Zhang_2022_Talanta_249_123664

Cobalt oxyhydroxide nanosheets (CoOOH) with peroxidase-like activity provide a promising probe for acetylcholinesterase (AChE) sensing through a ratiometric fluorescence strategy. Fluorescence of silicon quantum dots (SiQDs) at 457 nm was quenched by CoOOH on account of inner-filter effect (IFE). Meanwhile, the nonfluorescent o-phenylenediamine (OPD) was catalytically oxidized to 2,3-diaminophenazine (oxOPD) by CoOOH nanosheets with emission at 572 nm. The acetylcholine (ATCh) was catalytically hydrolyzed by AChE to enzymatic thiocholine (TCh), which decomposed CoOOH to Co(2+), recovered the fluorescence of SiQDs and reduced the emission of oxOPD. Fluorescence ratio at F(457)/F(572) serves as signal output for AChE detection within 5 x 10(-5)-0.05 and 0.05-10 U mL(-1), with a limit of detection (LOD) of 3.2 x 10(-5) U mL(-1). The sensing strategy was applied for AChE assay in human blood and erythrocyte.