Highly ordered surfactant micelles function as the extraction matrix for direct electrochemical detection of halonitrobenzenes at the ppb level

Halonitrobenzenes (HNBs) are a class of molecules that are highly toxic to human health and the ecological environment. Thus, effective and efficient approaches capable of monitoring and detecting HNBs are greatly desired. We report herein a simple and sensitive method for the detection of HNBs. The detection was based on the indium tin oxide (ITO) electrodes modified with a binary assembly of highly ordered surfactant micelles (OSMs) and silica mesochannels (SMs). The SMs have a diameter of 2–3 nm and a vertical orientation, which provide a hard support to stabilize soft OSMs. Moreover, each OSM consists of a hydrophobic core due to the organized assembly of surfactant hydrocarbon chains, which can selectively extract and concentrate lipophilic HNBs from aqueous media, allow their transport to the underlying ITO electrode surface and therein their detection by voltammetry. As a proof-of-concept experiment, 1-chloro-3-nitrobenzene, 1-chloro-4-nitrobenzene, 1-bromo-4-nitrobenzene and 2,4-dinitrobromobenzene were analyzed in aqueous solutions. A simple and fast detection was achieved in all cases, with a wide linear dynamic range, a high sensitivity and a low limit of detection at the ppb level. Apart from the extraction ability, the OSMs also prohibited the access of and surface contamination by unwanted substances, showing excellent anti-fouling and anti-interference power. Indeed, as we demonstrated, the sensor could be employed for direct electrochemical detection of HNBs in complex samples, such as lake water and soil dispersion, without any pre-treatment, indicating its potential usefulness in practical analysis.