Pore Confinement-Enhanced Electrochemiluminescence on SnO2 Nanocrystal Xerogel with NO3– As Co-Reactant and Its Application in Facile and Sensitive Bioanalysis

Herein, 10-fold electrochemiluminescence (ECL) enhancement from a porous SnO2 nanocrystal (SnO2 NC) xerogel (vs discrete SnO2 NCs) was first observed with NO3- as a novel coreactant. This new booster phenomenon caused by pore characteristic was defined as "pore confinement-induced ECL enhancement", which originated from two possible reasons: First, the SnO2 NC xerogel with hierarchically porous structure could not only localize massive luminophore near the electrode surface, more importantly, but could accelerate the electrochemical and chemiluminescence reaction efficiency because the pore channels of xerogel could promote the mass transport and electron transfer in the confined spaces. Second, the NO3- could be in situ reduced easily to the active nitrogen species by means of the pore confinement effect, which could be served as a new coreactant for nanocrystal-based ECL amplification with the excellent stability and good biocompatibility. As a proof of concept, a facile and sensitive sensing platform for SO32- detection has been successfully constructed upon effectively quenching of SO32- toward the SnO2 NC xerogel/NO3- ECL system. The key feature about this work presented a grand avenue to achieve the strong ECL signal, especially from weak emitters, which gave a fresh impetus to the construction of new-generation of surface-confined ECL platform with potential applications in ECL imaging and sensing.