Developing oxygen vacancy-rich CuMn2O4/carbon dots dual-function nanozymes via Chan-Lam coupling reaction for the colorimetric/fluorescent determination of D-penicillamine.

Defect engineering is a promising approach to construct high performance nanozymes due to its ability to regulate their physical and chemical properties. However, how to construct defects to improve the activity of nanozymes remains a challenge. Herein, for the first time, the Chan-Lam coupling reaction is used to construct the oxygen vacancy (O_V)-rich CuMn₂O₄/carbon dots (CDs) (O_V-CuMn₂O₄/CDs) dual-function nanozymes with fluorescent (FL) and oxidase-like properties, via regulating the low-valent metal ions (Cu⁺ and Mn²⁺) and O_v contents in the spinel CuMn₂O₄ and in-situ growth of β-cyclodextrin (β-CD)-derived CDs. Expectedly, relative to CuMn₂O₄, the O_V-CuMn₂O₄/CDs exhibited 35.8%, 8.5%, and 14.6% rise in the contents of Cu⁺, Mn²⁺ and O_v, respectively. Abundant O_v provides more O₂ adsorption/activation sites, and the charge transfer between O_v and metal atoms increases the charge density around metal atoms. This produces more low-valent metals (like Cu⁺ and Mn²⁺) to promote the electron transfer from metal to O atoms and O-O bond cleavage. Thus, the oxidase-like activity of O_V-CuMn₂O₄/CDs is 4.1 times that of CuMn₂O₄. Also, the in-situ growth of β-CD-derived carbon dots on CuMn₂O₄ endows O_V-CuMn₂O₄/CDs selective target recognition. Thus, a sensitive and selective colorimetric and fluorescence dual-mode method was established for determining D-penicillamine (D-PA), with the limit of detection of 0.25 and 0.048 μM, respectively. The method was applied to D-PA determination in real samples. This work demonstrates the Chan-Lam coupling reaction can be used to construct high performance nanozymes for developing dual-mode sensor for the detection of targets.