated the potential applications of CdS-Ru for sensitive ECL analysis in complicated reaction systems and enlightened the rational design for self-enhanced and highly efficient ECL materials.