A disposable electrochemical caffeine sensor based on a screen-printed electrode modified with a copper-metal organic framework and functionalized multi-walled carbon nanotube nanocomposite

Abstract

This study introduces a disposable electrochemical sensor for measuring caffeine (CAF) based on a screen-printed electrode modified with a copper-based metal organic framework and multi-walled carbon nanotube nanocomposite (Cu-MOF@f-MWCNTs/SPE). The f-MWCNTs improved the conductivity and specific surface area of the electrode, and the f-MWCNTs/SPE demonstrated excellent electrocatalytic activity toward CAF oxidation. Incorporating Cu-MOF with f-MWCNTs increased the number of active sites for CAF oxidation, leading to a significant increase in the oxidation current response of CAF. The morphology of the Cu-MOF@f-MWCNT nanocomposite was observed by scanning electron microscopy. The electrochemical behavior of CAF on different electrode modifications was investigated using cyclic voltammetry and differential pulse voltammetry. The optimal detection conditions were also evaluated. The linear range of the developed sensor was from 0.010 to 1.50 mM, and the detection limit was 7.9 μM. The sensor showed selectivity against six possible interferents and achieved recoveries from 85.0 to 104.6% of CAF in black coffee samples. Hence, the proposed disposable CAF sensor could be used in real-world applications.