Nanoclusterzyme for Dual Colorimetric Sensings: A Case Study on [Au₁₄ (Dppp)₅ I₄ ]²

The enzymatic activity of atomically precise metal nanoclusters has recently been recognized; however, the number of nanoclusterzymes is very small. Besides, the applications of nanoclusterzyme wait to be explored. Herein, a novel nanoclusterzyme is synthesized and its structure is majorly resolved by single-crystal X-ray diffraction and mass spectrometry, which reveal that the nanocluster consists of an Au₁₃ icosahedron capped by an exterior shell including four I, three Dppp (1,3-bis(diphenylphosphino) propane) ligands, and a rarely reported Dppp-Au-Dppp handle staple, which contributes a lot to the enzyme activity of [Au₁₄ (Dppp)₅ I₄ ]²⁺ nanocluster. The as-obtained nanocluster can catalyze oxygen to O₂ ^•- under visible light irradiation with a specific activity up to 0.182 U·mg^-1 and lead to the blue color of 3,3',5,5'-tetramethylbenzidine (TMB) in both solution and solid states. With the addition of acetylcholinesterase (AChE), the blue color of (Au₁₄  + TMB) solution system disappears due to the nanoclusterzyme activity inhibition, but the further addition of organophosphorus pesticides (OPs) into the above mixture can restore the nanoclusterzyme and recover the blue color. Based on the color turn-off and on, the various nanoclusterzyme-containing systems are used to colorimetrically sense AChE and OPs with the detection limits reaching 0.04 mU·mL^-1 and 0.02 ng·mL^-1 , respectively.