Glycine-Mediated Structural Evolution of ZnO Nanoparticles: A Robust Platform for Congo Red Mineralization and Glucose Detection

Abstract

Understanding the role of fuel chemistry in directing crystal growth is essential for tailoring the functional properties of metal oxide nanomaterials. In this work, ZnO nanoparticles were synthesized via a solution combustion route employing urea, citric acid and glycine as fuel agents to elucidate their influence on the structural evolution, morphology and functional performance of ZnO. Structural and microstructural analysis confirmed the formation of phasepure wurtzite ZnO with high crystallinity, while notable variations in crystallite size and morphology were observed depending on the fuel employed. Among the investigated fuels, glycine-mediated combustion produced ZnO nanoparticles with more favorable structural features, including improved crystallinity and porous morphology arising from the vigorous combustion process. These structural characteristics significantly influenced the functional behaviour of the material. Under visible-light irradiation, glycine-assisted ZnO (ZnO-G) exhibited superior photocatalytic performance toward Congo Red degradation, achieving an efficiency of 95.77%. Radical trapping experiments indicated that hydroxyl radicals (•OH) and photogenerated holes (h⁺) play dominant roles in the dye mineralization process.Electrochemical investigations further revealed that ZnO-G displayed enhanced electron transfer kinetics and reduced charge-transfer resistance during glucose sensing. This study demonstrates that glycine-mediated combustion effectively regulates the structural evolution of ZnO nanoparticles, establishing a clear structure-property correlation that enhances both photocatalytic and electrochemical performance. The findings highlight the potential of fueldirected crystal engineering strategies for developing multifunctional ZnO nanomaterials.