Electrochemiluminescence of Ultrasmall Silica Nanoparticles from Size Modulation and Multipath Surface State Adjustment for Ultrasensitive HIV-DNA Fragment Detection.

Here, ultrasmall SiO₂ nanoparticles (u-SiO₂ NPs, <5 nm) with obvious electrochemiluminescence (ECL) phenomenon, which was absent for conventional silica nanoparticles (c-SiO₂ NPs), were reported. In a finite ultrasmall volume, the u-SiO₂ NPs exhibited increasing ground state energy and higher optical absorption strength due to the electron-hole confinement model and favored catalyzing the reaction through the rapid diffusion of bulk charge, resulting in apparent ECL emission. Then, Zn²⁺-induced u-SiO₂ nanoaggregates (Zn/u-SiO₂-Ov nAGG) were synthesized and exhibited improved ECL performance via multipath surface state adjustment of u-SiO₂ from several aspects, including aggregation-induced ECL, the generation of oxygen vacancy (Ov), and more positive surface charge. In addition, an ECL biosensor was constructed for ultrasensitive human immunodeficiency virus-related deoxyribonucleic acid detection from 100 aM to 1 nM with a low limit of 50.48 aM, combining the ECL luminescence of Zn/u-SiO₂-Ov nAGG with three-dimensional DNA nanomachine-mediated multioutput amplification for enhanced accuracy and sensitivity compared to the single-output method. Therefore, exploring the ECL of ultrasmall nanoparticles via the adjustment of size and surface state provided a valuable indication to a wider investigation and application of novel ECL materials for clinical diagnostic.