Dual Enhancement of Electrochemiluminescence Imaging for Single Au-mSiO₂–CdSe Nanoparticles via Resonance Energy Transfer and Interlayer Conductivity

Single-nanoparticle electrochemiluminescence (ECL) imaging is a promising technique for investigating surface dynamics and cellular processes. However, due to the low luminescence intensity of individual particles, most current approaches utilize luminescent materials such as ruthenium bipyridine or luminol derivatives. Quantum dot-based single-nanoparticle ECL imaging, however, remains less explored. In this study, we present the application of the ECL-RET enhancement mechanism to design and synthesize a novel Au-mSiO₂-CdSe quantum dot nanoparticles (AmSQ NPs), enabling 90 nm single-nanoparticle ECL imaging without substrate modification. Experimental results demonstrate that the Au nanoparticle core and CdSe quantum dots were in the optimal distance (13 nm); thus, the Au NP enhances the local electromagnetic (EM) field. The enhanced EM field further increases the excitation and leads to a higher radiative decay rate (Γ_<i>m</i>), which finally enhances the ECL signals of AmSQ NP. In contrast, although the ASQ nanoparticles have a Au core, their insufficient interlayer conductivity prevented the production of detectable ECL signals. These findings confirm the feasibility of single-nanoparticle ECL imaging with quantum dots via the ECL-RET effect. Future studies will focus on optimizing assembly conditions and surface modifications to enable multichannel ECL detection.