Introduction of Lewis acid sites to endow cobalt phosphide with peroxidase-like and oxidase-like activities and application in colorimetric sensing analysis

Abstract

With more and more attention to health, developing a simple and effective method for detecting phenolic compounds is an urgent and challenging task. In this context, Mn-doped CoP (referred to as Mn-CoP) with a nanocage interior architecture has been successfully constructed. The formation of a hollow structure exposes more active sites, while the incorporation of Mn ion reduces the charge transfer resistance and accelerates the charge transfer. Consequently, Mn-CoP effectively provides electrons to activate H₂O₂ and O₂ producing OH^• and O₂^•, demonstrating excellent peroxidase-like and oxidase-like activities. Given its strong oxidase-like activity, Mn-CoP enables a straightforward colorimetric assay for detecting hydroquinone using 3,3′,5,5′-tetramethyl benzidine (TMB) as colorimetric substrate. Interestingly, the developed colorimetric detection method exhibits a broad linear range and a low limit of detection (LOD) for hydroquinone, showing good potential for application even in real samples. Detailed analyses reveal that the doped Mn ions serve as Lewis acid sites directly reacting with the amino functional group in TMB. The Lewis acid-base reaction between Mn-CoP and TMB is crucial for the chromogenic reaction of TMB. Moreover, doping Mn ion to enhance the oxidase-like activity of the nanozyme is a simple and feasible modification strategy with universal applicability. This work provides a valuable reference for designing nanozymes with oxidase-like activity.