A 3D-printed self-propelled, highly sensitive mini-motor for underwater pesticide detection

A three-dimensionally printed self-propelled mini-motor (SPM) for the detection of underwater pollutants is proposed. The device uses highly sensitive metal nanoparticles for colorimetric monitoring. Gold nanoparticles covered with Rhodamine B (RB-AuNPs) were prepared, based on established colorimetric and fluorometric approaches for detecting pesticides. The detection mechanism monitors the inhibition of the activity of acetylcholinesterase (AChE) by the pesticide, in which the production of thiocholine from the hydrolysis of acetylthiocholine (ATCh) catalyzed by AChE is reduced. As a result, the color of the RB-AuNP solution remains red, and the fluorescence of RB remains quenched. The RB-AuNPs were characterized by transmission electron microscopy (TEM), UV-Vis absorption spectroscopy, and X-ray photoelectron spectroscopy (XPS). Under the optimized experimental conditions, excellent reproducibility (with a relative standard deviation of 5.8%) and low sensitivity limits, ranging from 0.4 to 3.0 μg L^-1, were achieved. The limit of quantity (LOQ) was 0.3 μg L^-1,and the detection limit (LOD) was 0.23 μg L^-1, which was much lower than the maximum residue limits reported in the European Union pesticide database. With the aid of 3D-printed SPMs and nano-colorimetry, both qualitative and quantitative analyses can be performed for pesticide detection in river water. This is the first time a 3D-printed SPM has been combined with nano-colorimetry to realize a convenient, cost-effective, and high sensitive detection method for pollutants in water.