Archetypal sandwich-structured CuO for high performance non-enzymatic sensing of glucose

Abstract

In the quest to enhance the selectivity and sensitivity of novel structured metal oxides for electrochemical non-enzymatic sensing of glucose, we report here a green synthesis of unique sandwich-structured CuO on a large scale under microwave mediated homogeneous precipitation conditions. The physicochemical studies carried out by XRD and BET methods show that the monoclinic CuO formed via thermal decomposition of Cu₂(OH)₂CO₃ possesses monomodal channel-type pores with largely improved surface area (∼43 m² g⁻¹) and pore volume (0.163 cm³ g⁻¹). The fascinating surface morphology and pore structure of CuO is formulated due to homogeneous crystallization and microwave induced self assembly during synthesis. The cyclic voltammetry and chronoamperometry studies show diffusion controlled glucose oxidation at ∼0.6 V (vs. Ag/AgCl) with extremely high sensitivity of 5342.8 μA mM⁻¹ cm⁻² and respective detection limit and response time of ∼1 μM and ∼0.7 s, under a wide dynamic concentration range of glucose. The chronoamperometry measurements demonstrate that the sensitivity of CuO to glucose is unaffected by the absence of dissolved oxygen and presence of poisoning chloride ions in the reaction medium, which essentially implies high poison resistance activity of the sandwich-structured CuO. The sandwich-structured CuO also shows insignificant interference/significant selectivity to glucose, even in the presence of high concentrations of other sugars as well as reducing species. In addition, the sandwich-structured CuO shows excellent reproducibility (relative standard deviation of ∼2.4% over ten identically fabricated electrodes) and outstanding long term stability (only ∼1.3% loss in sensitivity over a period of one month) during non-enzymatic electrochemical sensing of glucose. The unique microstructure and suitable channel-type pore architecture provide structural stability and maximum accessible electroactive surface for unimpeded mobility of glucose as well as the product molecules, which result in the excellent sensitivity and selectivity of sandwich-structured CuO for glucose under non-enzymatic milieu.