MnO2 Nanosheet-Based colorimetric sensor Array: Toward identification of organophosphorus pesticides

Abstract

In recent years, two-dimensional (2D) nanomaterials have attracted more and more attention because of their high specific surface area and excellent physical and chemical properties. We herein demonstrate two kinds of 2D nanomaterials, i.e., MnO2 nanosheets and UFO-shaped Au@MnO2 nanosheets (denoted as MnO2 NSs and AM NSs), for qualitative identification and quantitative detection of organophosphorus pesticides (OPs). In the presence of acetylcholinesterase (AChE), acetylthiocholine iodide (ATCh) can be hydrolyzed to thiocholine (TCh), which is used as a reducing agent to etch ultrathin MnO2 nanosheets. During the etching process, the color of AM NSs solution changes from green to pink, and the MnO2 NSs solution changes from dark brown to light brown. OPs can inhibit the activity of AChE and thus inhibit the etching of MnO2. Based on this principle, five OPs (i.e., ethion, bromophos-ethyl, chlorpyrifos-methyl, trichlorfon, and omethoate) at 0.5 μg·L−1 were successfully identified by this sensor array. Besides, the distinction for diverse concentrations of each OP and different ratios of OP mixtures was demonstrated. The sensor array also reveals excellent anti-interference ability toward OPs in the presence of different potentially interfering substances. The feasibilities of the sensor array were further validated by differentiating the OPs in grape samples.