Dual Enhanced Electrochemiluminescence of Aminated Au@SiO₂/CdS Quantum Dot Superstructures: Electromagnetic Field Enhancement and Chemical Enhancement

Abstract

This paper reports dual enhanced electrochemiluminescence (ECL) of CdS quantum dot (QD)-decorated aminated Au@SiO₂ core/shell (Au@SiO₂-NH₂/CdS) superstructures. A maximum ECL emission of the Au@SiO₂-NH₂/CdS superstructures (Au core, ca. 55 nm) with a silica shell of 38 nm was 35-fold stronger than that of the counterparts (containing neither Au cores nor amino groups) with H₂O₂ as a coreactant. The fold of ECL enhancement is the largest, and the optical path of maximum ECL enhancement is the longest reported so far. The larger the Au cores in the superstructures, the stronger the ECL emission of CdS QDs was. Two types of ECL enhancement mechanisms were clearly proposed for the dual enhanced ECL of the Au@SiO₂-NH₂/CdS superstructures. One was the electromagnetic field enhancement induced by localized surface plasmon resonance of Au cores, and the other was the chemical enhancement from amino groups modified on the silica surface involved in the ECL process in the assistance of H₂O₂. It is the first time to put forward the new concept of chemical enhanced ECL that was directly related to the participation of other chemicals, which caused a decrease in the difference in the redox potential between emitters and coreactants for the increase of their redox currents. The constructed ECL platform was demonstrated to have promising applications in highly sensitive detection of glutathione (GSH), and the response mechanism of GSH was also explored.