Uniform honeycomb CNT-microparticles prepared via droplet-microfluidics and sacrificial nanoparticles for electrochemical determination of methyl parathion

Abstract Porous carbon-based nanomaterials have attracted much attention because of their specific structure and multifunctionality. We report on a strategy for constructing porous microparticles consisting of carbon nanotubes (CNTs) connected with honeycomb nanopores and their application for electrochemical sensors. The microdroplets containing silica nanoparticles (SiO2NPs) and CNTs are created using a microfluidic device, with droplet size and composition being tunable via the fluidic phases. Solid microparticles consisting of close-packed SiO2NPs and CNTs (SiO2NP-CNT-µPs) are obtained after water evaporation and calcination. Target honeycomb CNT-microparticles (h-CNT-μPs) are achieved after removing SiO2NPs from the SiO2NP-CNT-µPs. The glassy carbon electrodes (GCEs) modified with h-CNT-μPs and Nafion (h-CNT-μPs/Nafion/GCEs) show highly enhanced specific surface area and electrocatalytic activity. Under optimized conditions, h-CNT-μPs/Nafion/GCEs exhibit linear response to methyl parathion (MP) in the concentration ranges of 0.3-20.0 μM and 20.0-150.0 μM with the limit of detection of 0.092 μM (S/N = 3), showing good sensitivity, selectivity, reproducibility and anti-interference. Prepared electrochemical sensors have also been applied for determination of MP in practical samples of tomato and cabbage, showing comparable results to those measured using a high-performance liquid chromatography (HPLC). This proposed strategy is highly efficient for constructing microscale sensor units considering their size, uniformity and compositions, providing a reliable way for monitoring pesticide and other active components in fruits, vegetables and other scenarios of agricultural and industrial production.