Potentially tunable ratiometric electrochemiluminescence sensing based on conjugated polymer nanoparticle for organophosphorus pesticides detection

Abstract

In general, suitable double luminophores and their coreactants are necessary for constructing electrochemiluminescence (ECL) ratio strategy. However, the complexity of matching double luminophores and the stability and repeatability problem suffered by introducing exogenous coreactant would greatly limit the application of ratio detection. An original single-luminophore-based ECL ratio sensing was developed excluding any exogenous coreactants in this work. The poly [9,9-bis(3'-(N,N-dimethylamino)propyl)- 2,7-fluorene]-alt-2,7-(9,9-dioctylfluorene)] nanoparticles (PFN NPs) were explored to emit two anodic ECL signals. One centered at + 1.25 V (ECL-1) with the scanning potential of 0 ~ + 1.25 V and the other at + 1.95 V (ECL-2) with the scanning potential of 0 ~ + 1.95 V. ECL-1 showed a very strong emission without any exogenous coreactant. Importantly, hydrogen peroxide (H₂O₂) was able to efficiently weaken ECL-1 but strengthen ECL-2. When organophosphorus pesticides (OPs) were absent, the immobilized acetylcholinesterase-choline oxidase (AChE-ChOx) would catalyze the substrate acetylthiocholine chloride (ATCl) to produce H₂O₂, resulting in a quenched ECL-1 and an enhanced ECL-2. With the introduction of OPs, ECL-1 increased while ECL-2 accordingly decreased as OPs prohibited production of H₂O₂ by inhibiting activity of AChE. Highly sensitive ECL ratio detection for OPs was realized based on the change of the ratio of two signals. The dual anode emission properties of PFN NPs coupled with the opposite regulation of H₂O₂ on the two signals paved a new avenue for potentially tunable ECL ratio sensing strategy, and showed enormous potential applications for OPs analysis.

Keywords: Biosensor; Electrochemiluminescence; Organophosphorus; PFN NPs; Ratio.