Cu2O films without impurities fabricated via the mist spin spray technique using a mixed alkaline solution for flexible glucose sensors

Abstract

The mist spin spray (MSS) technique was used to fabricate crystalline Cu2O thin films on seed-free glass substrates and a flexible indium tin oxide (ITO)/polyethylene terephthalate (PET) substrate. In this technique, a solution containing Cu+ ions and a mixed alkaline solution of NH3 and NaOH were separately atomized by ultrasonication to generate mists. These mists were sprayed with a nitrogen carrier gas onto the substrates heated to 90°C on a rotating table under atmospheric pressure. This led to nanoscale-thick, dense, and high-purity Cu2O films with good adhesion to the substrates. The NaOH concentrations of the initial solution affected the film morphology, and the specimen films prepared with a NaOH concentration higher than 0.2 mol/L exhibited rough surfaces, whereas those prepared with a NaOH concentration of 0.1 mol/L and lower had dense and flat surfaces. The crystallized Cu2O film with nano-sized structure was fabricated directly on the ITO/PET substrate at 90°C to produce a flexible glucose sensor and exhibited good validity with a sensitivity of 561.6 µA cm−2 per concentration of mmol L−1.