Self-Propelled Micromotors for Naked-Eye Detection of Phenylenediamines Isomers.

Tubular micromotors composed of a hybrid single-wall carbon nanotube (SW)-FeO outer layer and powered by a MnO catalyst are used for phenylenediamines isomers detection and discrimination. Catalytic decomposition of HO as fuel results in the production of oxygen bubbles and hydroxyl radicals for phenylenediamines dimerization to produce colorful solutions in colorimetric assays. The combination of FeO nanoparticles along with the irregular SW backbone results in a rough catalytic layer for enhanced hydroxyl radical production rate and improved analytical sensitivity. Such self-propelled micromotors act as peroxidase-like mobile platforms that offer efficient phenylenediamines detection and discrimination in just 15 min. Factors influencing the colorimetric assay protocol, such as the navigation time and number of motors, have been investigated. Low limits of detection (5 and 6 μM) and quantification (17 and 20 μM) were obtained for o-phenylenediamine and p-phenylenediamine, respectively. The magnetic properties of the outer SW-FeO hybrid layer allow the reusability of the micromotors in the colorimetric assay. Such attractive performance holds considerable promise for its application in sensing systems in a myriad of environmental, industrial, and health applications.