Pore Confinement-Enhanced Electrochemiluminescence on SnO 2 Nanocrystal Xerogel with NO 3 - As Co-Reactant and Its Application in Facile and Sensitive Bioanalysis.

Herein, 10-fold electrochemiluminescence (ECL) enhancement from a porous SnO ₂ nanocrystal (SnO ₂ NC) xerogel (vs discrete SnO ₂ NCs) was first observed with NO ₃ ^- 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 SnO ₂ 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 NO ₃ ^- 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 SO ₃ ^2- detection has been successfully constructed upon effectively quenching of SO ₃ ^2- toward the SnO ₂ NC xerogel/NO ₃ ^- 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.