Disposable carbon nanotube-based antifouling electrochemical sensors for detection of morphine in unprocessed coffee and milk

The direct on-site detection of illegal additives in unprocessed food samples is usually a great challenge for electrochemical sensors because of electrode biofouling. In this work, a simple filtration method for the scalable fabrication of disposable single-walled carbon nanotubes (SWCNTs)-based antifouling electrochemical sensors is reported. This method employs flash foam stamp-assisted polydimethylsiloxane (PDMS) patterns to control the region-selective deposition of SWCNTs on polyvinylidene fluoride (PVDF) membranes during filtration, which enables the scalable fabrication of a SWCNTs three-electrode-based sensor with high conductivity, good reproducibility and excellent flexibility. The resulting SWCNTs sensor exhibits a sensitive response towards morphine with a calibration range of 0.2 ∼ 100 μg mL−1 and a detection limit of 0.06 μg mL−1 (S/N = 3). Moreover, probably owing to its unique nanoporous structure, this SWCNTs sensor possesses apparently improved antifouling ability as compared with the widely used glassy carbon electrode (GCE), and allows the direct detection of morphine in unprocessed complex foods such as milk and coffee. The present work thus establishes a simple approach to the scalable production of self-designed SWCNTs electrode arrays suitable for on-site food analysis, which may also provide an alternative to commercial screen-printed carbon electrodes (SPCEs) for electrochemical sensing applications.