Summary
Zinc oxide (ZnO) is a versatile wide-bandgap semiconductor whose optical behaviour can be tuned by doping, making electrospun ZnO fibres attractive for optoelectronics, sensing and photocatalysis. This study systematically examines how incorporating calcium (Ca), aluminium (Al), or both affects electrospun ZnO fibres. All the fibres are built from interconnected polycrystalline oxide nanoparticles with the zincite (wurtzite) structure, and the dopant controls the nanoparticle size and therefore the fibre surface roughness. The two dopants behave very differently: calcium segregates out as a separate calcite phase, whereas aluminium disperses inside the zincite lattice as an isolated impurity. Aluminium content in particular governs the ratio of ultraviolet-to-visible photoluminescence emission and shifts the main ZnO absorption — giving a practical route to tailoring the optical response of ZnO fibres.