Influence of calcination temperature on the crystal structure and morphology of ZnO particles synthesized by the glycine-nitrate method: boosting electrochemical performances of ZnO toward diclofenac detection via calcination

The influence of calcination temperature on the crystal structure ordering and morphology of ZnO particles, potentially on their electrochemical response for detection of diclofenac in water environment was investigated. ZnO particles were synthesized by the glycine-nitrate method and subsequent calcination at 500 and 900°C (ZnO-500 and ZnO- 900). XRD analysis confirmed formation of phase-pure hexagonal wurtzite ZnO at both temperatures, where the increased calcination temperature provokes a slight increase in the crystallinity (3.75%) and significant (more than 80%) increase in crystallite sizes. FESEM analysis revealed distinguish morphology transformation, from an agglomerated sponge-like morphology for ZnO-500 to a larger, compact polyhedral grains for ZnO-900. Electrochemical parameters evaluated by cyclic voltammetry confirmed that ZnO-900-2 modified screen-printed carbon electrode (ZnO-900-SPCE) possesses superior electroanalytical performance toward diclofenac compared with ZnO-500-SPCE: ZnO-900-SPCE exhibited a 77% higher electrochemically active surface area and an almost threefold higher heterogeneous electron-transfer rate constant than ZnO-500-SPCE, also, 89.5% higher sensitivity, and threefold lower LOD (1.92 vs. 5.81 μM) and LOQ (6.42 vs. 19.38 μM). Presented results reveal that electroanalytical performance of ZnO materials as potential sensors for diclofenac can be boosted by optimal calcination temperature which simultaneously conduct crystallite and particle i.e. grain size, crystal structure ordering and interfacial charge-transfer characteristics.