Assessment of Acetylcholinesterase\nActivity Using\nthe Gold Nanocluster–MnO<sub>2</sub> Nanosheet Pair for Detection\nof Paraoxon

The\natomically precise gold nanoclusters (AuNCs) and MnO<sub>2</sub> nanosheets\n(MnO<sub>2</sub> NSs) were synthesized and characterized\nas donor and acceptor pairs, respectively. A Förster resonance\nenergy transfer (FRET)-based highly sensitive “turn on–off”\nfluorescence (FL) response was achieved owing to the strong spectral\noverlapping between highly bright luminescence of as-synthesized vitamin\nB<sub>1</sub>-stabilized gold nanoclusters (VB<sub>1</sub>–AuNCs)\nand absorption spectra of manganese oxide nanosheet (MnO<sub>2</sub> NS)-based 2D material. The AuNC–MnO<sub>2</sub> NSs pair\nwas used as a probe for the assessment of enzymatic activity of acetylcholinesterase\n(AChE) as an effective alternative to Ellman’s reagent. Our\nwork predicts that an abundantly hydrophilic nano gold cluster surface\nwould be a promising material to improve the sensitivity and hydrolytic\nrate (<i>k</i><sub>cat</sub>) of AChE enzymes. The reconciliation\nand inhibition of AChE for the hydrolysis of acetylthiocholine furnish\nquantitative turn “on–off” FL signals in the\nlinear range of 0.53–1.6 × 10<sup>–8</sup> M of\nparaoxon. The excellence of this sensor is demonstrated by its exceptionally\nlow limit of detection (LOD) of 1.6 nM and limit of quantification\n(LOQ) of 4.9 nM values for detection of paraoxon. The applicability\nof the proposed sensing system was verified using environmental (farm\nwater) and fruit matrixes like tomato, grapes, and apple samples.