One step facile in-situ photochemical synthesis of hollow, doughnut-like ZnO nanoparticles and their alcohol vapor sensing properties

•Hollow, doughnut-like ZnO nanoparticles are synthesized by photochemical reduction.•Thiol-thioxanthone as the photoinitiator plays an important role in the shape of Nps.•α-aminoketone as Type I and thioxanthone as Type II are also used as photoinitiators.•Depending on the photoinitiator and irradiation time, the shape of the ZnO Nps changes.•The alcohol vapor sensing properties of ZnO nanocomposites are studied.